Fuel cut without boost leaks?

[twinturbozs]

Im getting some fuel cut when i punch the throttle hard early in the rpms before boost even maxes out. Ive done a boost leak test and found there's a slight hiss right at the turbo itself. Its very slight but audible. No leaks anywhere else. When i tested it, the IC pipes held a positive pressure for over 5 minutes, maybe dropping about 2psi a minute.

Im running a Lexus AFM with screw turned all the way out, 550's, AFPR

Im running a SP61GT, ive tightened the brass nipple off the turbo housing, but cant seem to pinpoint the leak. Its so slight:

1. Minimal leakage cause of fuel cut?

2. Where can positive pressure leak from the turbo?

 

[GrimJack]

What kind of pressure are you running through the SP61? I suspect you're just hitting FC at the limit of the Lexus AFM now...

 

[IwantMKIII]

What kind of pressure are you running through the SP61? I suspect you're just hitting FC at the limit of the Lexus AFM now...

you can do that?? hmm. What is the Hz limit on the lex AFM???

 

[GrimJack]

you can do that?? hmm. What is the Hz limit on the lex AFM???

Same as it is on the regular AFM - the electronics don't change, it just lets through more air for the same reading.

The frequency where FC hits is depandant on a bunch of other factors, too. Back when I was running one, I'd hit FC ~1400 on average as I recall.

 

[twinturbozs]

Im hitting FC at around 16psi, but even i punch it, im barely hitting 16lbs before it cuts out. Something leads me to believe its very premature. Other than IC leaks what else can cause fuel cut?

 

[IwantMKIII]

^bad injectors, not able to open up enough?

 

[GrimJack]

There are several factors that can contribute to FC, but the Hz reading off the AFM is the lions share for sure. The only ways you can boost this number that I can think of is:
- incorrect settings from an SAFC, MAFT, etc.
- Too much air going through the AFM
- Possibly, but not likely, a faulty AFM

 

[Mr. Y]

twinturbozs
are there any fuel tuning device? When I was running Lex AFM without SAFC, I was hitting FC at 18psi on T3/T4 (small enough) turbo. Lex+550 run very rich at high RPM/boost, so you can take away some fuel and get some more psi before fuel cut.

GrimJack
one more:
- Boost spike (due to WG actuator)

 

[BorHor]

He is running a SAFC.