Jump to content
SAU Community

Recommended Posts

Hi

Noticed my car was leaning out on lean cruise today, had previously been fine.

Went to play with the tune and my O2 feedback was off, so turned it on and the AFR hunts quite bad. It cycles between 14.6:1 and 15.6:1 at 60km/h (only had time to look at the 60km/h lean cruise AFR's)

Was just wondering if the AFR's are supposed to hunt like this with O2 feedback on, and is it worth having O2 feedback on at all or just tuning the INJ map at the cruise points to achieve constant desired AFR

Played with the INJ correction for O2 feedback, but didnt seem to make a difference. Came home for a look and in the Celica Forums and it says that the INJ correction value is the maximum value in the INJ Map that it will apply O2 feedback to

If i understood it right

Is an APEX'i Power FC in an R33 GTS't. Tuning with FC-Edit and FC-Hako interface

Thanks

Link to comment
https://www.sau.com.au/forums/topic/373417-o2-feedback/
Share on other sites

On cruise, the O2 is supposed to cycle rich - lean - rich - lean , it's called "closed loop". It's near impossible to exactly tune the system so that you get stoichiometric mixtures, so the ECU uses closed loop to continually make adjustments to the mixtures around the stoichiometric point.

Link to comment
https://www.sau.com.au/forums/topic/373417-o2-feedback/#findComment-5956093
Share on other sites

Oh I didn't think it was supposed to do this on closed loop (or at least not as much)

Seems less economical then setting the map to run at a set AFR which it had been doing. Except then it seems to vary slightly depending on coditions I guess?

Link to comment
https://www.sau.com.au/forums/topic/373417-o2-feedback/#findComment-5956134
Share on other sites

it sounds like your maps tuned leaner than 15:1 which will cause cycling problems with a power fc and o2 feedback. basically with o2 feedback turned on and a lean map it'll inject off your base map, read lean from the o2, drop fuel in until it reaches stoich then lean back out to the map again. if its tuned properly just turn o2 feedback off, you can get better economy without it. or the other option is to use your wideband to simulate a narrowband but change the values so the ecu sees stoich around the same AFR's you've tuned for (eg 15.5:1).

as for the o2 feedback setting your correct, it simply sets the correction figure limit for using o2 feedback, meaning any cells lower than this number will use o2 feedback (under the right cruise conditions) and any cells higher will ignore it completely. I usually just set it to around whatever figures are on the map in the area where you start going from cruise to light boost, usually around 14:1

Link to comment
https://www.sau.com.au/forums/topic/373417-o2-feedback/#findComment-5956194
Share on other sites

Ah sweet as, that's what it will be doing then. Lean cruise was set around 15.5:1 but all of a sudden yesterday it was leaning out to close to 17:1. On boost the AFR's were still the same so I saw O2 feedback was off and thought it must have turned itself off

So not sure what's happened to make it lean out like that but I'll tune it back to 15:5 and just leave O2 feedback off I think, seems like the easiest option.

Thanks heaps for that, explains exactly what was going on and now I know how the O2 feedback works

Link to comment
https://www.sau.com.au/forums/topic/373417-o2-feedback/#findComment-5956526
Share on other sites

Ok so quick question about the o2 sensor,

Would having it disconnected cause any sort of issues while the car is cold? I have noticed that while my car is cold and I am cruising on decel (using the gears to maintain speed, ie. going down a hill in 5th my car will just sit at 80km/h without needing to apply the brake or accelerator), or while cruising with only very slight throttle, my car - for lack of a better word - 'surges'. What I mean is that it feels like the engine is slowing down a little bit and then it speeds back up again. It's not really enough to affect my speed as the speedo hardly registers it. But it's enough that I can feel it happening.

As far as I can recall, it has only started happening since my tuner disconnected my o2 sensor and tuned around it. And it only happens while the car is cold and as I understand it, only while it would be in closed loop. Is this likely to be the o2 sensor or something else, TP sensor maybe?

Sorry if I'm hijacking, it seemed remotely on topic :P

Link to comment
https://www.sau.com.au/forums/topic/373417-o2-feedback/#findComment-5956843
Share on other sites

Do you have a power fc? If so check your hand controller to see if O2 feedback is on. If it's on and your O2 sensor is disconnected it may cause a problem - see your tuner to check if he has tuned it for lean cruise then you should just be able to turn this feature off

If it's off already then I'd say go see your tuner as well and ask him about it. It could be the TPS I guess as it helps determine the load point on the map. Not to sure if it would cause the problems your having but

Link to comment
https://www.sau.com.au/forums/topic/373417-o2-feedback/#findComment-5957018
Share on other sites

Do you have a power fc? If so check your hand controller to see if O2 feedback is on. If it's on and your O2 sensor is disconnected it may cause a problem - see your tuner to check if he has tuned it for lean cruise then you should just be able to turn this feature off

If it's off already then I'd say go see your tuner as well and ask him about it. It could be the TPS I guess as it helps determine the load point on the map. Not to sure if it would cause the problems your having but

Nah, NIStune. My tuner did say at the time that my o2 sensor was causing problems so he had to disconnect it, but it didn't matter because he just tunes around it anyway.

