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Old 11-15-2006, 12:40 AM   #26
rob
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The cliff notes version: is it sounds like you are loosing fuel pressure and running lean at boost. Check the vacuum line to the FPR for cracks and to make sure it is plumbed AFTER the turbo. Check your FP install for a leaking pickup pipe.

Long detailed version:You are reading absolute fuel pressure in the fuel rail. That's what you see on the gauge. Injectors work based on the *differential* fuel pressure. There are two pressures working against each other; the rail fuel pressure on the top side of the injector and the manifold air pressure on the other side. Differential pressure is the difference; rail pressure - manifold pressure.

Think of it this way, if you are reading 20psi fuel pressure in the rail, but your manifold pressure is 20psi as well, when your injectors open, nothing would happen. No squirt.

The job of the fuel pressure regulator is to move the rail pressure up and down in correspondance with the manifold pressure and keep the differential pressure constant.

If your reading 40psi at idle, then you subtract your manifold vacuum (-10psi as a fair guess). Your injectors see 50psi differential pressure;(40 - (-10)), . Now you boost up to 15psi and your fuel gauge now says 50psi that means your injectors are now seeing 35psi differential fuel pressure; (50 - 15).
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Last edited by rob; 11-15-2006 at 12:45 AM.
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Old 11-15-2006, 09:46 AM   #27
Jaxx
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Quote:
Originally Posted by rob View Post
If your reading 33psi at idle, then you add your manifold vacuum (-10psi as a fair guess). Your injectors shold see 43psi differential pressure;(33 +10), . Now you boost up to 15psi and your fuel gauge should say 58psi your injectors should now see 43psi of differential fuel pressure; .
fixed?

the stock FPR is 43psi/3bar that is always what the differnential pressure should always be


or is it a 2.5 bar
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Old 11-15-2006, 11:04 AM   #28
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Thanks guys, we will check this out.
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Old 11-15-2006, 12:28 PM   #29
rob
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Quote:
Originally Posted by Jaxx View Post
fixed?

the stock FPR is 43psi/3bar that is always what the differnential pressure should always be


or is it a 2.5 bar

He said at idle he sees 40psi on his fuel gauge. I used his numbers.

-Rob
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Old 11-15-2006, 03:28 PM   #30
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How lean is too lean? I am seeing with my LM-1 around 11:1 and enrichened it all the way to 9.7:1. There was no change in the hesitation.
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Old 11-17-2006, 02:13 PM   #31
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So we tried:
swap the MAP - nope
swap the ignitor and coil pack - nope
swap the pickup assembly and fuel pump - nope
changed the vacuum line to the FPR - nope

Next,
change the FPR
get injectors cleaned and tested
change fuel tank as the current has a dent under the pickup
check the wiring harnesses for damage
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Old 11-17-2006, 02:37 PM   #32
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This seems too simple to be this complicated. If your plugs were sooty when you pulled them then nothing should be running lean. And Kalder says he is reading below 11:1 which is nowhere close to lean that would cause this sort of lack in power.

My guess is still plug gap and/or fuel cut do to MAP signal. (Not saying the MAP sensor is bad, but maybe the signal is spiking).

On my ej20g I have to gap down to 0.025 to keep a spark at full boost/timing.
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Old 11-17-2006, 03:12 PM   #33
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I am going to try a different bcs and recheck gap. I don't get fuel cut at the map that I am seeing. I can go to 250 kpa and it starts to act up around 180 kpa. I have someone close with a legacy turbo that I can swap out stuff or I am going to do the GM swap. Hopefully this weekend while I swap exhaust.
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Old 11-17-2006, 03:29 PM   #34
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besides injectors and FPR my entire fuel system is brand new. mine still hesitates. so fuel system as a whole is not it.

