Correct pulley for '04

Looking to increase HP/TQ in my 2004 GTP (L32 engine-Series 3 3800SC), but want to keep everyday driveability. So far, I have put in MSP Cold Air Induction kit, NGK TR6 irridium spark plugs, 180 degree 'stat, and removed U-Bend (thinking about reson).

Now my issue; what size pulley? I have heard that the new Eaton Gen 5 supercharger runs more freely than the Gen 3 (from L67) did, and should use a 3.5" pulley to stay on the safe side of KR. But since I did the things mentioned earlier already, can I get away with running a 3.4" pulley without KR?

I'm hoping someone has had some experience with mods on the L32, and can perhaps offer some info on this for me. Thank you very much in advance.......

Looking to increase HP/TQ in my 2004 GTP (L32 engine-Series 3 3800SC), but want to keep everyday driveability. So far, I have put in MSP Cold Air Induction kit, NGK TR6 irridium spark plugs, 180 degree 'stat, and removed U-Bend (thinking about reson).

Now my issue; what size pulley? I have heard that the new Eaton Gen 5 supercharger runs more freely than the Gen 3 (from L67) did, and should use a 3.5" pulley to stay on the safe side of KR. But since I did the things mentioned earlier already, can I get away with running a 3.4" pulley without KR?

I'm hoping someone has had some experience with mods on the L32, and can perhaps offer some info on this for me. Thank you very much in advance.......

Just my 2 cents::2cents: I don't have much experience with your model GTP but the principles are still the same no matter what year you have. You might want to check with companies like Thrasher about KR (knock retard) and going to a 3.4 SC pulley. It could still be a concern.

I see you listed your mods but do you have a re-programmed ECU/PCM like the DHP v1.0?? The re-programmed tables for KR, spark advance, timing, fuel injection and MAF will make KR worries moot. The 3.4 pulley is excellent whether at the dragstrip or on the street. The DHP v.1.0 for 2004 model GTPs has been out for a while now.

BTW - I waited until the bumper to bumper warranty expired before modding. The dealers are not too forgiving when you take it in for warranty work.


http://www.photodump.com/direct/coolrex/gtp558.jpg
Thrasher CAI, DHP v1.0 ECU, Granatelli CAI Tuneable MAF,
3.4 SC pulley, Hi-Flow CAT, u-bend delete, 180 TS, TB spacer
ET: 14.3 @ 96 mph

I checked with the dealer prior to doing the mods I have so far, and they are cool with it. I haven't mentioned the pulley, and I understand that the 3.5" isn't very noticeable to the dealer either; so that could be a plus... No, I do not have an after-market PCM, nor do I intend to install one.

Has anyone put a 3.4" pulley on the L32 engine yet? And did you have to do additional mods to rid the system of KR? Please respond......

I checked with the dealer prior to doing the mods I have so far, and they are cool with it. I haven't mentioned the pulley, and I understand that the 3.5" isn't very noticeable to the dealer either; so that could be a plus... No, I do not have an after-market PCM, nor do I intend to install one.

Has anyone put a 3.4" pulley on the L32 engine yet? And did you have to do additional mods to rid the system of KR? Please respond......


Nice dealer...too bad they're all not like yours. I checked with our local GP club and we have one member with a 2004 GTP running a 3.4 pulley. He got a Thrasher from 3800performance.com. No modified ECU either.

He went with the GoodYear Gatorback SC belt to minimize any possible slippage and the following is essential for KR:

Change out the factory sparkplugs and go one range colder NGK TR55IX and gap them .005 under the now .060 setting that comes with from the factory, to help lower cylinder temperatures and optimize wide open throttle response. You can safely go up to 2 ranges colder. Plus he uses octane boost due to only having 91 octane premium gas in our area.

Other than that he claims no problems. DHP v1.0 ECU is not necessary unless you decide to drop down to a 3.25 pulley in the future.

Hope the info helps and good luck.

http://www.photodump.com/direct/coolrex/gtp558.jpg
Thrasher CAI, DHP v1.0 ECU, Granatelli CAI Tuneable MAF,
3.4 SC pulley, Hi-Flow CAT, u-bend delete, 180 TS, TB spacer
ET: 14.3 @ 96 mph