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Looking for information on why 2004 GTP's need a larger pulley

C

CopperGTP

New member
I've seen on multiple sites that sell pullies that they recommend adding .1-.2" to the pulley size with an 04 GTP compared to other cars, although the stock pulley size is the same at 3.8". Anyone know why that is? I'd really like to run a 3.4 inch pulley, and I don't think shelling our 100 bucks is worth it to only go down to a 3.6" pulley. I just ordered my headers, and Autolite 104's are a parts store trip away. I'll also be fabbing up my own fenderwell intake that I also plan on adding a "cold box" to. I'm designing an enclosure to run the intake tube through that can hold dry ice to really get intake temps down (for at least long enough to make a few passes before the dry ice vaporizes) I can get my hands on 93 octane here, and I usually run either 91 or 93 on a daily basis. Also, I'll be wrapping my headers to keep under hood temps down.

Thoughts?
 


got e85? if so get larger injectors and a tune and drop to a 3.2 pulley.

or add a fcic and drop to a 3.2 on 93 octane, then if you want more add a meth kit, and a 2.8, you'll need a tuner in hand for meth.
 
I'm staying mild with this car. Just want to know what I can get away with on pulley size with just what I listed. My fast car is a turbo LS C3 Corvette.
 
Oh, and E85 is very much a PITA to get here. There's only 3 stations that are kind of local, and one sells it in 5 gallon cans, leaving only 2 that actually have it at the pump, and those 2 are out of my way. Not really what I want to get into with my DD
 
in the end the gen 5 is a tad better than a gen 3. why they end up just dropping to a 3.6 and not a 3.4 gains would be about the same cause the gen 5 is a better blower.
 
the rules are different with a gen 5. you could run a 3.4 on your gen 5 if you installed a cam or an intercooler, otherwise stick to a 3.6.
 


Factory power output is also higher on a 2004 compared to say a 2000 car because the blower is a better design. It makes more boost with a smaller pulley diameter drop than a GEN 3 supercharger.
 
Maybe I'll look into doing 1.9 ratio rockers and good springs when the weather warms up. I gotta do the headers as soon as they arrive though, cause I got a real nasty exhaust leak at the moment!
 
Headers should be here by Thursday. Hopefully I'll be able to find a warm garage to borrow to get them on. I found a great deal on a 3.4" pulley, but I'll wait to put it on until I have the other stuff it takes. I'm thinking of just going with meth injection right off the bat. I don't need this thing getting into kr.
 
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