The FK8 Retro Flywheel is heavier than the OE flywheel.

[matt23fe1]

So it seems that it is mostly common knowledge that the 10th gen Si had a 32lb dual mass flywheel, that caused significant rev-hang in those cars. It also seems that most people know that the 11th gens have single mass “lightweight” flywheels. Even with that being the case, the rev-hang is still terrible in this car. So, I did some digging to see if the retro flywheel would make a difference.

According to Two Step Performance, the RV6 Retro Flywheel weighs 20.5lbs.

The ONLY place I’ve found an OEM 2022+ Si flywheel weight is a video posted by Sergeant_GiO on YouTube, but in the video his OE flywheel weighed 19.0lbs exactly. https://youtube.com/shorts/_ddDKjGT0rw?si=gAhIFxNjsdxGx952

I would have assumed that at least ONE of the aftermarket modification shops would have posted their weight comparisons between them, but none of them seem to have posted ANYTHING about it. The only comparisons posted by any of the shops is the weight differences between the 10th gens 32lb flywheel and the retro one.


So is EVERYONE putting a flywheel that is 1.5lbs heavier on their car and placebo-ing themselves into thinking the rev hang is better?


I understand most people don’t dig this far in to this stuff, but it seems weird to me that there’s testimonials from so many people that the rev-hang is better even though on paper it should be worse, if not the same.

Sponsored

 

[AZCWTypeR]

Rev hang is due to throttle body programming for emissions. A different flywheel won't make a difference on decel, unless you reprogram the ECU.

Acceleration in lower gears improves with a lighter flywheel, clutch, and/or pulley.

Also note crankshaft torsional vibration modes are tuned with the flywheel and pulley masses. Changing mass may adversely affect crankshaft life.

 

[SuperDave]

1.5 pounds doesn't seem like much which is a good thing. I'm just curious why there aren't more stock flywheel clutch upgrades. Why does everyone still recommend the FK8 flywheel over our stock flywheel?

 

[pwp25si]

The clutch plate is the fk8 part. Flywheel is not. There is another flywheel option that weighs 19lbs and made from stainless steel. Personally wouldn't mind something lighter.

1.5 pounds doesn't seem like much which is a good thing. I'm just curious why there aren't more stock flywheel clutch upgrades. Why does everyone still recommend the FK8 flywheel over our stock flywheel?

 

[SuperDave]

The clutch plate is the fk8 part. Flywheel is not. There is another flywheel option that weighs 19lbs and made from stainless steel. Personally wouldn't mind something lighter.

Yeah I worded that wrong. Since the 11th gen already has a lightweight, single mass flywheel, why aren't there aftermarket clutches that work with the stock flywheel?

That way I would only need to buy a clutch kit. VS having to spend over $1k in parts for a clutch plus RV6 flywheel.

 

[pwp25si]

I was wondering why the fk8 clutch woudlnt work with stock flywheel. Or does it? I would like something like 14 15lb flywheel.

Yeah I worded that wrong. Since the 11th gen already has a lightweight, single mass flywheel, why aren't there aftermarket clutches that work with the stock flywheel?

That way I would only need to buy a clutch kit. VS having to spend over $1k in parts for a clutch plus RV6 flywheel.

 

[DYI01]

The diameter of the friction surface is larger on the FK8 clutch/flywheel. FK8 clutch related parts aren't compatible with FE1 clutch related parts.

Sponsored