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Author Topic: Engine design and modifications Q/A thread  (Read 2441 times)

ace.cafe

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Engine design and modifications Q/A thread
« on: October 17, 2013, 12:35:53 AM »
If anybody wants to ask some questions about the design of engines, or their workings, or about performance modifications, then ask away, and I'll do my best to answer them or address your points of interest.

When I was just starting out, nobody ever bothered to explain anything to me, and I had to learn everything the hard way. So, if you ever wondered about something, I'll try to answer to the best of my ability.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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single

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Re: Engine design and modifications Q/A thread
« Reply #1 on: October 21, 2013, 03:46:18 AM »
Obviously,we are all pretty sure of ourselves.
Nice offer,Tom.

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Re: Engine design and modifications Q/A thread
« Reply #2 on: October 21, 2013, 02:21:00 PM »
I think you'll find they need your help on specific things.  Sometimes questions don't pop into our heads unless we have a problem to fix.
D
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Re: Engine design and modifications Q/A thread
« Reply #3 on: October 21, 2013, 04:04:59 PM »
Tom, I think maybe it's time to dig out a few of those instructional threads from a few years ago. Y'know, the ones that began "Let's talk about...". Those were great.
« Last Edit: October 21, 2013, 06:09:39 PM by Chuck D »
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ace.cafe

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Re: Engine design and modifications Q/A thread
« Reply #4 on: October 21, 2013, 05:05:01 PM »
Hi Chuck.
I'm going to have some exciting news for you later today.
I'll email you later with some pics and the news.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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Re: Engine design and modifications Q/A thread
« Reply #5 on: October 21, 2013, 06:08:25 PM »
Hi Chuck.
I'm going to have some exciting news for you later today.
I'll email you later with some pics and the news.
I'm on tenterhooks.
2006 Bullet Sixty-5 w/ Ace "Fireball 535" Kit (#10)
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Re: Engine design and modifications Q/A thread
« Reply #6 on: October 21, 2013, 06:40:13 PM »
I was wondering if the factory 535 cylinders are just standard cylinders bored out to their maximum like the Fireball's or are they able to be bored oversize?
Thanks,
Roger

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Re: Engine design and modifications Q/A thread
« Reply #7 on: October 21, 2013, 07:42:32 PM »
OK. I'll take a stab......Here you go Ace:
With the hi-lift rockers and Magnum cams in place, just how much more can you 'fill' the cylinder i.e. how close to 535cc at 1 barr at sea level. I am guessing it will vary with rpm.

ace.cafe

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Re: Engine design and modifications Q/A thread
« Reply #8 on: October 22, 2013, 02:39:49 AM »
OK. I'll take a stab......Here you go Ace:
With the hi-lift rockers and Magnum cams in place, just how much more can you 'fill' the cylinder i.e. how close to 535cc at 1 barr at sea level. I am guessing it will vary with rpm.
The hi-lift hi-port head can flow about 25% more at it's max lift than the regular Fireball head can flow. The highest efficiency of the flow comes at torque peak rpm, and the torque peak rpm of the hi-port head is at a higher rpm than the Fireball head.

We don't have the engine quite finished yet to do a dyno test of it, but it should be capable of 110% to 115% volumetric efficiency at torque peak. In other words, the cylinder should have a compressed load of 10%-15% more than the displacement. Somewhere around 600cc in a 535 cylinder.
Here's the port which flows 241 cfm at .600" lift.


Here's the first viewing of the new Ace hi-lift roller rocker system for the India-made Bullet 500 head.


Another shot.

« Last Edit: October 22, 2013, 02:42:14 AM by ace.cafe »
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Re: Engine design and modifications Q/A thread
« Reply #9 on: October 22, 2013, 02:49:42 AM »
I was wondering if the factory 535 cylinders are just standard cylinders bored out to their maximum like the Fireball's or are they able to be bored oversize?
Thanks,
Roger

Roger,
All the barrels are the same. The "factory" 535 ones are just the 500 barrels that are bored larger. The wall thickness is not any thicker than the ones we bore for the Fireball. Same thing.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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Re: Engine design and modifications Q/A thread
« Reply #10 on: October 22, 2013, 03:25:32 AM »
Well Tom another one from me. 

The piggy back ECU (I think it is Dynojet Power Commander) programmed for Suzuki ATV450 has been used on EFI REs to improve its performance with open pipe or other head/cam work. That ATV is also single cylinder 4 stroke engine but can rev way higher than G5, C5. Perhaps close to 11,000 as compared to 5500 or so for G5, C5. 

So question is what makes Suzuki engine safely rev so much higher and produce almost double HP than RE though both are about same volumetric size.

I mean what are the engine design features of Suzuki that are different from RE engine design that result in so much difference in them.
« Last Edit: October 22, 2013, 03:32:50 AM by singhg5 »
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ace.cafe

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Re: Engine design and modifications Q/A thread
« Reply #11 on: October 22, 2013, 03:34:11 AM »
Well Tom another one from me. 

The piggy back ECU (I think it is Dynojet Power Commander) programmed for Suzuki ATV450 has been used on EFI REs to improve its performance with open pipe or other head/cam work. That ATV is also single cylinder 4 stroke engine but can rev way higher than G5, C5. Perhaps close to 10,000 as compared to 5500 or so for G5, C5. 

So question is what makes Suzuki engine safely rev so much higher and produce almost double HP than RE though both are about same volumetric size.

