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Old 01-07-2008, 11:47 AM   #1
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Question Lightweight Flywheel and Turbo?

I'm getting a little rusty on my automotive theory, mostly about if having a Lighter Flywheel is good or bad or ugly on a car that utilizes a turbo.

I would imagine that it would help the response of the engine while off of boost and really not have any downsides while on boost...but what do I know

I've got a 10lb flywheel (1.8L) sitting on my desk and have intentions to install a begi kit at some point this Spring. I was also going to have the flywheel and new clutch installed prior, but don't want to make a mistake.

Any advice?
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Old 01-07-2008, 11:54 AM   #2
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You'll have no real problems with the flywheel. I find on my car it can take a second or two for idle to stabalize. Mine is a SPEC 8ish lb aluminum unit. If I had to do it again I would have stuck with a stock flywheel, any gain from the flywheel is overshadowed by the turbo.

I'd sell the flywheel to fund the turbo install.

Jay
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Old 01-07-2008, 02:31 PM   #3
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^ thats what i did, i had an ACT unit and then realized i wanted to build up a turbo, so i sold the flywheel after reading countless threads saying the gains were not enough to outweigh the cost...
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Old 01-07-2008, 02:35 PM   #4
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I have a lightweight flywheel on my 240Z, and it's tricky - car tends to bog when the clutch is engaged. Of course, that's with a beefy cam and no low end torque.

So, I guess maybe this has nothing to do with your thread. Oh well.

I wouldn't bother with a lightweight flywheel again, on anything. Throttle response is nice, but that's about it.
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Old 01-07-2008, 02:37 PM   #5
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I did it for the throttle response. And boy does it deliver. 7.3lb aluminum Fidanza.
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Old 01-07-2008, 02:41 PM   #6
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I have 1.6 Fidanza in 1.8 turbo motor. Works well and I don't regret it a bit. Might help on spool also.

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Old 01-07-2008, 04:01 PM   #7
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I hear a light weight flywheels biggest downside is in traffic as the engine no longer is able to pull the car along at idle.

I was considering a light weight flywheel too but living in NY I sometimes get caught in traffic. its nice to just put the car in second and have the engine idle pull the car along at 5 miles an hour. I imagine it would be a problem with a lighter flywheel.

Besides the throttle response on the miata is pretty quick as it is, i cant imagine what it would be like if it was faster.
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Old 01-07-2008, 04:08 PM   #8
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Due to the reduction of weight. The flywheel can not really give the same momentum as a heavier (oem) flywheel. This is what people have a problem with.
The lighter the flywheel the more you will lower your moment of inertia. That equals a faster up rev and down rev. Thats a good thing to me.
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Old 01-07-2008, 04:10 PM   #9
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I haven't had any problem letting it pull the car along at idle. Getting it to do that requires a little better throttle and clutch control to avoid bucking but that didn't take long to learn at all.
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Old 01-07-2008, 04:14 PM   #10
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The only downside I've noted is the slight increase in difficulty getting started in 1st, and the flywheel's tendency to exacerbate the idle droop problem when closing the throttle coming from boost (VTA + AFM)

Mine is the light (8 lbs?) Fidanza, ACT Xtreme, 1.6t.
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Old 01-07-2008, 04:17 PM   #11
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That'd be 7.3lbs Koto. I went ahead and recirced with a Bosch bypass valve and said goodbye to idle droop. But when I wanna feel cool I throw the Forge BOV back on.
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Old 01-07-2008, 04:29 PM   #12
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I installed my 7lbs Fidanza flywheel before installing the turbo and it helped a lot on throttle response. It was really worthed, the only turbo Miata I ever drove is my own and I think the Fidanza helps the turbo spool quicker.
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Old 01-07-2008, 04:31 PM   #13
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Turbo or no turbo, a lighter flywheel makes it very easy and quick to rev match on downshifts. You will notice it big time on the track.
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Old 01-07-2008, 05:07 PM   #14
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Quote:
Originally Posted by 90turboMX5 View Post
I installed my 7lbs Fidanza flywheel before installing the turbo and it helped a lot on throttle response. It was really worthed, the only turbo Miata I ever drove is my own and I think the Fidanza helps the turbo spool quicker.
But if it is the only one, how would you know?

It isn't going to help spool directly. It'll help the engine reach higher RPM faster (in theory), so it'll aid the turbo getting up to speed quicker. It isn't the same thing. Not like the flywheel makes the turbo spool 500rpm faster, it might make the engine get up to 4000rpm faster. It's like saying light weight wheels help the turbo spool faster.

My opinion is that it's placebo. Any percieved difference with the flywheel will be lost in the gains from the turbo. It'll be like tears in the rain (sounds cooler when Rutger Hauer says it).
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Old 01-07-2008, 07:57 PM   #15
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Quote:
Originally Posted by kotomile View Post
The only downside I've noted is the slight increase in difficulty getting started in 1st, and the flywheel's tendency to exacerbate the idle droop problem when closing the throttle coming from boost (VTA + AFM)

Mine is the light (8 lbs?) Fidanza, ACT Xtreme, 1.6t.
Would that be normal in an NA car? because mine does that sometimes...
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Old 01-07-2008, 07:59 PM   #16
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i couldnt tell a difference when i had it verse removed.

what i could tell a difference was when i removed it and a lot of the negatives went away.
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Old 01-07-2008, 10:04 PM   #17
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Quote:
Originally Posted by jayc72 View Post
It'll be like tears in the rain (sounds cooler when Rutger Hauer says it).
Blade Runner?
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