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Author Topic: Increasing power output in the engine.  (Read 3475 times)

ace.cafe

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Increasing power output in the engine.
« on: February 22, 2009, 05:18:34 PM »
Well, it's a lazy Sunday morning, and i felt like writing something.
So, considering spring is coming up soon, and people may want to "perk up" their Bullets for this year's riding, I thought I'd devote a little time to the subject.

What is "power"?
In an engine, "power" is basically divided into two aspects.
These are "torque" and "horsepower".
Strictly speaking, "torque is the "torsional force" or rotating force around the center axis of the crankshaft. Just like if you put a torque wrench on the crankshaft nut, and used the leverage of the torque wrench to turn the engine.
Horsepower is the work done by the torque, including time, which is usually described by rpms. And horsepower is a mathematical function of torque and rpm, specifically torque x rpm, divided by 5252(a constant).
Looking at this function, we can see that since the dividend in the equation is 5252, then torque will always be higher than horsepower up until 5252 rpm, and horsepower can then go higher than torque above 5252 rpm.
So, in our Bullets, it's easy to see that torque is the main aspect of power production that we will use in our daily riding. We cannot use rpms that are much higher than 5252, because of the strength limitations of the parts in the bottom-end of our engine. However, we can go a little above that, and usually 5500-6000 rpms would be considered the safe maximum limit for us.
And given this function of torque and horsepower, we can now address power production with these things in mind.

How do we increase torque?
Torque in an engine is the result of 2 things primarily. Those things are the leverage exerted on the crankshaft, and force exerted on the piston.
The leverage exerted on the crankshaft is dictated by the stroke length in our engine design. Specifically, it is the distance from the centerline of the crank, to the centerline of the crankpin. This distance is 45mm. But, you say that our stroke is 90mm? Yes it is. The 45mm goes up and down around the centerline, so the distance of 45mm is multiplied by 2 to get total stroke. But the actual distance involved for torque production is 45mm, because that is the distance of the crankpin from the crank center. This leverage is increased with longer stroke, and decreased with shorter stroke. It is fixed by the engine design, unless you change to a stroker crank.
The force exerted on the piston is the combination of the combustion pressure in the chamber, times the area of the piston crown. So you can increase this number  by enlarging the bore/piston size, or increasing the compression pressure, or both.
And this is commonly done with a big-bore kit and high compression piston.

Anytime you increase torque, you automatically increase horsepower, due the the nature of the mathematical function. But only at the points in the rpm range where that torque has been raised. It is entirely possible to gain torque in one part of the rpm band, and lose some in another part of the rpm band. So we want it to be broad enough in the torque curve, to provide good useful riding results. Some racing engines make power only in the highest rpms, and are very poor at low or midrange rpms. Conversely, some other engines pull like a tractor at low rpms, and can't reach high rpms very well at all. It's all part of how the engine designer picked the parts for the application.

Horsepower on the other hand, always follows torque. You can't have hp without torque. BUT, there is a special circumstance, where breathing efficiency allows torque to drop slightly, and the rpms can still cause horsepower to increase, as long as the engine can continue to pull in sufficient air/fuel mixture to increase rpms.

The "knee" in this curve is known as "peak torque rpm". It is the point where the engine is operating most efficiently for torque production. Everything is coming together just right at this rpm. As we accelerate from idle to peak torque rpm, the torque continuously increases until we reach peak torque rpm. Then it may hold on to the peak torque figure for a while, or it may begin to drop off at higher rpms.  Most times it will slowly decrease for about 1000-1500 rpms, and then drop off precipitously when breathing capacity reaches the limit. Even during the decreasing slope of the torque, engine rpm can increase and thus still produce higher and higher hp, until the breathing capacity of the engine is reached, and this is "peak horsepower".  The longer the engine can provide breathing capacity to rev higher, the longer the area from peak torque to peak hp will become.
So, there you have your 2 curves in power production of the engine, with the critical rpms for peak torque and peak hp. The rpms between the peak torque rpm and the peak hp rpm is commonly known as the "max power range".

How does the engine continue to make more power after it reaches the torque peak? Why doesn't it just stop there, if it has passed the place of best efficiency?
It's because the engine has capacity to breathe in more air/fuel mixture, at a rate which can be multiplied by rpms, even after max efficiency(peak torque) is passed. And it can continue to do this as the torque slowly declines, until that breathing capacity is limited enough to not be able to overcome the torque decline any more.
So, what we'd like to do is reach a high peak torque figure, and hold onto it as long as we can while the rpms rise further. And we'd like to place this range within the ability of our engine's structural integrity, so that we can access it without blowing the crank or rod. And in our case, this might be a torque peak of 4000 rpm and a hp peak of 5500 rpm, or maybe even a torque peak of 4500 rpm and a hp peak of 6000 rpm. The latter is pretty high, and probably reserved for a sport rider who likes to push the limits.

