Fuel Pressure Too High

[Lithium]

what injectors? i would not be too concerned unless its bouncing, its not uncommon to to run 60-80 base pressures depending on target boost and pump capabilities. ID recommend a base of 60-100psi depending on application. I generally run 60psi on bigger injectors ie 1000 and 2000cc.

Basically keep TOTAL pressure under the injectors limits.

ID725 - 8.5 bar, 123.5 psi.

ID850 - 7.0 bar, 101.5 psi.

ID1000 - 7.0 bar, 101.5 psi.

ID2000 - 9.0 bar, 130.5 psi.

Good point, worst come to worst can just aim for 60psi instead of have it happening as an effect, ID1000s will love it anyway. Only issue for him is he'll need the fuel table to be touched up to suit the new flow rates of the injectors if it is currently tuned for 43psi.

[34GeeTeeTee]

Interesting about the higher fuel pressure and bigger injectors.. Mine isnt setup that way

[Lithium]

It doesn't NEED to be, it's just that IDs like higher pressure. At 43psi ID1000s will not be actually flowing 1000cc/min - they'll be fine though.

Check this out:

[Marcus89]

what injectors? i would not be too concerned unless its bouncing, its not uncommon to to run 60-80 base pressures depending on target boost and pump capabilities. ID recommend a base of 60-100psi depending on application. I generally run 60psi on bigger injectors ie 1000 and 2000cc.

Basically keep TOTAL pressure under the injectors limits.

ID725 - 8.5 bar, 123.5 psi.

ID850 - 7.0 bar, 101.5 psi.

ID1000 - 7.0 bar, 101.5 psi.

ID2000 - 9.0 bar, 130.5 psi.

I was thinking this would/could be the case but didn't have any figures to back it up or any idea where to look first. It's not like his fuel pressure will rise much if any higher than what he is getting at idle either due to the motor using much more fuel when on boost. Not even close to the ID pressure limits

[scotty nm35]

Like Trent said, as long as the pressure is stable at that point, it can be tuned around. Simply bumping the base up to 60psi would help with the spray patterns, and you have the pump to supply such high pressures.

Just remember you need to add your boost pressure to the base pressure to get your maximum rail pressure, and the pump flow will drop off as it gets above 80psi.

[Kane_R32]

If the original 255L/PH was creating 43psi @ 14V then of course the 460L/PH will create a higher pressure at the same voltage as its flowing more fuel.

Just adjust the flow back to what its tuned at otherwise you will be running richer than normal.

[GTSBoy]

If the original 255L/PH was creating 43psi @ 14V then of course the 460L/PH will create a higher pressure at the same voltage as its flowing more fuel.

That's simply not true. The regulator controls the pressure to the setpoint, not the pump. But if perchance the regulator is too small to pass all the extra flow back to the tank, then it loses control and the pressure will rise until it is high enough to squirt the required amount of fuel back through the reg.

There is nothing you can do to adjust a reg which is simply too small.

Furthermore, and to add some caution into the advice that has been given so far........don't be tempted to just retune it to run at this new pressure. Doing so could be fatal to the engine. I will explain. Note that I am making the assumption that the reg is now too small to control the fuel pressure against such a large pump. If this is not true, then discount what I say in this case, but keep it in mind as a general warning.

The new fuel pressure is not controlled at 60ish psi. It is sitting there purely by virtue of the fact that the pump is running flat out trying to jam the fuel back through the port in the reg. If you now tune the fuelling to work at that pressure, that's all good, except that the flow/pressure characteristic of the pump may change. It may change as the pump wears (it might take years, or it might "wear in" over a period of a hundred hours - who knows). It may change with large changes in fuel temperature - so, winter to summer variation, or perhaps just the heating of the tank you get from passing so much fuel through the rail and back to the tank. I'm sure there are half a dozen other ways it might change. If it does change, then because the regulator is not in control, then the pressure will change. It might rise or it might fall. A fall is much more likely with most possible causes of change that I can think of.

Of course if the pressure falls away from what you've tuned at, and it is sufficiently lower than what you tuned at while you have load on the engine (that's debatable because by this time the engine will be using a bit of the fuel and relieving the task of the regulator) then you could damage the engine. It all really depends on how much fuel you need to be using in the engine before the regulator gets back in control and can maintain the rail pressure at the existing setting.

I'm just sayin'. I would be cautious if it were me. Find out the real cause for the out of control pressure before making decisions on what to do is my advice.