My car is booked in for a retune next week, but at a different tuner. So I wanted to see if I was correct about it being the o2 sensor or if I should ask my new tuner to investigate.

Link to comment
https://www.sau.com.au/forums/topic/373417-o2-feedback/#findComment-5957054
Share on other sites

Don't know enough about the nistunes but I thought seen as they run similar to the stock ECU that it might be expecting an O2 signal.

As I said though, I don't know enough about the nistunes to confirm this is what happens

Link to comment
https://www.sau.com.au/forums/topic/373417-o2-feedback/#findComment-5957260
Share on other sites

Nistune IS the stock ECU, so it CAN run exactly as the factory closed loop. But you can also turn off O2 feedback on it (by various means) exactly per the PFC example.

Hanaldo has a Neo engine yes? In which case, you can't turn off the O2 feedback in the conventional sense. You have to do it by bumping the feedback temperature limit up real high. There is no "closed loop" section of the fuel map like there is on most other Nissan ECUs (or rather, the O2 feedback flag is enabled across the whole fuel map and you can't turn it off). The selection of when to run closed loop is done by arcane means in the bowels of the ECU code and there is another map, the VE map, which covers a smaller load range than the fuel map that plays a part in that decision, and the resulting injection pulsewidth. It's all rather annoyingly complicated. Which means that there might be unexpected consequences of disabling/disconnecting the O2 sensor and not having the VE map adjusted to suit (however the hell that would be is not known to me).

cheers

Link to comment
https://www.sau.com.au/forums/topic/373417-o2-feedback/#findComment-5957393
Share on other sites

yer if it only happens cold you can rule out o2. is it cycling in and out of fuel cut? or is it a different kind of surging?

Sounds like on/off decel fuel cut.

And to the original poster it sounds like you have a dud o2 sensor - best way to test them is force the engine to run rich and then lean and make sure it goes above 900mV and below 100mV. The switch to high and low should be within a second.

Link to comment
https://www.sau.com.au/forums/topic/373417-o2-feedback/#findComment-5957705
Share on other sites

yer if it only happens cold you can rule out o2. is it cycling in and out of fuel cut? or is it a different kind of surging?

Surging is a bit of a misleading term I think, I don't think it is really surging. I don't know how else to describe it though.

It's not like a TP cut or anything like that where it feels like you have hit a wall. It's much more subtle. It's like if you were driving along, and you just tapped the accelerator quickly. It speeds up a little bit, slows down a little bit, speeds up a little bit, slows down a little bit, etc. Very minute, so hardly registers on the speedo at all, but you can hear it and you can feel it. Only ever while cruising, and only when it's cold. As soon as you put your foot down or decel quicker or the engine is warm, it doesn't do it.

Link to comment
https://www.sau.com.au/forums/topic/373417-o2-feedback/#findComment-5957716
Share on other sites

Nistune IS the stock ECU, so it CAN run exactly as the factory closed loop. But you can also turn off O2 feedback on it (by various means) exactly per the PFC example.

Hanaldo has a Neo engine yes? In which case, you can't turn off the O2 feedback in the conventional sense. You have to do it by bumping the feedback temperature limit up real high. There is no "closed loop" section of the fuel map like there is on most other Nissan ECUs (or rather, the O2 feedback flag is enabled across the whole fuel map and you can't turn it off). The selection of when to run closed loop is done by arcane means in the bowels of the ECU code and there is another map, the VE map, which covers a smaller load range than the fuel map that plays a part in that decision, and the resulting injection pulsewidth. It's all rather annoyingly complicated. Which means that there might be unexpected consequences of disabling/disconnecting the O2 sensor and not having the VE map adjusted to suit (however the hell that would be is not known to me).

cheers

It's unlikely to be too complicated - more than likely just a 2d scaler with tsp enable vs rpm.

But yes if you remove the o2 sensor it will trim an extra 20% of fuel in while in the closed loop section of the map. Hope your tuner took that I to account.

