Fuel Cutting with 550's and AFC: Need Help!!

[98autogstspyder]

I posted once already in this forum about by egy's going beyond 16000 degrees. i reach the conclusion that the car was pulling timing because of the duty cycle of the stock 450's. I changed them out to 550's. Now the car has some trouble starting sometimes, but that is not what i am concerned about.

Tonight on the highway i tried to do some driveability tuning. My turbo does not like to stay at low boost. dam thing likes to creep to 20 and stay put there. (even though i did the 34m flapper mod, have a ported manifold and have an 2.5'' o2 elinminator downpipe with 3'' catback.)

anyway, my friend was adding fuel as we were going through the rpms. At furst the car was not fuel cutting, but then it began to fuel cut alot. Then towards the end of the runs we i would floor it and the rpms would kind of skip on the tachometer. It would down shift and hit 4 grand then hit a fuel cut and skip to 5 grand and then skip to 5500. Very strange. Im doing my best to describe here. My friend would add fuel to get rid of the fuel cut, but the problem persisted. Any1 have ideas? Ask any ?'s u need and i will try to share more info with you.

Tyler


car : 1998 eclipse spyder gst automatic with 34,000 miles.

evo3 big 16g
exhaust mods r above
turbo xs manual boost controller (might be contributing to boost creep)
hks bov recirculated
upper and lower ic piping
greddy big fmic
550cc injectors (FIC)
apexi safc
egt and boost gauges
injen intake
intake filter surrounded by a heat shield
walbro 190lph fuel pump

 

[nine5raptor]

Adding fuel by increasing the amount of air that the ecu sees will only bring on fuel cut sooner. You have to lean it out to get away from fuel cut.

Just don't go too far without watching closely for knock.

 

[yo2001]

Sounds like rich missfire. Is your bumber all black?

I see no fuel cut with 550's and EVOIII 16G. but I do see 900C EGT under WOT. (my probe is right off the exhaust port, 1 inch from the head)

 

[kpt4321]

If your friend was richening the car up to aviod fuel cut, then it's time you stopped letting him tune your car.

Fuel cut happens when the ECU sees too much airflow. Increasing the output from the SAFC will only make this worse.

Follow this site's many tuning guides and you'll be fine.

 

[98autogstspyder]

ok sounds right to me. as soon as we hit fuel cut the first time, we kept hitting it, because he wood add fuel instead of taking it away. i will make a note of this . thank you

Tyler


even at WOT the upper rpms are still going to be somewhat negative right. with 550's running 19 psi on a 16g sized turbo. i understand every car is different, but in general, am i right?

 

[kpt4321]

Yes, with 550's in general you should be negative IF YOUR HAVE A STOCK MAF.

As long as your MAF is unhacked, you will probably end up around -10% or -15%, maybe -20%.

 

[gsxtacy]

remembers what Fuel cut is and why it was triggered so it will do it over and over again if you don't reset the ECU.

SAFC will hold settings but reset that ECU.

GSXTACY

 

[98autogstspyder]

wow i didnt know that.

so when trouble shooting fuel cut, be sure to reset the ecu before each new idea u try?

Tyler

 

[nine5raptor]

Originally posted by gsxtacy
remembers what Fuel cut is and why it was triggered so it will do it over and over again if you don't reset the ECU.

SAFC will hold settings but reset that ECU.

GSXTACY

??

The ecu simply has a set of parameters that when reached will trigger fuel cut. Those parameters are always the same regardless if you reset the ecu or not.

No need to reset the ecu unless you want to reset the fuel trims.

 

[nazthug]

WOW....scary

there should be a test given out before people modify cars

the future seems dim for this dsm