Fuel Pressure Regulators
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 23,218
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From: San Antonio Texas
Fuel Pressure Regulators
In a non performance application, is an aftermarket type of fuel pressure regulator any more accurate than a stock type? I'm thinking part throttle metering ability, if the tracking ability of an aftermarket regulator would follow the vacuum signal and respond/ regulate fuel any better than a stock type.
Race Director
Joined: Apr 2003
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From: moraga ca
Fuel pressure regulators are basically a spring, a diaphram and a disk that seals against the fuel rail base. The only difference with an adjustable regulator is the ability to increase or decrease spring pressure.
Team Owner
Joined: Aug 2005
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From: Riverside County Southern California
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I used an adjustable FPR on my stock 92 Vert. At that time Corvette Fever magazine published an article to read the stock pressure, and to rise that pressure by 2 psi max. I did the 2 psi, and there was a noticeable gain on performance.
Currently my Vettes are tuned to use the stock FPR.
Currently my Vettes are tuned to use the stock FPR.
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
My big concern with regulators is the different pressures used by GM through the years. 85 at 39 psi, and 90 and up at 44 and up. When replacing the diaphragm a fuel pressure reading should be taken and recorded. If the new one does not have the same pressure get an adjustable cap and reset to factory setting. Speed density may respond to 1 lb increase, and mass air cars like 2.
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Team Owner
Joined: Feb 2006
Posts: 23,218
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From: San Antonio Texas
I think it may be time to replace mine. I like to monitor the instant mileage display and lately I've noticed that after accelerating up to hwy speed, it doesn't pop up above the teens like it used to. If I back off the throttle for a second to build up vacuum, it pops right up there and tends to settle back a lot higher than if I didn't help it recover. Then when I set the cruise control I get good gas mileage on the highway. If I don't do that, the instant mileage reading stays down around 12 to 15mpg until I go down hill a little and the cruise backs off the throttle a bit before leveling off again. I keep track of mileage at fill-ups and lately it's been significantly down. Kind of makes me think the regulator is sticking or wearing out, because I haven't found a vacuum leak and everything else is good with plugs, wires Opti and O2's. So if I do replace it, I'm wondering if an aftermarket adjustable will be of any better quality or control ability than another stock one?
Safety Car
Joined: Aug 2009
Posts: 3,752
Likes: 276
From: Melbourne, Victoria, Australia
My 85 had only around 32 psi fuel pressure (85 has 24 lb injectors that may be the reason) 38 psi seems standard on later TPI's on what forum members have mentioned.
I remember there was a big mid range to top end improvement going to 45 psi, but the downside is a very rich idle (when the car was standard).
The one thing a TPI engine needs is long tube headers, that knocked almost a second of my quarter mile time. 14.4 standard
Returned a week later with headers and cold air intake got that down to 13.6 some new leads and a tune advanced timing 13.4.
I remember there was a big mid range to top end improvement going to 45 psi, but the downside is a very rich idle (when the car was standard).
The one thing a TPI engine needs is long tube headers, that knocked almost a second of my quarter mile time. 14.4 standard
Returned a week later with headers and cold air intake got that down to 13.6 some new leads and a tune advanced timing 13.4.
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
My 85 had only around 32 psi fuel pressure (85 has 24 lb injectors that may be the reason) 38 psi seems standard on later TPI's on what forum members have mentioned.
I remember there was a big mid range to top end improvement going to 45 psi, but the downside is a very rich idle (when the car was standard).
The one thing a TPI engine needs is long tube headers, that knocked almost a second of my quarter mile time. 14.4 standard
Returned a week later with headers and cold air intake got that down to 13.6 some new leads and a tune advanced timing 13.4.
I remember there was a big mid range to top end improvement going to 45 psi, but the downside is a very rich idle (when the car was standard).
The one thing a TPI engine needs is long tube headers, that knocked almost a second of my quarter mile time. 14.4 standard
Returned a week later with headers and cold air intake got that down to 13.6 some new leads and a tune advanced timing 13.4.
http://www.witchhunter.com/flowdatapix/b0280150223.jpg
Using this calculator let's run the numbers at both 39, and 32.
http://www.csgnetwork.com/fiflowcalc.html
39 psi = 22.535 lbs
32 psi = 20.413
My point is that fuel pressure should always be measured with no vacuum attached, otherwise it is a false reading. Zero vacuum is how the flowrate is calculated to enter into the programming.
TPiS created this chart some years back, and I've found it to be close, but not always accurate.
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Race Director
Joined: Apr 2002
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From: Anaheim CA
Anybody have a link to an article on this?
Drifting
Joined: May 2013
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From: Reno Nevada
Cliff, the fuel trim, or blm does not function with thr narrowband o2 at WOT. The added fuel created by the added pressure is used in WOT where the O2 capabilities are not accurate. Basically, the ecm defaults to open loop.
Race Director
Joined: Apr 2002
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From: Anaheim CA
For BLMs, the main difference between open loop and closed loop is that the ECM does not UPDATE the BLM table in open loop (because the O2 sensor reading is ignored and the INT is not calculated).
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
That's not strictly true. You are in open loop at WOT but the ECM still uses the BLM table as the basis for calculating the injector pulse width.
For BLMs, the main difference between open loop and closed loop is that the ECM does not UPDATE the BLM table in open loop (because the O2 sensor reading is ignored and the INT is not calculated).
For BLMs, the main difference between open loop and closed loop is that the ECM does not UPDATE the BLM table in open loop (because the O2 sensor reading is ignored and the INT is not calculated).
The proof will be in reading the datalogs and modifying the power enrichment table based on observed O2 results. If one tunes to .860 millivolts from the O2 it will be as close to 12.5 AFR or Lean best torque as posssible. There is no BLM, or INT at WOT whatsoever read in to the PE tables.
Cliff,
It takes C students to teach A & B students was one of the things I learned when obtaining my California Teaching Credential.
Pro
Joined: Mar 2013
Posts: 628
Likes: 13
From: Indiana
From what I've been told increasing the fuel pressure is for a better spray pattern. The ECM will just shorten the pulse width to compensate. The higher pressure will make for a finer spray and quicker response to changes. There is no reason under stock engines to increase beyond the recommended pressures. I replaced my regulator with two different new ones and both were on the low side so I bought an adjustable one and set it for factory max. Car is much more responsive to throttle changes now. The new one is an Areomotive. Solid billet, stainless spring, and direct replacement. $20.00 cheaper then the Holley and better construction. Here is a pic.
Burning Brakes
Joined: Jun 2000
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From: Auburn Michigan
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