Hmmm, I have a steady, like +/-50 rpm variation, idle with a 10lb flywheel. No lumps at all. If the variable resistor isn't doing anything in either direction, try this, unplug it and see if anything changes. The ECU should fall back on a fail-safe setting, personally I got a better idle with it removed but mine was uber fubared and not doing anything in either direction.

 

Whaaat??????? Dude, you know how much more hp at the wheels you loose with a stock fw??

I when I changed to an 11lb FW I went from a 14.1 to 13.5 at 10psi, true it was with an ACT clutch too, but that doesn't give you that much and the 14.1 was when the CF dual friction was still good.

 

it depends on the port work dDub, all the engines i experienced with the rough idle were turbo'ed with semi large streetports. i think it is more a turbo thing than a non turbo thing.

 

Possibly, but I have a combined secondary/aux port with no sleeves/actuators (open all the time), average primary streetport, slightly larger than streetported exhaust, and all the other shitty idle mods you can do with removing stuff.

Meh, s4 non-turbo's just pwn everyone at idle ability, its so easy to get them to idle properly.

 

On the subject of light flywheels, does anyone have the fidanza 8.5lb flywheel? I was thinking of that or the SR motorsports 9.5lb flywheel or 11lb one, Whats does streetable mean? lol

 

i thought about those fidanza ones but personally i have never heard of the manufacturer. i looked around and bought the 11.5lb ACT, not a bad price for $240 and it is steel so it can be resurfaced.

IMO, i don't think 2 lbs is going to make a huge difference when the stock flywheel weighs ~25lbs..

 

I have 2 of them, both on 20b, 500hp+ cars and they work great. Burnt up the stage 3 clutch before I will hurt the disk .

 

Why?

http://www.pengaru.com/forums/index.php?showtopic=52

One thing I did not mention in the thread linked above is I ran both the stock S4 and S5 lower intake manifolds on the shop vac with the manometer attached - pressure difference was pretty much the same on both manifolds for all runners. In all cases where there was a better one, the S4 LIM had more pressure difference (marginal, but still worse).

so what are you basing that on?


For the original poster -

A heavy flywheel can mask what would be a fluctuating idle, switching to a lighter flywheel can reduce the rotating mass enough for the condition which already existed to be manifested.

For the record, my car idled perfectly with that exact aluminum flywheel with stock ports and stock ecu.

Nowadays the idle fluctuates, due to porting and poor vacuum signal to my haltechs map sensor @ idle thanks to overlap and individual throttle bodies. A heavier flywheel would make the idle smoother but wouldnt be the right way to correct it.

Lighter flywheel is easier to accelerate/decelerate, so the idle fluctuates more easily.. the lighter flywheel is not the CAUSE of the fluctuating idle however.

 

I have the 11lbs from SR Motorsports, coudln't be happier, only minor drawbacks are as mentioned before. The guy at SR said that there's not much difference between them,

 

Which ones? Thanks

RX_AV8TR-I was leaning towards the 11lb one myself, did it include the counterweight?

 

dDuB,
I tried unplugging it. The cars idle was the same plugged in or not plugged in.
So what does that mean?

 

doesn't mean much, i doubt you will be able to tune it out as it is just a characteristic of the motor. i tried tuning it out on my friends engine and i wasn't able to even with an SAFC and the variable resistor.

 

I don't know, I bought it in special with the ACT clutch and it included the counterweight. Love it, ran super strong for three years of serious abuse of track and strip. Two differential mounts broken and then finally the metal base split in two then I put the car in hybernation, but the clutch and the fw never budged.