What can we do to help raise torque, keep a broad and useful curve, and increase hp too?
Well, we are pretty much limited in mechanical leverage by the stroke, unless we get a stroker crank. So that's about set in stone.
But we can get a big-bore kit and hi-compression piston pretty easily, and that can help out all thru the entire range.
But, those are only parts of what we can do.

How can we go further?
We can increase the breathing capacity of the intake and exhaust systems, and also increase the breathing capacity of the cylinder head. We know that a somewhat bigger carb, and a free-flow air filter can help, and many of us have done that. So does removing the very obstructed exhaust system, and replacing it with one that can let the gases out of the engine with less impediment.
This seems to make sense, right? We can bring more air/fuel mixture in, and get the exhaust gases out, better. And it works. To a point.

What is this "point" of which I speak?
Remember a few paragraphs back, when I mentioned that it's possible to gain torque or hp in one rpm range, and lose it in another. That is the issue that I'm referring to.
It's possible to set up the engine breathing so that it is very big, and flows alot at higher rpms, but this makes it flow slow and lazy at lower rpms. And that means that at lower rpms, not alot of air/fuel mixture is getting in, because of slow lazy flow that was created by making it all big enough to flow at much higher rpms, and that's what makes racing engines do poorly on the street. Conversely, if we make the breathing small enough to give us really high flow speeds at lower rpms, giving us great low-rpm torque, our ports(or carb or manifolds) can't flow enough mixture at the higher rpms to develop the power at the high rpms. So, for street work, we need a balance.

What is the "balance"?
The balance is to have breathing which can be fast enough to give good flow and good torque down low, and still be able to breathe well enough to allow the engine to access the high rpms. This means not going too far in either direction. Not too small, and not too large. So, we don't want an overly large carburetor, or overly large intake manifold, or over large ports. Nor do we want them too small.
We want it to be like "Goldilocks". Just right!
So, we select are carburetor size, manifold size and port size, so that we are good for our intended range of use, which is about 2000-6000rpms. It does us no good to set up the engine to do 9000rpm. We'll never get there without blowing up, and it will just wreck our low-speed running.
Happily, our India-made head has an intake port which is very nearly sufficient for our highest rpms, and doesn't really need enlargement. But, the shape of the port is poor, and while it may be able to pass enough air, it doesn't do it with good velocity. So what we need in our India-made intake port is improved shape, and not necessarily bigger size. The size"could be" bigger, IF the shape is improved sufficiently to get good velocities with that bigger size. That's not easy to do, but with the poor shape that we have in there, it could be possible, IF you really know what you are doing.
The same goes with the carb and manifold. If the carb is too big, then it just slows everything down, and you can't get the overall flow you need because velocity suffers. So, putting a big 38mm carb on our stock ports isn't going to help us. But, going bigger than the 28mm carb might certainly help us, because our ports are 32mm, and that makes the carb a restriction.
The whole idea is to get more air/fuel mixture in, which means sufficient volume, AND sufficient velocity, which combine to get most mixture in during the time the valve is open. And do it well enough at all our rpm ranges, so that we don't suffer weak spots in our riding range.
The more mixture that enters the engine at any given rpm, the more the combustion pressure is going to be exerted on the piston crown, and the more torque is going to result. So, it stands to reason that we want to get as much in as we can, at all the rpms that we plan to ride. Since this increases torque, it also increases horsepower, and everybody's happy.

So, in summation, we must strive to modify the engine within the expected range of use(rpms) to provide the best breathing possible in the bulk of that rpm range, and use that to produce more force exerted on the piston. And we can combine that with a piston that "squeezes" that mixture with more compression, to improve the result. And we can use a slightly bigger piston to give more area for that pressure to work on.

Of course, we could discuss how cams assist this, and the exnaust extraction effects, but I think we've bitten-off a pretty good chunk here, so we can chew on this one for awhile.
« Last Edit: February 22, 2009, 06:16:17 PM by ace.cafe »
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ScooterBob

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Re: Increasing power output in the engine.
« Reply #1 on: February 22, 2009, 09:18:41 PM »
ACE - Bravo!! .... Very well done, my good man .... A couple of questions tho ....

