So, I was reading some of the toyota tech articles about how the ECU controls fuel and what not. When I built my sentra, I removed all feedback from both O2 sensors. This caused the ECU to stay in open loop and made tuning so much easier since it prevented the ECU from attempting to change the tune by adjusting fuel trims over time. I could also tune for low load conditions at 16:1 which was perfectly safe and increased fuel economy. The transition to high load conditions was much smoother than the normal closed to open loop transition, no incredibly rich spikes. Also coming off throttle transition had no spikes. I did extensive datalogging with my LM-1 and have plenty of graphs that show how much more stable the AFR's were under differing conditions. All tuning was using SAFC2 and a 2 bar MAP sensor for the throttle input. My question is: has anyone done this on an OBDI ECU? If so, how did it go? I may do this on my supra after I install my SAFC2 and see how it goes.
Tuning option?
- Thread starter mixmastermatt
- Start date
Sounds interesting and has some merit to it perhaps. However simply removing the O2 sensor will throw an engine light and likely also throw off the ECU. Maybe a better thing to do is what a lot of LS1 guys do with their auxiliary O2 sensors. Put in O2 simulators, make the ECU think you are always running a certain A/F. Or better yet, tie the simulators into the tuning system and make them send the signal for whatever A/F you are trying to acheive at any given time. However, narrowband O2 sensors are not good for much. The ECU "knows" that, thus they are really only there to tell the ECU it's too rich, roo lean or just right. Basically anyhow.
I know removing the O2 sensor will throw a CEL, that doesn't really bother me. The O2 simulator you're talking about is for the secondary O2 sensor only, to prevent throwing a code when you remove the catalysts. An O2 simulator on the primary O2 sensor isn't going to work in the same way. The point of removing the primary O2 sensor feedback is to keep the ECU in open loop, so that tuning with an SAFC is much easier. Once I install the LM-1 and get some logs of how the ECU handles transitions, I'll analyze and see if doing this is worth it.
Sounds interesting, but I don't think I would ever sacrafice the ECU's ability to compensate for all different weather conditions and make sure you are always in the safe zone; this is of course assuming that the car would run remotely well without the 02 sensor being hooked up. Especially for me since its the DD.
mkIIIman089 said:
It doesn't affect how the ECU compensates fuel delivery during open loop operations. All it will do is force the ECU into open loop all the time. Then you can tune anyway you want. If you want to be extra safe, you can tune for a flat 14:1 during small loads, or you can tune 16:1 for fuel economy. As soon as you place the engine under load, you can tune for exactly 12:1 without the rich/lean spikes that occur during transitions. I'll try to find some of my old log files that show the difference.
I know exactly what you meant. I did say the auxiliary O2 sensors, same thing as secondary in this case.
Now as I was saying. What you would be doing is telling the ECU what your target A/F is whatever, 14:1. So you tune for 14:1 and wind up having it not matter if it's in open or closed mode, possibly. That is what I was trying to say.
Now as I was saying. What you would be doing is telling the ECU what your target A/F is whatever, 14:1. So you tune for 14:1 and wind up having it not matter if it's in open or closed mode, possibly. That is what I was trying to say.
The use of fuel trims is used to compensate for degraded fuel delivery over time. The problem is, once you tune with an SAFC, the ECU will compensate over time and return to a stock tune by adjusting the fuel trims. Some people don't tune themselves and have to rely on dyno tuning, which can get expensive if you're constantly fighting the ECU to maintain the tune you want. Using fuel trims is not required if you have upgraded the fuel pump, pressure regualtor and injectors. Yes, you will have to monitor your fuel system, and not depend on the ECU to compensate if you start to loose pressure slowly, but anyone who seriously modifies their car should be monitoring this already. If you are only concerned about keeping your daily driver on the road, then this may not be for you. All I am showing is a way for people to tune their vehicles without some of the problems that closed/open loop transitions cause and without the ECU trimming out any corrections the user has made.
If you find out when the ECU goes in to open loop mode(of course, this would be for people like myself who will be tuning with a wideband/datalogger in the car on their own) the ECU won't learn over when your tuning setup was since its not learning anything and you are simply adjusting what it defaults to after it has learned what it basically needs.
I'm not good at explaining what I'm trying to say here so:
Hot dry weather = the ECU pulls fuel to avoid running rich during closed loop, and this scales the open loop map to run over all leaner. Naturally it wants to run way rich anyway, so you are pulling a percentage of its leaner default map, keeping you in the green zone during that kind of weather.
Freezing weather = The ECU is pulling next to no fuel from the default map to avoid running lean. Therefor the map it uses in open loop will be over all richer then it was when you tuned in hot weather. Still pulling the same percentages out of the open loop map's default curve you won't run too lean since the entire thing has been made richer when the ECU learned the conditions and fuel needed. So even though you tuned in hot weather, you're still safe in the cold since the TCCS is helping you tune for weather.
With the setup you are talking about it would be like running and stand alone and having to make little adjustments all the time for temp/weather changes. And although you probably are right that forcing it in open loop all the time allows you to tune much easier, if you figure out what triggers the ECU into open loop in different conditions I think you can achieve a pretty smooth tune without loosing so much convenience.
I hope that made sence,
like I said, I'm interested to see what you come up with if you try it. I'm just saying that this would definitly not be for everyone since it requires stand alone like attention if it does work.
I'm not good at explaining what I'm trying to say here so:
Hot dry weather = the ECU pulls fuel to avoid running rich during closed loop, and this scales the open loop map to run over all leaner. Naturally it wants to run way rich anyway, so you are pulling a percentage of its leaner default map, keeping you in the green zone during that kind of weather.
Freezing weather = The ECU is pulling next to no fuel from the default map to avoid running lean. Therefor the map it uses in open loop will be over all richer then it was when you tuned in hot weather. Still pulling the same percentages out of the open loop map's default curve you won't run too lean since the entire thing has been made richer when the ECU learned the conditions and fuel needed. So even though you tuned in hot weather, you're still safe in the cold since the TCCS is helping you tune for weather.
With the setup you are talking about it would be like running and stand alone and having to make little adjustments all the time for temp/weather changes. And although you probably are right that forcing it in open loop all the time allows you to tune much easier, if you figure out what triggers the ECU into open loop in different conditions I think you can achieve a pretty smooth tune without loosing so much convenience.
I hope that made sence,
like I said, I'm interested to see what you come up with if you try it. I'm just saying that this would definitly not be for everyone since it requires stand alone like attention if it does work.
I like the idea of using the map sensor with the SAFC, I always wanted to try that on mine, but never got around to it. Is that a popular thing to do now?
Glen
Glen