Well I just got all the mods done of the summer before going back to school. Put in the 720s, Profec B, and Greddy FMIC. Driving it the other day and turned up the boost to about I guess it was 11psi and around 5k the car stumbled (felt like a fuel cut...sputtered) until I let of the throttle and got back into it but not full throttle. I had a buddy in the car with me and he said that the check engine light came on for a brief second. Going to go pull the codes tonight. Seems like it stumbles when I am at full throttle but its fine if I go only about 75 % or less. I am almost sure that it isnt Fuel Cut though because it does it at different boost levels, but it feels just like it. Not sure if this is because i am so rich. Havent tuned in the S-AFC, it is at 0% from 4k-7k. Still on stock turbo. I know I need to get to a dyno but school is approaching and wont have time till I get back to Orlando.
Reading in other post and saw a pretty good starting point for 720s is -10% to -14% on the SAFC. I will probably go try that, just cant afford to blow something before school so I am kind of hesitant to lean it out before hitting the dyno.
Chris

 

Hey Chris, I think you would know if it was fuel cut. It would act like you hit a wall almost.
A quick check would be to pull the plugs and inspect how they are. That would give you a indication of how things are burning. Good luck/skill

 

It might be my tps I dont know quite yet. I'll check plugs and go from there. I am going to try to do as many thing before I leave this Saturday just seeing if it is a quick fix before I do a bunch of work.

 

Without tuning those 720's you will be running too rich. This may or may not be the cause of your stumble.

To get back to factory mixtures, set the S-AFC to -13% above 3800rpm and see if that cures it.

 

Mine did the same thing that your describing a little while back... ended up it was my TPS.

 

mine is doing the same.... i put in the fcon today and it stumbles at 5500 or so... i dunno if its fuel cut... i thought it was/is but now i dunno.

theni put theled on my tps only one lights up.... so that meants its ok right?

 

NZ - That is intresting that you say -13% above 3800rpm to return to stock settings. So how did you arrive at that? Trial and error and a wideband?

James

 

actually 720s are 31% bigger than the stock 550s