[Lithium]

That's simply not true. The regulator controls the pressure to the setpoint, not the pump. But if perchance the regulator is too small to pass all the extra flow back to the tank, then it loses control and the pressure will rise until it is high enough to squirt the required amount of fuel back through the reg.

There is nothing you can do to adjust a reg which is simply too small.

Furthermore, and to add some caution into the advice that has been given so far........don't be tempted to just retune it to run at this new pressure. Doing so could be fatal to the engine. I will explain. Note that I am making the assumption that the reg is now too small to control the fuel pressure against such a large pump. If this is not true, then discount what I say in this case, but keep it in mind as a general warning.

The new fuel pressure is not controlled at 60ish psi. It is sitting there purely by virtue of the fact that the pump is running flat out trying to jam the fuel back through the port in the reg. If you now tune the fuelling to work at that pressure, that's all good, except that the flow/pressure characteristic of the pump may change. It may change as the pump wears (it might take years, or it might "wear in" over a period of a hundred hours - who knows). It may change with large changes in fuel temperature - so, winter to summer variation, or perhaps just the heating of the tank you get from passing so much fuel through the rail and back to the tank. I'm sure there are half a dozen other ways it might change. If it does change, then because the regulator is not in control, then the pressure will change. It might rise or it might fall. A fall is much more likely with most possible causes of change that I can think of.

Of course if the pressure falls away from what you've tuned at, and it is sufficiently lower than what you tuned at while you have load on the engine (that's debatable because by this time the engine will be using a bit of the fuel and relieving the task of the regulator) then you could damage the engine. It all really depends on how much fuel you need to be using in the engine before the regulator gets back in control and can maintain the rail pressure at the existing setting.

I'm just sayin'. I would be cautious if it were me. Find out the real cause for the out of control pressure before making decisions on what to do is my advice.

When I mentioned retuning to the new pressure I meant to change the FPR setting to target 60psi... not just leave it at the current setting to hold 60psi, if that makes sense?

[GTSBoy]

Yeah, that makes sense, although you'd want to be winding it up to a pressure higher than what it is doing now, so that it actually does take control. Then you really have to retune the whole fuel map, not just the low load section.

[Lithium]

Bare in mind that the 60psi will not be differential pressure while the engine is running, and it is also probably damn near the worst case scenario for the FPR to have to deal with while the engine is idling - as soon as load or rpm go up the injectors will work more and the FPR will need to return less.

[Hanaldo]

what injectors? i would not be too concerned unless its bouncing, its not uncommon to to run 60-80 base pressures depending on target boost and pump capabilities. ID recommend a base of 60-100psi depending on application. I generally run 60psi on bigger injectors ie 1000 and 2000cc.

Basically keep TOTAL pressure under the injectors limits.

ID725 - 8.5 bar, 123.5 psi.

ID850 - 7.0 bar, 101.5 psi.

ID1000 - 7.0 bar, 101.5 psi.

ID2000 - 9.0 bar, 130.5 psi.

I'm using ID1000's, so that should work if I can't get the pressure back down. Although I will have to double check whether the pressure is stable or bouncing, it may have been bouncing...

Have you tried adjusting the base pressure when the engine is running?

If not, do that and report back

I haven't, no. I was going to, but thought it was all working correctly prior to the new pump, so if it's all correct then it shouldn't have changed? I didn't want to cover up any error I made by changing something else. Though I guess if the reg/return hose is too small then I just won't be able to lower the pressure at all?

That's simply not true. The regulator controls the pressure to the setpoint, not the pump. But if perchance the regulator is too small to pass all the extra flow back to the tank, then it loses control and the pressure will rise until it is high enough to squirt the required amount of fuel back through the reg.

There is nothing you can do to adjust a reg which is simply too small.

Furthermore, and to add some caution into the advice that has been given so far........don't be tempted to just retune it to run at this new pressure. Doing so could be fatal to the engine. I will explain. Note that I am making the assumption that the reg is now too small to control the fuel pressure against such a large pump. If this is not true, then discount what I say in this case, but keep it in mind as a general warning.

The new fuel pressure is not controlled at 60ish psi. It is sitting there purely by virtue of the fact that the pump is running flat out trying to jam the fuel back through the port in the reg. If you now tune the fuelling to work at that pressure, that's all good, except that the flow/pressure characteristic of the pump may change. It may change as the pump wears (it might take years, or it might "wear in" over a period of a hundred hours - who knows). It may change with large changes in fuel temperature - so, winter to summer variation, or perhaps just the heating of the tank you get from passing so much fuel through the rail and back to the tank. I'm sure there are half a dozen other ways it might change. If it does change, then because the regulator is not in control, then the pressure will change. It might rise or it might fall. A fall is much more likely with most possible causes of change that I can think of.

