rx7 cruising problems
 

Hello, I've been restoring my Turbo II for sometime. It's now generally a pretty good car. The problem is that after I boost for the first time, when I'm cruising and just trying to maintain speed the air/fuel ratios will continually get leaner and leaner until I romp on the gas to bring the ratio's back down. They'll stay rich for a few seconds until they lean out again to the point where the car starts to cut out (17-18). This problem only occurs when I'm trying to cruise at a constant speed and it seems to occur only after I've boosted. Thanks for any help you can give.

More information is going to help you get a better answer. What's been done to the car? Is it stock, what ECU is in the car/who tuned it, how are you determining AFR (datalog, visually with gauge), what's been deleted/removed, what series is the car, what troubleshooting have you already performed, etc.

87 Turbo II, Aggressive streetport, to4b hybrid, Apexi N1 exhaust, bigger injectors, upgraded just about everything but ecu. I'm using an innovate LC-1 to get my AFR's. I know I should have upgraded the ecu by now but people make insane power numbers on it due to the overly excessive timing advances. That being said, the stock ecu should have no problem computing AFR's when cruising.

the stock ecu has its limit when its computing things, you're way over it.

I know, I'm looking for a good rtek or possibly a power fc. Until then what could be make it continually more lean to the point where it cuts fuel completely when cruising? Could a bad o2 sensor cause that?

When the ECU sees no signal from the oxygen sensor it defaults to a particular setting. Whether it's contributing to your problem or not you need an O2 sensor, and the sensor is used for cruising purposes only. And was the stock ECU made with stock injectors in mind? I think the answer is a resounding yes. Lastly, the stock ECU is not geared to run as much boost as you are currently throwing at it.

Since you brought it up, Rtek is such an outdated and limited solution at this point...with Adaptronic and other PnP solutions there's no reason to not go with a true standalone anymore on a car with this much modification. I just can't believe you're running this setup on a stock ECU...

sounds like a vacuum leak, however it may also be saving the engine before your apex seals begin having vacuum leaks.

I know, I just ordered a Power FC and an adapter kit so I can use it on my car. Lyger, what are you trying to say?

He's saying your car not boosting property is probably the only thing keeping your motor from popping like a cherry with the way it's currently set up.

I'm only boosting to 15 psi.

only 15?

on a stock ECU with no piggyback?

with a hybrid T04B?

are you retarded?


somehow i feel trolled, or you are extremely lucky to have just thrown the right combination of parts at the car for the upgraded turbo at that boost level. nonetheless you are likely already at the limit of the turbo's efficiency and that doesn't even address the issue with the ignition timing. the stock ECU is about as ignorant as a brick when it comes to fuel trimming, even with the narrowband O2 sensor it does jack all shit. you can't just upgrade the injectors and expect the ECU to compensate, this car was built in the mid 80's and this was one of the earliest attempts at fuel injection from mazda in mass production, meaning it is a rather rough system with rather strict variables that it can accommodate.

i'm sure you will have a witty comeback, like to the effect of you did tons of research on what has worked for other people with that setup. all i gotta say is "good luck with it". sure it is possible to do the above but if you had the knowledge to do it you should have the knowledge to diagnose and or tune the cruise fuelling.

if you really wanna continue with your time bomb project you can install a SAFC and trim the cruise AFR's manually.

i had a similar, but more mild setup back in the day (stock engine, v trim S5 turbo, full exhaust, +some fuel), and when it was cruising the o2 was basically just turning the engine on and off.

its been my experience that the stock fuel system is only good to about 10-12psi, and that is WITH some kind of fuel controller (the Fcon's historically work quite well) and a pump.