1). How strong IS the coffee that you drink on Sunday morning?
2). Just when are we going to share a pint or two and discuss port velocity and rotational force over time ..... ?? Hahaha!! You have a "bit better than average" understanding of this stuff .... I love it! I LIVE there when I am not buried up in other endeavors .....

I'm bettin' that there is some untapped torque in the old Bullet - I'm also guessing some of my work in getting nearly 650ft/lbs out of a normally aspirated Olds engine at 2800rpms might apply. Port velocity SEEMS to be the factor here - as long as it isn't supersonic! I'd LOVE to make a Bullet pull like an Unlimited Class John Deere diesel at a tractor pull ....  ;D
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ace.cafe

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Re: Increasing power output in the engine.
« Reply #2 on: February 22, 2009, 10:38:19 PM »
Hi Bob,

Yeah, I make the coffee pretty strong! And I drink alot of it!

I do think there's some "untapped torque and hp" available left in the old Bullet.
But it has to be carefully tapped, so that we can keep the nice midrange that we all love about our Bullets.

Since you're an Oldsmobile enthusiast, I'm sure you are familiar with a guy named Joe Mondello.
I've got quite a surprise coming up for you and all the Bullet faithful here.
But I'm not quite ready to discuss the details just yet.
You can ask Kevin about the details.

We'll have to see how it goes along.
Here's my train of thought.
I think a well-prepped 535 Bullet can reach the power output levels of the  612 performance kit.
If I can find 3 extra foot-lbs of torque in the 535 somewhere, and hang on to it reasonably well, into the upper rpms, then it can produce just a hair under 40hp at 6000 rpm, with about 35-36 ft/lbs of torque peaking around 4500 rpm..
And do it with a crisp and punchy midrange and low-end too.
On pump gas.
35 foot-lbs x 6000 rpm , divided by 5252 = 39.98hp @ 6000 rpm.
That's my goal.  A 10% torque boost out of a 535, with a 6k rpm redline.
612 power out of a 535, which gives lower piston speeds, and better durability.
Basically like a Fury that doesn't blow up. Very close to a Gold Star DBD34.
And totally streetable and reliable, with good road manners.
We'll see if we can hit it.

You know, this Mondello guy knows a thing or two about heads.


« Last Edit: February 22, 2009, 10:54:22 PM 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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ScooterBob

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Re: Increasing power output in the engine.
« Reply #3 on: February 22, 2009, 11:03:55 PM »
Uh, yeah .... Joe Mondello IS the "head master" when it comes to Olds stuff ... It was his stuff that inspired me to further tinker with the buddy's drag car to get "fasterness" out of it. I'm really intrigued by your Bullet project - but I'm really thinking that there is even five MORE torques in there than you are hoping for .... I'm thinking "cylinder charging" and burn time vs. crank rotation .... You know the old 340 Dodge trick of switching the offsets on the pin holes to effectively get more dwell at TDC and all that - why not increase the length of the rod (plenty of room!) on the Bullet for the same net effect? The OTHER thing on the old Bullet IS the intake port .... a fellow needs to DevCon the poop out of one and do some "spare-uh-mintin'" on it to get the velocity (and therefore the torque) up a bit in the middle range. Just food for thought .... The worst thing of all of it is trying to get it to run on that miserable azeotropic bag of crap they call motor fuel these days! I have tested some of it - and "Inconsistent" is its name .... I'd LOVE to build a powerhouse, torque-bastage Bullet ... but I'll be pretty happy just to get to RIDE one after THIS winter in Minnesota!! Hahaha!! Perhaps the bug will hit HARD this spring ... we must share a note or two ... perhaps we can make each other go faster!! Hahaha!!
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t120rbullet

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Re: Increasing power output in the engine.
« Reply #4 on: February 22, 2009, 11:15:45 PM »
The OTHER thing on the old Bullet IS the intake port .... a fellow needs to DevCon the poop out of one and do some "spare-uh-mintin'" on it to get the velocity (and therefore the torque) up a bit in the middle range.

Or get a 350 head and machine it to fit on the 500 cylinder spigot and go from there.
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ScooterBob

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Re: Increasing power output in the engine.
« Reply #5 on: February 22, 2009, 11:17:22 PM »
Hmmmmmm - I think there is one of those on my desk!! .....  ::)
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ace.cafe

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Re: Increasing power output in the engine.
« Reply #6 on: February 22, 2009, 11:31:45 PM »
The OTHER thing on the old Bullet IS the intake port .... a fellow needs to DevCon the poop out of one and do some "spare-uh-mintin'" on it to get the velocity (and therefore the torque) up a bit in the middle range.

