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Author Topic: Engine design and modifications Q/A thread  (Read 1919 times)

cyrusb

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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.

ace.cafe

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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 »
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

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cyrusb

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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

singhg5

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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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ace.cafe

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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.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

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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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ace.cafe

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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.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

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AussieDave

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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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ace.cafe

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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
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

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Arizoni

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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?

Scottie
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ace.cafe

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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.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

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High On Octane

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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?

Scottie
Bulldog Kustoms - Denver, CO
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The Blackhawk
1958 Enfield/Indian 711cc Twin

Building the 1st EVER Supercharged RE Twin
FULL RACE motor with ACE Performance