Of course if the pressure falls away from what you've tuned at, and it is sufficiently lower than what you tuned at while you have load on the engine (that's debatable because by this time the engine will be using a bit of the fuel and relieving the task of the regulator) then you could damage the engine. It all really depends on how much fuel you need to be using in the engine before the regulator gets back in control and can maintain the rail pressure at the existing setting.

I'm just sayin'. I would be cautious if it were me. Find out the real cause for the out of control pressure before making decisions on what to do is my advice.

Yeh this was my thought, I wanted to be careful about changing things, hence this thread.

Good point, worst come to worst can just aim for 60psi instead of have it happening as an effect, ID1000s will love it anyway. Only issue for him is he'll need the fuel table to be touched up to suit the new flow rates of the injectors if it is currently tuned for 43psi.

Getting the car retuned isn't an issue, I'm in the process of setting the car up for flex-fuel so it was going to go back on the dyno for that anyway. The issue is I suppose it won't be driveable until I do get it tuned?

I just had another thought about what may be causing the higher pressure, as I realised how I set the regulator up when I installed it. I put it at the top of the strut tower, but didn't want to relocate or delete the stock fuel dampener that sits right next to it. So I looped the fuel hose coming out of the regulator down around the fuel filter, and then back up again into the dampener. If you follow? It's not a tight loop, the hose doesn't kink at all I was trying to think about flow. In fact it seemed like it would be less of a restriction than having the hose come straight out of the regulator and 90 degrees into the dampener. But perhaps this is something that I've done on my car that explains why it hasn't been a problem for anyone else?

Fortunately my Zeitronix ECA kit should be arriving today sometime and I need to install that in the return line anyway, so I will try unbolting the dampner and unlooping that hose, see if it changes anything.

[R31Nismoid]

It doesn't NEED to be, it's just that IDs like higher pressure. At 43psi ID1000s will not be actually flowing 1000cc/min - they'll be fine though.

Check this out:

43psi is only at idle though, once you take into account 20psi and the reg now sitting at 63psi (give/take) - works out ok?

[89CAL]

Sorry if I'm missunderstanding that table, but at 43.5psi the injectors look like they flow 1015cc/min. The other numbers are dead time values

Am I missing something here?

[Lithium]

The dead times are under the voltage heading, flow rate is under the flow rate heading to the far right

[Hanaldo]

Is there any reason for me to keep the fuel dampener? Was going to relocate it, but if I don't need it at all then I may as well just delete it?

[Kane_R32]

That's simply not true. The regulator controls the pressure to the setpoint, not the pump.

Correct, but I would've thought changing pump only, and not reg aswell to suit higher capacity pump, then of course you will see a increase in pressure at the reg because its now pushing almost double the amount of fuel. as before. And as you mentioned if the reg cant return the excess back quick enough then up she goes!

[Hanaldo]

Correct, but I would've thought changing pump only, and not reg aswell to suit higher capacity pump, then of course you will see a increase in pressure at the reg because its now pushing almost double the amount of fuel. as before. And as you mentioned if the reg cant return the excess back quick enough then up she goes!

Well I can eliminate that theory, just tried adjusting the FPR without any luck. Can't get it below 60psi no matter how far I turn it. I turned it up to about 63psi, though I think I will turn it up a little bit more just to be sure the regulator is in control again.

Just to be sure, would this be considered a 'stable' fuel pressure? Or is this bouncing too much?

[89CAL]

The dead times are under the voltage heading, flow rate is under the flow rate heading to the far right

Yeah this is how I read it, but someone said before that at stock Fuel pressure the injectors wouldnt actually be flowing 1000cc, wasn't sure if I was missing something. All good

Is there something restricting the FPR fuel return flow or inlet flow? What sort of Reg is it?

[GTSBoy]

That fuel pressure is rock steady.

[Hanaldo]

Yeah this is how I read it, but someone said before that at stock Fuel pressure the injectors wouldnt actually be flowing 1000cc, wasn't sure if I was missing something. All good

Is there something restricting the FPR fuel return flow or inlet flow? What sort of Reg is it?

It's a Sard FPR, I forget what type, but same as this one:

http://justjap.com/store/product.php?productid=16736

I'm not sure if the loop I've got in the return line before the dampener is causing any issues. It could be.

That fuel pressure is rock steady.

Awesome, thanks mate.

How far should I up the fuel pressure to be sure that the regulator has control again? Just over the minimum I can run, or should I up it by a bit, say to 70psi?