GTX motor cutting back at 4.5k

[Foescort]

My gtx swap has been running really well, i had a problem of it cutting back bad at about 3.5k and found a loose charge pipe to be the problem. Now another problem has come along. IT acclerates hard when boost hits and keeps accelerating then at 4.5k all of the sudden it feels like someone shoved a potato up the tail pipe. It feels like the motor just stops flowing. Basicly its just cutting back. Any ideas? maybe a boost leak? Why would it all of the sudden stop acclerating like that.

[Lex]

Either boost cut or another type of fuel cut past 5k rpm ... something to do with not grounding a certain pin. The aussie guys at Fordlaser.com can tell you more about it.

[FE3-323]

isn't having a fuel cut instead of an ignition cut extremely dangerous on a boosted motor? wtf was mazda thinking.

[Foescort]

Ok so give me some more info here. When does boost cut normally turn on? How does it turn on? What activates it? When does fuel cut normally turn on, what would activate it? Thanks

[mikeflys1]

isn't having a fuel cut instead of an ignition cut extremely dangerous on a boosted motor? wtf was mazda thinking.

not really, cause you're not running it lean....you're just not running at all. And a spark cut ruins the cat.

[FE3-323]

how would you not run lean? even for the slightest moment?

[Lex]

you don't get any ignition of the air inside the cylinders if you get no fuel.

[sysopt]

Check for other boost leaks before comdemning anything else. If you have to, take the the intake track apart to inspect all rubber goods and connections.

[TurboProto]

What size injectors are you runnin? Ive got 460's in mine and I had the same problem so I tuned my afc controller and tuned my timing to fix the problem. but mine is a n/a motor w/ the gtx turbo setup and n/a ecu.

[Foescort]

Stock injectors. My buddies that work at dealerships all agree that it is fuel cut not boost cut. What makes fuel cut turn on? We are going to get a FCD from an rx7 and see what happens.

[Lex]

Fuel cut = the result of boost cut. Basically if your VAF flap opens past a certain point, the ECU thinks you'rs overboosting and it cuts fuel.

Now have you tried slowly getting to 4.5k rpm? So that you are not making any boost? Because it might be something else if its the same rpm in every gear. Like I said, check fordlaser.com for info as well. They were talking about a certain 5k rpm cut

[Foescort]

If i accel slow it doesnt do it. But i know there is no way that im running 14psi to hit boost cut. I havent got a boost gauge yet, still waiting on it. But i know what 14psi feels like. Yea i have been reading that website.

[Foescort]

Im going to buy a new thermostat and thermoswitch for my gtx motor. Do these need to be actual gtx parts or will normal BP parts work?

[Lex]

BP ones will work fine .... you can buy a colder thermostat if you want ... it will keep the engine cooler

[Tazman2]

Fuel cut = the result of boost cut. Basically if your VAF flap opens past a certain point, the ECU thinks you'rs overboosting and it cuts fuel.

Maybe his flap is misadjusted too much and thus hitting that "magic" spot WAY too early?!