frustrating fuel pressure issue

[Murray_Calavera]

23 minutes ago, damnonrs said:

So you are telling me a reputable shop built and documented a 2.8 build by hand and gave the car to the customer that goes through a fuel tank in 100km and ran his car on the dyno leaning out and he drove it for 4-5 years like this? 
 

anyways I’m focused on the present. What would your next step be knowing all this? 

Replace the fuel pump. 

Post your ESP map. 

Log every channel and go for a drive. Post your data log. 

You might be surprised to learn that there are many of us here that have built and tuned their own car. I don't know why you are fighting the advice as hard as you are. 

If your car is truly getting 65 litres per 100km, it should take me all of 5 seconds to see what is wrong in your tune if you post the map and data log.  

[damnonrs]

12 minutes ago, Murray_Calavera said:

Replace the fuel pump. 

Post your ESP map. 

Log every channel and go for a drive. Post your data log. 

You might be surprised to learn that there are many of us here that have built and tuned their own car. I don't know why you are fighting the advice as hard as you are. 

If your car is truly getting 65 litres per 100km, it should take me all of 5 seconds to see what is wrong in your tune if you post the map and data log.  

I don’t have my laptop but I took these pictures earlier. I can log tomorrow. You recommend buying a new fuel pump even though it’s brand new? 

[robbo_rb180]

Yep they do things like that. Also depends on calculation used for power.... Japan hp is not Australian hp or North American hp

When I was tuning at a shop would show customers how we can give them higher readings. Change barometric pressure, temp sensor on/near manifoldsand ramp rates. Looks on their faces when a 400hp car makes a 1000hp 🤣 

 

Number 1 change fuel pump, 2 check how fuel pump is wired (40amp relay and 5mm wire minimum), 3 get a log and tune file to @Dose Pipe Sutututu or @The Mafia , 4 if issue still there find/borrow a fuel regulator.

Japanese workshops aren't all that great and stuck in 2005.

 

[Murray_Calavera]

12 minutes ago, damnonrs said:

I don’t have my laptop but I took these pictures earlier. I can log tomorrow. You recommend buying a new fuel pump even though it’s brand new? 

Yes, as everyone keeps saying, please replace your brand new fuel pump with a modern pump. 

Those tables look ok at a glance. Can't really offer much more commentary without the map and data log though. 

Rob's advice is even better again, I'd go down that path for sure. 

[damnonrs]

Okay got it, before I dive that deep i want to check something, Is there anyway to find a full fuel line diagram? That goes from the pump to the regulator. Return line included

ive searched but can’t find anything

[Dose Pipe Sutututu]

1 hour ago, damnonrs said:

I don’t have my laptop but I took these pictures earlier. I can log tomorrow. You recommend buying a new fuel pump even though it’s brand new? 

Need your tune file, the logs you posted before were pretty terrible lol.

There should be another table for RPM vs MAP too. The RPM X TPS only shows part of the picture.

Highly suspect your fuel pump is garbage.

[Murray_Calavera]

15 minutes ago, damnonrs said:

Okay got it, before I dive that deep i want to check something, Is there anyway to find a full fuel line diagram? That goes from the pump to the regulator. Return line included

ive searched but can’t find anything

You shouldn't need a diagram, it will take you 5 minutes to locate them all if the car is in the air. 

Locate the fuel pump hat, its in the boot hidden under a panel with 4 bolts. With the panel removed you can see the fuel lines. Those lines connect to hard lines that run along the length of the car. The hard lines connect to rubber lines that come up into the engine bay. You'll be able to see where they go very easily. 

[TurboTapin]

Hey, has anyone here recommended to OP that he change his small prehistoric and obsolete pump as they don't support 600WHP? Oh, right everyone has... multiple times. 

CHANGE YOUR DAMN PUMP. 

[damnonrs]

Okay okay, I still find it weird a 044 is peaking at 400rwhp but i have a new plan which will most likely work and worst case power through my problem. 
 

if I buy a nismo fuel pressure regulator I can set the idle fuel pressure to what I want and not go over the 3 bar idle standard for the rb28 (I’m assuming a 2.8 is the same fuel pressure)

and from there I will upgrade to dual very high flowing fuel pumps so I can just run e85 anyways. 
 

with that being said what do you guys recommend in terms of installing a dual pump and which pumps? Thanks

[TurboTapin]

6 minutes ago, damnonrs said:

Okay okay, I still find it weird a 044 is peaking at 400rwhp but i have a new plan which will most likely work and worst case power through my problem. 
 

if I buy a nismo fuel pressure regulator I can set the idle fuel pressure to what I want and not go over the 3 bar idle standard for the rb28 (I’m assuming a 2.8 is the same fuel pressure)

and from there I will upgrade to dual very high flowing fuel pumps so I can just run e85 anyways. 
 

with that being said what do you guys recommend in terms of installing a dual pump and which pumps? Thanks

I agree a healthy 044 should be capable of handling more than 400whp, you may have multiple problems. Nismo FPR's are also on the prehistoric side and meant to be used with stock 5/16 fuel line.  Which leads me to another question... are you still using the stock 5/16 fuel line? 600WHP is also asking a lot from such a small feed line.

