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Discussion Starter · #1 ·
Hi guys,

Basically cutting the story short I have my LET phase 2, set blacktop FSE to 3.5bar using the mini gauge that sits on the front of it, did this without the engine running.

Plug everything in and start her up, she revs up to 1.5 and revs die back as they should... then it stalls. This will happen everytime, no ECU codes.

I did however find out that turning the FSE up to anything between 3.0 and 3.5 bar bar with the engine RUNNING she runs fine! This is cold, when she gets warm you can turn it down to 2.0-2.5 and it will idle and rev fine (have been told that the fuel pressure should be about 2.0-2.5 bar idling normally).

With the engine hot I did reset the FPR to 3.5 bar without running, it does start and run but the gauge reads about 1.6 bar which is low right?

I have changed the CTS and ATS to no effect (Thought these might have been causing the ECU to think the coolant or air is hot and not increase the fuelling to compensate for the cold engine).

Back to the FPR, is it possible the gauge is a lying sack'o'cack and giving me the wrong readings?

My next plan of action is to eliminate them totally by putting the standard 3.0 bar FPR back on and reverting to standard chips and see what happens, but before I do that tomorrow is there any ideas or info you guys might have on this?

PS I can't find any vacuum leaks, infact the boost gauge reads a healthy level of vacuum.

John.
 

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Discussion Starter · #3 ·
see I have been told by a few peeps there is about 2.5 ish under vacuum, whereas the gauge on mine goes down to about 1.6/1.8 bar.

Duff gauge?
 

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if you can borrow another guage, connect it between the rail and the fpr and see what it reads.
 

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Discussion Starter · #5 ·
Yeah thats one thing I wanna do tomorrow, borrow one from work. They should have one kicking around.
 

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i'd put the standard regulator back on, but squash it in the vice till it give you your requirted pressure

rodgerq
 

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Discussion Starter · #7 ·
Would rather use the blacktop, the FPR itself is fine... but if the gauge is telling lies it can easily be replaced or blanked off (or just left on reading whatever pressure it feels like)
 

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Discussion Starter · #8 ·
right got a proper fuel pressure gauge from work, plugged it into the valve port on the rail and got the fuel pump going. Gauge reads exactly the same as the small one on the FPR itself.

I re-fitted the standard LET chips, reset to 3.0 bar and tried again, same result.

Going to replace the Blacktop FPR with the standard known-working unit and see if that changes anything.
 

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Discussion Starter · #10 ·
Thats not how they work.
 

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Discussion Starter · #12 ·
the fuel pump delivers fuel at a certain rate, the fuel pump has a 'range', the FPR regulates the pressure within the pumps range, if the fuel demand goes beyond the range of the pump your fuel pressure will decrease (like as you reach max rpms and the demand is too high).
 

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Discussion Starter · #14 ·
The pump provides a more than ample supply for the pressure without the engine running, otherwise how would an engine start?
 

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the pump pums about 3 times what the engine needs, all the fpr does is provide a restriction in the system to increase the pressure. So to set it you jam the pump on my shorting the relay and adjust it till it reads right.
 

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Yep, get all that, I know the pump moves far more than the engine needs, hence the reg on the return allowing most of it back to the tank.
What I can't help thinking is that, you set the pressure with the pump going but the engine not. Then you run the engine and pump's able to pump just a little harder and there's a second loss in the form of the injectors.

But anyway, I guess it's not enough to make much of a difference.
 

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it makes no difference at all, the extra flow from the pump is taken care of as the fpr still opens at the same pressure
 

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regardless the generally accepted way of doing it is to set it with the vac line off and the engine idling, so try this first, or at the very least look at the guage readout with the engine idling and vac line off
 

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i used to run my let with a black top fse on. it gave me nothing but problems. the pressure fluctuates all over the place when it hits boost. couldnt react quick enough, causing car to go to lean before rich (on wide band lambda gauge). changed it for a cossie webber one and its been perfect ever since. nothing but a bad experience the fse reg
 

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Discussion Starter · #20 ·
so noted chap, replacing FSE with standard unit in the next hour or so, reverted the chips to standard now. Will see how it does.

But from what you have just said I won't run it, will sell it on to a TB'd XE owner or someone who can make use of it.

John.
 
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