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Old 05-30-2003, 05:44 PM   #1
sasha143aid
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Default fuel pressure regulator

I recently purchased an adjustable fuel pressure regulator and am planning to install it this weekend. Does anybody know what I should set it to for optimum performance. My mods include weapon-r intake with cold ram air package, borla headers, 2.25 rallispec catback and I'm also installing Mr. Josh's crank pulley. Any info would be great. Thanks
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Old 05-31-2003, 09:45 AM   #2
joefocker20
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I seriously doubt that you need one with the mods that you have. I have a Ganzflow CAI, K&N Filter, LW Crank Pulley, Borla Headers, trackpipe, Stromung Catback, PROECM, and a Exedy Clutch and 13lb flywheel is going on my car today and my car still needs no additional fuel yet. I think the only way that you need to up the fuel pressure N/A is if you do a serious build-up like Dan did.
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Old 05-31-2003, 02:09 PM   #3
sasha143aid
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The reason I want to install the regulator is because i'm running rich due to the intake. I wanted to lean it out a little bit
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Old 06-06-2003, 10:25 PM   #4
Legacy777
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Leaning out the car by fuel pressure is not the answer.

Doing so would be an archaich form of a/f controls.

I just got done with a week long combustion characteristics class for huge industrial engines. Adjusting fuel pressure is the worst way to balance adjust a/f ratios.
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Old 06-09-2003, 12:53 PM   #5
sasha143aid
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What then should I do if not with the fuel regulator? I figured if somebody would know the perfect setting to have our cars at, it would solve my problem
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Old 06-09-2003, 06:59 PM   #6
Legacy777
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Look at what you did to cause the car to run rich. You added an intake. That changed how the ECU interpretted the signal from the MAF.

Rather then change/fix a symptom, fix the cause, which in this case would be the intake track.

Either put the stock box back on, or get some sort of controller to alter your a/f settings, like the s-afc.

I know it's probably a more costly solution, but it should work better. Still no guarantee the settings and such will stay due to the ECU learning, or so I've been told by people running the s-afc.
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Old 06-10-2003, 11:09 AM   #7
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First off, I am not trying to disagree with what you are saying.

But...

if altering the fuel pressure is such a bad way to control your AF ratio, why does everyone use it for their turbo cars?

I can understand that every injector has a max operating pressure, and a min operating pressure. If you dropped the fuel pressure enough to prevent the injector from working then that would be bad, but would dropping the fuel pressure a couple of PSI really make that much difference?

I know you said you took a class that dealt with this. Can you tell me in 10 words of less why its such a bad thing to do?

Thanks.

J
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Old 06-10-2003, 11:56 AM   #8
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So what makes you think your running to rich? You have a map sensor not maf sensor.

Changing fuel pressure (leaner) isn't to bad as long as you have a EGT gauge(even NA). Running higher fuel pressures (turbo car) put a higher strain on the injectors, but the stock bosch units are well up to the task.

If your new FPR happens to be a Mallpassi( ), send it back and shell out a little more money on a higher quality unit.
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Old 06-10-2003, 06:43 PM   #9
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Quote:
Originally posted by jeffg
if altering the fuel pressure is such a bad way to control your AF ratio, why does everyone use it for their turbo cars?
I wouldn't really qualify that as adjusting/controlling your a/f ratio.

Most of the time I hear about upgrading fpr's is when you've up'd the boost or added a turbo kit. In both cases, you engine is wanting more fuel then the original fuel pump/regulator was designed to handle.

If you use a 2:1 or 4:1 rrfpr or larger pump, you are just supplying more fuel to the injectors. The injectors control the amount of fuel going in.


Yes you can alter pressures to affect how much fuel actually flows through the injector, but it is a very inefficient way to do things, and the computer will most likely adjust around it, by getting readings from the O2 sensor.

The ECM controls the a/f ratio. If you drop pressure going to the injector in an effort to supply less fuel, the ECM will see there is less HC & CO (which are direct results of fuel) and increase the injector duty cylce to compensate for the lower pressure and get things back to the "preset map" If you adjust pressure again, ECM will adjust and you end up in a loop until you've run out of fuel pressure to adjust, or the ECM can no longer increase injector duty cylce.

The computers in our cars are pretty damn sophisticated. Yes their maps may not be tuned for max performance, but they do learn and can adjust. If the car is running excessively rich by adding an intake.....you've simply corrupted the data it uses to adjust a/f ratios, etc. The proper way to fix things is to fix the data, or the cause of the problem, not the symptom.

I know that's not 10 words or less.....sorry.
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Old 06-11-2003, 11:02 AM   #10
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I would agree that the ECM would probably try to compensate for this, and it might make it tricky to get the settings to stick around for more than a few days.

I would agree the best way to handle this would be to alter the ECM, but that is expensive (not so much now that they can remap the stock box).

A lot of people have complained that the ECM has learned around their SAFC's as well. This would mean that altering the airflow meter signal would not work either.

It seems like the best way to control this would be to alter the O2 sensor feedback signal. Since the ECM uses this signal to determine how well the map is doing. Of course I dont know of anything that would do that for us.

J

PS, sasha143aid, call Cobb Tuning or one of the other shops that can remap your ECU and have them retune the car.
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Old 06-11-2003, 05:57 PM   #11
sasha143aid
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So is it safe to say that the purchase of the regulator was a waste of money then? If so, then that's upsetting
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Old 06-11-2003, 06:37 PM   #12
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If you don't want it, I might take it off your hands...
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Old 06-11-2003, 06:48 PM   #13
Legacy777
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Quote:
Originally posted by sasha143aid
So is it safe to say that the purchase of the regulator was a waste of money then? If so, then that's upsetting
Unless you got plans for an aftermarket turbo......then yeah....I don't see it doing you much good.
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Old 06-11-2003, 09:23 PM   #14
Kevin Thomas
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Default Re: fuel pressure regulator

Quote:
Originally posted by sasha143aid
I recently purchased an adjustable fuel pressure regulator and am planning to install it this weekend. Does anybody know what I should set it to for optimum performance.

If you had an EGT gauge, I would say set it so that your EGT doesn't go over 1550F at WOT in 3rd or 4th gear. If you had an air/fuel ratio meter/gauge, I say set it so that your car does not go lean at WOT. If digital, I'd say set it so that your car doesn't go under .86 voltage.

I wish I could give you a simple answer but in order for you to set your fuel pressure regulator for optimum performance, you have to have something to gauge your before and after results. Track time, EGT gauge, air/fuel ratio gauge, etc. We don't know if you are running to rich or to lean so we can not simply say set it at so and so psi.

If you must get a suggestion right now, I'd say leave it set so that you have your stock fuel pressure. *Yeah right* Ok, take it to the track and test out your 1/4 mile times with your fuel pressure regulator set at different settings. *Not advised* Your results will vary. Take care!
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Old 06-12-2003, 09:31 AM   #15
sasha143aid
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It seems by what I've read, my information thread will be converted into a sale thread. Thanks to everybody for the info. Obviously I wish it was more optimistic but at least I'll save myself time and hectic trying to install it since I don't need to.
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