Adjustable Fuel Pressure Regulator
Thread Starter
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
Adjustable Fuel Pressure Regulator
Yesterday, I installed an adjustable fuel pressure regulator from TPiS. My 85 has a rebuilt 350 that was bored .060 over, 10:1 compression, a Competition mild cam and Corsa exhaust. I have replaced the injectors, fuel pump, ignition, etc. but I have always had a significant ping. I thought I would have to replace the cast iron heads to get rid of it.
I increased fuel pressure from 39 psi to 47 psi. The ping is gone. The added benefit is more power. I hoped the increased fuel pressure would promote a more efficient burn and the O2 sensor would see a lean condition and increase the injector pulse. I never expected the increase in power I feel. Has anyone else had a similar finding? If what I'm felling in power is true, this is some pretty cheap horsepower ($69).
I increased fuel pressure from 39 psi to 47 psi. The ping is gone. The added benefit is more power. I hoped the increased fuel pressure would promote a more efficient burn and the O2 sensor would see a lean condition and increase the injector pulse. I never expected the increase in power I feel. Has anyone else had a similar finding? If what I'm felling in power is true, this is some pretty cheap horsepower ($69).
Team Owner
Joined: Feb 2006
Posts: 23,218
Likes: 117
From: San Antonio Texas
Haven't done it on the Vette yet, but I replaced the fuel pump on my Mustang 5.0 with a higher capacity one and also added an adjustable regulator. I didn't up the pressure but only about 4lb. but I could feel a BIG difference in the mid range pull of the motor. I think the stock pumps in most cars are right at the edge of their capacity when just normal driving. Trying to get much performance from them, specially after a few years on the road, is more than they can supply, and I think the car's performance suffers from "tired pump syndrome". The Vette's day is comming and it will get a fresh pump and FPR and I bet it will wake up too!
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
Yesterday, I installed an adjustable fuel pressure regulator from TPiS. My 85 has a rebuilt 350 that was bored .060 over, 10:1 compression, a Competition mild cam and Corsa exhaust. I have replaced the injectors, fuel pump, ignition, etc. but I have always had a significant ping. I thought I would have to replace the cast iron heads to get rid of it.
I increased fuel pressure from 39 psi to 47 psi. The ping is gone. The added benefit is more power. I hoped the increased fuel pressure would promote a more efficient burn and the O2 sensor would see a lean condition and increase the injector pulse. I never expected the increase in power I feel. Has anyone else had a similar finding? If what I'm felling in power is true, this is some pretty cheap horsepower ($69).
I increased fuel pressure from 39 psi to 47 psi. The ping is gone. The added benefit is more power. I hoped the increased fuel pressure would promote a more efficient burn and the O2 sensor would see a lean condition and increase the injector pulse. I never expected the increase in power I feel. Has anyone else had a similar finding? If what I'm felling in power is true, this is some pretty cheap horsepower ($69).
Last edited by 383vett; Mar 16, 2009 at 10:29 AM.
Team Owner
Joined: Jul 2002
Posts: 22,267
Likes: 15
From: The light that never warms.
St. Jude Donor '12
'85s benefit from an AFPR like no other year. The factory setting is really low, and the increased pressure just helps the injectors atomize better. I first put a TPIS AFPR on an '85 Trans Am I had with the LB9 ( TPI 305), and later put one on an '85 Vette. They both responded really well.
Thread Starter
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
I don't have any way to monitor the O2. I considered having a new chip burned. But several people told me the 85 computer should take care of the mods I have.
Drifting
Joined: May 2002
Posts: 1,509
Likes: 3
From: Hazel Park MI
From my lurking in the scan/tune section, I've found the 85 computer to be on the slow side, and not very informative. For example, on my autoxray I can't get some real time data the other L98 computers give. When I called autoxray, they said it was my 85 computer setup, not the autoxray scanner. As long as I get O2 voltage variation, I figure I'm good to go with lean/rich conditions. You need a chip tune fo sho with a cam swap to get the most out of it. Also, watch that FPR if indeed you used your stock diaphram - my diaphram gave out and I had gas way up the intake.
Team Owner
Joined: Feb 2006
Posts: 24,460
Likes: 7
From: sw Ohio
I'm sorry but 47 psi is just too high for an '85 even with a few mods. I would hook it up to a scan tool and see whats really going on. I have a feeling the added fuel is masking something.
The highest i've ever adjusted mine to was 55 psi (by accident) and it was spewing fuel out the tailpipes. I currently have mine set at 36.
The highest i've ever adjusted mine to was 55 psi (by accident) and it was spewing fuel out the tailpipes. I currently have mine set at 36.
Drifting
Joined: May 2002
Posts: 1,509
Likes: 3
From: Hazel Park MI
Ya know, I was going to mention something about what demonic is touching on. When I bumped my FP up to 51, it would cut out at WOT for a millisecond, then catch and haul *****. After thinking it was a timing issue & messing with that, I lowered the FP to 47 and it stopped the cut out. But it smelled way rich throught the exhaust, and what my O2 sensor was telling me when scanned. It is now at 44.
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Drifting
Joined: Oct 2006
Posts: 1,934
Likes: 3
From: Citrus Heights California
I see you're from California. I failed a visual because of an adjustable fuel pressure regulator. The emissions were good but I still failed. I had to remove the AFPR and reinstall the stock regulator.
I think you should get a custom tune.
I think you should get a custom tune.
Thread Starter
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
The AFPR I bought from TPiS has a CARB number so it is CA legal.
Thread Starter
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
I'm sorry but 47 psi is just too high for an '85 even with a few mods. I would hook it up to a scan tool and see whats really going on. I have a feeling the added fuel is masking something.
The highest i've ever adjusted mine to was 55 psi (by accident) and it was spewing fuel out the tailpipes. I currently have mine set at 36.
The highest i've ever adjusted mine to was 55 psi (by accident) and it was spewing fuel out the tailpipes. I currently have mine set at 36.
