damnonrs

finally fixed this issue and was able to get my 2.8 fully tuned, the car is an animal now! pretty much the issue was a bad fuel pump relay 😆, hence the fuel pump pressure dropping with load

so i spoke to my tuner, and he said he just changed the wiring that goes from the battery to the pump, the line in the fuel tank and the wiring in the fuel tank is still OEM at like 22 gauge or whatever it is. is that essential to upgrade or would that restrict the voltage?

i will hard wire it for now until my problems are resolved and get it dyno tuned again. i'm just worried about fuel temperature running the pump at 100%, is that a problem or its ok to just have it on full blast at all times

is there any write ups on doing this for the 34 gtr? i know 33 and 32 are different

Awesome, I’ll look into this on Monday. Thank you for your feedback so far!

What’s a fpcm? this is what the fuel pressure does plugging it in and out. It raises when you unplug it IMG_7522.MOV

I will check again tomorrow, could I have a pretty bad vacuum leak somewhere in the surge tank or something

It’s plumbed like this

Yea that’s exactly it, and yes the fuel pressure goes up like I said earlier when I remove the vac line

Dampener is after the fuel pressure regulator on the rb26, removing the vac line changes the idling by like 0.05 bar or something like that If it satisfies you I also ran the car with the hose right off the fuel pressure regulator as stated and nothing changed

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 IMG_7513.MOV

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!

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?

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

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

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?

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?

I'm in canada lol can you explain how the car as is in japan 4 years ago with a lesser flowing fuel pump than whats in there now was making 550rwhp and i can't get past 400 with the same exact setup except 4 years later. the car had been sitting for a bit. i dont know how else to explain its not a fuel pump issue unless the pickup is leaking. I understand how a fuel regulator works and buying a new regulator and playing with it could damage my engine. its the stock regulator on there which is good for heaps of power, the car has been tuned around this problem (which is no good i understand) i am trying to solve it and put it back on a dyno asap.

from the googling i did, i dont see anything like that. i also just tried priming the pump. it primes to 4.11bar and then drops to 1.1, are the pumps supposed to hold the pressure at around where it primes to? I also tried without the gas cap and it acts the same way as with it screwed on.

yea i kinda agree, hes smart and the car came with this problem from japan so it was the logical thing to go to a new fuel pump. but i agree maybe 044 wasnt the best choice. anyways the fuel pump is not the problem here, its a fuel pressure issue where it idles too high fuel pressure and drops under load. I have attached some data logging. this was from the last time i drove the car, car is put to storage while im trying to figure out this problem. i think fuel pressure logging wasnt turned on by the tuner but i have attached a video of what the fuel pressure does under boost. https://imgur.com/a/qjr8yuY I inspected every single line in the front and underneith. what im thinking is maybe a vaccum line or a vent line ontop of the fuel tank is broken and it cant build pressure under boost in the fuel tank. 2022-12-06_0528pm_Logs323to386.csv

I also want to mention that the car gets about 150km on a full tank with normal driving and just spews fire non stop

My tuner put me on this fuel pump which actually made the flow a bit better than my previous pump. I attached a picture of what the car was doing in japan with a less flow fuel pump, we put it on a dyno here and it couldn’t even break 400hp with the fuel pump the car came with. Fuel pressure is all wacky and fluctuates. Also they made a new 044 pump

im using a bosch 044 which is good enough for 600ps. but bosch 040 you said is also good for 700hp. my car leans out at 450hp on the dyno, i dont think this is a fuel supply issue, i think im chasing a vaccum or fuel pressure problem.

hey guys, very long term lurker here. I always use the search function for most things but im stumped here. I got a built hks rb28 car from japan, it came with documentation of the build and dyno numbers, car should make around 600awhp. Ever since i received the car i hadnt floored it since it was tuned on japan fuel so i ordered a haltech 2500 and went for a tune locally. On the dyno we found that it was dropping fuel pressure from 4.1(idling pressure is at around 4 bar, i know that idle fuel pressure should be 3 bar this is another tell tale that somethings wrong ) to all the way leaning out so the tuner called it quits and told me i should probably replace my fuel pump. I ordered a bosch 044 with a new sock filter, 1050cc injectors, higher flowing fuel filter and a 30 amp relay for the fuel pump we also changed the fuel regulator to an AEM one.. went on the dyno and same exact problem occured except the tuner said its a little bit better. this time, he sent me off with a 6000rpm red line so i dont get into leaning out territory and keeping the car drivable. Here is what the car is doing on the fuel pressure with higher rpms. https://imgur.com/a/qjr8yuY the mechanic and tuner don't really know what the problem is and they are recommending to change all the fuel lines to new braided lines so everything is fresh or performing a fuel pressure test, i've spent close to 4k chasing this problem and im kinda burnt out. Could this be a leaking vent hose, either on the fuel tank or the charcoal cannister? maybe a bad fuel damper? replacing the fuel pump to a stronger one than before made car lean out a bit later in the rpms but still is running way too rich to lean, what could this mean? Any leads would help! thanks

will the tail lights fit the r34 gtr? are they the same tail lights? if so I want them