I have a ls vtec with 12 to 1 comp. r head with skunk2pro 1 cams and valve train. Long story short i have a fuel prob. doesnt matter if i in vtec or low cam it looses fuel evry time at 7500. Its the same wether i use my rc 440 or my stock ls injectors. Installed a new walbro 255 pump with filter and strainer. Made no diff. Any help would be great.

 

Its in a 94 ls integra.

 

is isnt suppost to rev even that high... whats the ecu?

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i know nothing about lsvtec, but you wanna have your tune and ecu up so when someone who knows what theyre talking about looks at this, they can help you.

 

i have a tuning ecu. crome with a inovative wide band. My bottom end was built to turn 9k safely. Eagle h beam rods. All arp hardware and balanced crank along with arias forged pistons. I have tried everything i can think of. I have made a heavily modified gsr map as a base map.

 

NEED HELP!!! Dont want to sell car but i been fightin it for 7 months. Any idea would be apreciated!!!

 

What do you mean by it loses fuel? Is it hitting the rev limiter? Does the pressure drop? Or does it start to surge?

 

i have acess to a tuning ecu with wide band. My rev limiter is set at 9500. at 7400 my air fuel raio(says the wide band) is 12.8 to 1. At 7500 it jumps straight to 19.7 to 1. I have maxed out my 440cc and it makes no difference. I even disabled v tec and it still leans out. I tested resistance to the injectors and distributor. all is good. My fuel psi is set at 50 even at 7500. I have tried changin dirtributor,cams,injectors. Im out of ideas.

 

is your fuel pump working properly?

 

So i have a fully built motor that falls on its face at 7500, it stops pullin and im afraid of poppin it cause it so lean. Thanx to anybody with any suggestions, it is greatly appreciated!

 

Yes, I recently installed a walbro 255 fuel pump(Same pump on my buddys k24 turbo layin out 450 on pump gas)So it is plenty for all motor. cleaned all lines and tank. All hoses are good and pressure is set at 55psi.

 

I am assuming that there isnt any fuel leaks anywhere, like the o-ring that goes on the rail to the injector, or any of the lines. is it a stock rail and stock regulator?

 

I have a skunk2 carbon composite fuel rail and after market regulator, made no difference does the exact same thing with the stock ones, no fuel leaks!

 

Since the AFR change is associated with a physical loss of power, it would be interesting to see the fuel pressure at that point. If the fuel pressure is fine, perhaps there is something wrong with the tune.

 

The fuel prussure is good, hooked up a gauge in the car. I make the tune, I have a tuning ecu. I run crome with a inovative wide band. I have tuned many other cars with no prob. My injectors bout 45% duty cycle at 7400rpm. At 7500rpm i turn them to 100% and it still leans out. Even in low cam. Its like the injectors are not gettin the signal at high rpm. I have tried many diffrernt ecu and checked the injectors with a volt meter. All tested good, did the same to the injector plugs. My harness is in great shape. This car is drivin me nuts, had two shops look at it and they are dumbfounded.

 

Have you tried another ECU? Tracking wiring is going to be tedious.

 

The tuning ecu and my chipped ecu do the same. I checked all the wires, evrything was to spec. Dont know what else to do.

 

you seem like you know what your doing but i have to ask. if your ecu is pulling to much timing at 7500 then your going to blow flame out your exhaust and it will look like your AFR is lean becuase your cooking your O2 sensor

 

I have pulled alot of timing away so i dont pre detonate and mess melt a piston since its so lean. So im sure thats not a problem but i will check and see. It is so bad that i am afraid of meltin all my pistons above 7500. It will rev out to redline(set at 8700) but has no power. It doesnt matter what i do to the motor or fuel system it wont get to the cylinders. I know that the distributor also controls the timing of the injectors but i have tried many diffrent ones and same thing. I do appreciate all advice cause i have know idea what it is

 

it sounds like you might be pulling to much timing. try to add some timing and see if it richns out. also you said your running a modified gsr tune. you might not know this but when you timed it with a timing light that a gsr motor is set at *16 degrees base timing. so if your pulling timing from the ecu your pulling a lot more if you set the base timing at TDC

 

I have messed with the timing qiute a bit. I just retarded it so it is safe and i wont worry bout blowin it up. When it was built with the stock itr head it pulled good and only little lean. Its been like this for 5 months. I have thrown timing at top end and it made no change in the afr. It just amkes no sense. at 7500 in high or low cam it wont get the fuel. Never had this much trouble tunin a car.

 

wow man i cant think of much else. maybe somebody else might have some good info.

 

Only 1 other person gave some info. I fyou think of anything let me know. Thanx for the help, I really appreciate it

 

Have you considered the plugs and plug wires? Especially check the plug gap. The high CR could be impeding the spark. Perhaps adjust the gap a bit smaller.

Also, is the knock sensor functional at 7500 RPM? (This could be retarding the timing if functional.)

 

Thanks for all the help on this one guys, I've messed with this car for quite some time now, and have no idea where to go. We ran a map with vtec disabled to datalog a/f at 7500 and at 7500 on the dot it hits a wall of no fuel. Second we engage vtec at 3500 (just for tuning purposes) and at 7500 hits a wall again. Fuel pressure remains at 50psi throughout no matter what rpm, even when it runs lean, so I am assured fuel is getting to the rail, we've even tried another rail, different hoses, new crush washers, regulator, etc.

I've come to the conclusion that something is happening electrically to cause the ecu not to open the injectors correctly at 7500 rpm. We've tried two other known good distributors as the cyl. position sensor may be having issues, but see the same problem. I would think possible the tuning program is at fault, but it is the same tuning ecu/ program that we tune with daily and haven't seen the problem with any other cars.

Any and all help and ideas no matter how rediculous are appreciated and thanks everyone for the ideas

 

Going back to the rev limit on the ECU. It is set originally by OEM below 7500 RPM, new ECU has rev limit set higher at 9500. Seeing as the original components where built for limit below 7500 RPM it would follow that the ROM program in the originally ECU was only given parameters for running specs (timing, fuel, etc) below 7500 RPM. Even if rev limit set higher on the new ECU, if the ‘running specs’ are not changed/modified at the same time then engine will not rev past ‘running specs’ limits no matter what the “rev limit” is set at on the new ECU. Its not only the rev limit that has to be modified but the rest of the programming (stored specs) has to follow.

Just a thought, BDV