Fuel Tuning advice from experts please!

[217gsr]

I recently installed my new B&M Commandflo and a Cartech 20005. I installed my Cartech first, so I've pretty much gotten down how to adjust the static FP and how changing the rise rate adjustment affects driveability and detonation.

My questions is, how does the B&M's setting for static FP affect driveability? For instance, what would setting the static FP at 52 psi and the Cartech at 54 psi do, versus setting the B&M at 42 psi and the Cartech at 54 psi do? I've been told that INCREASING the difference between the Cartech's static and the B&M's static will begin fuel enrichment for boost EARLIER, thereby reducing tip-in detonation. Does that sound right?

Thanks in advance.

[Holden]

I'm currently using different static pressures on my two FPR's. The Cartech is set at 35psi and the AEM is set at 40psi. I used to have them both at 35psi, but have gone this new way to make the 0-3psi range smoother.

Max FP is the same as always, but FP around 0-3psi is a bit higher. It seems to work (make the engine smoother in that range).

[217gsr]

Holden, is the 5 psi difference between your Cartech and B&M arbitrary? Or did you try varying differences first (ie. 2psi, 5psi, 10 psi differences)?

I can see how a small difference might make the lower boost transition smoother, but what would be the upper limit that you can move the two static FP's apart? Right now, my car "seems" to work alright with a 12 psi difference between my B&M and my Cartech. Is this too large? Should I decrease that difference? Thanks.

[5 Liter Eater]

Weird that you set your FMU lower than your FPR Holden. I always thought it was better to have the FMU overlap the FPR. When I was tuning my regulators I had the FPR's static at 52 and the Cartech's static at 55 so there was no delay while the Cartech had to "catch up" to the FPR. This was to aid the transition from vac-boost/tip-in.

I guess the downside to having too much overlap would be the spike at 0 PSI. The B&M is rising at 1:1 to 42 PSI at atmospheric and the Cartech bumps it to 54 all the sudden. Seems like there would be a kick there.

[Holden]

The 5psi "bump" I did to the AEM was arbitrary. I assume the limit on how high I could set the AEM comes from two factors:

1) I want a max FP of 67psi. If I set the AEM to 55psi static or higher, the AEM will override the Cartech and increase max FP.

2) At some point (probably before #1 happened) the ECU would throw "too rich" codes. I use 320cc injectors.

I don't want to touch my Cartech because I spent a buttload of time tuning it last year and my WOT peformance is great.

One thing to keep in mind is that raising FP in a broad enough range of vacuum/boost will cause the ECU to start trimming out fuel. I'm hoping that since I'm only raising FP around 0" vacuum, where I don't spend much time at, the ECU won't "learn" anything.

I plan on resetting the ECU before dyno tuning and the resetting the ECU again before events to make sure I get the same results I got on the dyno.

[217gsr]

Wow. I didn't catch that you had your FPR static higher than your FMU static, Holden.

I guess since I don't have an AEM, and my B&M doesn't have a 1:1 rise rate, I'll just keep the B&M static lower than the Cartech for this time. But does 12 psi difference still sound like a lot to you guys?

JRCivic told me that if I increase the difference between the two, I might be able to tune out some tip-in detonation, which I was having. He also mentioned that if the difference was too large, I might get some tip-in detonation because of overfueling (as I understand it). The tip-in detonation is gone now (which happens occasionally, so I don't know if it's because of anything that I did directly), and I'm wondering if I should raise my B&M static to more closely match, but not match exactly, the static FP at the Cartech. I was also hoping someone could explain to me why this is.