i was told that simple revs is not what spools up your turbo but the amount of work or load your on your engine is what determines how fast your boost builds.
assuming this is true wouldnt a ballanced stock flyweel be better than a 12# wheel.
on a street engine anyway.
any thoughts on this
flyweel to lighten or not to enlighton
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bren
- Posts: 858
- Joined: Mon Jul 03, 2000 12:01 am
flyweel to lighten or not to enlighton
i heard the same thing.. i heard a light flywheel makes for a lot of lag on a turbo motor, so stock balanced 'wheels are best? anyone with any real life experience of this care to comment?
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Muffler Mike
- Posts: 3186
- Joined: Tue Feb 20, 2001 12:01 am
flyweel to lighten or not to enlighton
Well I think you may be on to something, or at least a good theory. It would take more to get a heavy flywheel to spin thus creating more load on the motor and in turn maybe being able to spool up the turbo. But I really couldn?t tell you if that would even be enough of a load. (I kind of think not) This may all be a matter of exhaust tubing size, turbine size, motor size, bla bla bla.
I personally have very limited turbo experience. But what I do have I will share. I actually used a friends street turbo motor to make it to some races. And in the beginning, being very unfamiliar on how this motor was going to work, I resorted back to my old days, tried to rev the motor up to bring it off the line. Needless to say, it wouldn?t get out of its own way when I did this. (this was a little 1915cc with a small cam, no heads and 14lb flywheel and maybe a turbo that was probably sized a touch big.) So I treated it like the whore that it was, (just like I do with my own aspirated motor) and put it on the rev limiter on the next launch. What I found was on the rev limiter, it created boost rapidly. By the 2nd or 3rd back fire through the exhaust, it was on boost and eventually put my car on the bumper for some butt puckering wheelies. And went on to win the two races I used it with.
My theory. On the limiter, you are dropping raw fuel, which is much thicker then air or exhaust gasses. Then when some of it ignites in the exhaust header, this speeds up the thicker charge through the turbo, thus spooling it up quick. Simulating a load.
You can think of it like this, a gust of wind will not likely knock you down, but If you can take the same volume of water as the gust of wind, like a wave at the beach, this will more then likely knock you over and tumble you across the sand at the bottom. Oh that?s another story.
In the end, I think I would size the flywheel according to what I really wanted to do with it. Drag racing with a somewhat heavy car will typically benefit from a heavy flywheel to help it get out of the hole. (at least to a certain extent, lots of variables to this and a whole different discussion.)
I personally have very limited turbo experience. But what I do have I will share. I actually used a friends street turbo motor to make it to some races. And in the beginning, being very unfamiliar on how this motor was going to work, I resorted back to my old days, tried to rev the motor up to bring it off the line. Needless to say, it wouldn?t get out of its own way when I did this. (this was a little 1915cc with a small cam, no heads and 14lb flywheel and maybe a turbo that was probably sized a touch big.) So I treated it like the whore that it was, (just like I do with my own aspirated motor) and put it on the rev limiter on the next launch. What I found was on the rev limiter, it created boost rapidly. By the 2nd or 3rd back fire through the exhaust, it was on boost and eventually put my car on the bumper for some butt puckering wheelies. And went on to win the two races I used it with.
My theory. On the limiter, you are dropping raw fuel, which is much thicker then air or exhaust gasses. Then when some of it ignites in the exhaust header, this speeds up the thicker charge through the turbo, thus spooling it up quick. Simulating a load.
You can think of it like this, a gust of wind will not likely knock you down, but If you can take the same volume of water as the gust of wind, like a wave at the beach, this will more then likely knock you over and tumble you across the sand at the bottom. Oh that?s another story.
In the end, I think I would size the flywheel according to what I really wanted to do with it. Drag racing with a somewhat heavy car will typically benefit from a heavy flywheel to help it get out of the hole. (at least to a certain extent, lots of variables to this and a whole different discussion.)
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Sharkey
- Posts: 966
- Joined: Sat Jul 22, 2000 12:01 am
flyweel to lighten or not to enlighton
A lightened flywheel is a PITA to drive on the street in stop & go traffic. You have been warned. I'd give anything to go back to a stock weight flywheel, but mine is wedgemated so I'd have to replace both the flywheel and the crank!
As for the theory whether or not a lightened flywheel will increase spool-up time, I'd reckon to guess that the difference is minimal. Spinning up a flywheel super-fast isn't as big of an issue when you remind yourself that it is still attached to an 1800 lb car.
To continue the discussion, I'd say that a lightened flywheel will be more likely to allow you to do burnouts than a stock flywheel because you can overcome the static friction between the tires and the ground easier using a rapidly accelerating flywheel. This would be contradictory to quick turbo spool-up times, since spinning wheels aren't as much of a load as those that stick
As for the theory whether or not a lightened flywheel will increase spool-up time, I'd reckon to guess that the difference is minimal. Spinning up a flywheel super-fast isn't as big of an issue when you remind yourself that it is still attached to an 1800 lb car.
To continue the discussion, I'd say that a lightened flywheel will be more likely to allow you to do burnouts than a stock flywheel because you can overcome the static friction between the tires and the ground easier using a rapidly accelerating flywheel. This would be contradictory to quick turbo spool-up times, since spinning wheels aren't as much of a load as those that stick
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Spindley
- Posts: 16
- Joined: Sat Jan 06, 2001 12:01 am
flyweel to lighten or not to enlighton
The heavier the crankshaft the more momentum it will have and therefore you will lose less rpm between gear shifts. This will reduce lag, but we're not talking about a whole lot here. I don't know how noticeable it would be, but the idea is to keep the sucker spining, not slowing down.
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DaveM
- Posts: 102
- Joined: Mon Feb 26, 2001 12:01 am
flyweel to lighten or not to enlighton
Let's remember, to make turbo's more responsive we make them smaller, lighter and consequently they have less inertia. The compressor map provides a guide to rpm vs pressure, but for better response MAKE IT LIGHTER!
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Jerry D
- Posts: 457
- Joined: Tue Mar 13, 2001 12:01 am
flyweel to lighten or not to enlighton
I have run the same 2110 with a CB EFI turbo setup with a stock weight flywheel and with a 6lb. Scat aluminum flywheel the difference I have noticed is that you dont notice the lag as much with the light flywheel because the engine spools up quicker and before you know it your making boost.
This is in a Manx buggy which I know is'nt as heavy as a full bodied bug but boy is it fun in the SCCA Autocrosses. This summer it's autocrosses with the wheeliebars on.
[This message has been edited by Jerry D (edited 03-20-2001).]
[This message has been edited by Jerry D (edited 03-20-2001).]
This is in a Manx buggy which I know is'nt as heavy as a full bodied bug but boy is it fun in the SCCA Autocrosses. This summer it's autocrosses with the wheeliebars on.
[This message has been edited by Jerry D (edited 03-20-2001).]
[This message has been edited by Jerry D (edited 03-20-2001).]