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I have the S2000 AP2 F22C engine in my Locost "Scrap Metal". The AP2 came with a flywheel over 20lbs where as the AP1 (F20C) had a 14lb Flywheel.
I found this 7.5lb flywheel on Ebay http://www.ebay.com/itm/FX-6061-T6-FORG ... 43&vxp=mtr and wondered if you guys think it is a good choice.

My Rx8 has an 8lb flywheel but you need to add a counter weight which brings it up to about 13LBs and I have had no issues with it.

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2015 & 2016 EMod Florida State Autocross Champion
2013 & 2014 DSP Florida State Autocross Champion

Scrap Metal Build Log viewtopic.php?f=35&t=14558

These cars are so lite that you do not need a heavy flywheel. I installed a lite Wt flywheel, and it made a noticeable improvement in the lower gears. I assume you are going to Auto-X, I think it is probably one of the best modifications you can make. Dave W

Here are a few thoughts to consider. That's pure race flywheel weight, but full race setups also use lightweight clutches. If you're still using a stock style clutch, that's going to put it lighter than most street setups yet heavier than a full race setup. The stock style clutch will accommodate much more slipping than a race style clutch, and in cars this light, less inertial weight is required to get them moving from a stop. It should definitely be a bit touchier on the throttle though too. However I've never driven any car with a flywheel that light, let alone a Locost, so I can't actually state how your car with that flywheel would or would not feel to drive. I think it would definitely be worth a try, but would also exercise caution with any off-brand (if this is one) flywheel regarding the safety of its design/manufacture and balancing for use on a high rpm engine.

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

No.

Oh wait I changed my mind ...

No.

I have driven a car with a flywheel that light, and it wasn't fun at all on the street. It also had a full race clutch with metal friction surfaces so that might've had something to do with it. Engagement was great once you were up to speed, and over 4000 RPMs the flywheel had plenty of inertia, but taking off from a stop without drawing a lot of attention to yourself was almost impossible. Great track setup, horrible around town. Got rid of it. Just my experience, though, YMMV.

The lightest I've seen anyone run on an S2000 and like it was 9 or 9.5#. 9# is what Brian was recommending on the Ultralites IIRC

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mobilito ergo sum
I drive therefore I am

I can explain it to you,
but I can't understand it for you.

It also depends upon the displacement of the engine. I have a 7-lb flywheel but it's offset somewhat by the engine being a largish 2.4 liter. Also, while there's less rotational inertia to get the car moving, the car weighs much less than what the engine came out of, I don't get a sense of it feeling much different. The net effect is an engine that spins up faster but gets off the line just fine - I've never stalled it - and it doesn't have to be reved up any more than a "normal car."

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Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

I was also discussing this on Facebook and I think that brand is not such a good one. There is however an 8.5lb Chromoly Flywheel from ACT which is a little more expensive but I think would be a better choice.

I have an Aluminium Flywheel in my Rx8 and like the benefits especially in the low gears. It needs a little more revs to get off the line but that does not bother me at all.

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2015 & 2016 EMod Florida State Autocross Champion
2013 & 2014 DSP Florida State Autocross Champion

Scrap Metal Build Log viewtopic.php?f=35&t=14558

i have a 7.5 lbs flywheel, ''stage 1 clutch''(look and weight like a stock one) and all aluminium pulleys on my sr20, i still feel that the setup is too heavy for what i need. the crank itself is a beast on those engines.

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Making a Deman SR27 lapping and street car
Any question on driveshaft, i will be more than happy to answer!

I lot of people don't put real light flywheels in because of transmission noise, like that is an issue in our cars. Flyin Miata recommend not using the lightest possible flywheel for that reason. I had a friend with a Murkur XR4TI that removed a light flywheel because of the transmission whine. I put the lightest I could find in the Miata trans, it did help in AutoX situation as the car would rotate better. Maybe you have to be a little more precise with the throttle and clutch for a smooth get away, but the change is slight. I think I used a Fidanza 9.5 pounds.

Graham