3bar idle is standard for all RB's and 80% of engines out there.

If you plan on running E85, that's a whole other ball game. Everything must be compatible (Fuel pump, injectors, line, etc.)

I always recommend AEM 320/340's as I have yet to ever see or hear of one fail. I'm currently running two of them in a radium 3 pump hanger. 

[damnonrs]

8 minutes ago, TurboTapin said:

I agree a healthy 044 should be capable of handling more than 400whp, you may have multiple problems. Nismo FPR's are also on the prehistoric side and meant to be used with stock 5/16 fuel line.  Which leads me to another question... are you still using the stock 5/16 fuel line? 600WHP is also asking a lot from such a small feed line.

3bar idle is standard for all RB's and 80% of engines out there.

If you plan on running E85, that's a whole other ball game. Everything must be compatible (Fuel pump, injectors, line, etc.)

I always recommend AEM 320/340's as I have yet to ever see or hear of one fail. I'm currently running two of them in a radium 3 pump hanger. 

Oem r34 gtr fuel lines are good for well over 1000hp. I’m assuming the nismo fpr should work as all I need it to do is just set a target of 3 bar. 
 

right now my car idles at 4.11bar with a stock fuel pressure regulator somehow 

 

does the pump hanger need modding to fit?

[TurboTapin]

1 hour ago, damnonrs said:

Oem r34 gtr fuel lines are good for well over 1000hp. I’m assuming the nismo fpr should work as all I need it to do is just set a target of 3 bar. 
 

right now my car idles at 4.11bar with a stock fuel pressure regulator somehow 

 

does the pump hanger need modding to fit?

I'd love to know where you're getting your information from. 5/16" (8mm) fuel hose is as good for "Well over 1000hp" as your single Bosch 040/044 pump is. 

Your car right now idles at 4.11 with an OEM FPR due to it's internal orifice size, your aftermarket pump and possibly your 5/16" return line. Just an fyi, base fuel pressure is measured with the vacuum line disconnected from FPR. 

Does what pump hanger require modding? OEM? The Radium I mentioned?
 

[Duncan]

I don't want to take away from the recommendation that you start with a suitable fuel pump, but I will add that there have been plenty of cars that have lost hundreds of horsepower between the japanese seller's dyno chart and what happens the first time you run it on a dyno yourself.....dodgy middle people are not limited to a single country.

As stated earlier, japanese workshops naturally led the way in tuning these cars in the 90s and early naughties but that really has changed since.  Messing with a small pump but pushing up base fuel pressure is a dangerous way to tune a car compared to just fitting a correctly sized pump and tuning to standard pressure. In particular it affects injector spray pattern and increases risk of a lean out when you are pushing the whole system right to it's limits.

I'm not aware of complete coverage of the fuel system; B6 in the R32 GTR manual is pretty brief and doesn't cover the venting at all. There is information on the main hoses in and out though.

[joshuaho96]

High fuel pressure means even higher demands on the fuel pump. 600 whp with what sounds like small fuel lines and a lot of fuel pump sounds like it could easily cause the pressure relief valve on the pump to be permanently damaged and not flow properly anymore. Had this happen in the past so I recommend being careful with it.

[BK]

Let's just back all this up. The question is why have you got such high fuel pressure at idle ? - and it's definitely not because your pump flows too much.

An 044 or 040 flows about 300lph at 3 bar, so up to 40% more than a stock standard pump which is nothing outrageous, but a single 044 should still support at least 350kw + on unleaded.

Those stock fuel lines, a properly functioning stock fuel reg and an 044 should sit happily at 3 Bar on idle, unless there is some sort of restriction on the return line. Look for stuffed fuel reg, rail blockage into fuel reg, return line blockage or kink, standard location fuel filter in return line blocked and so on.

The fact is the reg creates a controlled restriction in the return to set rail pressure, so it's not a restriction or starvation in the supply line as then you'd get a low fuel pressure scenario which is not happening at idle here.

Something is restricting the normal flow of fuel back into the tank - find it. 

[damnonrs]

20 hours ago, BK said:

Let's just back all this up. The question is why have you got such high fuel pressure at idle ? - and it's definitely not because your pump flows too much.

