I know what they do in an actual car and what forza claims they do in the game but I can’t say I notice any difference. Sometimes I’ve have setup up a car and can squeeze a flywheel or something like a clutch or something similar and almost never go with a flywheel bcuz usually it doesn’t show any change or it’ll sometimes even show a negative impact. Just feels like I’m missing something. I’d imagine forza makes just for weight reduction only?
Years back, my go-to starting car in Gran Turismo 3 was the Daihatsu Mira. It was small, lightweight, cheap, and qualified for several early race series with nice payouts. To get an edge over everything in the class without spending much, I bought only one mod: the lightweight flywheel. That mod alone shaved seconds off my laptimes and made those races all easy mode.
Does that hold true in FH4? No idea - I haven’t tested it. Outside of the reduced weight, I’d expect to see bigger RPM drops when shifting (possibly detrimental on slow-shifting builds). I’d also expect to see better acceleration through the top end. Might test this a little once the season rolls around to Summer.
Ran some tests with a '98 VW Golf VR6 Mk III. One build was stock, the other had just a race flywheel. I used the Horizon Festival Drag Strip to test, shifting at 37mph and 63mph. The flywheel build was 0.46% lighter and had a 0.78% greater PI. Ideally, if you pay 0.78% more PI, you’d expect a car that’s 0.78% faster.
Final times showed a benefit of 0.42%, which not only failed to meet the PI cost, but also failed to meet the weight savings. It was barely worth half the PI cost on this car.
I decided to run another test, using street valves instead of the race flywheel. This had 516 PI, +3hp, but same 2800lb weight as the stock car. Again, I would hope to see 0.78% benefit. This version ran 0.61% better than stock. However, it had a little wheelspin, so the time-for-PI benefit was probably pretty close to expected. It’s definitely better than the flywheel for the same cost.
All that said, this was just one FWD car with minimal mods on a 1/4 mile drag strip. Other cars may benefit more, but what I saw didn’t justify the PI. I may have to rethink my position on flywheel upgrades going forward.
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The PI values for the various items are supposedly derived from test laps driven by an AI around some reference track.
It’s not too clear how they isolated the effect of individual components as the number of test laps the AI would have to drive to test every combination of equipment on every car is exponentially large.
So, at this point, its not at all clear why the flywheel is valued. It’s only listed effect is a weight reduction - if it has an effect on the engines power or response it doesn’t effect the engines power or torque curves at all.
Use race flywheel when using any other race engine upgrade except exhaust. Same with sport flywheel and so on.
You will notice improved handling, if you use it solely though you get inferior handling actually. It does cost PI for a reason but you need to use it in the right context and it will be beneficial.
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No Fifty Inch, it will not improve handling.
A lighter flywheel will do two things; improve the engines response-time and (slightly) reduce lower rpm tourque. It is up to you to decide if it is needed and how much you want to lighten it. Will depend on how quick the gearbox is and off course how slow the stock engine revs up. And if you`re tuning up a Buick GSX or a Citroen 2CV
This, clutches and driveaxles does not improve a close to stock car much but matters when a car is maxed for racing
B,C,D Class, I use a street flywheel.
A Class I use sport flywheel.
S1, S2, X Class I use a race flywheel.
It can help RWD cars with high torque to behave, but even if the difference is slight in some cars, the 1 or 2 PI cost is good filler for a perfect 800 / 900 / 998 build.
Definitely better than adding 20KG with an intercooler or oil cooling.
It seems you’ve already figured this one out, clutch upgrades will reduce more weight from your car for less PI and will make you shift faster if you play on auto or manual without clutch. Not necessary if you use manual w/ clutch but still a useful upgrade to fill in that one last PI point. If you need another reason not to upgrade your flywheel, you won’t notice too much of a difference. Even if forza took account for specific types of weight, the flywheel and clutch are all a part of the same rotating mass when the clutch is engaged.
It seems you’ve already figured this one out, clutch upgrades will reduce more weight from your car for less PI and will make you shift faster if you play on auto or manual without clutch. Not necessary if you use manual w/ clutch but still a useful upgrade to fill in that one last PI point. If you need another reason not to upgrade your flywheel, you won’t notice too much of a difference. Even if forza took account for specific types of weight, the flywheel and clutch are all a part of the same rotating mass when the clutch is engaged.