R34 Fueling Issues - Seeking Diagnosis/input

[PSIKO]

Hi chaps,

It seems whenever I take my car to the local track (Barbagallo), I experience the following:

• fuel surge when tank is approx <60% full
• high fuel consumption - roughly 6 laps will consume 1/4 of the tank

Additionally, when at the tuners, they said that the injectors are maxed out; they're not completely sure what the reason is. Initially it was believed to be a lazy pump, however after swapping that out, it seems to still be the same.

My fuel setup (and other possibly pertinent information) is as follows

• R34 GT-Four (not sure if they run a different style fuel tank, or smaller fuel hosing, given it used to be an N/A car from factory)
• RB26DETT
• Approx 515hp on a hub dyno, which is usually reading a bit higher than roller dynos
• Running E85
• Deatschwerks 1200cc injectors
• Walbro 460lph intank fuel pump
• Standard fuel rail and FPR
• Unsure of fuel filter, I don't think it's anything fancy, but has been changed a couple of times since switching to E85

Since swapping fuel pumps, not completely sure if the surging is still present, as I kept the fuel topped up each time I went out; however the workshop said the previous pump was secured well, and was low down, so there was no reason for it to surge previously.

I am considering putting in a fuel surge tank, -10 micron filter, new fuel rail and an adjustable FPR to try and fix all the above items, however just wanted to see if someone has any ideas before I embark down this road.

The other strange thing is that I know another car which is exactly the same fuel pump and injectors as me, however is sitting at 100hp more with breathing room on the injectors, and another car which has same injectors (different fuel pump), but is over 700hp

Thanks!

[scotty nm35]

Do you have a fuel pressure gauge on it? Generally that's the only way I can tell if the pump can't supply enough fuel to the rail, whatever the issue.

[KiwiRS4T]

You should have heaps of fuel for that power level. Fuel rail and FPR "should " be up to it. Have you tested the fuel pressure? Maybe you have struck a dud pump. Have you wired the pump for full battery voltage? Have you seen the afr chart? Is it possible that it is a problem with the tune?

[PSIKO]

Hey guys, thanks for that!

I don't have any fuel pressure gauges on it, that's something the tuner did and said they had maxed out

Pump is wired up for full voltage, the AFRs were previously a bit on the lean end up top, which has now been rectified so that they're "safe", but I don't have a copy of it sorry ...

The tuner is very good, I don't think there's any issue on that front

Sorry for the noob question, but I if I had a fuel pressure gauge on it, and for example the fuel filter is blocked, that would then be able to tell me that the filter is blocked and the injectors are over-working/hitting max duty-cycle, due to the reduced fuel flow (given by the pressure)?

[PSIKO]

Sorry missed the other one Kiwi, the fuel pump is brand new as the last one was suspected of being the culprit. Although I guess there's nothing to say I didn't manage to strike up another lazy pump perhaps

[Kinkstaah]

My R34 has had issues with fuel filters before. Changed to an Earls and changed that when it became blocked, but I noticed this by the car running lean under power, which coincidentally was about the same amount of power you have

All it took for me was to run one tank of 98 and switching back to E85 to see my filter full of stuff. Pretty much want to change it any time I do an oil change now, I would lose my mind if I didn't have a wideband that will cut the engine if the event of a lean condition as I'm super paranoid about fuel filters now.

[KiwiRS4T]

^^^what he said. Take out your in-line filter and cut it in half to see what its like inside.

[STATUS]

those are 1000cc with normal rail pressures, those DW are a 4 or 5 bar base 1200cc rating.

your power is around 390rwkw and is around right for getting close to max. (390-420)

[scotty nm35]

It's interesting how DW and other brands feel the need to rate injectors at higher pressure to make them sound larger than they are.

My 1000's are actually 5000cc at 100 bar rail pressure.

[PSIKO]

^^^what he said. Take out your in-line filter and cut it in half to see what its like inside.

Here we go; looks alright to me though