Hi Singh,
The Suzuki engine has a much shorter stroke, which reduces the piston speeds dramatically, so that it can rev to that much higher rpm. It also will have a bore size that is much larger than the Bullet, since it will need that to have that size displacement with the shorter stroke. This allows bigger valve area for more flow.
So, basically, since hp = torque x rpm/5252, the more rpm we can reach, the higher our hp will be, as long as we can hold on to our torque at that high rpm. The shorter stroke's slower piston speeds allow this torque peak rpm to be pushed up the rev range, because it won't reach it's maximum piston speed until much higher in the rev range. This also typically will weaken the lower rpm torque to some degree, which is usually what we see in the higher revving bikes. They like to wind it out at higher rpm speeds, while our thumpers like to cruise along at lower rpms. It's a different kind of ride.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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Re: Engine design and modifications Q/A thread
« Reply #12 on: October 22, 2013, 04:50:51 AM »
The short stroke reduces the dynamic stress in the connecting rod and crankshaft.

Basically, the mass of the big end of the connecting rod is traveling around a smaller circle around the main bearing axis so the centripetal forces are less at any given speed.
 That allows the upper limit of the rpm to increase before the stresses in the rod and crankshaft began to tax the materials strength.
Jim
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Re: Engine design and modifications Q/A thread
« Reply #14 on: October 23, 2013, 07:28:04 AM »
"One thing that's needed to know about ratio rockers is that the effective duration between the .050" lift points is extended, and this will lower your working compression some. So be prepared to make a compression increase when using this package.  With the Ace Magnum cams, the .050" duration is extended by about 24 degrees, with 12 of those degrees on the inlet closing side. That is probably going to drop the compression test psi by about 10 psi. You can reduce the thickness of your barrel base gasket stack, or you can use the 3-way timing pinion to advance the valve timing by 4.5 degrees, to help compensate the compression. Advancing the cams also changes the lobe center angles, and will affect power curve characteristics on a peakier way, and you need to watch out for valve/piston clash when doing that. A test during the build,  of slowly rotating the engine by hand, with a thin(.060") layer of soft clay in the piston's valve reliefs is the usual testing protocol. " From Ace in his new parts thread

I have been thinking about my Fireball back in the states and I rebuilt it just as I had been running it at 4500' with not plate and just one cylinder base gasket. Now that I have my bike in Boston which is pretty much sea level I am wondering if I may end up with too much static compression. I copied Ace's write up above as it got me thinking that maybe if I end up with too much compression I can switch to the Shotgun 410's which by extending the valve timings a little might reduce my static compression so that I don't need to add an extra gasket or spacer. And get a performance boost as well.....I had been thinking of these rockers for after I get the engine broken in again but if I find when I get back to it that I am over compressing it this might be a good option....

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Re: Engine design and modifications Q/A thread
« Reply #15 on: October 23, 2013, 09:55:44 AM »
Tom, I think maybe it's time to dig out a few of those instructional threads from a few years ago. Y'know, the ones that began "Let's talk about...". Those were great.
+1
 I read most of your Articles on the yahoo page( awful to navigate by the way) and I reckon ye should publish them in a chapter format somehow.... Didn't jump in right away coz well to many posts makes Aussiedave a PITA... But I was wondering about mixture flow as it leaves the injector manifold into the inlet chamber ( bowl?) does the bowl act as a Venturi type affair and speed up the flow as it reduces volume to the inlet port or does it act to slow the flow down and increase the static pressure? Or should it try to maintain the existing velocity? Also previous posts have mentioned that the length of the efi manifold functioned to decrease turbulence- I think some one said their mileage decreased when they put pods directly on the injector. But isn't turbulence a good thing - keeping the fuel in suspension and helping an efficient burn?
« Last Edit: October 23, 2013, 10:26:33 AM by AussieDave »
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ace.cafe

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Re: Engine design and modifications Q/A thread
« Reply #16 on: October 23, 2013, 10:52:08 AM »
RGT,

Yes, that is a viable option.  The Ace Shotgun Rockers have lower ratio,  but they will have some of that effect.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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ace.cafe

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Re: Engine design and modifications Q/A thread
« Reply #17 on: October 23, 2013, 01:55:43 PM »
+1
 I read most of your Articles on the yahoo page( awful to navigate by the way) and I reckon ye should publish them in a chapter format somehow.... Didn't jump in right away coz well to many posts makes Aussiedave a PITA... But I was wondering about mixture flow as it leaves the injector manifold into the inlet chamber ( bowl?) does the bowl act as a Venturi type affair and speed up the flow as it reduces volume to the inlet port or does it act to slow the flow down and increase the static pressure? Or should it try to maintain the existing velocity? Also previous posts have mentioned that the length of the efi manifold functioned to decrease turbulence- I think some one said their mileage decreased when they put pods directly on the injector. But isn't turbulence a good thing - keeping the fuel in suspension and helping an efficient burn?

Okay Dave, I'll take these things in order.
First, your terminology of "inlet chamber(bowl)" is probably more accurately termed "inlet port", and there is a "bowl" there at the valve end of the inlet port, where the port turns a bit and opens up behind the valve itself.

The injector nozzle in the UCE is essentially a port injector, and it is aimed into the inlet port at an angle that is as close to the back of the inlet valve as they can make it. The object of this is to have the least reliance on the air flow for atomization and delivery of the fuel. The fuel is sprayed in a very fine mist at the last moment as the valve opens, so that it is carried in by the air immediately when the valve is open. This helps to reduce fuel drop-out and puddling, in comparison to what is often seen in carbureted engines. Injected engines generally do better at delivering the fuel in a better atomized state as it enters the cylinder.

