Procharger pulley reduction and 91 octane

[Bartly]

I know there are some other conversations going on about pulleys and Prochargers, but hoping I can get some input on my situation. I have the stage two setup and my dyno said I was at 582whp and 8.75psi boost. That was with a previous tune where my knock sensors were going off in the +2 - +4 range at WOT. Now I’m on a completely different tune through the SCT X4 and am loving it because my knock sensors rarely go positive with 17* timing advance WOT. Got me wanting more (go figure). I’m restricted to 91 octane gas and am 4500ft elevation (not sure how much that matters). Just wondering what kind of input I can get from all of you. I really do like seeing the knock sensors (almost) always negative, but guessing if I drop a pulley size that will change?? I’m on the stock PC 4.75” pulley, wonder do they make a 4.625”? What would you guess for whp increase with a change to 4.5” or 4.625” pulley? Also been reading that with a minor pulley change my current tune would adapt? Is this true, what’s the “rule” on that? 91 octane is my problem, but unfortunately that’s all I have. Thanks for any input.

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[Tommy V]

Usually one drop in pulley size does not need a retune but i would data log it and have it looked at.U must have a p1 to be at 8 psi of boost on 4.75 pulley??.I would be careful going up to much higher just because your using 91 oct.

 

[Bartly]

Usually one drop in pulley size does not need a retune but i would data log it and have it looked at.U must have a p1 to be at 8 psi of boost on 4.75 pulley??.I would be careful going up to much higher just because your using 91 oct.

Yep, I do have the p1sc-1. Yeah, that’s kind of what I was thinking from reading, one pulley size without a retune. Wasn’t sure if that was 1/8” smaller or 1/4” smaller. Not sure what either of those sizes would do with my knock sensors, or what Whp increase would result. If it only was 20hp or something wouldn’t even be worth it to me, but guessing it would be more than that, so thought I’d ask

 

[ProChargerTECH]

we make a 4.63"

 

[Bartly]

we make a 4.63"

Thanks, any insight to the rest of my questions? Hoping for just a ballpark guess to what I could expect to see relating to knock sensors and hp increase going to either the 4.63 or maybe even down to 4.5”.

 

[SolarFlare]

What are your other mods? I would get a manifold instead.

 

[DR_]

Do you log OAR? If so it would give you a clue if your 91 octane gas situation will support more boost.

 

[Bartly]

What are your other mods? I would get a manifold instead.

No other mods to the engine/drivetrain, well I have a catback but that shouldn’t make a difference, but do have to keep my catalytic converters for emissions testing. Thought about the manifold, but guessing that isn’t going to give more than 20-30 hp if I’m lucky, would think a small pulley change would add more than that.

Do you log OAR? If so it would give you a clue if your 91 octane gas situation will support more boost.

Not sure what that stands for, have logged lots of things, but that one doesn’t jog my memory.

 

[SolarFlare]

You will get more from a manifold than one step down pulley. Guaranteed.

 

[DR_]

Not sure what that stands for, have logged lots of things, but that one doesn’t jog my memory.

Octane Adjust Ratio. If it is -1 then your gas isn't causing much knock on your tune. On the other hand if it is +1 then it would be unwise to up the boost and you should be running better gas. The affects of winter gas can easily be watched as well.

 

[Bartly]

You will get more from a manifold than one step down pulley. Guaranteed.

Good to hear, you might have just given me a new direction to look into. Thanks.

Octane Adjust Ratio. If it is -1 then your gas isn't causing much knock on your tune. On the other hand if it is +1 then it would be unwise to up the boost and you should be running better gas. The affects of winter gas can easily be watched as well.

Kind of sounds like the Knock PID? - means good, + means bad. Does OAR PID work with regular gas or is it for E85 and/or flex fuel tunes?

 

[r1lovin]

Who's your tuner? Im at the same altitude about 4700 Colorado and ran 11 to 12 lbs of boost on 91 octane. Never saw positive knock. 17* timing, knock sensors were adding 4.5* all the way to 7200. Remember cars are also less prone to knock at altitude because of less atmospheric pressure. Also less power lol.

 

[Bartly]

Who's your tuner? Im at the same altitude about 4700 Colorado and ran 11 to 12 lbs of boost on 91 octane. Never saw positive knock. 17* timing, knock sensors were adding 4.5* all the way to 7200. Remember cars are also less prone to knock at altitude because of less atmospheric pressure. Also less power lol.

I’m tuned by Rob Shoemaker. 11-12 psi sounds like I could add some perhaps. I don’t see positive knock anymore now that I’m on this tune. I’ll have to go look at some logs, but I don’t recall my kr sensors adding the timing advance your seeing with the boost increase from what I have going on, but if I recall, was at 17* as well. Been told, and see reference to west coast gas being crap, could be why my knock sensors aren’t adding as much as yours? Who knows.

Funny on the less power at altitude thing. When I bought the car and started shopping FI I figured the lower power would help get me more miles out of the engine. Now I’m satisfies and wanting more. Only real way for me to find out is to swap the pulley, I’m going to stew over it for a bit. Curious if anyone can tell me what the “approved procedure” is for taking off the pulley warranty cap on a Procharger head unit?

 

[ahl395]

If you're at the limit of 91, dropping a pulley and increasing boost will just result in less timing. So your kind of at a wash between the two.

If your 91 quality is decent dropping a pulley and maintaining the same timing will increase power. But you wont know till you try it and log it and/or get the tune adjusted if necessary.

If your flatlining around 6500-7k a manifold change will bring up your peak hp more, as others said.

As far as I know once you change pullies you void the Procharger warranty. I had mine done by a shop just in case even though I do all the rest of my work myself.

If you're looking for more midrange power pulley down and wastegate it.

 

[r1lovin]

I’m tuned by Rob Shoemaker. 11-12 psi sounds like I could add some perhaps. I don’t see positive knock anymore now that I’m on this tune. I’ll have to go look at some logs, but I don’t recall my kr sensors adding the timing advance your seeing with the boost increase from what I have going on, but if I recall, was at 17* as well. Been told, and see reference to west coast gas being crap, could be why my knock sensors aren’t adding as much as yours? Who knows.

Funny on the less power at altitude thing. When I bought the car and started shopping FI I figured the lower power would help get me more miles out of the engine. Now I’m satisfies and wanting more. Only real way for me to find out is to swap the pulley, I’m going to stew over it for a bit. Curious if anyone can tell me what the “approved procedure” is for taking off the pulley warranty cap on a Procharger head unit?

Take a look at the logs first see what the knock sensors are doing. You could also run torco

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