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Adjustable Fuel pressure regulator question(s) by AL87
Started on: 08-14-2013 02:48 PM
Replies: 9 (802 views)
Last post by: fierogt28 on 08-21-2013 08:51 PM
AL87
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Report this Post08-14-2013 02:48 PM Click Here to See the Profile for AL87Click Here to Email AL87Send a Private Message to AL87Edit/Delete MessageReply w/QuoteDirect Link to This Post
okay on my 2.8 there is an adjustable fuel pressure regulator,
1st question: which way do I turn the adjustment screw on the top to increase/decrease pressure?

what would happen if the pressure was lower than stock? higher?
why would I want the pressure higher/lower?
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Arns85GT
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Report this Post08-14-2013 05:24 PM Click Here to See the Profile for Arns85GTClick Here to Email Arns85GTSend a Private Message to Arns85GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
It depends on the regulator. If it is a bypass Mallory, you screw the allen screw downward to increase.

If it is the Holley, I believe it is the same. The one on the car should be a 43.5 preset.

Hope this helps.

Arn
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Blacktree
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Report this Post08-14-2013 11:01 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Reducing fuel pressure will make the engine run leaner. More pressure will make it run richer. For all intents and purposes, you're changing the size of your injectors (more pressure = bigger, less pressure = smaller).
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AL87
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Report this Post08-14-2013 11:49 PM Click Here to See the Profile for AL87Click Here to Email AL87Send a Private Message to AL87Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Arns85GT:

It depends on the regulator. If it is a bypass Mallory, you screw the allen screw downward to increase.

If it is the Holley, I believe it is the same. The one on the car should be a 43.5 preset.

Hope this helps.

Arn


I cant tell the difference, it looks like a dome with a small bolt sticking out the top.

would I be able to read pressure at the rail, and adjust accordingly?
pressure is at 40 during idle.

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Blacktree
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Report this Post08-15-2013 12:39 AM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by AL87:

would I be able to read pressure at the rail, and adjust accordingly?

If you have a gauge, yes.
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trotterlg
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Report this Post08-15-2013 01:30 AM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
In is most always higher, but just increasing the pressure will not make it run richer, the computer looks at the mixture (via oxygen sensor) and adjusts the output pulse width of the injectors to get to it's programmed mixture. There is a fairly wide range of pressures that the computer can work with, higher pressures will allow the computer to keep the proper mixture at higher demands, but there is a limit. If your fuel pressure is within specs then you will end up with proper mixture control. Larry
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Blacktree
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Report this Post08-15-2013 10:03 AM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
In open loop mode and PE mode, the O2 sensor is ignored. Fuel pressure will affect fueling during these times.
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AL87
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Report this Post08-21-2013 01:07 PM Click Here to See the Profile for AL87Click Here to Email AL87Send a Private Message to AL87Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Blacktree:

In open loop mode and PE mode, the O2 sensor is ignored. Fuel pressure will affect fueling during these times.


it wouldn't be a good idea to put it into open loop and take it down the strip a few times, would it?

ALSO, doesn't the 2.8 start to run really rich at high rpm, because the intake cant supply?
wouldn't it be better to set the pressure lower in that aspect?

but then again, you said the O2 sensor makes the injectors compensate.
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fieroguru
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Report this Post08-21-2013 02:37 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by AL87:


it wouldn't be a good idea to put it into open loop and take it down the strip a few times, would it?

ALSO, doesn't the 2.8 start to run really rich at high rpm, because the intake cant supply?
wouldn't it be better to set the pressure lower in that aspect?

but then again, you said the O2 sensor makes the injectors compensate.


Back before ecm tuning was wide spread, after you did some mods you would adjust the fuel pressure to dial in the A/F ratio at WOT (which is also open loop), then let the O2 sensors and the built in BLM feature in the ecms try to keep everything else in check under all other conditions. Tuning is by far the best method, but the adjustable regulator was used as a crutch for quite some time.
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fierogt28
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Report this Post08-21-2013 08:51 PM Click Here to See the Profile for fierogt28Click Here to Email fierogt28Send a Private Message to fierogt28Edit/Delete MessageReply w/QuoteDirect Link to This Post
The only benifet of installing a fuel pressure regulator is if you are doing modifications to your
set-up. For normal driving, it does nothing. I have one on my 88s and a gauge to see the
pressure in real time. If you swap in a 3.4PR engine with fiero V6 components
maybe you may want to have one. Or a highly modded 2.8l with a turbo, etc.

It depends what you are doing. Day to day driving, keep the stock FPR.

------------------
fierogt28

88 GT, Loaded, 5-speed.
88 GT, 5-speed. Beechwood interior, All original.

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