This question about whether the port is acting as a venturi for speeding up or slowing down the mixture, or keeping it at the same speed is dependent on the design of the port, which can vary greatly on different engine designs. In the Bullet, and our Ace ports, the shape turns and expands into the bowl as it approaches the valve, with the purpose of slowing the flow and increasing the pressure recovery there, so the air can better make the turn, and become partially pressure-recovered as it will then make its way past the valve into the combustion chamber where it will recover more pressure and then move down into the cylinder itself. During all of this pressure recovery phase, it is slowing down and trading velocity energy for pressure energy, because energy must be conserved. If it does not recover pressure properly, it will become turbulent and produce vortices and eddies and find all possible ways to dissipate the energy in that turbulence. When it does that, the flow energy is released into this chaotic mess, and the speed plummets, and pressure is slow to recover, and the turbulence creates blockage and impediments to the air stream coming behind it. These are flow losses, but they come after the valve. Flow losses after the valve comprise about 50% of all the flow losses in the system, but we have very little methods to control these losses, and just concentrated on what we could control with the port and valve. It's only recently that these flow losses after the valve are being addressed, and we use methods with our porting to address this to reduce some of our flow losses in our heads.
The purpose of the port is to speed up the air in a venturi as it travels from the outside atmosphere into the port, trading the atmospheric air pressure for air stream velocity, and then as it gets near the cylinder, trade off the velocity for pressure recovery in a controlled way, to get the air back into its atmospheric-pressure condition in the cylinder with the least loss of flow energy. Ideally, you want it to behave as close to a Bernoulli lab experiment venturi as possible, like we see the tube with the narrow waist in the middle that has gradual narrowing and expanding on each side of the narrow portion. Of course, it never gets anywhere near that good, but that is the ideal which we are trying to simulate with our efforts. The shapes and sizes and methods use will vary, based on the challenges of the physical restraints of the engine shape and intention of the design, so not all ports are designed the same.

Regarding the turbulence in the UCE throttle body, it seems that this turbulence influences/confuses the mass-air pressure sensor, and thus has a negative influence on the accuracy of way the ECU delivers its fuel charge to the injector. That system seems to respond better to a smoother air flow, which is typically served by a still-air column or chamber prior to entering the throttle body, so that the sensor gets a better reading.
Turbulence is a fact of life, and we try to minimize it in most cases, but in other circumstances it can be utilized in small and local ways to do some jobs for us, as long as we keep it under control to do only/mostly what we want it to do.

This is a really big subject on fluid dynamics which could have MUCH more detail, but I hope that I got the highlights across in an understandable way with the brief discussion above.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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Re: Engine design and modifications Q/A thread
« Reply #18 on: October 23, 2013, 10:23:17 PM »
 Yes , thanks Ace , that helps my understanding muchly. I find it remarkable that you are able to create a positive pressure in the cylinder with your raised port design, just using induction and the momentum of the air! My understanding is that most engines still have a slight vacume at the end of the induction stroke- that is , they don't fill completely to atpospheric pressure. It certainly is a tricky environment for air flow and I find it fascinating. Wish I could see your flow bench in action. I'm curious as to how you model the changes you make-are there simulations you can run try different shapes in the passages? I hope I'm not encroaching on your trade secrets:)
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Re: Engine design and modifications Q/A thread
« Reply #19 on: October 23, 2013, 11:00:12 PM »
Yes , thanks Ace , that helps my understanding muchly. I find it remarkable that you are able to create a positive pressure in the cylinder with your raised port design, just using induction and the momentum of the air! My understanding is that most engines still have a slight vacume at the end of the induction stroke- that is , they don't fill completely to atpospheric pressure. It certainly is a tricky environment for air flow and I find it fascinating. Wish I could see your flow bench in action. I'm curious as to how you model the changes you make-are there simulations you can run try different shapes in the passages? I hope I'm not encroaching on your trade secrets:)

Dave,
Typically it requires wave tuning in the inlet and exhaust tracts to achieve over 100% volumetric efficiency.  And it doesn't always happen with the first attempts.
Essentially, the techniques involve setting appropriate tube lengths which work at certain harmonic frequencies with the targeted engine rpms to cause extraction waves in the exhaust pipe and ramming waves in the inlet tract. The extraction waves in the exhaust tract are timed to scavenge the last remaining gases in the combustion chamber so it is completely empty, and also create a suction to assist the inlet mixture to begin coming in prior to the piston descending on its intake stroke. The ramming wave in the inlet tract is timed to provide a positive pressure wave just prior to the closing of the inlet valve, to help push in some extra mixture at the last moment and prevent any reversion back up the inlet port from the building cylinder pressure created by the ascending piston. It's a very timing-sensitive matter, and is only effective at a certain bandwidth of rpms where it is intended to operate.
« Last Edit: October 23, 2013, 11:04:20 PM by ace.cafe »
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

Please visit my new website:
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Re: Engine design and modifications Q/A thread
« Reply #20 on: October 23, 2013, 11:09:15 PM »
Ok- wave tuning. Will now go read all I can find! Thanks!
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Re: Engine design and modifications Q/A thread
« Reply #21 on: October 28, 2013, 04:10:20 PM »
This is a general question on engines, related to kick start gear.

The electric starter motor gears are connected to crankshaft through sprag clutch mechanism that transfer power when required. I guess there is no such sprag clutch mechanism for the kick start gear.

How does kick start gear engage and disengage from the transmission shaft that it rotates to start an engine ? Do you have any pictures to clearly see how it is connected in RE ?
   
« Last Edit: October 28, 2013, 04:20:39 PM by singhg5 »
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Re: Engine design and modifications Q/A thread
« Reply #22 on: October 28, 2013, 04:30:29 PM »
This is a general question on engines, related to kick start gear.

The electric starter motor gears are connected to crankshaft through sprag clutch mechanism that transfer power when required. I guess there is no such sprag clutch mechanism for the kick start gear.

How does kick start gear engage and disengage from the transmission shaft that it rotates to start an engine ? Do you have any pictures to clearly see how it is connected in RE ?
 
It is a simple ratchet/pawl system. It is not engaged during running, like the sprag. A sprag ts sort of like a ratchet mechanism too, but it stays engaged with the engine gears all the time, and so it is vulnerable.

I am posting from my phone right now, so I can't put any photos up. The kick start ratchet and pawl parts can be seen in the exploded diagram in the parts book.

Also,  these kick start pawls and springs sometimes break too, but it is cheap and easy to fix it.

