Problem Identified? (P0172)

[Captain KRM P5]

any ideas what idle setting should give me ample fuel pressure at 6.5psi of boost?

remove the vacuum line from the RRFPR and clamp that end off. using the TOP screw set your base fuel pressure to 50 psi. when you reattach the hose it should drop to about 35 to 40 psi. under full boost at 6.5 psi should need no more than 75 to 80 psi of fuel. you adjust that with the bronze/gold trim knob. 100 psi is way too much gas and i imagine your gauge does not even go past 100 and is just topping out.

 

[Matthew]

i cant remember, the bronze knob is turned all the way clockwise = more or less fuel ?

i will reduce pressure to 40psiish tonight at idle just to satisfy curiousity.

 

[Captain KRM P5]

i cant remember, the bronze knob is turned all the way clockwise = more or less fuel ?

i will reduce pressure to 40psiish tonight at idle just to satisfy curiousity.

it is turned all the way in? lol your gas mileage should be in the toilet you loosen that knob to reduce your rate of fuel pressure gain not the base pressure, etc

 

[Matthew]

yes yes yes i know that, im just trying to remember which way you turn the knob to reduce top pressure.

or wait, youre saying that knob doesnt change the amount of fuel at 6.5psi WOT, just how quickly it gets there?

bear with me, its been quite awhile sinc ei farted with it.

 

[Captain KRM P5]

yes yes yes i know that, im just trying to remember which way you turn the knob to reduce top pressure.

or wait, youre saying that knob doesnt change the amount of fuel at 6.5psi WOT, just how quickly it gets there?

bear with me, its been quite awhile sinc ei farted with it.

i am not trying to treat you like an idiot man i am just used to people screwing this up.

the top screw on the RRFPR sets your base pressure. you set that by removing the vacuum line from the RRFPR, leaving it on the car and clamping it shut. using an alan key / hex key you set that to 50 psi. reconnecting the hose will cause your pressure to drop from 50 to about 35 to 40 on a stock fuel pump. the copper set knob sets the rate of gain, think exponentially. fuel pressure will increase proportianal to boost pressure based on how far in or out that knob is set. so it will add X pressure of fuel for Y pressure of boost if that makes sense. the knob sets X, so to speak. you want to loosen that knob so that pressure at full boost is about 75 psi. you are probably well over 100.

 

[Matthew]

check this out. i lowered my pressure to about 40-42 (you know how that thing changes once its warmed up and driven, temp, etc), and still at 6.5psi i am 100psi of fuel.. ill hav eto tinker with it, but i can only imagine what my fuel press was at.

 

[Captain KRM P5]

check this out. i lowered my pressure to about 40-42 (you know how that thing changes once its warmed up and driven, temp, etc), and still at 6.5psi i am 100psi of fuel.. ill hav eto tinker with it, but i can only imagine what my fuel press was at.

the pump can probably put out over 125 psi of fuel if it is anything like the pierberg

 

[Matthew]

but at 40psi idle it should go that high? maybe just turn the knob?

 

[Captain KRM P5]

but at 40psi idle it should go that high? maybe just turn the knob?

your base idle pressure is just that - pressure at idle. the copper knob is what adjusts how much fuel is added when you start adding boost.

 

[Matthew]

turn it CW or CCW? interesting. maybe its getting the 0172 code because the base pressure is so mcuh. but i thought that to get the most of your pressure you had to up your base press? so dropping down about 15psi should improve my gas milage, no?

 

[Captain KRM P5]

turn it CW or CCW? interesting. maybe its getting the 0172 code because the base pressure is so mcuh. but i thought that to get the most of your pressure you had to up your base press? so dropping down about 15psi should improve my gas milage, no?

the tighter the copper knob, the richer the FPR will run. lefty loosey righty tighty...

base pressure should be set at 50 with the hose off, 35 to 40 with the hose on. no more, no less. set that with the hex key up top, tighten the little nut around it and leave it alone. you do not alter your base pressure once that is set. all tuning after that is done with the copper knob.

 

[Matthew]

got it, ill work with it this week (i dont drive much)

 

[Captain KRM P5]

got it, ill work with it this week (i dont drive much)

basically : top screw; set it and forget it. your fuel pressure in boost is tuned with the copper knob. thats what you will tune with. period.