--keith
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Old 11-17-2006, 10:33 PM   #35
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I am thinking it is some kind of signal problem. It was all good one day and crap the next. All the remaining sensors should either give a CEL or run like crap all of the time.
It wasn't sensitive to plug gap before and I used to have them gapped much wider.
The FPR may be it though.
I won't be getting back to this thing for a couple of weeks. Fricking Subaru!
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Old 11-19-2006, 12:42 AM   #36
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add one to the list, my car does this too. AND i also have a FMU.

but im aftermarket forced induction. anyone replace the MAF sensor, thats what I think is the culprit. Or running 80+ psi of fuel pressure borked my fuel system.
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Old 11-19-2006, 11:59 AM   #37
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LoL. well i have a similar problem as well, cutting out at anything over 1bar(im running a PFC). and it seems that at night when its colder it does it worst then during the day when its warmer. Im going to check all my coils again, and then take out my iridium NGK 6's and put in normal NGK 7's. as well as set my gap to .025, do a cyl. pressure test. Hope i can find the problem.
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Old 11-19-2006, 08:46 PM   #38
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turboL
It wasn't the MAF on mine. I tried that.
Snowman
I am using NGK 7's and tried 3 different coilpacks.
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Old 11-20-2006, 11:28 AM   #39
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SO usually my ej18t would do this at around 15psi. I THINK my headgasket is bad, but now im rethinking that. Last night I ran 13psi fine. It had a few hiccupps around 4500 (where it hits peak booost), but other than that its fine. Ill be installing bigger injectors, a bigger turbo, and a new headgasket soon. maybe that will help things lol
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Old 12-04-2006, 10:19 AM   #40
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Turns out that the induction pipe into the turbo was borked. All good for now.
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Old 12-04-2006, 12:56 PM   #41
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did you order the silicone one?
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Old 12-04-2006, 01:18 PM   #42
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Not yet, my mechanic put together a WRX pipe for now. I will check out the link you gave in the other thread.
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Old 12-04-2006, 06:27 PM   #43
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so the maf wasnt getting the rights flow metering because air was being injested after it? My maf sensor is in my FMIC piping....maybe it needs a cleaning. I also think my coolant temp sensor is borked.
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Old 12-05-2006, 03:06 PM   #44
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hooray! an early christmas present from the NASIOC community! thanks guys!

--keith
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Old 12-05-2006, 06:52 PM   #45
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so i tried burping the system last night, didnt work. Car does not overheat, but the coolant overflow bubbles and gets high. I am out of ideas, it has to be the headgasket.
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Old 12-05-2006, 10:26 PM   #46
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Take out your plugs and see if there is water(coolant) on them, do a cyl leak down test. look to see if there is oil in the coolant. sense the oil system runs higher pressure then water, there would be oil in it.

Kirill
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Old 12-05-2006, 10:38 PM   #47
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i compression tested it and the numbers came back ok. the plugs all looked decent. I think i need one step colder plugs and to install my sti injectors.


i still think there is a TON of air in the system
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Old 12-06-2006, 09:29 AM   #48
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it took four times to bleed air out of my coolant system when starting the swap for the first time this june. it's definately harder than a 240sx with a bleed plug in the top of the system! i just kept running it and filling it up when it got low. this was like an hour long process altogether.

--keith
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Old 12-06-2006, 09:37 AM   #49
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ugh i am not looking forward to doing this. What if I disconnect one of my long coolant lines going to my turbo and hold it above the engine. Will that help get all of the air out.
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Old 12-06-2006, 09:54 AM   #50
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i think you'd need a flow of coolant to push the air up there. say if you had a hose horizontal and pushed up in the middle of it creating a high spot inside, the air would get trapped in there. at which point you need to bleed it out like poking with a pin. but not possible(poking the hose with anything is bad mmkay).

i think the air would still be in there(maybe less air) if you just held it up in the air to bleed. im not 100% sure. it can have an air bubble in a place you cannot move or manipulate at all either. i was thinking jack up the front of your car and use the rad opening if you got one. but the top mount filler on my JDM STi is def the high spot in the system so that'd be my opening. but that may move the bubble around.

good luck!

--keith
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