FPR overrun?

Artago · Mar 7, 2011

Hi all,

I have a Walbro 190 (not rewired yet), FIC 750s, DSMlink, and a stock FPR with 240,000 km on it.

Part throttle cruising I get a backfire from the exhaust between shifts audible pop). Also, it goes rich under WOT. Like 9.5 AFRs

Could I be overrunning the FPR?
Is there a way to check the base fuel pressure using DSMlink?

I'd grab a gauge to measure it but that would require me building a test harness. At that point I'd just get a FuelLab AFPR and call it a day. So I'm just looking for some advice on an EASY way to check the FPR system.

Any advice?

Thanks, Tom.

Jafro · Mar 7, 2011

That setup should work fine.

Pull the vac line off the regulator and see if there's fuel in the hose or pouring out of it.

9!'clipseDOHC · Mar 7, 2011

You shouldn't be overrunning it. It's probably something in the tune, not the regulator. You can turn the fuel pump on with link but you would still need a gauge to see what the pressure is.

donniekak · Mar 7, 2011

It's the tune. A fpr doesn't over run at wot. If your idle was rich, and everything else was dead on, then maybe.

Artago · Mar 8, 2011

donniekak said:
It's the tune. A fpr doesn't over run at wot. If your idle was rich, and everything else was dead on, then maybe.

Idle is spot on at 14.7 AFR. It goes rich during WOT.

The backfire happens under normal driving between shifts. It's a loud pop. I'm guessing I'm shooting flames

9!'clipseDOHC said:
You shouldn't be overrunning it. It's probably something in the tune, not the regulator. You can turn the fuel pump on with link but you would still need a gauge to see what the pressure is.

Tune is pretty much stock. 750s are set to 330ms dead time and 40% global fuel.

Also, during idle I can hear a bit of a garble from the exhaust every few seconds. Just a little hiccup.

I'll make a video and post a log.

bastarddsm · Mar 8, 2011

FPR overrun will hardly cause issues. It will cause a skewed low throttle fuel trim. Remember that the extra flow comes as the sqrt of the ratio of (over run psi / ecu expected psi). Usually its less than 10%, which will skew your trim 10%.

Its really not that big of a deal. A small boost leak has more of a detrimental effect on the entire fuel map than a slightly overrun FPR.

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FPR overrun?

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