Or get a 350 head and machine it to fit on the 500 cylinder spigot and go from there.

The original Redditch 500 heads had 29mm intake port, so they can be opened-up to the proper diameter, but the shape is still "backwards.
However, it's less work that using a 350 head.
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Alaroyal

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Re: Increasing power output in the engine.
« Reply #7 on: February 22, 2009, 11:44:01 PM »
Anybody ever create a four valve head for a Bullet?  Lots of folks think 4 valves only work at high RPMs but that's not the case, they can be VERY efficient at low AND high RPMs.  They are small enough to keep the air flow speed high at low engine speeds, but have enough combined area to give good breathing at high RPMS.

The Ford and Dodge pickup diesel engines each went to four vave heads and got a noticeable power bump, and Ford kept pushrods.  Detroit Diesel's Series 60 engines for road tractors have four valve heads and rarely see more than about 2100 or so RPM.

Jim Feuling (and others)  developed four valve heads for Harley Davidsons and they worked great.

Overhead cams might be out for RE's, but I'd LOVE to see a 535 with a nice four valve hemi head, with dual ports for intake and exhaust, two exhaust pipes, a  sparkplug in the center of the combustion chamber,  and two carbs or fuel injectors.

If you're gonna dream, make it in technicolor !
« Last Edit: February 22, 2009, 11:46:00 PM by Alaroyal »
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ace.cafe

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Re: Increasing power output in the engine.
« Reply #8 on: February 22, 2009, 11:47:09 PM »
Uh, yeah .... Joe Mondello IS the "head master" when it comes to Olds stuff ... It was his stuff that inspired me to further tinker with the buddy's drag car to get "fasterness" out of it. I'm really intrigued by your Bullet project - but I'm really thinking that there is even five MORE torques in there than you are hoping for .... I'm thinking "cylinder charging" and burn time vs. crank rotation .... You know the old 340 Dodge trick of switching the offsets on the pin holes to effectively get more dwell at TDC and all that - why not increase the length of the rod (plenty of room!) on the Bullet for the same net effect? The OTHER thing on the old Bullet IS the intake port .... a fellow needs to DevCon the poop out of one and do some "spare-uh-mintin'" on it to get the velocity (and therefore the torque) up a bit in the middle range. Just food for thought .... The worst thing of all of it is trying to get it to run on that miserable azeotropic bag of crap they call motor fuel these days! I have tested some of it - and "Inconsistent" is its name .... I'd LOVE to build a powerhouse, torque-bastage Bullet ... but I'll be pretty happy just to get to RIDE one after THIS winter in Minnesota!! Hahaha!! Perhaps the bug will hit HARD this spring ... we must share a note or two ... perhaps we can make each other go faster!! Hahaha!!

Ok, here's the trick.
You need  to get enough CFM going in to make the power, so you need some decent port volume.
And you need to get it in at good velocity.
We need to have enough port to not choke at full lift, but still flow well at low-lift.
And we are very lift-limited.
Seemingly at odds with each other.
It's all in the shape.

Regarding the other stuff, definitely the long rod will give us the dwell time, and we have a stroke/rod ratio of nearly 2 right now. Plenty of dwell to use the late intake valve closing timing for extra cylinder charging, and that will be involved. Got one of the leading cam grinders on board for this task.

I think that there may be more to be had than my goal, but I don't want to aim too high, particularly since I'm working within a limited rpm range for street use, with a low redline dictated by piston speeds.
If more can be gotten, we'll see about it. It has to be streetable.

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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ace.cafe

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Re: Increasing power output in the engine.
« Reply #9 on: February 22, 2009, 11:51:51 PM »
Anybody ever create a four valve head for a Bullet?  Lots of folks think 4 valves only work at high RPMs but that's not the case, they can be VERY efficient at low AND high RPMs.  They are small enough to keep the air flow speed high at low engine speeds, but have enough combined area to give good breathing at high RPMS.

The Ford and Dodge pickup diesel engines each went to four vave heads and got a noticeable power bump, and Ford kept pushrods.  Detroit Diesel's Series 60 engines for road tractors have four valve heads and rarely see more than about 2100 or so RPM.

Jim Feuling (and others)  developed four valve heads for Harley Davidsons and they worked great.

