safe boost level T28 50 trim

[NateS]

Well last night I finished it up and took a run. I had it set at 15psi. It had no problem no fuel cut or anything. BUT, today I took it for a run and I was accelerating through 2nd. It hit full boost then at about 6K I heard a loud pop and the car jerked then kept going. I did this one more time and it would jerk after about 5.5k. I figured this was fuel cut off so I turnt it down to about 13psi. It runs fine now. Only thing that I am puzzled about is that it did not hit fuel cut off last night. It was colder last night than it is today. I am just wondering why I didn't hit fuel cut off last night but, I did today. I thought maybe a blew a coupler so I checked and couldn't find any signs of slipping. I will build a boost leak tester asap but, untill then my boost will stay at 13.

[kjewer1]

Did the injectors get installed and the appropriate adjustments made to the AFC?

[NateS]

I did not install the injectors yet. I am still running the stock injectors. I am waiting on an fpr to install the injectors.

[TheRomer]

cant the stock head gaskets only take 23 psi... which is really really pushing it. id be safe and install some arp head bolts if i was you. thats what im doing until i swap my motor next winter for a 6bolt stroker

[NateS]

It already has the arp head bolts in it. I looked at the bill for the motor rebuild and saw that the bolts they put on were about 100 bucks. So I looked up the part number and all and it is the ARP head bolts.

[kjewer1]

So there's no real surprise it hit fuel cut, since the airflow signal hasn't been chopped down yet.

You can never never measure the strength of a headgasket in PSI. PSI is pretty meaningless. Cylinder pressure is the value that is going have a limit for a given gasket and a given set of circumstances. I ran a stock headgasket with ARP studs into the low 11s, others have run low 10s on them, which requires 30 plus psi, even on strokers, for a point of reference.

[NateS]

Okay, well when I hit fuel cut a black puff of smoke came out of my exhaust. Is this normal with fuel cut off? I thought black smoke means you are running rich? There was also a pop when this happened(maybe backfire or coupler?) Well I am now thinking that maybe a coupler slid off when I hit full boost causing my car to temperarily run rich. Because the kit came short of 2 t-bolt clamps I had to use 2 worm clamps instead. The coupler that I think would have slid loose I put an extra clamp on. I think tommarow I will play with it a little bit and see if it was the coupler or not. I want to build a boost leak tester but, I do not have the supplies right now. But, is black smoke common when you hit fuel cut? Like I said I took it for a test drive when I first got done and it was a really cold night but, I ran 15psi no problem.

[NateS]

So, is a puff of black smoke and a backfire/pop common for fuel cut?

[kjewer1]

Never saw my car hit fuel cut from the back Not sure, but it wouldn't be unlikely. I would ASSume it is, since you haven't done anything to prevent it yet, and it goes away at lower boost. If once you do the injectors and AFC you find it still does this, then I would be worried.

[NateS]

Damn, that just intensifies my excitement for my income tax refund money which is buying my a fpr. I want to start some tuning but, it all is waiting on a damn fpr. I am dling my software and all to my comp and pocket logger sometime this week and I will play with it untill I get my FPR so I will already be familiar with it. I will let you all know how it goes.

[ez1286]

Does fuel cut actually cut fuel or spark? I'd think it cuts spark (if it cut fuel then it'd get too lean) If it cut spark then it would puff some smoke and possibly backfire.

[NateS]

Makes sense.