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Old 04-05-2008, 12:21 AM   #1
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Default Stock FPR

I am wondering if I can leave the fpr connected to vacuum with my turbo on the car. It's at around 5 psi and the previous owner unplugged the regulator and left it open to atmospheric pressure. If I reintroduce it to a vacuum line and go into boost will the fpr be able to handle it? I've heard of diaphragms going crappy under boost and don't want that to happen.
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Old 04-05-2008, 12:23 AM   #2
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Shouldn't be a problem.
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Old 04-05-2008, 12:24 AM   #3
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oh btw it's a 1.6L with 209 000 km or 130 000 mi
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Old 04-05-2008, 01:15 AM   #4
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The fuel pressure regulator works to maintain a certain fuel pressure relative to manifold pressure. Flow is based on deltaP. It seems to me that by removing it's vacuum/pressure signal, it can no longer function as intended. I haven't heard of positive pressure being a problem for the FPR. Maybe somebody with more experience will chime in.
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Old 04-05-2008, 01:16 AM   #5
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well when removing vacuum and submitting it to atmospheric pressure it's basically like simulating WOT or wide open throttle to the regulator.
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Old 04-05-2008, 01:23 AM   #6
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Quote:
Originally Posted by momo182 View Post
well when removing vacuum and submitting it to atmospheric pressure it's basically like simulating WOT or wide open throttle to the regulator.
True for an N/A car. But now the FPR thinks at all times the manifold is at atmospheric pressure, so it is increasing the absolute fuel pressure to keep deltaP constant. However, your manifold at idle is not atmospheric, so actual deltaP is larger and more fuel will be injected. I'm not sure how much it is making a difference.

For a turbo car, WOT is generally not 0 psig, but rather whatever boost pressure you are running.

I suppose this all doesn't matter much if you have a standalone ECU because you can just tune the fuel map to compensate for the different fuel pressure.
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Old 04-05-2008, 03:04 AM   #7
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The stock fpr acts like a 1:1 fmu under boost.
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Old 04-05-2008, 03:13 AM   #8
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Wait... The previous owner disconnected the vacuum line to the stock FPR? Reconnect that bitch! The stock FPR's job is to maintain a constant pressure differential across the injectors. It has no problem at all with seeing boost.
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Old 04-05-2008, 12:00 PM   #9
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It has no problem at all with seeing boost.
That's what I wanted to hear Thanks.
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Old 04-05-2008, 12:32 PM   #10
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Mine is living a happy life at 12 psi... don't see a reason why 5 psi would bother one.
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Old 04-05-2008, 12:57 PM   #11
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Had one crap out at 10 psi a couple of years back. Probably unrelated to boost, but it did have 200K miles on it.
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Old 04-05-2008, 01:20 PM   #12
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I know someone that had the FPR go bad on a non-boosted 97. Drove him nuts trying to find the problem since no one though of the FPR on a NA car.
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Old 04-05-2008, 01:25 PM   #13
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Quote:
Originally Posted by 04 Miata View Post
I know someone that had the FPR go bad on a non-boosted 97. Drove him nuts trying to find the problem since no one though of the FPR on a NA car.
Funny... that's one of the first things I usually check. I had 2 go bad on my cavalier, 1 on my brothers camaro, and 1 on the wife's taurus. I always suspect the FPR first.
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Old 04-05-2008, 02:23 PM   #14
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Quote:
I know someone that had the FPR go bad on a non-boosted 97. Drove him nuts trying to find the problem since no one though of the FPR on a NA car.
Quote:
Funny... that's one of the first things I usually check. I had 2 go bad on my cavalier, 1 on my brothers camaro, and 1 on the wife's taurus. I always suspect the FPR first.
I can't remember offhand what the symptoms were when mine went out, but yeah, it was PITA. I picked up an extra one at one point because it's such an easy part to switch out to diagnose first, compared to checking everything else out in the fuel system.
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Old 04-05-2008, 02:31 PM   #15
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IIRC this guy had bad idle, a stumble on acceleration and bad fuel mileage.
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Old 05-10-2011, 06:29 PM   #16
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Back from the death:

On 1.8s there is an actuator between the FPR signal line and the intake manifold.
What does everyone do on a MSPNP boosted car? Just remove it and connect FPR to intake manifold directly?
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Old 05-24-2011, 01:08 AM   #17
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Just install a one way valve, whatever it is called. I got gazillions of those everytime I go to the junkyard I grab a handful from turbo Volvos, Saabs, RX7s.

In fact back from the dead.
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