Overhead cams might be out for RE's, but I'd LOVE to see a 535 with a nice four valve hemi head, with dual ports for intake and exhaust, two exhaust pipes, a  sparkplug in the center of the combustion chamber,  and two carbs or fuel injectors.

If you're gonna dream, make it in technicolor !

That could be done.
But it requires a new head casting, or a CNC billet head to be made.
I think it is cost-prohibitive for our market.
In fact, I'm a little worried about the modified head being cost prohibitive.
We don't have a huge market to absorb large numbers of these things, so that has to be taken into consideration.
I'd love to do a project like that, but I think it would end up with the heads costing thousands of dollars each.

RE had Dr. Stuart McGuigan prototype a 4-valve head for the Bullet, but as a diesel engine, during the 1990s. It was pretty cool. Never saw daylight, though.
« Last Edit: February 22, 2009, 11:55:26 PM 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.

Please visit my new website:
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BigDon

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Re: Increasing power output in the engine.
« Reply #10 on: February 23, 2009, 03:44:10 AM »
Ace you are killing me with the little blurbs here and there lately! ;D

When man when!!!!!
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ace.cafe

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Re: Increasing power output in the engine.
« Reply #11 on: February 23, 2009, 02:33:51 PM »
Don,
All in good time, sir.

Actually, I'm expecting to have my first one in my hands within a couple of weeks.
Then I"m gonna put it on my bike and test ride it.
After verifying that all is good, I'll get some prices listed.

I've contacted Kevin about it already, so that he has the first opportunity to list them in the CMW catalog, if he wishes to do that. I suppose that it all depends on whether he feels it hits a price range that he considers right for him.

I'm expecting that the mods will be done on the customer's own head that he sends in. This will help to keep the price down a bit, because you don't have to buy a new head casting. If your head is damaged, then you need to send in a new casting, or we can procure one for you.
But since this is premium work done by the world's best head porting expert, it isn't going to be a cheap item. My instructions were to try to keep the retail price as close as possible to the Stage 2 head currently offered. We'll see how close he can come to that. I think it will cost a bit more, but I don't know exactly how much more.

I understand that the Bullet market is generally a very cost-conscious market.
However, I expect the market to understand that I'm bringing something in that has never been done before, in attempt to raise the bar of performance for Bullet owners.
« Last Edit: February 23, 2009, 02:43:59 PM by ace.cafe »
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Cabo Cruz

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Re: Increasing power output in the engine.
« Reply #12 on: February 23, 2009, 03:03:28 PM »
Well, Brother Ace, all this deserves, you can easily guess, a huge:

                            WOWZAA!!!

                                        ;D
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cyrusb

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Re: Increasing power output in the engine.
« Reply #13 on: February 23, 2009, 05:16:15 PM »
Do you think the added poop will cause the head to leak? Some stock bullets have that problem at 22 hp. The stock bullets have some pretty slim studs holding the head-jug assembly down.

ace.cafe

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Re: Increasing power output in the engine.
« Reply #14 on: February 23, 2009, 05:46:01 PM »
Do you think the added poop will cause the head to leak? Some stock bullets have that problem at 22 hp. The stock bullets have some pretty slim studs holding the head-jug assembly down.

No, I don't think that's a problem associated with the power production issue.
It mostly comes from a mismatched spigot height on the barrel, which is a little too tall for the recess in the cylinder head. Then it doesn't compress the gasket well, and oil leaks at the pushrod tubes.

Many people are using the hi-compression pistons, and not suffering oil leaks at the head joint. But, it is a very good idea to match the spigot height to the recess in the head, so that leaks can be avoided in any case. Also, if you have too little spigot height to make a good compression seal in the recess, compression can leak out and blow the gasket.
The whole central theme of good head sealing in the Bullet is to get a good match in the spigot/recess joint, and still be able compress the gasket to seal the pushrod tubes. I think that "ideally", the spigot should be about .010" taller than the recess in the head. This leaves room to use a .015"-.020" thickness head gasket, and be able to compress it to seal the pushrod tubes, and also still seal the compression well at the recess.

