zRotary

hey guys, i really need help.



i have read and discusses, thought about it etc.. and i am still helpless about my problem, because i cant see any reason for what my car is doing.



it runs very well until 6400rpm, from 6400rpm- 7500 it gets LEANER AND LEANER with each revolution.

You will say "yea its your Power FC which isnt programmed well in this area" but thats NOT the reason.. i even tried out, and MAXED the field from 6000-8000rpm out, that it should theoretically give me AFR of 8:1 or something like that.

The Injectors are NOT MAXED OUT, duty cycle shows me 75% (2x 550cc pri, 2x 800cc sec).

Engine ist Streetported, and like i told before, all is AWESOME under 6400rpm.



it goes like that:

6000rpm (14psi) = 10,7 AFR

6500rpm (9psi) = 12,4 AFR

6800rpm (6psi) = 12,8 AFR

7000rpm (5psi) = 13,4 AFR

7200rpm (4psi) = 14,5 AFR

7500rpm (4psi) = 14,9 AFR



well, that are NOT the true numbers i get, but something like that. like you can see, the AFR get freaky high, but my Fuel and ignition maps are totaly OK! they are even OVERrichen from 6000rpm-8000rpm fot testing purposes..

My Fuelpump is a Walbro 255lph, rewired, and since it produces enough pressure in under 6000rpm and 14psi, it should be well with 7000 and 6psi in any case.



do you have an idea what reason it could be..? i am clueless.. i only thought about the fuel pressure regulator.. could it be that bad guy?



any advise would be very appreciated.

1Revvin7

Yeah sounds like a fuel pressure problem. Time to get a fuel pressure gauge..

Jims5543

I had the same problem.



What kind of turbo and boost are you running?



My first suspicion is the fuel pump.

zRotary

Hey thanks for the replys.



Well, its the Stock Turbo at ~13psi. But the problem also occurs with stock boost pressure, doesnt matter!



The Walbro Pump was in there as i bought the car, for sure there is no original pump, because i hear it clearly pumping for 1-2 sec as i turn on the ignition.



1Revvin7,

If there is enough fuel at near 14psi at 6000rpm, why should be there LESS pressure at 7500rpm and only 4psi of boost?

If the pump is able to handle 14psi at 6000rpm, then it should be at least be able to operate properly at "lower" fuel consumption at 7500 and 4psi?



i am able to richen the AF mixture up abit threw "overdrive".. increasing the range from 7000-8000 from 100% to 110% or increasing the injector lag-time..

but thats like fighting the devil with the beelzebub, and it is not a solution of the true problem (which i dont know lol)

Jims5543

That is totally bizarre!



I will ask around next week and see what I can come up with.



More questions:



Do you have a fuel pressure gauge?



How are you measuring your A/F?



Have you done a pull on a dyno and watched the fuel pressure to see what it is doing?



When was the last time the fuel filter was changed?







I had a similar problem, always running out of fuel in the upper RPM band at higher boost. I hooked a pressure gauge up to my fuel line and did a 3rd gear pull on the street with the gauge taped to my windshield. My pressure was dropping off horribly at the upper RPM's.



I ended up tearing out the entire fuel system, I pulled the fuel pump and made a pickup for the tank and went with a external pump, I then ran huge fuel lines from the back of the car to the front in addition to a fuel pressure regulator and big fuel rails.



I am not saying this is your solution but I am just telling you I had to go to extremes to get my fuel right.



I would start with the fuel filter if it is not fresh, then the pump.

j9fd3s

only add in, is the fd power fc will go to 90% duty, have you played with the injector sizing? if the fuel curve is right, changing the injector sizing a little will give you an overall mixture change

zRotary

well if i change injector sizing, i would just trick around but not solve the problem. Now i am fine with the AF mixture because i told the PFC to add extra fuel from 6500rpm on. but that are just electronical tricks.. there seems to be a mechanical problem, so i wanted to know if it could be for example the fuel pressure regulator.



at 5500rpm and near 14psi, the duty is at 81% with the 800cc secondaries. but at 7000rpm where the boost is really low and it gets leaner and leaner, the duty goes down also! lol most of the time i have around 70%~ in that area.



if nobody knows a solution, then i just have to spend the extra $$ and try out an aftermarket regulator.. maybe running parallel-fuel rails too? any idea where i could buy a "kit"?



oh yea, my fuel filter is 1 year old, maybe 3000miles on it. bought from rx7.com.



well.. i think its time to get a fuelpressure gauge and a regulator

Jims5543

How are you measuring your A/F?



Is the car popping at high RPM?

zRotary

i have LM-1 Wideband attached to it. Lambdafeedback is off in Power FC.



what do you mean with popping? its running smooth up to 8000rpm, but lean in area from 6500rpm on.

zRotary

hey me again..



could it be really the fuel-pump..? i havent heard good things about walbro fuel-pumps, but could it really be the pump?



also, what are your FPR and Fuel-Pump recomendations for up to ~480whp? i dont have 480whp haha, but if i should buy a pump.. why not to go sure for the future?