I personally think that a "bendix" type of electric starter, like cars have, would be a better choice than a sprag starter system.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

Please visit my new website:
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Re: Engine design and modifications Q/A thread
« Reply #23 on: October 28, 2013, 04:46:54 PM »
It is a simple ratchet/pawl system. It is not engaged during running, like the sprag. A sprag ts sort of like a ratchet mechanism too, but it stays engaged with the engine gears all the time, and so it is vulnerable.

I am posting from my phone right now, so I can't put any photos up. The kick start ratchet and pawl parts can be seen in the exploded diagram in the parts book.

Also,  these kick start pawls and springs sometimes break too, but it is cheap and easy to fix it.

I personally think that a "bendix" type of electric starter, like cars have, would be a better choice than a sprag starter system.

So the pawl can break on a kick back, if the kick lever is held down and not allowed to return !

That would require splitting the crankcase, isn't it ?
« Last Edit: October 28, 2013, 04:55:51 PM by singhg5 »
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Re: Engine design and modifications Q/A thread
« Reply #24 on: October 28, 2013, 05:15:07 PM »
So the pawl can break on a kick back, if the kick lever is held down and not allowed to return !

That would require splitting the crankcase, isn't it ?
No,  at the bottom of the kick stroke it disengages as it moves past the last ratchet tooth. Then it can safely return to the top, propelled by the return spring, with the pawl in the free direction.

 The typical breakages would be a kick back in mid-stroke, or the user trying to repeatedly kick the engine thru the compression stroke without using a decompressor, which over-stresses the pawl with too much load.

 In the Iron Barrel engine bikes, the kick start ratchet/pawl/return spring are easily accessible under the outer transmission cover for roadside servicing, if necessary. If it is inside the engine case on the UCE, then that would be much more difficult to service a broken pawl or return spring. I would hope that they would be behind an engine cover, and not inside the engine case halves.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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Re: Engine design and modifications Q/A thread
« Reply #25 on: October 28, 2013, 09:48:47 PM »
The Service Manual seems to show that the kick starter spring can be replaced by removing the right side cover and then the small cover that the kick starter shaft comes out of.
To do anything to the ratchet or the gear it drives, the engine case must be split and the transmission gears removed.  Only then will the kick starter gear/ratchet be able to come out of the engine. :(
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Re: Engine design and modifications Q/A thread
« Reply #26 on: November 01, 2013, 05:26:28 PM »
Tom:

Can you discuss the use of two smaller size intake/exhaust valve set vs one larger valve for intake/exhaust in an engine ?

How do you decide when to use 2 valve-set and when to stick to 1 valve-set ?
« Last Edit: November 01, 2013, 06:30:07 PM by singhg5 »
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Re: Engine design and modifications Q/A thread
« Reply #27 on: November 01, 2013, 06:46:00 PM »
Tom:

Can you discuss on the use of two smaller size intake/exhaust valve set vs one larger size valve for intake/exhaust in an engine ?

How do you decide when to use 2 valve-set and when to stick to 1 valve-set ?

Singh,
The common practice today is to use 4 valves per cylinder(2 intake, 2 exhaust). This provides more valve area for a given bore size.  Two valves for the intake or exhaust also have lighter mass per valve, so revving higher is easier to do without the valves getting out of control.

Generally speaking, pushrod engine designs will be 2-valve, and overhead cam engines could be either 2-valve or 4 valve.

The decision would be based on the need of the engine in its normal role. If the job can be done with one intake and one exhaust valve, it's cheaper to produce. This would be a relatively low revving design, like the Bullet.
For high revving short stroke screamers,  they need to operate at high rpms where low mass and high flow rates are very important.
« Last Edit: November 01, 2013, 11:57:40 PM by ace.cafe »
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Re: Engine design and modifications Q/A thread
« Reply #28 on: November 02, 2013, 01:48:24 AM »
Tom - On my '59 Chief that I'm building for Bonneville I've decided for my initial build I'm going to go high compression as opposed to a turbo set up.  I want to build either 13:1 or 14:1 compression ratio pistons and run on methanol.  I'm also going to use the 1 piece alloy Interceptor cylinder/s from Hitchcock's to help create clearance for the dome top pistons and help keep the motor cool.  Keeping in mind I'm sending my cams out to have them custom ground to whatever profile I want/need (basically as big of a lobe I can fit inside the crankcase), how far can I retard phase the intake camshaft to achieve a 7500-8500RPM redline?  My thoughts are to still build the cams as radical as possible with a pretty large duration to flow in/out the high compression charged cylinders, but phase the cams with an ideal overlap between 4000-7500RPMs.  Essentially full race style set up with the idle set at 1500RPMs and sounding like it wants to die, snapping and spitting, but then when you hit the throttle it rattles your bones loose.  Thanks.   :)

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Re: Engine design and modifications Q/A thread
« Reply #29 on: November 02, 2013, 03:00:16 AM »
You can close the intake valve as late as 90 degrees ABDC.
The Fireball closes the intake at 78 degrees ABDC.
« Last Edit: November 02, 2013, 03:04:32 AM by ace.cafe »
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Re: Engine design and modifications Q/A thread
« Reply #30 on: November 03, 2013, 01:15:56 PM »
Ace, since bullets make make most of their power at relatively low rpm's, has there ever been any work done in the "short rod engine" area? I know years ago it worked well with the harley flat trackers. The penalty is high piston side loading and shorter engine life, but if its a race engine or if you are going for a record, who cares? thanks cy.

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Re: Engine design and modifications Q/A thread
« Reply #31 on: November 04, 2013, 03:31:54 AM »
Ace, since bullets make make most of their power at relatively low rpm's, has there ever been any work done in the "short rod engine" area? I know years ago it worked well with the harley flat trackers. The penalty is high piston side loading and shorter engine life, but if its a race engine or if you are going for a record, who cares? thanks cy.