The "cheesy" studs can be an issue sometimes, but I don't think they are the main offender. It wouldn't hurt to use better studs if you want to, though.
But watch out for the next link in the chain, which is pulling the stud threads out of the crankcase.
I actually use about 10% less torque than the manual specifies on the head studs.
« Last Edit: February 23, 2009, 05:54:16 PM by ace.cafe »
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cyrusb

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Re: Increasing power output in the engine.
« Reply #15 on: February 23, 2009, 09:00:29 PM »
Well, how well it fares remains to be seen. Remember, these are not British made, so there is a lot in the wind here. The studs pulling out of the cases is certainly another area to worry about. All that extra pressure must be supported somewhere. Good luck.

ace.cafe

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Re: Increasing power output in the engine.
« Reply #16 on: February 23, 2009, 09:49:12 PM »
Well, how well it fares remains to be seen. Remember, these are not British made, so there is a lot in the wind here. The studs pulling out of the cases is certainly another area to worry about. All that extra pressure must be supported somewhere. Good luck.

Yes, I understand the concerns, and appreciate your input.

We do have some examples to look at and see what can be done.
I think that the 612 is a good example that this level of power can be reliably handled by the Bullet engine cases and studs.

From what I've seen, most of the stud breakages have come from people trying to cure oil leaks by tightening down the head nuts, when the problem is that the spigot is too tall, and stopping the head from compressing the gasket. So they tighten and tighten, and then snap the studs or pull the threads, and never do cure the leak.. The leak can only be cured by cutting down the spigot to the proper height. They could tighten the head till doomsday, and never cure the leak. And this is very common.

So, while the Indian-made studs and alloy may be suspect, they are not always the cause of these problems we see.
But, for a person who is particularly concerned about this issue, it is not too difficult to install helicoils in the engine case, and install studs with higher tensile strength. That might give better peace of mind, and that's a perfectly fine way to address that issue.

And you are very right in pointing out that hi-performance modifications are not done in a "vacuum", and the stresses involved can affect other parts. This is part of the game, and people need to know this.
« Last Edit: February 23, 2009, 10:05:12 PM by ace.cafe »
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ScooterBob

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Re: Increasing power output in the engine.
« Reply #17 on: February 23, 2009, 09:53:17 PM »
You know, Cyrusb, I'm guessing that old ACE MAY have done this once .... back in 1976 .... Hahaha!! You gotta remember that the old pig iron engine is way over-engineered for the maximum abuse on the muddy roads of old India .... I have faith .... !!
Spare the pig iron - spoil the part!

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Re: Increasing power output in the engine.
« Reply #18 on: February 24, 2009, 07:04:42 AM »
How can we go further?
We can increase the breathing capacity of the intake and exhaust systems,  going bigger than the 28mm carb might certainly help us, because our ports are 32mm, and that makes the carb a restriction.
The whole idea is to get more air/fuel mixture in, which means sufficient volume, AND sufficient velocity,
   The stock intake port is 32mm you say? So a 32mm mikuni would be quite realistic. With the free flow exhaust and filter would the torque/hp bands remain streetable with stock bore/stroke? I have also like your idea about refazing the intake cam a tooth in another thread you  wrote about but would  do  this at a later date. In the meantime would a 32mm carb be  fine on a iron barrel ?    Been watching  your tech posts a  while,  manny  thanks on all  your info.   Gerry
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Re: Increasing power output in the engine.
« Reply #19 on: February 24, 2009, 02:13:47 PM »
How can we go further?
We can increase the breathing capacity of the intake and exhaust systems,  going bigger than the 28mm carb might certainly help us, because our ports are 32mm, and that makes the carb a restriction.
The whole idea is to get more air/fuel mixture in, which means sufficient volume, AND sufficient velocity,
   The stock intake port is 32mm you say? So a 32mm mikuni would be quite realistic. With the free flow exhaust and filter would the torque/hp bands remain streetable with stock bore/stroke? I have also like your idea about refazing the intake cam a tooth in another thread you  wrote about but would  do  this at a later date. In the meantime would a 32mm carb be  fine on a iron barrel ?    Been watching  your tech posts a  while,  manny  thanks on all  your info.   Gerry

Hi Gerry,
Yes, a 32mm carb is a good match for the stock Indian-made intake port.Since the port is already 32mm, you can increase the carb and manifold up to that size without reductions in torque, because the port is already defining air speed at its 32mm dimension. Sure, air might come thru a smaller carb at a higher speed, but then it just slows down at the 32mm port anyway. The iron barrel Bullet can use 32mm just fine.
However, since the stock intake manifold is only about 28mm inside, it needs to be replaced or modified. Gasket too.
Externally, the intake manifold mounting tube is about 33mm, so you can't realistically bore it to 32mm without leaving the walls too thin. So, boring it out completely, and then welding a piece of aluminum tube into it, with 1.25" I.D. and 40mm O.D. would be a good idea. Then you can just hone the I.D. open to the 32mm size to match the port, and have good wall thickness.
The Mikuni 32mm flat slide has a round mounting tube which is 40mm.
So, with a 40mm tube size on both intake mainfold and carb, you can use a straight rubber hose to match up well on both ends.
If you don't do something with the intake manifold, then you have a 28mm restriction there, instead of at the carb, and the carb isn't going to do what you wanted.
There's also a complete rubber manifold from Sudco which will be approximately the right size, which you can replace the entire intake manifold with. But, it's rubber, which is subject to tears and deterioration from the fuel, and I don't know how long they will last.

