You have yours set up the standard way in series: feed - bank 2 - bank 1 - fpr
Correct?

And you're seeing bank 1 trims higher than bank 2 right?

 

I am seeing b the same thing. But only above 26 psi of boost. I suspect that pressure is falling just a little bit and the difference is only then noticeable. I have verified boost between banks matches (pre-throttle).

Are you on the stock regulator? I have the smaller Fuelab one set to stock base pressure.

 

I had the fuel lab one sucks so bad so we put the four innovations one in still the same

 

you should try running dual feeds, fore innovations stage 3 kit or whatever does this. Have a line running from the pumps to a y in the bay and that goes to each rail and then have the output of each rail go into the FPR (most have 2 inlets and 1 outlet). I would suspect that would solve the issue

 

Agreed. This is the best method from what we have seen over the years, not just with the GT-R but other high horsepower cars as well. For example, on high horsepower Supras, which are an inline 6 with only one long fuel rail, we will run one feed line to the front of the rail, a second feed line to the back of the rail, and have the return line between the #3 and #4 fuel injector which leads to the fuel pressure regulator. It is more consistent with fuel pressure throughout the rail(s).

 

I'm having the same issue.

Under light load trims are higher on bank one

I don't think it's your rail setup as a have the same issue with factory rails over 900 hp as well.

Does your trims level out under a little load 0 psi and up?

Sean, I think yours is fuel flow at high volume.

 

Also... How low is too low for base fuel pressure? Any problem running 34psi base pressure instead of 43? Big injectors are much easier to control with lower base pressure but is there a real downside to this?

And by base I mean with the engine not running but the fuel pumps on.

 

Stock base pressure is 50psi, he could try dropping it to help out flow if he has enough injector but that isn't going to fix the bank imbalance

 

Tuner Rob Harper set my base psi lower to like 38 at idle , it's definitely just more pressure is building up on one side and need to reroute it to a parallel to set up

 

Let me know if this addresses the problem. I will do the same. I'm confused though because I have the AMS fuel rail setup and they do it in series too.

 

I would imagine those running closer to or at the point of being out of fuel pump would see this more than someone with plenty of fuel pump.

I know with my stock fuel filter, I'm on the edge. Especially when boost gets up there. I only have a slight split above 26 psi and a 1-2% increase in split from the point it starts to separate and red line. I have plans to run an aftermarket fuel filter to get rid of that soon. But it's such a small difference for me now that it's not a big deal. I constantly look at logs so a change won't go unnoticed.

 

I bet that is entirely true, didn't even think about that but yea the closer you get to the max flow of your pump system the more you'll run into a difference between banks. Good call!!

 

So I checked everything today all pipping is leak free, no vac leaks fuel pumps and fuel lines are leak free and good to go , but still , STFT are off from side to side by .6-7 at idle , at 2500 rpm and up ! Example, b2 will say 107 and and b1 will say 114, or 90 and 96 ? Could it be in injector going bad spark plug not working right??

 

This is the biggest pet peeve I have right now with my car.

Same thing your describing but it fades from side to side randomly also when its out of vacuum it usually smooths out.

What I've done to check it
Fuel pressure at idle 43
Checked all gaskets and downpipes.
Switched from lc5 to lc4. Read that some where so I figured I would try
All 4 new o2's
New injectors
New plugs
Compression test
Smoke test
Checked manifold with carb cleaner and water to see if there was a leak somewhere

Audio, lmk if you find anything.

And when you did a leak test for vacuum leaks how did you do it ?

 

This is the biggest pet peeve I have right now with my car.

Same thing your describing but it fades from side to side randomly also when its out of vacuum it usually smooths out.

What I've done to check it
Fuel pressure at idle 43
Checked all gaskets and downpipes.
Switched from lc5 to lc4. Read that some where so I figured I would try
All 4 new o2's
New injectors
New plugs
Compression test
Smoke test
Checked manifold with carb cleaner and water to see if there was a leak somewhere

Audio, lmk if you find anything.

And when you did a leak test for vacuum leaks how did you do it ?

hey, I know its an old post but did you get this issues resolved and how? i'm having the same exact issue, fuel banks are 5% difference.