I need to know what the part number is for the fuel pressure regulator that a few people have put on there 3.4 conversions. Or any Stock Fiero Fuel Rail. I have one of Watt's fuel pressure guages on my car and did some testing last night my fuel pressure is about 38psi at warm idle and 48psi with the vaccumm line removed from it. I need to drop the pressure down to about 30 at idle cause I am running the 19# injectors on my car. I know that Fiero Sound has an awsome one.
------------------ David 85GT
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09:30 AM
PFF
System Bot
coinball Member
Posts: 1526 From: Raleigh, NC, USA Registered: Apr 2002
where can i get "Watt's fuel pressure gauge" at? thanks.
------------------ Eric '87 GT 5-speed Gold/Tan 75,000 as of 5/6/02
Work in progess-getting ready for 3800 series 2 SC swap. items left to get: 1.Held Sport Front suspension 2.Held rear coilover kit 3. 10.25" brake swap
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09:42 AM
Capt Fiero Member
Posts: 7657 From: British Columbia, Canada Registered: Feb 2000
I think he was selling them in the mall area of the site, his email is watts@dccnet.com if he does not post a pic I will when I get home tonight. (at work right now)
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10:29 AM
Jun 20th, 2002
Capt Fiero Member
Posts: 7657 From: British Columbia, Canada Registered: Feb 2000
Here is a pic of the new fuel pressure regulator. I could had a cast one that did not look as nice and did not have a big wheel on the top for easy tunning, for 20$ less. But I wanted one that I could reach under the plenuim and adjust at any moment.
------------------ David 85GT
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09:41 PM
Capt Fiero Member
Posts: 7657 From: British Columbia, Canada Registered: Feb 2000
It works awsome, I read the same thing about not going below 35 with it, but I can set this thing to 20 if I want when at idle. That is the only time I want it to go low is for idle.
------------------ David hotrodfiero@shaw.ca 85GT 2.9 4spd
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07:39 PM
Jul 5th, 2002
Rick johnson Member
Posts: 30 From: Torrance, Ca. 90503 Registered: May 2002
You really cant adjust for high pressure, it is runs about 15-18psi higher when vaccume is removed. I have it set for about 28psi right now, and when I remove the vaccume line, it shoots up to about 45-46psi. If I were to run it at 40psi I would get like 56psi when vaccume is removed.
------------------ David hotrodfiero@shaw.ca 85GT 2.9 4spd
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05:10 PM
Howard_Sacks Member
Posts: 1871 From: Cherry Hill, NJ Registered: Apr 2001
Originally posted by Capt Fiero: I need to know what the part number is for the fuel pressure regulator that a few people have put on there 3.4 conversions. Or any Stock Fiero Fuel Rail. I have one of Watt's fuel pressure guages on my car and did some testing last night my fuel pressure is about 38psi at warm idle and 48psi with the vaccumm line removed from it. I need to drop the pressure down to about 30 at idle cause I am running the 19# injectors on my car. I know that Fiero Sound has an awsome one.
As I understand it the idle and part throttle injector settings are determined by the computer in response to O2 sensor inputs. The ECM then self learns and modifies it's internal map to compensate for slightly different fuel pressure settings allowing the engine to run well under all part throttle conditions. I know that another mfg's ECM has a fixed map for wide open throttle settings. If our Fiero V6 also has this fixed map, we should be able to change our WOT richness using the fuel pressure regulator.
So my thought would be to set the pressure regulator for the WOT richness we desire and then let the ECM self learn the part throttle settings based on the O2 sensor.
Does anyone truly understand the ECM operation - is my assessment correct for the Fiero ??
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05:33 PM
Capt Fiero Member
Posts: 7657 From: British Columbia, Canada Registered: Feb 2000
Was the car running cleanly before you put the regulator on? I have 19#s on mine and it's backfiring and shooting flames out the exhaust.
See my post also in tech . . .
The car had been running very rich, stinging eyes rich at idle before I installed the regulator as well as a bog at low RPM's. It just did not feel crisp. I guess I was just running too much fuel. Everyone says that the computer will compensate for some of it, but it just could not do enough. Especially seeing as the stock regulator was designed with stock vaccume and my engine does produce less vacume at idle.
The one I have is Holley P# 512-501
------------------ David hotrodfiero@shaw.ca 85GT 2.9 4spd
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05:41 PM
Rick johnson Member
Posts: 30 From: Torrance, Ca. 90503 Registered: May 2002
I am sure that lowering the presure is your cure. My concern is conceivably you could lean it so far that the ECM might richen the mixture at idle and part throtle but it might be too lean at WOT because cars generally run open loop - no help from the O2 sensor - at WOT (I do not know for sure but I would want to monitor my air fuel ratio somehow to confirm WOT)
It would be nice to grt info from someone who has successfully used oversize injectors.
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09:21 PM
Capt Fiero Member
Posts: 7657 From: British Columbia, Canada Registered: Feb 2000
I know where you are comming from, I have been trying to get an Air/Fuel Gauge for some time now. I even paid a friend to build me one but he has not had the time to finish it. I may just go out and buy a new one from one of the local hot rod shops.
As for the injectors, The only reason I am running large injectors at low pressure rather than small injectors at high pressure is that "I AM" going add more stuff to this motor that will need larger injectors. As soon as funds permit, I will get a NOS or a turbo or both and make this car fly.
------------------ David hotrodfiero@shaw.ca 85GT 2.9 4spd
The reason that a larger injector does not work all that well at idle is that the ECM has a minumum pulse width set in code. IOW, it will try to adjust the pulse width at idle to obtain a decent mixture, but can only narrow the pulse so far.
Problems also result upon the transition to power enrichment mode, since the BLM is so far out from optimum that there is an abrupt change, which usually causes some hesitation. And of course at WOT the ECM enters an open loop mode which uses the inj pulse widths specified by the fuel maps, so an extremely rich condition occurs.
I suggest obtaining a scanner, and then adjusting the fuel pressure until you achieve a BLM of 128 at idle.
Anyone serious about Fiero performance should have a scanner in their toolbox. The cheaper handheld scanners can be found for around $160. A laptop based equivalent can be put together for much less, if you already have the laptop.
Seem to remember someone around here offering ALDL interface cables for around $10, the software can be obtained for free.
Lots of very useful information can be obtained without ever moving the car, so that 486 desktop computer gathering dust in the closet (or the one you are using to read this message) can now take upon the much more valuable role of "garage appliance".
[This message has been edited by 00lE (edited 07-06-2002).]
I could had a cast one that did not look as nice and did not have a big wheel on the top for easy tunning, for 20$ less. But I wanted one that I could reach under the plenuim and adjust at any moment. 
