AMRX7

So I understand that when too high boost levels are reached (about 11.5psi at lower rpms, peaking around 13) for a certain amount of time the stock ECU will cut fuel. What happens then? Will the ECU stop controlling the solenoid so that the wastegate reverts to mechanical only control (and around 7psi)? To "fix" this you have to recycle the ECU?

Thanks in advance.

rynberg

No, the fuel-cut is just that, a momentary cut in fuel to the motor. The ecu doesn't stop cycling the solenoid or anything.

AMRX7

Well, I've spoken to people that ran stock cars with straight pipe exhausts (cat-back) that said they would sometimes (rarely) have the computer cut back to 7psi. What causes this to occur? I got the impression that it was in response to over boost?

Mahjik

iTrader: (1)

Nope, as rynberg already stated, fuel cut kills the fuel. The car pretty much loses all power at that point (and it's not a fun feeling).

As for the boost dropping down to 7 PSI, that sounds more like an intermittent wastegate/turbo control problem. There is a lot that can go on with the sequential system:

http://www.autosportracetech.com/RX-...leshooting.htm

AMRX7

Yeah, I've been to that site (tried to some research before asking). What are symptoms when you hit the fuel cut? Obviously loss of power, but does the car recover? How fast?

That's interesting on the 7psi. I've asked a couple of knowledgeable people that ran into this problem where they would hit a boost spike and the ECU would start restricting to 7psi. They would have to turn the car off/on to get back to normal. They didn't say anything about uncovering a physical problem with the system.

Thanks for the replies. I'm still trying to figure out if I'm talking about two separate cause/symptoms or the same thing.

Mahjik

iTrader: (1)

It does recover, not immediately. It feels almost like running into a speed limiter on other cars. The lost of power all of a sudden almost throws you forward in the car.

Yes, I believe you are talking about two separate problems. Generally, when you hit fuel cut, you definitely know what it is as you'll think you blew the motor.

AMRX7

So the fuel cut come from the ECU detecting too much time in the over boost zone from the following picture...

http://www.autosportracetech.com/RX-7/ecu.htm


If this fuel cut is triggered, you can get right back on the cut if you try again without restarting the car? And you think that if the car cuts back to 7psi it is due to some other condition? I would think that if the ECU sees an overboost it would do the fuel cut, but then also restrict you from hitting it again to protect the motor (thus the 7psi condition).

If the computer stops cycling the solenoid on purpose, what other condition would cause that (other than the over boost mentioned above), do you think?

moehler

iTrader: (12)

when the car cuts the fuel, it will scare the sh*t out of you and you'll instinctively pull your foot off the gas. The rpms and boost will then drop and you'll be back in it. restarting the car is not needed... at least that's how it was when I hit the fuel cut on my pfc, I've never done it the stock ecu, but I assume it's the same.