Cyrus,
Yes, it has been done, and still is being done by some people.
The rod can be lighter if it's shorter, and for some things it may be better.
Other issues are involved, and the rod length affects breathing characteristics and cam specs. The whole engine would need to be set-up to work with the shorter rod. It breathes better in the early part of the intake cycle, and it makes more torque at the early part of the power stroke where the pressures are still very high. It does have its good aspects.
The thrust-face loading also involves more than just longevity. The heavier thrust-face loading causes more friction losses and costs some horsepower. The overall package might be be good enough to overcome the added friction losses and make very good power, if it's done right.

There is more than one way to skin a cat, and a short rod has its merits, if the rest of the engine is set-up to suit it.
All my Bullet work is on the long rod, and I like that arrangement. But I think I could make a good short rod engine too. And one of these days, I might get a chance to do that. I have been thinking about it for a while.
« Last Edit: November 04, 2013, 03:34:18 AM by ace.cafe »
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Re: Engine design and modifications Q/A thread
« Reply #32 on: November 04, 2013, 09:08:57 PM »
Thanks for the info Tom. I have been wondering about it for years. Like you say , it may be worth looking into. Cy

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Re: Engine design and modifications Q/A thread
« Reply #33 on: November 11, 2013, 03:44:53 PM »
Tom:

Have you seen any kind of damage in the rocker assembly of REs and if so what was it ?  What caused it ?

Can engine kick-back crack or damage or loosen any part of rocker assembly ?
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Re: Engine design and modifications Q/A thread
« Reply #34 on: November 11, 2013, 04:55:52 PM »
Tom:

Have you seen any kind of damage in the rocker assembly of REs and if so what was it ?  What caused it ?

Can engine kick-back crack or damage or loosen any part of rocker assembly ?

Singh,
I have seen rocker damage in the Iron Barrel bikes. There have been some problems with damaged lash caps and their corresponding wear surfaces on the rocker arm. Also, there have been some wear issues in the rocker shaft wearing out the rocker block, and they get loose in there.

Regarding the UCE, I have not seen many rockers from them, but I have seen one that had worn valve guides at a very early stage which may have been caused by rocker issues. It may have been an anomaly. Valves were also slightly bent.
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Re: Engine design and modifications Q/A thread
« Reply #35 on: November 15, 2013, 04:45:30 PM »
Here is another one:

.....And I am only asking you to guesstimate (since your guestimate is much more informed than mine) : If the flowed, ported UCE head with the performance valve job was to be bolted back (without high lift rockers) on to the stock cylinder&piston, do you think the stock ECU would be able to keep up......If not, how much performance gain would you guestimate if this was mated with a remapped piggy back ECU that you are developing?

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Re: Engine design and modifications Q/A thread
« Reply #36 on: November 15, 2013, 05:01:11 PM »
Here is another one:

.....And I am only asking you to guesstimate (since your guestimate is much more informed than mine) : If the flowed, ported UCE head with the performance valve job was to be bolted back (without high lift rockers) on to the stock cylinder&piston, do you think the stock ECU would be able to keep up......If not, how much performance gain would you guestimate if this was mated with a remapped piggy back ECU that you are developing?

The stock ECU might keep up with the modded head at the stock lift. The stock lift is so low, that it hardly gets the valve open. So, the performance gain would be minimal, in my estimation, unless the lift is increased.
Since the ECU can do virtually no good at all unless more air is getting in there, then it won't help much if very little more air gets in.

Basically, the idea is like this. If you only have the door open a crack, then not much wind can blow in. If you have the door wide open, then a lot of wind can blow in.
See?
Same thing with valves.

The head is on the way to Chumma, and we are taking over the rocker work by doing it ourselves. We're tired of waiting.
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Re: Engine design and modifications Q/A thread
« Reply #37 on: November 18, 2013, 04:04:02 PM »
That sounds promising!
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Re: Engine design and modifications Q/A thread
« Reply #38 on: November 20, 2013, 12:35:51 AM »
Here's another: Have you had an oportunity to look at the rare, almost mystical, twin exhaust port head. As rare as it is, would it provide with more performance options. This one: http://www.royalenfields.com/2009/04/for-sale-very-rare-royal-enfield-twin.html#comment-form

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Re: Engine design and modifications Q/A thread
« Reply #39 on: November 20, 2013, 02:13:46 AM »
Here's another: Have you had an oportunity to look at the rare, almost mystical, twin exhaust port head. As rare as it is, would it provide with more performance options. This one: http://www.royalenfields.com/2009/04/for-sale-very-rare-royal-enfield-twin.html#comment-form

Yes, I have been aware of it for years.
It was a big waste of money. Performance suffers from too much exhaust size, it adds unnecessary weight from the unnecessary second exhaust system, and CMW discontinued having them made.
They are fine for a conversation piece, or a door stop. ;D
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Re: Engine design and modifications Q/A thread
« Reply #40 on: November 20, 2013, 04:24:27 AM »
The twin exhaust port engines were popular back in the 1930's and Royal Enfield offered them on some of their bikes.

Back then the commonly believed thoughts about exhaust was to get it out of the engine as fast as possible with as little back pressure as possible.  It seemed having twin exhausts would help to accomplish this.

This was also back around the time that the first vertical twins were being introduced.
Having twin exhaust made the engine look like a twin.  Not a bad thing and it sold a lot of bikes.

The problem was, few people recognized the advantages of a high velocity exhaust gas exiting the cylinder thru "undersize" ports and pipes.
They didn't fully understand the things a high velocity exhaust sysem could do to purge the cylinder of exhaust and draw in additional air/fuel thru the intake if the valve overlap and exhaust pipe were properly designed.

