Have bought a lightweight flywheel for my hill climb STi V3. This will be fitted over the winter with an organic racing clutch.
Andy F has said this is not a good idea for the violent starts (as in drag racing) with the car on very sticky slicks.
The lower inertia in the new flywheel and the physics behind the energy stored a flywheel is sound thinking, but will it realy matter in practice. Lots of respect for Andy F, any other racers out there to help me?

Graham.

I would (and do) listen to Andy F. He held class lap record at Knockhill for some time as driver whilst also doing all the engineering work himself. He only lost the record when he sold the car to a commercial outfit that took a lot of extra time and money on the same car to beat his record. He extracts results from a specification of car apparently below that of his competitors and excels repeatedly. Regarding drag racing, he built a V8 drag car from drivetrain and chassis parts that are seemingly incompatible and was into the 9s at Crail.

[Edited by john banks - 11/13/2003 7:11:24 PM]

did andy not have a very light one though?

Yup, but will I regret fitting the flywheel?
Graham.

I think his was ultra light yes. I think mine is about 7kg, not had chance to try it in anger yet :)

Nah John, I'm just lucky ;)

Graham

I used to dragrace the scoob with std fly/clutch on toyo's, it launched well at around 4500rpm and was very consistant off the line with a little chirp from the tyres.

I then fitted soft yokohama semi slicks and lost time due to either bogging it at 4500 rpm or spinning the clutch if I used more rpm, couldn't get any tyreslip.

I then fitted a 4.2kg flywheel from TEG and AP racing paddle clutch. The launch was either fantastic or (more often) terrible ! There was such a narrow window where rpm/boost/throttle and clutch would 'come together' for the perfect launch.

I then tried the 4.2kg flywheel with the organic clutch but that had the effect of either bogging the engine if launched below 5k rpm or slipping badly if launched above 5k. No real sweet spot.

I'm now back on a std flywheel and new (subaru OE) organic clutch, 4500 rpm +or- 250 rpm for launch, lift one foot, down with the other and she's off...... very consistant :) Not as quick off the line as a perfect launch with the paddle but very repeatable.

I hate the thought of this big heavy flywheel whirring away absorbing power as I accelerate :( however, all is not lost as the energy you put into the flywheel as you accelerate is returned to you when you change up a gear and the revs drop again :)

To summarise, as long as you have not gone too light you should still be ok, you may just need to use a few more rpm and hold them exactly the same each launch now where before you may have had a bigger window.

Andy

Thanks Andy for the reply. You have exactly described a hill climb launch! I ended up this year with the stock flywheel, STi clutch and 4500, then dump the clutch. I was on Kumho v70's. My launch on Toyo's was much more consistant. I could pull 1 G every time. On the Kumho's I could sometimes. Those tenth's are precious!
So, what to do? I will weigh the 'wheel when it's back from the grinders. It is a TEG unit which I think is 5Kg. If so I will sell it on and buy a new STi clutch.
Is the STi unit much the same as , say , an AP organic?
I am hoping that the RA trans I am fitting will help overall on the hills, but that start is so critical to the overall time!
I am up against EVO 5's with 480 bhp so need ALL the help I can get.....
Thankyou all for the help.
Graham.

I bought a paddle clutch and just cannot seem to get off the line quickly anymore. I managed the 'perfect' start just once so far.

Will try some more, but am starting to regret the decision and may well swap when the new motor goes in.

Richard

That EVO above has a twin plate HKS unit (£1250)anti lag, launch control and sounds like every microchip is fighting to win just before the launch. He has wide Dunlpo D7's. My STi on toyo's, standard drive train can beat him off the line....
I think the flywheel will soon be for sale.
My old 911 hill climber once had a sprung paddle clutch and aluminium cover and the launches went cr*p. Changed to the stock clutch with cast iron cover and launched nearly as good as the STi!
I don't learn too quickly do I?
Graham.

Graham, you just need another 100 bhp, problem solved.

Mark A

!!!!!!!!!!!!!!!!!!!!!!!
100 bhp = Engine @ £5000 + Box @ £3000 + AP brakes @ £1500.

No wonder there are so many people selling bits for Scooby's!

Cheaper and more effective is a very big bravery tablet just before a full out hill climb run.....those trees that line the track get mighty close!
Graham.

lol @ bravery tablet :D Don't they come as std with early 911's ;)

I'd sell the flywheel and use the money as a deposit on a US Sti 2.5 short motor (£1400 ish), retain a smallish turbo and build it to have a nice wide flat torque curve and it will be like a bullet out of the corners :)

Andy