Duke

I don't think you see the bigger picture here.. spool vs rpm by itself means nothing in terms of how quick it is! That is the issue with the dynos that does not contol the rate of acceleration - the larger the mass for the engine accelerate the slower the rate of acceleration is and the longer the available time window is to build boost. That does not make the car quicker!!

Now if your argument were true, the car would be quicker with an even heavier flywheel. That also means that the car would be quicker the heavier the FW is... so if we put a 1000 kg flywheel on the engine which take forever for the engine to accelerate we would probably get the turbo to spool say 1000-2000 rpm sooner. Question is - do we have a quicker car? Now please drop this, at least in my thread. Please open a separate thread if you want to continue to talk about this and try to explain your theories (not "take it to the dyno").

Dutch944

refresh951

Rob - Please honor the OP's request to move this OT discussion to a separate thread.

Duke

I did not attack you. YOU came into this thread with claims out of the blue. I questioned your claims and tried to explain why a dyno run is useless for the purpose of flywheel weight. But let's just agree to disagree and move on. Sure it's a public thread. But this is why I don't post much here anymore. I share a race video because I'm hoping some people will be interested, the same way I like other peoples race videos. Instead the thread turns into a discussion I never wanted to have in my thread. It was you who entered this thread with claims that was never on the table for discussion. So instead I've ended up regretting even starting this thread as the fun is lost. I cannot stop you from entering and posting so I guess it will lead to me stop posting

Chris White

Here is another way to look at it -
once you engage the clutch you are spinning the entire drive train - torque tube, transmission gears, axle shafts and wheels - is a lighter or heavier flywheel going to make much of a difference to that? maybe a percent or two - not worth considering the effect.
Is the lighter flywheel going to help with up and down shifts? Yes, in a big way. Much more responsive on the track but kind of alloying on the street (stalls at stoplights very easily).

Chris White

Duke - lets bring the fun back - is Dutch944's picture a jet pack or a self ignited fart?? Inquiring minds want to know!

Dutch944

Chris, see the two buttons with the small control box? Those are button to control the sparkplugs which are placed on the backpack. I use those to ignite the farts!

67King

It isn't, but it also won't show up on a dyno if you take finite measurements (i.e. hold at RPM, take measurement, increase and hold, measure, etc.). It will slow down the engine's ability to accelerate (F=ma) because for the engine to accelerate, it takes more force (torque is a force, hp is a force per unit time).

Anyway, I don't understand the argument. Who cares where in the RPM band the boost hits? If it hits lower because the car is accelerating more slowly because of a flywheel, how is that an advantage? 0-full boost in 0.7 seconds at 4500 RPM is supposed to be better than 0-full boost in 0.6 seconds at 4750 exactly how? Plus the car isn't as far down the track. Call me crazy, but I'd rather the car be accelerating more quickly and further down the track, and hitting full boost more quickly relative to TIME than farther back, less quickly, later relative to TIME, but a little bit lower down per the tach. I know it certainly didn't slow down my car when I went to a lighter flywheel, but I think I had done some other things, so I can't give a non-confounding, absolute answer.

Of course, the argument is entirely academic since we are talking about driving on a track, and if you can go from 0% throttle to WOT instantaneously, you are probably slowing down way too much for the turn, or applying throttle way too late. What kind of experience do people arguing have with driving a turbocharged car on a racetrack at a somewhat high level, say advanced solo or higher? I simply cannot think of a turn where I am not at part throttle for at least some of it. If you've done it, did you not develop an awareness of your inputs when you were learning? Once you are at WOT somewhere between the apex and track out, the lighter flywheel is an advantage.

Duke, there are two other options you have. The 968 flywheel is larger, but it is dual mass, which isn't as good. Another is to drill and tap the perimeter of a larger, turbo flywheel and put in cap set screws. You can use the factory location of the reference sensor, and feed your PCM (I'm assuming it is all aftermarket). Might cost you a bit to have a machinist do that, but I would expect that it'll work. The sensor just look for a PIP.

Chris White

It would have to be 58 cap screws! Duke is using the 60-2 tooth flywheel that was stock on 944S and S2.

Chris White

In theory, if you can open the throttle before the apex you have over braked into the corner.

Chris White

Hmmm....I suppose you have thrust vectoring controls too!

Duke

Guys, I know it can be done with a 951 flywheel... but I don't like it. Now how the hell did my track video turn into 3 pages of flywheel discussion

67King

That's why I said it might cost a bit!!!!! I have an acquaintance who said he could do it for me for what I hope to eventually get around to doing. I've got 16V engine parts laying around all over the place, but no time

reno808

Duke this is Rennlist!<- Sparta Voice. I guess i am the one to blame

Duke

Here's with the exhaust on the left side. A bit too loud for the new 95 db regulations