Fuel Cut #3

[sleepydsm]

92 TSI AWD 5spd

The car hits fuel cut. I know it's fuel cut. It even fuel cut on the dyno at the last dyno day. The car stopped hitting FC, found out there was a big boost leak before the maf, once it was fixed it hits FC again. Sounded like one or two smallish boost leaks from the throttle body area also.

I notice when it hits FC the wideband is like at 12.8

WHY does this happen?

Fresh 6 bolt
14B (15psi)
AFPR at stock FP
GM MAF/MAFT in blow through
"fuel cut" switch is "off"
FMIC
255HP
Disconnected FIAV coolant lines

[Shane@DBPerformance]

It's possibly fuel cut, if you are on stock injectors. The MAFT can't truely get around fuel cut. The only thing it could do is clamp the signal going to ECU, to try to avoid fuel cut, but that has the very dangerous side effect of causing the car to run lean, because it has stopped reporting the real airflow.

[scheides]

Dude, exhaust, FMIC, and a decent intake is enough to max out the stock maf and injectors on just the stock 14b. 12.8 is lean, this is another sign of this :)

I have a set of evo 560cc's off of my car...slap them in, you will be set! Dial back the MAF-T one or three clicks and it'll run like a kitten.

[sleepydsm]

SO I should slap that "fuel cut" switch back to the on position I guess.

Will boost leaks after the GM MAF affect anything?

Is the solution to this problem find some way to let the ECU read or allow the current airflow, and provide adequate fuel for that siuation?

[scheides]

THE solution is to provide more fuel, or turn down your boost (so you don't require as much fuel).

With the MAF-T, you can read as much air as you need to, but if you don't have enough fuel to go with that air, you will fuel cut (or blow up your motor by disabling it). :)

[123abc]

If you know you have boost leaks, I would fix them before upgrading to larger injectors.

I have much of the same setup as you except I have the stock pump and maf. I hit fuel cut around 5k under boost, but I know I have a couple leaks at the tb.

[scheides]

Sleepy, If you upgrade to the evo 560's, you can turn the boost up to 18 :)

[Shane@DBPerformance]

Boost leaks after the MAS, whether it's a stock setup or a blow through MAFT setup will make the car more likely to hit fuel cut and make it run richer, because it's reporting more airflow to the ECU than is actually making it to the engine. Boost leaks before the MAS on a blow through MAFT setup would just make the car lose power and be more prone to knock because the turbo is having to work harder than normal.

You don't want to use the "fuel cut" clamp hack of the MAFT, it's a very poor solution. As Chris said, you need to put in bigger injectors and then dial down the MAFT. It's the same trick that people have been doing with the SAFCs to avoid fuel cut forever.

Or you could get an EPROM ECU in there with fuel cut removed. The stock 450ccs can handle a decent amount more power once the fuel cut in the ECU is removed. Fuel cut has nothing to actually do with fuel supply problems, it was designed as a way to save the car from a wastegate/vacuum line failure that would cause a serious overboost.

[A//// Guy]

The maft really doesnt disable it, like it should if you flip that switch.

Upgrade your injectors, switch the settings on the maft to acknowlegdge it, and then turn up the boost. Thats the only way to get rid of fuel cut. Then throw it on the dyno and get her tuned.

[Shane@DBPerformance]

If you are just barely on the edge of hitting fuel cut, then you might be able to take a different route, since you spent money on an AFPR. If you cranked the base fuel pressure from the stock 1G 39psi to 55psi, then you would turn those injectors into 534cc injectors and then might be able to lean out the MAFT.