This "get the exhaust out thru huge exhaust pipe" thinking carried on well into the early 1960's.
Remember the big straight exhaust pipes on the Indy cars back then?
Remember how everyone laughed at the "bundle of snakes" on Jimmy Clarke's Lotus Cosworth  until it kicked ass in no uncertain terms?
Tuned exhaust using high velocity exhaust gas strikes again.  :D
« Last Edit: November 20, 2013, 04:26:58 AM by Arizoni »
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Re: Engine design and modifications Q/A thread
« Reply #41 on: November 20, 2013, 07:24:29 AM »
Ace, since bullets make make most of their power at relatively low rpm's, has there ever been any work done in the "short rod engine" area? I know years ago it worked well with the harley flat trackers. The penalty is high piston side loading and shorter engine life, but if its a race engine or if you are going for a record, who cares? thanks cy.
I have only just spotted this; I did this with one of our 350 race engines, currently in the bike and running very well. It would be difficult to guage any big differences between it and the 'ordinary' type engine in 'real life', but there are theoretical differences on paper. Bottom line is, it is a very compact engine and I removed a weight of 1 1/2 LBS from the alloy barrel alone in the process of shortening it for this project, always useful on a race bike ! It would make a handy 'off road' type engine, too, because it could be mounted higher up, in a Crusader type frame [as used by us for the racer with low mounting] to give a good performing machine with good ground clearance.
 B.W.

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Re: Engine design and modifications Q/A thread
« Reply #42 on: November 24, 2013, 04:26:24 PM »
Tom - I have questions about porting my intake manifold for my twin.  Basically I have a Y-manifold that is about 3" long.  I'm not exactly looking to go Gung Ho, but I would like to be able to create a better fuel charge.  As we all know these bikes aren't power houses, so every little bit counts.  Last night I did a light porting job and nice polish.  After doing so I discovered this was actually not the correct thing to do.  So I did some research, basically freshened up and my P&P education.  So, a perfectly polished finish like I did is actually good for forced induction, but as you previously said, a hindrance for N/A motors or anything that isn't direct fuel injection.  I'm not going to touch the heads, but I would like to at least gasket match the runners into the heads.  Also I noticed that the carb flange on the manifold is actually oval shaped and was thinking about opening up the lower and upper portions of the flange to make the mating surface to the crab more true and less restrictive.  Then I'm thinking of going back and resanding everything with 320 grit paper and attempt to sand the runners in a spiral direction to try and achieve a bit of a swirl effect.

What are your thoughts Tom?

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Re: Engine design and modifications Q/A thread
« Reply #43 on: November 24, 2013, 04:55:23 PM »
Tom - I have questions about porting my intake manifold for my twin.  Basically I have a Y-manifold that is about 3" long.  I'm not exactly looking to go Gung Ho, but I would like to be able to create a better fuel charge.  As we all know these bikes aren't power houses, so every little bit counts.  Last night I did a light porting job and nice polish.  After doing so I discovered this was actually not the correct thing to do.  So I did some research, basically freshened up and my P&P education.  So, a perfectly polished finish like I did is actually good for forced induction, but as you previously said, a hindrance for N/A motors or anything that isn't direct fuel injection.  I'm not going to touch the heads, but I would like to at least gasket match the runners into the heads.  Also I noticed that the carb flange on the manifold is actually oval shaped and was thinking about opening up the lower and upper portions of the flange to make the mating surface to the crab more true and less restrictive.  Then I'm thinking of going back and resanding everything with 320 grit paper and attempt to sand the runners in a spiral direction to try and achieve a bit of a swirl effect.

What are your thoughts Tom?

Scottie

Scottie,
First, before cutting any metal, we must define our goals and our approach.
Regarding carb size and manifold matching, assuming you want to keep the same carb, just make the manifold entry the same size as the carb throat I.D., and make a nice perfect transition there. Definitely do not make the manifold entry smaller than the carb. But larger than the carb is not real good either. Try to make it the same as the carb, so the flow "sees" it as going down one pipe with no transition bumps.
If the port entry in the heads is larger than the manifold exit holes, you can match them up perfect too. Just leave the port alone for now. The main idea is to remove any restrictions or flow obstacles from the manifold
Preferably use some 60 grit sandpaper to score up the inside of the manifold(ouch!) with the scores going cross-wise in the manifold in a tight spiral like you mentioned sort of like a screw-thread would look, but not as deep. The idea is that as any fuel drops out of the mixture(which it will), it drops into these scored scratches in the manifold, and the air moving above the tops of the scores will pull the fuel back up into suspension with the air, just like the carb jet works.
We also use a similar technique on the valve seats when we make the cuts for the flow angles. It's called "fuel shearing".
This technique also helps the air speed inside the manifold or port because it produces a "boundary layer" on the walls of the manifold or port, which reduces the surface drag of the walls by creating a thin little layer of turbulence all along the walls that acts sort of like little "roller bearings" for the main column of air to ride on, free of surface drag from the walls.

To go any further with real power mods, the single carb set-up needs to go, and you can move to tuned individual runner intakes. But this stuff should help with the single carb set-up that you have now.
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Re: Engine design and modifications Q/A thread
« Reply #44 on: November 24, 2013, 05:08:35 PM »
So what you are saying is that it is ok to match the intake port on the heads to the gasket and manifold as long as I'm just opening the initial edge of the runner on the head?

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Re: Engine design and modifications Q/A thread
« Reply #45 on: November 24, 2013, 05:44:13 PM »
So what you are saying is that it is ok to match the intake port on the heads to the gasket and manifold as long as I'm just opening the initial edge of the runner on the head?

Scottie

I am surmising by your question wording that your manifold is bigger than the entry to the head?
If that is so, then there may already be a problem.
Ignore the size of the gaskets, they are not sized to be anything related to performance. Make your own gaskets that are the right size.

I can't say if it is okay to open up the port entry to match. Maybe it is, maybe it's not.
I would have to see the rest of the port in question.

We are dealing with a system that begins with the bellmouth, and ends in the cylinder, and every millimeter of that entire system must be designed to work together to achieve the goal. Just "matching the ends" of two parts, when it's likely that neither one is actually the right size for the system, is not getting anywhere.

