Leaning out at 15psi of boost?

[87turbot-type]

So I've just started doing some wot test runs in the car to see what bugs I may have and weed them out. After logging a few runs and playing around with fuel pressure and fuel control setting in the chip. Everytime I hit 15psi of boost I start to lean out and it seems as if it must be loosing fuel pressure. (I'm at 10.5:1 and will go as high as 12.8:1 at 20psi) I'm going to borrow a fuel pressure gauge to that I can hang on the windshield and see if my theory is right.

My fuel setup is GS340 fuel pump, Racetronix sending unit with -8an line out, -8an SS front to back, champion intake with rails, 80lbs injectors (75% duty cycle @20psi)

Turbo is 6131DBB with S cover (So not that big of a turbo)

Only thing I haven't done is install the hotwire kit I have, which I will be doing this weekend.

Has anyone else had any issues like this and what did they find the issue to be. I can't see the hotwire kit solving the problem but will see.

Thanks Brandon.

 

[~JM~]

...I can't see the hotwire kit solving the problem but will see.

Thanks Brandon.

You may be surprised & it definately won't hurt.

Good luck
~JM~

 

[Reggie West]

Spark plug gap?

 

[Racetronix]

Only thing I haven't done is install the hotwire kit I have, which I will be doing this weekend.
Has anyone else had any issues like this and what did they find the issue to be. I can't see the hotwire kit solving the problem but will see.
Thanks Brandon.

 

[kidglok]

75% duty cycle on 80lb injectors is about ~750 hp. At 15psi, id be looking at fuel pressure.

 

[Racetronix]

Install harness FIRST!!! Low voltage can cause a 20%+ hit in fuel pump volume.

 

[blackdeathtrap]

with that much power you should either have a isolator and a fp gauge inside the car or like me and get the tr customs one hood mounted and isure 1 to 1 fp gain to boost

 

[Nick Micale]

We checked voltage at the pump connector on 2 stock GN's this past week.

One had 10 volts, the other 7.4 volts, neither enough to satisfy the demand for fuel even on a stock engine.

If you want to do it properly, also run the ground wire from the connector to the engine when installing the hot wire kit.

 

[87turbot-type]

Spark plug gap should be ok .032 on autolite 104's

Nick thats some low numbers. I'm gonna do the same test on my connector with and without the kit. I installed it today so I'll do the test in the morning tomorrow. And I have a separate ground on the hotwire kit running to the frame to the body ground (added)

Racetronix - Everything is from you guys. I switched every relay in the engine compartment to your stuff. (i'm in ontario to) I'm gonna make another order from you this weekend to get a junction block and clean up the wiring to the hotwired pump and injector harness.

If the weather is nice I'll make another pull and log it and see what happens, and also post the voltage at the pump hotwired and not.

I'm going to look into buying the sender to log fuel pressure on the powerlogger.

I also pulled the turbo off to port the WG hole bigger to see if I can get the boost to stay around 18psi. Right now I have a 5psi spring in there and still hit 21psi. Just feels like several stages of boost as it overpowers the bypass. Slow, fast, faster LOL.

Thanks Brandon.

 

[Nick Micale]

........... And I have a separate ground on the hotwire kit running to the frame to the body ground (added)..........

Some people seem to think the frame and body are a good ground, but we prefer to ground critical items, like the fuel pump, directly to the battery.

This lesson, like many in life, has been learned the hard way with real world experience.

 

[oldsracer]

I would say install the hotwire and see if your problems are still their^^lot of experts have chimmed in so id listen to them

 

[87turbot-type]

I will look into running a ground from the tank ground to the engine block ground.

After installing the hotwire kit and logging another file. Car is back in fuel control holding pretty steady at 10.8:1. Also porting the WG more has the turbo producing 16-18 psi and fluctuating in between. I will install the 11psi spring in the wastegate and see if it still holds around 18psi. Supposed to get snow in the next couple of days so will be a bit before I get back and post results.

Going to have to look into a catch can system for the breathers as I seem to be pumping oil out the breathers now as well.

Engine not running voltage switched from from 12.3V to 12.5V hotwire kit. I know it would be a better test to check it running but I didn't have my good meter kit with t-pins to backprobe the connector.

Brandon.

 

[TR Custom Parts]

I just took Nick's suggestion and ran a ground from the fuel pump directly to the battery ground using an extended post, will see if it makes any difference on my GN. Still chasing a low fuel pressure issue, last time out hit 28-29 lbs of boost and only 62-3 lbs of fuel pressure. Wasn't dropping, that was just the max pressure it would put out. Was told that maybe the relief valve in the pump is opening too soon?

 

[Amelio]

When I swapped out my drive train to the car I have now it ran like crap! I scratched my head for a few hours and could not find why.....the same engine and everything in another car ran great....same fuel pump evrything.....The one item I did not put in the new car was my hotwire kit because it got burned up from the other car.(car wreck fire....bad memories)

Anyway I got a new hotwire kit and that fixed the car......I could not believe it so I went back and checked the voltage and it was stupid low I dont exactly remember but lie Nick stated it was something around 7 volts