Fuel Pressure...how much is too much?

[Trevor]

Hey guys...been working fueling today on the new Ty. First off it has a modified GM BBZB 1580 chip with stock fuel & timing but revised limiters. It also has a K&N barrel filter in place of the stock airbox and a Borla catback. Last weekend I changed the old O2 sensor for one of those new Denso units (it rocks BTW...transition counts are amazingly fast). I took it out afterwards and datalogged it with the stock FPR & old fuel filter.

Closed throttle block learn (BLM) : 137-138
Open throttle block learn (BLM) : 147-150
WOT O2's : 863-934
WOT IPW : 14.9-18.6

Obviously the ECM was adding alot of fuel.

Today I installed a new AC Delco fuel filter, an adjustable regulator, and a tiny fuel pressure gauge on the rail then I started tuning for 128 open throttle block learn numbers. It took alot of fuel pressure to get there...

Fuel pressure with vaccum connected : 53-54 psi
Base fuel pressure (disco vaccum) : 62 psi
Closed throttle block learn (BLM) : 111-115
Open throttle block learn (BLM) : 126-129
WOT O2's : 894-938
WOT IPW : 12.5-15.6

Knock improved a hair (still have to do ignition though) & it doesn't feel like it's drowing (still very responsive). So what do you think? Is there a reason I should turn the fuel pressure down?

 

[leroy]

Trevor,

I've seen a lot of variation between gauges. If you are really interested, send me the gauge. I'll test it with a dead weight tester and calibrate it if possible.

Jim

 

[4LINKSY]

Trevor,

I've seen a lot of variation between gauges. If you are really interested, send me the gauge. I'll test it with a dead weight tester and calibrate it if possible.

Jim

Can you calibrate a sears gauge, I know mine reads high?

 

[Trevor]

That's part of what I was thinking since it's a $20 summit brand FP gauge. It was showing 39 at idle with the stock FPR which is maybe 1-2 psi high...putting me somewhere around 60-61 psi actual base pressure. I'm pretty sure that's still really high to be getting neutral block learns. Maybe the truck has heads and a cam and I dont know it. :lol:

I wonder if maybe the output of the Denso is a little lower voltage than a stocker...a different calibration and all. If that's the case though my mileage should suffer but it actually got better with the Denso O2. :-?

I need get a wideband for the Ty. Now that I've used one in the Stealth I can't see tuning without one.

 

[leroy]

Trevor,

I've seen a lot of variation between gauges. If you are really interested, send me the gauge. I'll test it with a dead weight tester and calibrate it if possible.

Jim

Can you calibrate a sears gauge, I know mine reads high?

Most cheaper gauges don't have a calibration adjustment. I could test it and see how far off it is, if you want.

Jim