In the Mondello head, I have specified a 40mm O.D. alloy tube be permanently affixed to the head at the port entry, to take the place of the intake manifold, and it will be perfectly matched into the port as a port-extension that eliminates the need for a separate manifold and gasket.
That will allow the port to be perfect from the carb into the engine, and will be as good as it can be. And eliminates any chances of mismatch or air leaks.
However this type of mounting excludes bolted-flange carbs like the Amal, so this will be a head for use with Mikuni or Keihin type carbs that use rubber hose type mountings. The flat slide types are the carbs we have in mind, for performance reasons.

Of course, it would be recommended to support the carburetor with a bracket to the frame, so that the weight of the carb doesn't cause stress on the rubber hose, and make it fail early. Support the carb with a bracket, any time you have removed the stock air filter system and replaced the carb and filter that is unsupported on the "flying end". If you fail to bracket it, then it will make the rubber hose fail pretty quickly. Just a simple strut from the frame to the air filter hose-clamp will do. Simple and effective.
« Last Edit: February 24, 2009, 02:26:15 PM by ace.cafe »
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Re: Increasing power output in the engine.
« Reply #20 on: February 24, 2009, 03:53:41 PM »
How about balancing? I too,May have done this before (although not to a bullet) and have never met an engine that did not benefit greatly from a good dynamic balance job. It can do two things, 1 increase output, 2 increase life.

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Re: Increasing power output in the engine.
« Reply #21 on: February 24, 2009, 05:38:16 PM »
CMW also sells the rubber manifold and alloy spacer for a 32mm carb. They were less expensive than Sudco when I called. The mounting flange is actually a Mikuni VM34/200 and is intended for a 32-34mm carb I do not know who makes the spacer.

-Rick
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Re: Increasing power output in the engine.
« Reply #22 on: February 24, 2009, 05:50:10 PM »
How about balancing? I too,May have done this before (although not to a bullet) and have never met an engine that did not benefit greatly from a good dynamic balance job. It can do two things, 1 increase output, 2 increase life.

You are absolutely correct! Balancing will help out the old pig iron by not having it shake to bits as it runs - AND it will, indeed free up the ponies by NOT shaking everything to pieces ..... Of course, the harder you plan to spin it, the more critical that dynamic balancing becomes. This is probably NOT the case with my daily driver - I'll bet I never get it much over 3500rpm's .... !! I'm the guy you don't wanna be behind on the road!! Hahaha!!
Spare the pig iron - spoil the part!

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Re: Increasing power output in the engine.
« Reply #23 on: February 24, 2009, 07:19:33 PM »
How about balancing? I too,May have done this before (although not to a bullet) and have never met an engine that did not benefit greatly from a good dynamic balance job. It can do two things, 1 increase output, 2 increase life.

Yes, certainly! I agree.

Crank should be true, and balanced well for your set up.
Bearings should be of good quality.
The whole bottom end needs to be in best condition, if anyone considers making any significant power mods, and it can help a stock engine work better and longer too.

Perhaps I didn't emphasize this in my writing, and I should have.
The bottom end needs to be able to take what you plan to throw at it, in terms of power.
At this time, the European Performance Crankshaft assembly is the best available option, and is rock-solid.
« Last Edit: February 24, 2009, 07:26:29 PM by ace.cafe »
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Re: Increasing power output in the engine.
« Reply #24 on: February 24, 2009, 07:31:47 PM »
At this time, the European Performance Crankshaft assembly is the best available option, and is rock-solid.

It is funny, but that single part costs almost half what I paid for my bike last year with only 600 miles on it. Fortunately I didn't see you indicating that it would be required with your secret project.

Thanks again for your technical articles, Ace.

-Rick
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Re: Increasing power output in the engine.
« Reply #25 on: February 24, 2009, 08:08:51 PM »
At this time, the European Performance Crankshaft assembly is the best available option, and is rock-solid.

