Flywheel help

old-git

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Elan & Robin Hood
I need some feedback on my flywheel conundrum.

My engine (turbo YB Cosworth) is fitted with a flywheel weighing in at 8.6Kg. A lightweight replacement can be down to approx 4Kg. Although that is a lot of rotating mass removed I am concerned about the effect on standing starts. A heavy flywheel helps to stop the engine bogging down in a normal car that weighs over a tonne. However, mine will weigh almost half that and with 450lb/ft I contend that a heavy flywheel isn't so important on my vehicle and the saving in rotational mass is significant. In sheer weight alone it is equivalent to 4bhp/tonne.

Any racers out there got any thoughts or advice?
 
I seem to remember a chap on here with a very silly powered Sierra Cosworth.
Everything was bespoke and he was going for some sort of high speed record? I think I remember something about flywheel issues/works.
His name might have been Steve??? :blink: worth a look around the General Car Chat area OG, sorry I cant be more helpful to you. If you find him then a PM to him might reveal some answers to you. Good luck!
 
That was Rod Tarry. His Sapphire is the fastest in the world (over 207mph). Different engine/weight combination so his setup wouldn't work on mine. However, I will give him a call, thanks T9.
 
The theory on this is interesting. The flywheel is effectively storing energy, the heavier it is the more energy it stores and the less likely it is to bog down on the start.

However there was a test done but I can't recall the source now, I think it was a US magazine and they found that the ET time was better on a lighter flywheel, the start was marginally slower but the acceleration afterwards was better.

What about a secondary flywheel that is only engaged on first gear;) :confused:
 
You're getting me thinking now and that is never a good thing!

Get a dual mass flywheel, put the outer mass on a free spinning bearing. Then all you need is a mechanism to clamp the two together in neutral and first gear and release the tether when second gear is engaged! SIMPLES! :lol:
 
You're getting me thinking now and that is never a good thing!

Get a dual mass flywheel, put the outer mass on a free spinning bearing. Then all you need is a mechanism to clamp the two together in neutral and first gear and release the tether when second gear is engaged! SIMPLES! :lol:

I can see one tiny, weeny, problem - The bloody weight!!!!!
 
Dang I'm really thinking this one through. Move a gear cog on the driveshaft that connects to the flywheel to pick up both wheels, then push this gear cog backwards so it is only interfacing with the outer fly wheel on the second gear selector and the inner one is just spinning on it's own.

The tech problem now is stopping the flywheel moving when the cog moves but the inertia itself may help to prevent this.
 
:lol: To get round the weight, tie a helium balloon to it.

Do they do water/mercury filled flywheels? Dump the water or mercury when you start off. There's no obvious environmental concern here in dumping mercury is there?
 
Thanks, Stamford, interesting acticle. However, It doesn't really address my question about standing starts. I will make contact with Puma Racing to see if they have more info.
 
To my simplistic mind I view a lighter flywheel as giving an increase in power at the expense of some torque. As a loss of torque wouldn't matter for a lightweight highpowered car I say lighten away.
 
To my simplistic mind I view a lighter flywheel as giving an increase in power at the expense of some torque. As a loss of torque wouldn't matter for a lightweight highpowered car I say lighten away.

If it was that simple I wouldn't be asking for help:)

A lighter flywheel doesn't increase an engine's BHP or reduce its torque.
 
No, I do realise that, but a lighter flywheel gives the illusion of more power in that it lets the engine spin up more quickly. But this is at the expense of inertia of the engine itself, its resistance to a change of spin. I'm not explaining very well and I know you know all this anyway but in my limited experience of them (I had one once in a v6 vectra) what you get is analagous to more power transmitted to the wheels traded off against a little less pulling/engine braking.

So your cossie engine should be torquey enough to cope with a loss of flywheel inertia especially in such a light car.
 
