Thread: Pulley drop time?

i wouldnt say kr free but you could drop but id deff get a tune first

You need something to scan knock with..then that'll tell you what size pulley u can run

so you dont run it lean and chip a piston or it runs too rich and fuel wash it

Invest in a aeroforce scan gauge first before you even think about dropping pulleys.

Originally Posted by jman44

I have a 99 gp gtp coupe. has speed daddy headers, no cat, magna flow mufflers, roller rockers. My question is what can i safely drop to on my s/c and run kr free?

I'd guess you can go with a 3.4 without KR but like the others mentioned a scan gauge would be smart. I'm assuming you have an intake also right? I'm running a 3.3 with similar mods except for a mild cam and a little bowl porting on the heads. I have an Aeroforce and have not shown any KR. I've got a 3.2 on the way and will keep an eye out for knock.

Originally Posted by tms8582

I'd guess you can go with a 3.4 without KR but like the others mentioned a scan gauge would be smart. I'm assuming you have an intake also right? I'm running a 3.3 with similar mods except for a mild cam and a little bowl porting on the heads. I have an Aeroforce and have not shown any KR. I've got a 3.2 on the way and will keep an eye out for knock.

Factory programmed PCM or something else?

Originally Posted by ILoveGM

As far as the pulley drop and everything, hit up zzp's 3800 section on their website. They have info on the order of mods to do and how big to go with mods. Just check it out!

I prefer to never follow what ZZP says.

The parts for the most part are good and customer service is mostly good these days, havent seen many people have issue lately.

Is just the way they say you can add mods is whats wrong. The first build sheet says all you need to run a 3.4 pulley is a 180 thermostat, colder plugs, their pcm and a downpipe. I bet for just about any car, it will still see a decent amount of KR and need for exhaust flow to be safer.

I didn't think that was all they said. Maybe for a 3.6 or 3.5 pulley. I don't know. Oh well lol

Originally Posted by Elite6

Factory programmed PCM or something else?

I was running a factory tune without any KR but I did have my buddy change the fans to come on sooner. That's one area where the factory tune really sucks imo. The fans don't come on until 220... Now I have an intense tune with raised shift points. Both tunes showed zero KR. I can't say the Intense tune made a huge difference except for the higher shift points. In fact I think I'll even raise the shift points higher because the motor really pulls over 6000. I think the balanced crank, Xtreme cam and 105 springs can really handle some RPM's. Right now the car shifts at 6300 and I will change that to 6500. I'm going to give the 3.2 a try and maybe increase the WOT timing a little too and keep a close eye out for KR. he original poster talked about rockers... I assume he meant 1.9 rockers? If so I's guess he will be good with headers and rockers and a 3.4.

I bet the PCM runs pretty rich too, its how most mail in tune battle the KR.

Originally Posted by hollas13

how does a tuned pcm get rid of kr? i have ported manifolds, cai, 180 tstat, al 104's, 3" dp and a 3.4 mps i want to put on. also i have a way to scan.

I am not an expert on tuning by a long shot but I know if you had a custom tune on a dyno they could tell right away what pulley you should run safely. They do this by an educated guess on the pulley size then dyno the car and pulley down a size or two if they can without KR. A lean fuel/air mixture can result in KR the stock PCM adjusts the amount of fuel based on the MAF and O2 readings. I'm guessing that some tunes may include adjustments to the fuel trims and increase the fuel mixture to eliminate a possible lean condition. I think with lightly modded cars with stock injectors this is not much of an issue with even a stock tune. The easiest way to get KR is to not have good exhaust flow and run a pulley too small. Your jamming to much hot compressed air into the cylinders and the hot gasses don't flow out fast enough causing excessive heat and early detonation (KR) I topped off my build with a tune from Intense. John really knows his stuff and you can call him with questions if you need to. INTENSE-Racing.com: INTENSE™ Reprogrammed 3800 Powertrain Control Module (PCM) The web site lets you choose a canned tune based on your mods.