It is funny, but that single part costs almost half what I paid for my bike last year with only 600 miles on it. Fortunately I didn't see you indicating that it would be required with your secret project.

Thanks again for your technical articles, Ace.

-Rick

Rick,
The truth about the Bullet 500 bottom end is that it is  reliable for long term in stock form, up to about 5000-5500 rpms, as long as it's made right and wasn't assembled with a hidden defect.
Anything higher than 5500 rpm on a regular basis may have an effect of shortening the lifespan, or even having a catastrophic failure in certain circumstances.

I think if the stock rod gets a good inspection and polishing-out of any nicks and other stress-risers on the surface, and is a good example of the forging, it may be reliable to 6000 rpms, and I know of at least one successful Bulllet racer who runs his stock rods to 6000 rpm in races all the time, and they stay in one piece.
But, that doesn't mean that ALL of them will do that, because of the spotty Indian quality control. And we must take that into account.

I targeted the 6000rpm redline for the stuff I'm making, because a PROPER Indian-made crank and rod should be able to get there without blowing up, ON OCCASION. I don't recommend making a habit out of it.
I think that 5500 rpm is a much more "sane" rpm limit for street use with the stock bottom end, and perhaps even limiting it to 5250 rpm.
I can't be certain of the quality of every single stock rod out there. And neither can anybody else.
So, what I did was to pick an rpm range that could be of use to those who have both types of cranks and rods. The stock system, and the Performance Crank/Rod.
The people with the Performance Crank have a very safe bet at 6000 rpm.
The people who have stock cranks and rods have a more "iffy" proposition. But it is possible that good ones can do the full 6000 rpms.
In any case, the power curve that I'm working on here is a wide one.
You don't have to do 6000 rpms to get alot of power. It will do very fine with a 5500 rpm limit, or even less.
So, each person can select how far up the rpm range he is willing to risk, for his personal use. It's his bike, and he can use it the way he wishes.
But my recommendation would be to hold a stock bottom end down to under the 5500 rpm limit, and leave the full 6000 rpms to the guys with the stronger crank and rod.
Or, at least don't go visiting the 6000 rpm redline as a frequent occurrence if you have a stock bottom end.
I can't control the build quality of your bottom end. That's done at the factory, unless you do something to it to improve it. And I think that in some cases, the factory Indian made bottom ends can indeed withstand the 6000 rpm limits fairly regularly. But, I don't know which ones, or for how long.
So, prudence would be good advice on this matter, and rev on the conservative side, unless you are willing to take risks.

However, if you wish to run like a racer, then it might be best to get the performance crank/rod system, or make regular tear-downs to inspect the integrity of your parts, just like the racers do.
I am aware of the bottom end situation, and I didn't go there, frankly because I don't have enough money to be doing that right now. I have my efforts focused on the top end power production bits. There is a top-grade crank/rod system currently available already, although it is spendy. But it's good.
If, at a later time, I may undertake some bottom end parts, then I can address that issue as I think best. But that is not for now. And I have to be realistic about what people have available to run with. So, I make rpm limit recommendations in the hopes that people don't blow up their engines.Some can take it, and some can't, and that's the "Enfield gamble".
I provide the power parts, and it is the individual responsibility of the owner to ensure bottom end integrity to his own satisfaction, or his own risk.

I think that for someone who is serious about performance modifications, the Performance Crank/Rod assembly and a top-grade set of main bearings(not stock Indian ones), would be a pre-requisite.
But it's not mandatory, if you are sensible about how far you go with the mods, and how you  use it on the road. Be aware of the limitations of stock parts, because they are NOT racing parts.
« Last Edit: February 24, 2009, 09:00:06 PM by ace.cafe »
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Re: Increasing power output in the engine.
« Reply #26 on: February 24, 2009, 08:26:12 PM »
 ........ so I'm good at 3500rpm's ....... Heeheehee!!! ;D
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Re: Increasing power output in the engine.
« Reply #27 on: February 25, 2009, 08:22:13 AM »
Thanks again ace,  I been out of the loop quite a while. these flatsides are new to me. Think I'll give one a try when $ permits. Thanks all for the  great info.  Gerry
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Re: Increasing power output in the engine.
« Reply #28 on: February 18, 2013, 12:27:18 AM »
And another.
2006 Bullet Sixty-5 w/ Ace "Fireball 535" Kit (#10)
Ace "GP" head in the works.

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