TRE fuel pump

[peter thomson]

Hi fitted a TRE pump I bought from ghanda today but when I blip the throttle the fuel pressure does not rise as it did with the original pump. I have modded the wiring as well so it has power direct from the battery through a relay. Any chance I have done something wrong or does the pressure not rise much when the throttle is blipped with the direct battery connection.

[Kieran]

Peter - what pressures are you seeing and how are they being measured?

The 'battery' mod, as far as I am aware, just supplies a constant 13.5 (or whatever the main system volts is) to the pump, so it's always operating at full speed. The pressure regulator on the end of the fuel rail takes care of system pressure and it governs this by engine vacuum. I believe that standard base idle pressure is 43psi on the VR-4.... My thinking is that 'hot wiring' the pump is pushing up the pressure slightly, so that you're not seeing a rise when you blip?

[peter thomson]

Peter - what pressures are you seeing and how are they being measured?

The 'battery' mod, as far as I am aware, just supplies a constant 13.5 (or whatever the main system volts is) to the pump, so it's always operating at full speed. The pressure regulator on the end of the fuel rail takes care of system pressure and it governs this by engine vacuum. I believe that standard base idle pressure is 43psi on the VR-4.... My thinking is that 'hot wiring' the pump is pushing up the pressure slightly, so that you're not seeing a rise when you blip?

Hi Kieran I have one of the adjustable fuel pressure regs fitted which was set to 42psi initially as per Bern's article. When I connected up the TRE pump fuel presure had jumped to nearly 60 psi. I adjusted the regulator back down to 42 but when I blip the throttle the fuel pressure may actually drop slightly rather than jump up as before.
I thought that it being at the same voltage all the time now may be the reason for this but was just checking with others that have this mod and I have not the potential to run lean when on boost.
I'm fitting an SAFC2 this weekend as well and then a boost controller before getting the controller set up on a dyno

[Gly]

the feul pressure should not change until your car is boosting.

if its a 1:1 raising rate fpr it will raise 1psi of fuel pressure for 1 psi or boost..

or something along those lines....

also how did you set the fpr?

did you remove the vacc line and then set the base pressure(43ish psi)?
and re-attach the vacc line to the fpr?

[peter thomson]

the feul pressure should not change until your car is boosting.

if its a 1:1 raising rate fpr it will raise 1psi of fuel pressure for 1 psi or boost..

or something along those lines....

also how did you set the fpr?

did you remove the vacc line and then set the base pressure(43ish psi)?
and re-attach the vacc line to the fpr?

Gly does that mean blipping the throttle without any load will have little effect on pressure.

I set it up with the vacuum line disconnected but as per another post there was little difference when the line was reconnected. The standard pump showed a noticeable difference

[Gly]

actually now that i think about it, it should go up....

but different pumps have different characteristics,

the TRE fuel pump doz not flow as well as a walbro at low pressure,
but out flows it at higher pressures,

and i cant say how bad the factory pump is?

a blip on throtal may not be enough to alter pressure...
have you tried holding the revs up higher to see if the pressure changes?

[peter thomson]

actually now that i think about it, it should go up....

but different pumps have different characteristics,

the TRE fuel pump doz not flow as well as a walbro at low pressure,
but out flows it at higher pressures,

and i cant say how bad the factory pump is?

a blip on throtal may not be enough to alter pressure...
have you tried holding the revs up higher to see if the pressure changes?

I thought the pressure may just rise in the standard pump due to the voltage increasing when the engine is reved but that boost would now be needed to cause the fuel regulator to increase the pressure.
I ordered a sard regulator earlier in the week after reading about the problems with this regulator and I hope this sorts it out.

i will try holding up the revs to see what effect that has but it was a bit to early today to scare the neighbours

[peter thomson]

The fuel pressure does not rise when I hold the throttle open.
I then connected back up as the original pump and I cannot get the fuel pressure above 40 psi but when you blip the throttle it jumps up to 60ish and then settles back down to about 40psi when I assume the regulator takes control of the pressure again. I assume this is normal for the standard pump as well .
When i hotwire the pump again pressure adjustment is fine again but when the throttle is blipped the guage hardly moves.

[Gly]

did you solve this?

[peter thomson]

Hi I have fitted a sard regulator now and after setting the pressure at 42psi I then attached the vacuum pipe which has resulted in a more obvious drop in pressure but again when the throttle is blipped there is not that great an increase . This must be due to having the voltage constantly at 12 volts rather than jumping from 8 to 12 when it senses the throttle position has been moved. I'm fitting a boost controller just now and then I can get the SAFC set up and see what the AFR are like unless I have bought a wideband myself to check they are OK.
Do you think the pressure is OK

[Gly]

pressure seams fine...

the thing about the TRE pump, it is not as good as a walbro at loew pressures,
and may not be as good as the stock pump either? or maybe not as responsive?

it does outflow the walbro units at higher presures, according to the charts...

but yes diffinately fit the wide band a check the AFRs,

report back im keen to buy a TRE pump myself.

[peter thomson]

Refitted the TRE pump today with the mod that Kenneth used and all seems fine now. Initial problem as mentioned in my other thread about a misfire appears to be due to the fact it does not seal well and must leak resulting in not another pressure at the injectors