Link to comment
https://www.sau.com.au/forums/topic/373417-o2-feedback/#findComment-5957722
Share on other sites

The ECU won't be in closed loop when the engine is cold, because the ECU is running the engine quite rich while the engine warms up.

O2 feedback temperature is 30°C standard on Neo. That's not long after start up. Granted, warm up enrichments will still be around for a while, but it could go into closed loop earlier than you think.

Edited by GTSBoy
Link to comment
https://www.sau.com.au/forums/topic/373417-o2-feedback/#findComment-5957775
Share on other sites

O2 feedback temperature is 30°C standard on Neo. That's not long after start up. Granted, warm up enrichments will still be around for a while, but it could go into closed loop earlier than you think.

Yeh my issue occurs from when I turn the key to just before operating temperature. Not sure exactly what temp it is when it stops, probably around 60-65ish degrees (water).

Link to comment
https://www.sau.com.au/forums/topic/373417-o2-feedback/#findComment-5957797
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • I know why it happened and I’m embarrassed to say but I was testing the polarity of one of the led bulb to see which side was positive with a 12v battery and that’s when it decided to fry hoping I didn’t damage anything else
    • I came here to note that is a zener diode too base on the info there. Based on that, I'd also be suspicious that replacing it, and it's likely to do the same. A lot of use cases will see it used as either voltage protection, or to create a cheap but relatively stable fixed voltage supply. That would mean it has seen more voltage than it should, and has gone into voltage melt down. If there is something else in the circuit dumping out higher than it should voltages, that needs to be found too. It's quite likely they're trying to use the Zener to limit the voltage that is hitting through to the transistor beside it, so what ever goes to the zener is likely a signal, and they're using the transistor in that circuit to amplify it. Especially as it seems they've also got a capacitor across the zener. Looks like there is meant to be something "noisy" to that zener, and what ever it was, had a melt down. Looking at that picture, it also looks like there's some solder joints that really need redoing, and it might be worth having the whole board properly inspected.  Unfortunately, without being able to stick a multimeter on it, and start tracing it all out, I'm pretty much at a loss now to help. I don't even believe I have a climate control board from an R33 around here to pull apart and see if any of the circuit appears similar to give some ideas.
    • Nah - but you won't find anything on dismantling the seats in any such thing anyway.
    • Could be. Could also be that they sit around broken more. To be fair, you almost never see one driving around. I see more R chassis GTRs than the Renault ones.
    • Yeah. Nah. This is why I said My bold for my double emphasis. We're not talking about cars tuned to the edge of det here. We're talking about normal cars. Flame propagation speed and the amount of energy required to ignite the fuel are not significant factors when running at 1500-4000 rpm, and medium to light loads, like nearly every car on the road (except twin cab utes which are driven at 6k and 100% load all the time). There is no shortage of ignition energy available in any petrol engine. If there was, we'd all be in deep shit. The calorific value, on a volume basis, is significantly different, between 98 and 91, and that turns up immediately in consumption numbers. You can see the signal easily if you control for the other variables well enough, and/or collect enough stats. As to not seeing any benefit - we had a couple of EF and EL Falcons in the company fleet back in the late 90s and early 2000s. The EEC IV ECU in those things was particularly good at adding in timing as soon as knock headroom improved, which typically came from putting in some 95 or 98. The responsiveness and power improved noticeably, and the fuel consumption dropped considerably, just from going to 95. Less delta from there to 98 - almost not noticeable, compared to the big differences seen between 91 and 95. Way back in the day, when supermarkets first started selling fuel from their own stations, I did thousands of km in FNQ in a small Toyota. I can't remember if it was a Starlet or an early Yaris. Anyway - the supermarket servos were bringing in cheap fuel from Indonesia, and the other servos were still using locally refined gear. The fuel consumption was typically at least 5%, often as much as 8% worse on the Indo shit, presumably because they had a lot more oxygenated component in the brew, and were probably barely meeting the octane spec. Around the same time or maybe a bit later (like 25 years ago), I could tell the difference between Shell 98 and BP 98, and typically preferred to only use Shell then because the Skyline ran so much better on it. Years later I found the realtionship between them had swapped, as a consequence of yet more refinery closures. So I've only used BP 98 since. Although, I must say that I could not fault the odd tank of United 98 that I've run. It's probably the same stuff. It is also very important to remember that these findings are often dependent on region. With most of the refineries in Oz now dead, there's less variability in local stuff, and he majority of our fuels are not even refined here any more anyway. It probably depends more on which SE Asian refinery is currently cheapest to operate.
×
×
  • Create New...