4th gear fuel cut?

[tweak666]

i've been trying to break in my motor, and just recently started driving it beyond my block. in forth gear, between like 4 and 5K rpm, i hit fuel cut. i'm stock spec, except for the intercooler and pipes, walbro, and cone filter. one of the nipples on the bvsv had broken mostly off. could that be enough of a leak to cause fuel cut? i've checked all the clamps and other lines and hoses. what else might cause this? could a loose fuel dampener cause it?

 

[Dan_Gyoba]

The nipple on the BVSV shouldn't make that much difference. You should look elsewhere for a boost leak. You're running at stock boost levels, too? Definitely not.

 

[tweak666]

so, i've been reading this thread: http://www.supramania.com/forums/showthread.php?t=70953
his problem is sounding like mine, but have different mods than him. i have another problem which i'm not sure, but could be contributing to my fuel cut issue (http://www.supramania.com/forums/showthread.php?t=69911)
i've replaced all the vacuum hoses and checked all the intercooler clamps. everything seems to be ok, but after 4000 rpm at more than half throttle i'm still hitting fuel cut. if i ramp up on the throttle, i can sometimes make it to 5000 rpm with no fuel cut, but i won't push past that as the engine hasn't reached its break in yet.
in one of the other threads on fuel cut, armondos thread, someone mentioned larger piping and intercoolers might be the problem. i'm running the ETS intercooler and pipes, so that might be part of the equation, but i've seen bigger intercoolers run without fuel cut. could my AFM be the problem? its the stock 7m AFM. i also read on a thread that you can introduce air after the AFM and it might help, but i'm unsure as to how i should go about that. also, i've noticed that my intake gets HOT, hotter than my fathers supra, and he's running a bigger turbo. could that cause a problem with the electronics of the AFM?

 

[bountykilla0118]

Sounds like a boost leak.... fuel cut comes from the AFM singal and since the AFM is first in the system the IC and pipes would not effect fuel cut unless it is leaking boost pressure. Boost leaks cause the AFM to read a certain amount of air coming in, but that air that was accounted for is actually leaked out and so your engine receives one thing and your AFM sees another.

 

[nosman4]

Wait, back up a second. Are you still on the stock turbo?
If you are why did you put in a walbro?
What boost psi are you running?
If you are not on the stock turbo, then you are probably hitting fuel cut because you have the stock afm and you are getting boost creep.
At what psi are you getting fuel cut?
Do you have any way to tune the car or know what your afr's are. Lean afr's would be my thought when you say your exhaust manifold is hotter than your dad's.

Just a couple things to think about.

Ian

 

[tweak666]

had to change the pump, so i went walboro, rather than put another stocker in and have to change it again. i've seen as high as 8-10psi maybe, hard to watch afr and boost at the same time. in boost the afrs are usually in the 10's, sometimes they get into the 13's though and i let off. its still the stock turbo. i have a wideband and a super AFR, but haven't really adjusted the settings yet. what causes boost creep?

 

[nosman4]

At 8-10 psi you shouldn't be hitting fuel cut, but anything can happen I guess. My impression of boost creep is that it is caused by the wastegate not flowing enough or being sensitive enough to regulate boost. That is why in the upper rpm range the boost will start to creep. You shouldn't get boost creep on that turbo at 8-10 psi though. What are the afr's right before you hit fuel cut?

 

[tweak666]

usually mid-10's to low 11's

 

[tweak666]

ok, need more input. did a quick street tune, back out the AFM adjustment screw, and took her for a test drive. now i think i have a new problem: 3rd gear, 3/4 throttle, mid 4000rpms, 15psi on the boost gauge. my AFR's were steady at 10.2, but i don't think i should be hitting that much boost on the stock turbo. i hit fuel cut around mid 5000rpms. what are my options? manual boost controller to keep it at 12psi? if i keep backing out the AFM screw, is it gonna keep building boost?

 

[bountykilla0118]

wait are u on the stock afm or a lex afm?

 

[tweak666]

stock afm