I've been reading the stumble threads. It seems that a few of us are having similar issues. I know the rtek guys are working on it. I have also found that 2 heads are better than one. So I'm putting in my 2 cents, as a brainstorming thing. If it helps great, if not oh well. If anybody can add something useful, be my guess.


I remember reading that at cruise and lite throttle the ECU is in closed loop. (My stumble happens @ lite throttle @ 3500ish)

 

well it depends which stumble you are talking about.. seems to me people are having two different problems:
1: hesitation/lean at secondary injector transition
2: hesitation/lean at cruise (no where near secondary transition points)

IMO, problem number 1 is not specifically an RTEK problem. i believe it is caused by running low impedance injectors on an ecu designed for high impedance. there is no easy way around this except to install an injector driver between the ecu and your low-imp injectors
check this thread for a better explanation:
https://www.rx7club.com/single-turbo-rx-7s-23/goodby-resistors-hello-peak-hold-666741/

what would be really nice, is if RTEK could modify the stock ecu for higher current injector drivers. and have an option to run peak-hold injectors vs saturation injectors. that would fix the staging problems


problem number 2 is different. from what ive noticed, it only happens under vacuum (secondaries off) and from 2500-2900 rpm, and when the ecu is in open loop mode.. its almost like an injector has stopped working. when its in closed loop, the problem is fixed due to the ecu injecting more fuel to compensate to get 14.7 afr
to those with this problem, try unplugging your o2 sensor and take it for a drive. the hesitations get a LOT worse

 

Hey, check out my new thread I added. Can you hook a volt meter to the primary injectors and drive around? My voltage to the primary injectors goes mad around 2500-2800 rpm.

 

Unplugging the o2 shouldn't put you into closed loop? Should it?

Is there a way to disable closed loop? That would fix the problem with a little loss in gas mileage right? I mean, it's not like we drive these cars for mileage anyways.

 

no.. the problem only happens for me when it is in open loop. when you unplug the o2, it is forced to stay in open loop

 

Sorry, I have to disagree with this. All of the RX-7s that use low impedance injectors from the factory are still high impedance ECUs using resistors in series with the injector. Those of us that have converted to low imedance injectors are using resistors in the same fasion as stock.