An 044 or 040 flows about 300lph at 3 bar, so up to 40% more than a stock standard pump which is nothing outrageous, but a single 044 should still support at least 350kw + on unleaded.

Those stock fuel lines, a properly functioning stock fuel reg and an 044 should sit happily at 3 Bar on idle, unless there is some sort of restriction on the return line. Look for stuffed fuel reg, rail blockage into fuel reg, return line blockage or kink, standard location fuel filter in return line blocked and so on.

The fact is the reg creates a controlled restriction in the return to set rail pressure, so it's not a restriction or starvation in the supply line as then you'd get a low fuel pressure scenario which is not happening at idle here.

Something is restricting the normal flow of fuel back into the tank - find it. 

thanks for pointing that out, its what ive been thinking too. looking at the service manual it says this 

how can i test my fuel pressure regulator? or even check that its being blocked? are the return lines mostly all visible? should i just pinch the lines? from what i understand its two lines running under the driver seat all the way to the tank, one feed one return. rail blockage do i just take a peak in there and hope i see gunk? just kinda thinking out loud since i visually inspected and didnt see anything wrong. should i even bother with the damper thing..? thinking back the tuner threw on a AEM fuel pressure regulator on the dyno and it was still leaning out up top. he never mentioned to me if my idle fuel pressure was still high.

 

thanks!

[joshuaho96]

2 hours ago, damnonrs said:

thanks for pointing that out, its what ive been thinking too. looking at the service manual it says this 

how can i test my fuel pressure regulator? or even check that its being blocked? are the return lines mostly all visible? should i just pinch the lines? from what i understand its two lines running under the driver seat all the way to the tank, one feed one return. rail blockage do i just take a peak in there and hope i see gunk? just kinda thinking out loud since i visually inspected and didnt see anything wrong. should i even bother with the damper thing..? thinking back the tuner threw on a AEM fuel pressure regulator on the dyno and it was still leaning out up top. he never mentioned to me if my idle fuel pressure was still high.

 

thanks!

Pull the return line where it goes to the chassis rail from the plenum. Get a bucket to catch the raw gasoline that will be coming out of it. Get someone to start the engine, make sure it's safe to do so before you catch your hand in the radiator fan or something like that. Check to see that fuel is coming out in a steady stream. A bad fuel damper can block the return line so only tiny little spurts will come out. Then verify that with the return line open to a bucket your fuel pressure is still the same pressure as when you put the line back on. To try and eliminate the impact of engine idle tuning you want to do this test with the FPR vacuum line disconnected. If there is a downstream restriction there will be more fuel pressure with the return line connected properly vs draining into a bucket. If there is a restriction you're going to have to measure fuel pressure in various sections of the line to find where the blockage is. It will be the source of pressure drop so somewhere downstream of high fuel pressure but upstream of low/zero pressure.

Diagnosing this stuff is just how it goes with any significantly modified engine. This is likely not the first time this engine has needed this kind of work, nor will it be the last. Everything you're saying is pointing to a fuel system issue as others have mentioned.

[Butters]

As others have said, HP sold is not HP tested.  1050cc injectors are the first tell, a setup for 650 crank, not wheel really. 

The 044 should be able to get you to 600rwhp ... JUST. 

 

The bigger thing here is the fuel reg, you will need to squeeze those injectors and need an adjustable reg to do it. 

I've also had fuel regs run higher pressure at idle due to being faulty and then drop pressure when demand is on. 

 

I got suckered into upgrading fuel lines and pumps when all the time it was the faulty fuel reg.  

[GTSBoy]

It would take someone to be familiar with how much volume of fuel flow they expect to see out the back of the reg at idle load to b able to tell if what they were seeing was normal or not.

The correct way to diagnose fuel pressure problems is to plum a fuel pressure gauge into the fuel line in the engine bay before the fuel rail. Anything else is just guesswork.

And, by the very definition f being a back pressure regulator, the fuel pressure regulator, if undersized for the pump (or, perhaps a little blocked) will cause high pressure at idle and maybe low pressure up top. The low pressure not being the fault of the reg, but of the pump or other restriction on the supply side (not the return side).

[damnonrs]

So I dove into the fuel system today, 

I removed the line coming out of the damper and plugged it into a fuel canister. The idling pressure dropped from 4.25 idling to 4.05 steady. I’m assuming the 5% improvement is because of all the twists and turns tk get back to the fuel tank. So damper isn’t the problem. But then I also tried plugging it straight from the regulator and it was the same thing. All that’s left to test now is regulator itself or the rail… which brings me to: do I buy a radium fuel rail with damper and fuel pressure regulator in one? Also check this out. When I rev the car the pressure just goes to 3.5 and jumps back to 4.2 I posted a video