Adjustable Fuel Pressure Reg

[Bish400]

Had the chim on a rolling road last week for a health check and it came back with solid results however....

It ran a little lean across the whole rev range. The garage recommended fitting an adjustable FPR but there are so many to choose from.
What are the trusted/recommended brands?

TIA

[Classic Chim]

I hate to be negative on this so do get one that’s recommended as another TVR owner fitted an adj one and not cheap but it wouldn’t hold pressure and the car would run dangerously lean within 10 minutes of setting it.
I think he went for a constant 3 bar one in the end but I can’t be sure about that.

[Bish400]

Classic Chim said:

I hate to be negative on this so do get one that’s recommended as another TVR owner fitted an adj one and not cheap but it wouldn’t hold pressure and the car would run dangerously lean within 10 minutes of setting it.
I think he went for a constant 3 bar one in the end but I can’t be sure about that.

Nah that's a fair statement. I've spoken with a good friend who owns a motor sport company and had a good recommendation from him for a Deatschwerks FPR and gauge. I paid £150 with 20% off so I will report back once its fitted.

[spitfire4v8]

Did the garage actually measure your fuel pressure ? and if so did they correctly diagnose the regulator, or pump, or wiring to pump, or run any diagnostics on the ecu or anything else ?

[Bish400]

It was showing lean using their diagnostics, we also had RS-rv8 plugged in. Wiring is good as is the fuel pump.
The lean running was consistent across the rev range.
I will put a gauge on with the new reg but as for the pressure, every engine is different I guess so this will allow me to set it for the best results applicable to my engine as opposed a generic setting. I've looked through PH and the given pressures vary by 10psi.

[spitfire4v8]

cool as long as they've gone through a proper diagnosis then all ok.

[blitzracing]

Bish400 said:

It was showing lean using their diagnostics, we also had RS-rv8 plugged in. Wiring is good as is the fuel pump.
The lean running was consistent across the rev range.
I will put a gauge on with the new reg but as for the pressure, every engine is different I guess so this will allow me to set it for the best results applicable to my engine as opposed a generic setting. I've looked through PH and the given pressures vary by 10psi.

Umm... if the fuel pressure was low then you should be seeing lots on + add fuel trim in closed loop, to richen the mixture, followed by it going lean as it goes open loop when there is no feedback so Id expect a shift in AFR at that point. I do believe there is about a 20% correction value available. What did RS-RV8 tell you?

[Bish400]

Can't remember exactly what was going on with rs-rv8 as I've slept since but here's the printouts.

[spitfire4v8]

First off i doubt that engine revved to 6900rpm so they've not set their rpm correction on the dyno properly

Also it's initially so flatly clamped to lambda1 that it looks like the ecu never saw full throttle enrichment point.

Edited by spitfire4v8 on Thursday 1st April 12:43

[phazed]

^^^^^^^^^^^^

I agree with Joolz as he knows far more than me

Which Rolling Road did you use out of interest?







Edited because I don't know the difference between what and which ............

[blitzracing]

The issue you have if you do alter the fuel pressure is when do you know its correct and your AFR is OK? Are you going to do another rolling road session and tweak the pressure? You cant blindly adjust the pressure without measuring the results. I'd be trying another stock regulator to start with or at least checking the fuel rail pressure. It does not look like a fuel delivery problem as this shows up as the engine getting leaner as fuel demand goes up. You can use the stock lambda probes to verify if the issue is fixed, as Id expect 1.2 volts or more at WOT if you can fit a test meter with long leads for a passenger to read. Id expect the current voltage to be 0 as its leaner than lambda 1. Id also open up the ECU and just check whats written on the ECU chip, just in case someone has been in there before.

[Bish400]

Of course it will be going on the roller to set the FPR.

[spitfire4v8]

Further to this I would be stepping well away from the adjustable regulator to begin with .. as Blitz says you need to actually measure your current pressure at idle with intake vac pipe on and off , and under load to make sure you have no pressure issues at high fuel demand, or at least work out what your pressure issues are if you do.
You also need to get the ecu to see full throttle signal otherwise it will always show as weak under 4000rpm because the lambda feedback will clamp it to 14.7afr.

Only when you have ascertained that you have the fuel pressure correct with vac on and off (to prove the regulator is responding to intake vacuum) , and the full throttle enrichment engaged in the ecu, can you hope to get a real idea of what the mixture is actually doing.

This is all separate from the point that the dyno people don't seem to understand their own graphs... assuming of course you haven't built yourself a solid lifter screamer ..

It reminds me of a dyno shootout i went to near northampton one time .. beautiful garage with some stunning cars in, and dyno facility all spotless with people in lovely corporate clothes. First tvr on (a RV8 engine) and graph said the engine revved to something like 8000rpm .. The 3 garage workers all saw it and not one of them picked up on it. All the gear and no idea.

Edited by spitfire4v8 on Friday 2nd April 11:36

[davep]

We have seen evidence of TVR/R2967 tunes with a 7000+ RPM max rev limit set (8561 for Map 2 and 7183 for Map 5):



Why so high ... I don't know!