This is entering an area which is a big issue with people who are just beginning to get into the performance area, and it's very common in Enfield "DIY" circles, where people just "put parts together" expecting something good to happen. I can tell you that is where a lot of people go wrong. If you look at what we do at ACE, the whole system is matched to reach a certain goal.

You need to measure those parts out, find out what the relationships and shapes are like from the bellmouth to the valve, and get some strategy going, BEFORE you cut anything.

Here's some good basic criteria.
Find out your bore size.
The intake valve should be about 53% of the bore diameter.
The exhaust valve should be about 80% of the intake valve diameter, but it might be larger because Enfield commonly used a large exhaust valve. This can be compensated in cam design.
The intake valve throat should be 89% of the intake valve diameter on a typical street application.
The port minimum cross sectional diameter should typically be about 75% of the valve diameter for a port that has the usual angle that an Enfield port has. The carb should be the restriction, for best atomization.

As you can see, this is not even addressing the matching of two parts. The matching of the parts comes in AFTER you know what the sizes and relationships and tapers and shapes need to be. THEN you can match things up.

So, given what I have just explained, IF your intake manifold is larger than the intake port entry at that junction, here is what I would do to it.
I would leave the port alone, if you are not going to do a full porting job.
I would bolt the manifold to the head in such a way that the tops are aligned for best flow, and leave the mismatch at the floor.
Then I would fill the floor of the intake manifold with some JB-Weld, and shape it so that it matches to the port entry nicely, and sand it and finish it with that rough surface finish that we discussed previously. I'm not saying to JB-Weld the manifold to the head, just use the JB-Weld to fill the floor for shaping inside the manifold to match the port floor in the head, for flow matching purposes.
Make a gasket that fits that hole exactly, and use it.
Put it all together carefully with the carb off, so you can see that everything lines up the way you want it to at the junction of the ports, and then put the carb on it.
This gets you the flow match you want, and doesn't cause potential damage to the port entry when you don't know for sure what is going to be needed to be done to the port in the future. We never want to cut ports until we know exactly where we are going with them, because if it gets done wrong, then it's very hard to deal with later on when we want to do it right.
« Last Edit: November 24, 2013, 06:03:51 PM by ace.cafe »
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Re: Engine design and modifications Q/A thread
« Reply #46 on: November 24, 2013, 07:56:34 PM »
OK.  After pulling the intake back off and taking a closer look at things I realized that the intake ports on the heads are considerably smaller than the gaskets themselves, where as the gaskets are pretty close to the same size as the ports on the intake.  So I decided to not do anything in that department as it is going to take a considerable amount of work to match the intake, and rather wait until I have you do these heads and build a pair of custom dual intakes like we've spoken about.

Now on the carb side, as I had mentioned the port on the carb flange for the manifold was slightly smaller than the opening of the carb at the top and bottom, so I definitely wanted to address that.  I took the Dremmel and very carefully removed maybe .25mm off of the opening of the top and bottom.  I also had a brand new thick paper gasket so I went ahead and trimmed that up to perfectly match the intake opening.  I also noticed there was a bit of a lip protruding about 3/4" in from the flange opening on the outer side of each runner so I went ahead and removed those as well.  I then took 80 grit paper and smoothed out my grinding marks by wet sanding.  Then I took 180 grit paper and a piece of tubing and sanded in a circular motion down the runners.  After that I took a very small wire brush wheel in my drill and at a slow speed made spiraling motions down each runner.

Does seem acceptable and correct?









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Re: Engine design and modifications Q/A thread
« Reply #47 on: November 24, 2013, 08:13:53 PM »
Matching up the manifold and carb was good.
As for the step-down at the manifold/ head junction, that will need to be addressed at some point in the future. Just let that be for now.
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Re: Engine design and modifications Q/A thread
« Reply #48 on: November 25, 2013, 05:50:29 AM »
............. So, if you ever wondered about something, I'll try to answer to the best of my ability.

concerning the UCE engine, Electra piston, and squish.

Is the compression height of the stock UCE and the stock electra piston the same ?   Are there any clearance issues with this combo ?  how much does it raise the compression ?
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Re: Engine design and modifications Q/A thread
« Reply #49 on: November 25, 2013, 01:42:39 PM »
concerning the UCE engine, Electra piston, and
Is the compression height of the stock UCE and the stock electra piston the same ?   Are there any clearance issues with this combo ?  how much does it raise the compression ?

I haven't worked on an Electra, but it is my understanding that the compression height and compression ratio are the same as the UCE. The combustion chamber appears to be the same too, and the valve lift height too.

So, I would surmise that that AVL piston should be compatible withe the UCE. However, there might be bore clearance issues if trying to drop it into the same hole , without using an over bore size piston and boring to suit.
I would not expect any real compression change with this swap, but I don't know if there are any small differences in the dish volumes.

Apparently,  Scooter  Bob says that the AVL 535 flat top piston will drop right in and work with no issues in a 535 bored cylinder. That will have some compression increase due to the bigger displacement compressing into the same chamber, along with a flat top reducing the working chamber volume. I don't have the dish volume figure so I can't say exactly how much compression increase.

Regarding squish, the examples of UCE which we have seen, and AVL which we have seen reports about, did not get the piston close enough to the head for proper squish distance. I haven't measured the piston-to-valve clearance over TDC with the stock piston yet, so I can't tell you how much clearance there will be. The stock lift is very low, so I would suspect no contact problem there, using stock cams, but doing a clearance check with clay on the piston is advised whenever moving the piston or valve closer together over TDC.