 

[Matthew]

ill lean it out before i leave for work tommorrow. i was misinformed the first time i got one i guess.

 

[Mr. Win]

When you ask why now matt its like i told you before... all that time of high psi you may have f-ed your injectors. Causing them to stick open thus you get the rich code. Try tunning like ken stated and it may cure your problem. It could very well be that the code is whats causing the ecu to pull fuel.

 

[Matthew]

i think its like a vicous circle, so ill try to lower the fuel pressure (i was given bad info on how to set it up the first time) and see what gives.

 

[Keith]

Okay, I'm back from vacation. Sounds as if you made some decent progress between the time you pinged me and now.

If your base fuel pressure was set too high, it means that your car would be running rich all the time. The ECU would be able to compensate for this in closed-loop operation which is why you saw the 14.7 cruise numbers. But even then, it would cause a code over time because it was having to compensate. It's found a problem and it's trying to tell you about it, exactly as it is supposed to do.

If you have access to an OBD-II scanner that will show you long-term fuel trim you'll probably find it's a relatively large negative number. That's the result of the ECU having to deal with a consistently rich condition.

With your base pressure down where it belongs you might find that you have better driveability.

Keith
Flyin' Miata

 

[crayz_d]

Stock ECU + Turbo Kit = Fuel Problems

MPI, Microtech, Haltech, whatever, just get one.

I ran my first turbo setup with an MSD Inline Fuel Pump and a Aerodyne RRFPR, no clamps though. On the dyno the ECU would run it lean at 14.7 until it hit open loop. The place that tuned it on the dyno (www.dynocomp.com) said that 14.7 is WAY TOO LEAN for a turbo setup on any car, so they set it up to go to 10.8 on open loop. All I can say is I went in with 121 WHP and came out with 168 WHP just from tuning the fuel system. They also suggested getting an EMS. I forked out the money to get the MPI with my new setup, and yea it's debt, but it will be worth it.

Just some background on DynoComp, the owner, Rich, who tuned my car has a 540 WHP STI that he built and races. In the shop that day they were working on an R32 Skyline, 2 R32 Golf's, an Audi S4 rally car, and a 911 Carrera Turbo. This guy knew his stuff and the results speak for themselves.

Without some kind of EMS computer our Protege's do not boost well or safely. Rich said that if I ran my car too hard with the ECU at 14.7 I was GUARANTEED to blow the motor, he said it is just a ticking time bomb at that point.

 

[Captain KRM P5]

Stock ECU + Turbo Kit = Fuel Problems

MPI, Microtech, Haltech, whatever, just get one.

Without some kind of EMS computer our Protege's do not boost well or safely. Rich said that if I ran my car too hard with the ECU at 14.7 I was GUARANTEED to blow the motor, he said it is just a ticking time bomb at that point.

this is false false false. i and several others have driven FMU and RRFPR setups with no problems. I drove with an RRFPR and voltage clamp for over 30,000 miles. Not even with an inline pump for most of that. If the setup is done right and tuned right, an RRFPR is fine on this car.

i used an AEM wbo2 and found that RRFPR held constant and smooth 11:1 or 12:1 ratios under all ranges of boost.

 

[crayz_d]

this is false false false. i and several others have driven FMU and RRFPR setups with no problems. I drove with an RRFPR and voltage clamp for over 30,000 miles. Not even with an inline pump for most of that. If the setup is done right and tuned right, an RRFPR is fine on this car.

i used an AEM wbo2 and found that RRFPR held constant and smooth 11:1 or 12:1 ratios under all ranges of boost.

I am not saying you can't. I even said in my post that I saw a 47 WHP gain from having my RRFPR/Inline Pump setup tuned right. An I wasn't having any problems with mine either, there is just the potential for future problems because you can't tune enough of the car's fuel system and timing, etc with just a RRFPR a Pump and some clamps. You are limited. You get a lot more gains with proper tuning, as you said, you just can't tune as much, as accuratly and consistently without an EMS. That is all I was trying to say, not that the setup won't work.

I've had that setup on my car, I know it works. It is just limiting.

Just my $0.02, not trying to flame or anything, just offering my experiance with my Protege5.