Thread: 91 Octane On Smaller Pulley

Hey whats up,
I'm the proud owner of a 2004 GP GTP Comp G and thanks to this site I changed out my LIM gasket and valve cover gaskets with no problems. My question is if I have all supporting mods plus an OverKill PCM but only have access to 91 Octane is it worth dropping a pulley size or will I likely see too much KR. I do not have access to a tuner at the time. Would it be possible to get my PCM programmed to run a smaller pulley on 91 Octane to not see any KR. If not worth doing the pulley drop, I would assume that just the supporting mods themselves would give me a noticable increase in power, correct me if I'm wrong. Thanks in advance for any advice.

IF you have no kr you can run the pulley. You need a scanner to check. If you do have some kr the mods will give you a noticeable boost in performance.

Well...you are supposed to run 91 octane or MORE all the time. What are all of your mods. The GenV blowers take pulley dropping a lot more serious than the GenIII's in the 97-03 cars. If anything...probably a 3.6" pulley vs. your stock 3.8"

I ran a 3.1" with 91 octane on a colder day with no knock and a 3.25" on a HOT day with 91.

Maybe, I'd still get a scanner. I've got all those mods without the PCM and I'm still going to scan beforehand. I've read of some guys needing an IC to run a 3.4 and of guys with less mods run a 3.4. Every car is different.

AeroForce Scan Gauge it was my First MOD best money spent

You could still knock with a stock pulley...its all about the car or tune...

Just get the supporting mods on and then wait till you get the mod bug again and get some more supporting mods then drop a pulley. Get all of your list then wait and get rockers or cam and port your throttle body and blower. Then scan and see what you can do.

I've got the same mods on a 3.6 pulley. This is the lowest pulley drop i could go with my mods.

im not going to drop a pulley again until i get rockers and headers.

yup...'04+ cars are tricky with mods...

Originally Posted by Street Wolf

I run 91 octane in mine all the time. In 100+ degree temps.

Drop it a size.

93 all day long in northern IL =] still have the stock pulley =[ cuz i have no funds lmao

Originally Posted by bluegtp91

Well...you are supposed to run 91 octane or MORE all the time. What are all of your mods. The GenV blowers take pulley dropping a lot more serious than the GenIII's in the 97-03 cars. If anything...probably a 3.6" pulley vs. your stock 3.8"

I ran a 3.1" with 91 octane on a colder day with no knock and a 3.25" on a HOT day with 91.

Owners manual for a 2006 with a series 3 S/C engine states you only require 87 octane, and reccomend 91 octane.

I have ran 87 octane w/o adverse effects. I didn't really notice any drop in power, or any knock/engine noise. I did not time 1/4 mile times, but 87 octane is fine, and you do not void your warrenty running it.