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Well while I'm at it.

1577 Views 30 Replies 12 Participants Last post by  KyleKidd
I know its been discussed a million times, but I'm debating on getting an UD pulley while the engine it out and everything. Possibly a lightened flywheel as well for my new manual transmission.

Can anyone give me an educated guess as to what kind of improvement I could expect to see in a 0-60 launch from an UD pulley, lightened flywheel, and 2.5 straight-through exhaust?

Say I ran a 7 second flat 0-60 before these mods.

Think It would drop .5 seconds or more? Or am I expecting too much?
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UD gives roughly a 5 HP improvement (at best). For an NA engine -- I think it's best to assume a 5HP gain per simple mod as the rule of thumb. Ex: 5HP for better intake, 5HP - lightened flywheel, 5HP - ECU tuning, 5HP-lightened drive shaft, etc. For what's posted above -- doubt you'll get 0.5 seconds of improvement - but car will be a bit more responsive.

So net here -- UD is helpful in being additive. Are you doing a better intake too (or perhaps car already has that?).

Generally this topic is open to a lot of opinions and caveats -- others here likely will have their viewpoints as well and may or may not agree with mine?
Highly doubtful you'll notice any improvement in acceleration....maybe if your butt dyno is super sensitive. I've got an UD pulley and a JWT lightened flywheel, the car revs in neutral extremely fast. But for comparisons sake, I bought it with both installed so I don't know how it behaved before hand.

You'll also want to look into getting and OVERdrive pulley for your waterpump/fan. The UD crank will cause both fan and pump to spin slower, the OD pulley will return them to their normal rotating speed. I got mine from Bernie over on tt.net.
I have a cold air intake already
Underdrive pulleys give you more power with more RPM. So if you are mixing Underdrive crank and lightened flywheel which makes it rev much quicker.. it only makes sense that it would be well worth it. Even if it is only a 10hp-15hp increase. Especially since you have the motor out already and all the work is easy.
I'm already close to hitting my budget so we'll have to see.
Those mods dont actually "give" you horsepower. They are just freeing up power. Youll notice a quicker rev in higher RPM's when lightening parts. Id say get them though, any little bit can help right :)
Oh I know Kandy, but thanks for the explanation anyway.

I'm sure my car will be MUCH more spry after I'm done with everything.

Fixing vac leaks, UD pulley, Lightweight flywheel, new exhaust, and manual transmission should give me a noticeable increase in acceleration I am hoping.
Youll have a lot more fun with a 5spd for sure. Are you elimintating the carbon canister and other extra things also?
EGR, AIV so far on my list. Haven't considered the carbon canister.

EGR is actually already gone. I'm taking a short break from working on the engine and am going back over in a few min.
Well you should delete the canister also.
Those mods will definitely make your Z feel like a lighter car. I did not do the overdrive for the waterpump/fan and have had no problems either in Florida or here in Austin. You will like the feel.
Why delete the canister?
i think weight is the main reason... That and some people attribute it to a raw fuel smell.. (I think)
I can confirm a raw fuel smell after removal. I suggest leaving the carbon canister in if it functions properly (i.e. vacuum ports hold vacuum). Due to mine causing a vacuum leak I bypassed it, since then I get a raw fuel odor when the tank valve releases.

I have a plan for solving this but haven't had a chance to try it yet.
Just more places for Vac leaks...
I'll keep it under consideration.
I priced out a brand new lightweight flywheel, clutch set, and UD pulley set.

All for $484 with shipping from flea bay.

Here are the links if you want to check it out:


You dont need the whole pulley set, the crank pulley is the only one youll see any gain from. The others are there to look pretty. As for the clutch/flywheel. Go with Fidanza or Joe's (spdracer) steel flywheel. DONT get an "ebay" clutch. Your better off with a stock replacement from Rock Auto or your local parts store.
fwiw I have a UD pulley and no overdrive pulley, and stock TT radiator/fan. Temp gauge didnt move on the track. Overdrive water pulley is overkill as far as im concerned.
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