GHG reported that after some minor shaving of the barrel height, he got the squish distance to just about .060", which is the largest acceptable squish distance, and is very marginal in operation.
The range for squish is from .020" to .060" distance from the head. The minimum recommended by the NHRA for squish on stock class engines is .021". If you get near .060" the squish is barely working, and might not be working. The sweet spot is around .040" squish distance from the head.
Any squish distance bigger than .060" and less than .100" is a "danger zone", where there is a propensity to increase the likelihood of detonation. So, if it is more than .060" it needs to be moved even further away than .100" or it may be a problem. Or, you could bring it closer, so it's in the squish range.
« Last Edit: November 25, 2013, 03:22:33 PM by ace.cafe »
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jedaks

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Re: Engine design and modifications Q/A thread
« Reply #50 on: January 14, 2014, 12:50:39 PM »
Hi Ace, I have a question about ignition systems.

I have kept the points ignition, partly for sentimental "traditional" reasons and for the ability to do roadside repairs/replacements if ever necessary. They have a get-you-home fiddle factor to them.

I'm also aware the modern electronic ignition sytems are very reliable and once the timing is set then it is set for good and you can forget it. (I've been told if a bike with e-ignition ever pings, it has to be due to fuel mixute and not timing.) Consequently, I am guessing, fuel economy and power generation are better.

But, how much better? Are those of us still using contact breaker points ignition missing out on very many benefits? Would a town/country commuter Bullet doing 30 klm a day really be improved over old fashioned points?

I'm not convinced about value for money.

Thanks
« Last Edit: January 14, 2014, 12:53:54 PM by jedaks »

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Re: Engine design and modifications Q/A thread
« Reply #51 on: January 14, 2014, 01:13:56 PM »
Speaking strictly from my own personal experience:

The K2F magneto was bad in my old '58 Twin.  I tried several attempts at replacing the points, the brushes, the HT leads, and I was down to only 2 options.  Either have the mag rebuilt and play the waiting game for how long it would be before it failed again.  Or By-pass it and install electronic ignition.  They were both going to cost $300, so I opted for the Thorspark Electronic Ignition Conversion.  This system uses the existing magneto, but you remove the points plate and replace it with an electronic trigger plate, which sends a signal to an external coil.  All in all it only took about 2 hours to install and set the timing, which brings me to this:


I'm also aware the modern electronic ignition sytems are very reliable and once the timing is set then it is set for good and you can forget it. (I've been told if a bike with e-ignition ever pings, it has to be due to fuel mixute and not timing.) Consequently, I am guessing, fuel economy and power generation are better.


YOU STILL NEED TO HAVE YOUR TIMING CORRECT!  For example, it took me about 6 weeks of micro-adjustments every other day before I had the timing Perfect.  But I'm also a perfectionist and I knew there was more to be gained from where it was at.  Since I got it dialed in, the only issue I had was the screws that mount the trigger to the mounting plate backed off, loosening the trigger and causing a misfire.  A little bit of loctite on those screws and my ignition has been ROCK solid ever since, almost always starting on the first kick regardless of conditions.  Quite easily the BEST $300 I spent on the restoration.  In fact, I don't think I could ever go back to points now.

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ace.cafe

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Re: Engine design and modifications Q/A thread
« Reply #52 on: January 14, 2014, 01:24:13 PM »
The problem with the Enfield points ignition is not the points. The points are fine, considering what they are for maintaining etc. They perform the same switching function as any other switch.

The problem is that the mechanical advance system is inadequate to deal with the engine needs in certain circumstances.  This is where a more modern type of ignition system can be an improvement.
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jedaks

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Re: Engine design and modifications Q/A thread
« Reply #53 on: January 14, 2014, 02:12:18 PM »
The problem with the Enfield points ignition is not the points. The points are fine, considering what they are for maintaining etc. They perform the same switching function as any other switch.

The problem is that the mechanical advance system is inadequate to deal with the engine needs in certain circumstances.  This is where a more modern type of ignition system can be an improvement.

Fair point well said. What about the claims that e-ignition improves fuel economy and power?

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Re: Engine design and modifications Q/A thread
« Reply #54 on: January 14, 2014, 02:46:46 PM »
Fair point well said. What about the claims that e-ignition improves fuel economy and power?
It might, or it might not.
If the previous system caused the ignition timing to be wrong, and the new system caused it to be right,  then power and/or fuel economy might be improved. If the previous system was correctly timed, then no improvements will be seen.
If the old system had a weak coil, and the new system has a strong coil, then that might be cause for some improvement to occur from the stronger spark.
Again, it's not a matter of whether it is "electronic" or not. It's a matter of if the timing is correct. The engine has no idea what kind of controller is being used, nor does it care. All the engine knows is if it's getting the spark at the right time, or not.
It is entirely possible for an electronic ignition to get the timing completely wrong, if the advance curve was programmed by somebody who didn't know what he should know, or if the end user incorrectly set up the timing.

What we know for sure about the stock Enfield ignition is that it swings to full advance almost immediately upon applying any throttle above idle speed, and stays at full advance until returning down to just slightly above idle speed.
If any load is encountered at rpms below torque peak, such as the need to accelerate with a passenger aboard, or climb a hill , or both,  then the system has no ability to retard the spark for these conditions,  and so it then tries to perform the task with the ignition too far advanced. This causes ping, overhearing, and often seizes the piston in the bore.

Some electronic ignition systems might be able to retard the ignition under circumstances like this , but many cannot.

There is no panacea from some nebulous category like "electronic". Each ignition system needs to be considered based on how well it deals with the things that we need it to do.
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Re: Engine design and modifications Q/A thread
« Reply #55 on: January 18, 2014, 05:34:28 PM »
Is there any advantage of long-skirt piston over short-skirt piston with bracing ?
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ace.cafe

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Re: Engine design and modifications Q/A thread
« Reply #56 on: January 18, 2014, 06:02:04 PM »
Is there any advantage of long-skirt piston over short-skirt piston with bracing ?

Yes, a long skirt piston supports the piston better in the bore, and can be better at minimizing piston "rock".
However, a long skirt weighs a bit more, so sometimes it is abbreviated to save weight in performance applications.
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