That is also my thought, but I have read a lot of articles about the subject and it isn't, unfortunately, that simple. Unless I can get a definitive answer from an experienced drag racer I will probably play safe and go with what I have got as it will not bog down. I am just, as always, looking for that little bit extra :)
 
Fair play. What makes you think it would bog down though? I guess the clutch is far more on/off than a normal one? Just interested as I don't have any experience with very powerful cars./
 
I guess if looking for a quick drop and go from a standing start a standard weight flywheel will store the energy longer and less prone to slowing down the engine revs. However on the minus side it would be alot slower reving to the optimum levels required for acceleration of the 1/4. If too light then the engines revs would drop alot quicker on take off (hence bogging down) thus losing power and therefore time on a run. It does sound like finding the right balance between the two. I can see your dilemma, weight of car plus driver, torque and bhp at take off point before any losses etc. Not to mention engine and drive trans twisting due to take off torque, a nice problem to have!
 
Exactly my thinking, Stamford. If I didn't have these problems I wouldn't have enough power which would be harder to overcome. I think I prefer the too much power problem :)
 
Fair play. What makes you think it would bog down though? I guess the clutch is far more on/off than a normal one? Just interested as I don't have any experience with very powerful cars./

Correct, it is an Alcon 7 1/4" twin plate cerametallic beastie. Not quite an on/off switch but not far from it :)

The idea is to have launch and traction control switched on, throttle wide open and when the light turns green side step the clutch pedal.
 
If I could afford it I would seriously consider a sequential gearbox and a powershift system. I was helping develop such a system back in the early/mid 90s before it was outlawed. Probably plenty of similar systems out there now. I did start designing a pneumatic gearshift system, simple actuator, solenoids etc that got shelved as the club I was racing with decided to ban the design once they caught wind of what my intentions were! Needless to say the very same people in charge of the regs were the same class racers!
 
Luckily I am not trying to comply with class rules so I can do what I like :)

I am using an Elite IL300 6 speed sequential gearbox. Cost a fair bit but it had to be done. My long term aim is to have the ECU control the gearshift through either an electric or pneumatic solonoid, making the car an automatic on the strip. Which would you recommend, electric or pneumatic?
 
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Luckily I am not trying to comply with class rules so I can do what I like :)

I am using an Elite IL300 6 speed sequential gearbox. Cost a fair bit but it had to be done. My long term aim is to have the ECU control the gearshift through either an electric or pneumatic solonoid, making the car an automatic on the strip. Which would you recommend, electric or pneumatic?

I would go for electric as you'll have a tip top car so no issues with supply. Pneumatic was considered for my track car purely for supply as we never ran alternators, battery juice was enough for the heats so a small bottle would be enough for the gearshift. With an electronic solenoid it'll be quicker and direct from the ecu, easier to program and less parts.
 
Those were my thoughts, but I have been told that they are more severe on gearboxes as the change is 'hard' rather than 'soft'. The big advantage of electric is cost.
 
Re flywheel size

I am at santapod for japshow this weekend and will be drinking with some of the hks drag series guys who all like a chat

I will ask your question
 
Yes Please!!!!

520bhp on pump fuel. 620 on Q16 race fuel
650kg including driver
245mm wide rear tyres
 
apologies OG I didnt go because the launch control started playing up to the extent that even a no boost start was a problem .

As I was only going there to do timed 1/4s the 4 or 5 hour drive just didnt appeal
sorry
 
No, I just will never speak to you again!............................:)
 
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It sounds like you've spent a lot of time and money doings this so I don't think my next suggestion will be much trouble......

Why not try them both?
 
If only it was that easy. In order to change the flywheel the engine has to come out and, with the engine bay crammed with pipes and wires and all sorts of stuff an engine change will be a nightmare.

Discussing it with my engine and suspension guru, I will now be sticking with the steel flywheel I have. The slightly slower pickup will help with getting off the line as the engine won't rev up so quickly reducing the risk of breaking traction. The downside is slightly less speedy RPM drop at gearchanges making changes not quite so quick, but we will work on that. Need to get the car actually running first, though :)
 
I've just never seen it on here.....
I will be reading it and absorbing information but right now I need sleep as I had none last night (serisouly....) talk to you tomorrow I imagin

Brett
 
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