Fuel Cut, Dont know why?

[dugjr24]

I just put on a FP big T28 yesterday and Im trying to get it tuned. I have a 255 fuel pump, 550 injectors, s-afc, a datalogger, 3 in turbo back exhaust and thats about everything that would matter. Im running 93 octane, running about 19-20 psi and im only leaned out -8 % across the board on high throttle. Im bringing in pretty good amount of air. Its reading close to 1900 Hz in Karman. Im hitting fuel cut around 5500 rpm in 2nd every time and dont know why. Any suggestions would be appreciated.

 

[boostvr4]

try leaning it out some more, 14% or so. hows your timeing?

 

[Defiant]

Im bringing in pretty good amount of air.

Do you know what causes fuel cut, why it's triggered?

Im hitting fuel cut around 5500 rpm in 2nd every time and dont know why.

No, obviously not.

http://members.shaw.ca/costall/ECUprimer/ECU_ch7.html

 

[gsxtacy]

The SAFC's job is to LIE to the ECU about how much air is coming into the engine.
The -zero- correction for 550's would be -18 across the board.
By telling the ECU that -8% air is flowing in, you'll still reach fuel cut, especially at 4700-7000 where the engine is really loaded pulling the wieght of the car.
If you have a datalogger, check your timing and keep pulling the "air flow" back until you reach a timing retard. Then add some "air flow" till you get the desired timing map.

Theoritically your HI settings should be like:

1K 2K 3K 4K 5K 6K 7K
-13 -14 -15 -18 -18 -18

You may still run into fuel cut, but considering the amount of air the FPBig28 is capable of it should be expected with 550's.

I run FIC 650's and I have never felt fuel cut. EVER. I see 2000- 2170 Karman. In comparison to the stock T25, (1480 Karmen) My FPBig28 flows 600+ more Karman. In Karman terms thats nearly twice the airflow.

good luck.

gsxtacy

 

[dugjr24]

ill try leaning it out some more tommorow and see what happens. By the way thanks for that link. I knew fuel cut was from seeing to much air, but i figured if I richened the mixture it would equal things out. I guess I was wrong. Im still very new at tuning and obviously need a lot of practice.

 

[CanadianTSi]

ill try leaning it out some more tommorow and see what happens. By the way thanks for that link. I knew fuel cut was from seeing to much air, but i figured if I richened the mixture it would equal things out. I guess I was wrong. Im still very new at tuning and obviously need a lot of practice.

If you richen things up with the S-AFC that would make the ECU see even more air and make you hit FC even sooner.

Another reason you hit fuel cut early is becuase of boost leaks. HAve you pressure tested your system to check for leaks?

 

[dugjr24]

well i leaned it out to -15% across the board just to see what would happen and you guys were right no more fuel cut. It felt a lot stronger. my timing was ranging from about 13-19 deg. my o2's were anywhere from .97 to 1.00 which is still a bit rich. and I know thats not the best thing to go by but its a ballpark.. As for the leak test i havent done one in awile, I know I have a small exhaust leak where my downpipe connects to the 02 housing. I appreciate the help a lot. thanks