RonD.

On my new to me 89 Turbo it came with a LR Adjustable FPR, fuel rail pressure gauge, LR Chip set all circa 2006. The rail gauge reads 40 psi warm idle with FPR vacuum line attached. Car runs very well AFR's on 17 psi WOT read slightly rich low 11's. Is the 40 psi at warm idle a typical +/- good number?

Darwantae951

Yes, 40psi is essentially 3 bar (43psi). Is this reading with the vacuum line disconnected?

RonD.

Reading is with vacuum line attached. I assume if I disconnect the vacuum line I would need to pinch it closed. What kind of reading should I be looking for?

Darwantae951

Which FPR is it? With the line disconnected you should adjust pressure for whatever the car is set up to run. Factory was 2.5 bar, and a common practice is to up pressure to 3bar to cover most moderate tunes. IDK what your car is set up to run, so don't take this as literal changes to make.

moalaska

Low 11s at 17psi seems pretty good to me. I'm assuming you are still on the barn door afm. Are you on stock injectors at that boost level? They will handle it but they will be at a high duty cycle in my opinion.

RonD.

Yes, stock air meter and injectors. Chip set requires either 3 Bar or Adjustable FPR. My rail gauge is at 40 psi warm idle with vacuum line on Adjustable FPR. Dave at LR feels low 11's is a little Fat, he prefers to see 11.6, suggested reducing fuel press. slightly (2 psi) and check the AFR's. What I didn't confirm was, and if it's necessary, to make the adjustment with the vacuum line attached or not?

Darwantae951

Your FPR should be set with the vacuum line disconnected (this is your base pressure setting before the regulator actually starts regulating after sensing vacuum/boost). Once you apply vacuum, it will adjust pressure in the rail so that you aren't running stupid rich under low/no load conditions (Idle/cruise/etc...). I shoot for 11.5-12:1 when under load.

RonD.

I just adjusted as per instruction. Warm idle vacuum line disconnected and pinched, gauge went from 40 to 46. Adjusted to 44. Now with vacuum gauge reads 38. Will do some cautious AFR testing tomorrow. Is 40 to 46 typical? The other thing I'm curious about is after turning off the engine the gauge went up to a hair above 40. Normal??

Darwantae951

What you're likely seeing is the equalization of rail and line pressure once the vacuum signal from the engine is gone and the FPR opens.