Hey all, I think I may be hitting fuel cut on my Aristo swap. I have a #1 decat/downpipe, but it still connects to my stock exhaust including the second cat.

The car pulls hard and builds boost, but somewhere around 4 or 5k it hits what feels like a jerky rev limiter. It has only done this once to me, and I was beating it pretty hard for the first time. Normal or 3/4 throttle boosting wont do it.

Plugs are new NGK iridiums, but I forget exactly what number. Stock heat range AFAIK. All coil packs looked fine and new connectors were put on all of them too.

I am not running a restrictor ring, but figured the stock exhaust and second cat would be enough restriction to keep from overboosting. I have a boost gauge on order to confirm, but should I be hitting fuel cut with my stock exhaust? I figured I would be good to go for now. Motor is all stock except TTC mod.

 

Any input? I did some more testing, and it is for sure an issue that is boost related. If I roll into it and keep boost low or nill, it will rev to redline(or at least what sounds like redline, I still have no tach).

1st gear is pretty much unaffected at any RPM. I think it is because it spins through it so fast it cant build too much boost.

If I stomp it in 2nd from a slow roll and boost builds, it will pull to about 5k and then start sputtering. I say sputtering, but it acts pretty much like a 2 step would. With a bit of surging.

3rd and 4th behave like 2nd, but seem to hit the cut/surge sooner.

I would just like to know if I am in fact hitting fuel cut, or if I have other issues I need to sort out. The CEL never lights, so I almost wonder if it is in fact fuel cut. Doesn't the CEL always light when you hit fuel cut?

Depending on when the boost gauge shows up, I may post a vid up so you all can hear what I am hearing.

Oh, plugs are BKR6EIX-11 (3764).

 

what fuel pump you running?

 

i doubt its the fuel pump unless its bad because im running my stock fuel pump on usdm turbos and its perfectly fine.

 

I'm running a Walbro 255. I ordered a boost gauge so I can see if it is boosting to fuel cut levels. If so, I will restrictor ring it and put it on the dyno this weekend to verify AF ratios.

 

It sounds like boost cut. It probably has something to do with the TTC mod because the turbos will behave differently than stock in that configuration, and its possible you are overboosting some, double check how you have the wastegates setup. you can get a boost gauge for like $25 at the local store just to test it out.

 

The boost does build kinda all at once AKA single style. Not so linear like stock sequentials. I dont mind, but my boost gauge is on the way and may even be here today. This weekend will be troubleshooting/bug chasing time. Overall though, it seems to run really well.

I will check the gate, but really there is nothing to it now. The one gate is plumbed directly to the compressor outlet on #1 turbo. Everything else related to sequential and or boost control is gone or wired open

 

i just finished my aristo swap last week and i also did a 3 inch no cat no nothing all the way back and im cutting out at around 4-5 also when im on full throttle... sometimes i can go pass 4 of 5rpms if i play with the throttle. from 4th to 3rd and 100% throttle then it will cut out... if i go from 1st to 2st only thinng i can think of is.....aristo 5krpm limit something to do with the nss and boost cut or fuel cut.

im running stock aristo 2jzgte 3 inch intercooler piping 3 inch exhaust all the way back and r154 swap

 

Man with totally open exhaust its no wonder you're hitting fuel cut. Its a known issue with the JDM turbos overboosting due to no exhaust restriction. My boost gauge is due to come in today and I will report back with the boost levels I see.

 

Doesn't the JDM 2JZGTE have boost cut if it goes over 1 bar psi like the 1JZ? You probably need a fuel cut defencer. And you will also need a speed cut defencer if you plan on going over 180kmh (112mph).

 

Yeah it does. Boost cut/fuel cut, same thing. Instead of a BCC, I plan to just lower the boost back down below the trigger threshold for now.

 

Well darn. I have good news and bad news. Good news, the car pulls hard for 11 psi. Bad news, its running at 11 psi and therefore should not be fuel cut

So what to check next. Coils? Plugs are new as I said, but have the factory .045 gap. Should I try a different plug or should the NGKs I have be ok?

It is boost related, and not RPM dependent. Now that I have a tach I have verified that if I keep boost low, I can rev past 6k easy.

I could probably rig up my meter to watch map voltage just to make sure its not maxing out or anything. I guess I can still put it on the dyno this weekend to verify its not leaning out as well.

Any other ideas?

 

Man, lots of people on SF say they gap iridiums at the standard .030 or less that most people run on copper plugs. I read over and over that you dont regap iridiums to whats up with that?

 

Im running copper ngk 4464 i believe gapped at .028 they are cheaper. Many of the supra guys who run these are bpu. Plus they are pretty cheap for a set. Have you checked your coils to see if there are any cracks?

 

I glanced at them before I put them in and they looked ok but I am going to check them again. I am also contemplating the 12v mod to rule out fuel ecu misbehaving and leaning it out... Hmmm this is very sad. I think I am going to put it on the dyno tomorrow to check AF and rule out lean misfire.