Do these O2 sensor graphs look ok?

[Skylarking]

... less error is less calculations the ecu has to consistently make from 02 feedback so the better the engine runs...

As long as the CPU still has the ability to process the required calculations in a given time frame, then I’d think the engine will still run sweet...

I’d thing if the O2 sensors have some large offset error that results in too large a LTFT’s being required, then there would be any issue to resolve. I’d think the correct way to resolve such would be to replace the O2 sensors so they read within the required spec and accuracy, not by reprogramming the fuel maps. LTFT is doing just as it is supposed to do (adjust fuelling for variations in hardware).

Obviously you can change the characteristics of the engine and make it burp and fart in different ways, or produce more power, all by playing with fuel maps. But all you’re doing is changing the factory compromises made to balance consumption agains pollution and power, given the standard tolerances of the hardware put into these engines. If in the process you set up the table to narrower equipment tolerances within your specific car that doesn’t make it run sweeter as such.

Put another way, if O2 sensors are reading correctly and within the limits designed within the ECU, the fact LTFT is not zero doesn’t really matter. The engine should still run sweet. It’s only when you have conditions which are due to a hardware fault (leaky or part blocked injectors, faulty O2 sensors) where the ECU can’t compensate enough to resolve the fuelling, then action is then needed. That action is repairing the faulty parts (not changing fuel maps).

The fact an engine may run better with O2 disconnected is somewhat irrelevant as that's the normal running mode but rather a fault situation. Still, it’s admirable but somewhat irrelevant

Don’t get me wrong, I’m not criticising, it’s either I haven’t understood what you’ve said or it seems what you’ve said is a little wrong (w.r.t the little this layman, me, knows about ECU’s and how they control engines).

Playing with ECU mapping is something that I’d be interested in once my car is out of warranty, so guess I have to increase my knowledge somehow

 

[shane_3800]

ur thinking that factory is way more dialled in then they actually are they are not spot on, the fuel maps u think have millions of data is my VE table i have 1089 cells to adjust which is more then the engine will ever actually use (MAF sensor only has 66 cells to adjust), then i have multiplier tables for ECT, IAT, IVT, ITT and more then the injector data has all the offsets for delta pressure/flow, short pulse, min pulse, voltage/map offset, IAT offset, VOLTS offset, INJ tip temp offset its all there to adjust, fuel type flex setup and knock sensors all have there own settings u can adjust.

im not an engineer i just like to tune and go through as much as i can to see exactly what it adjusts and how it affects all other tables its the only way u gain knowledge about it, i have no issue with 02 sensors when they are running good but i also know that if u disconnect the 02's on a factory tune the engine will run like garbage because its not that dialled in it needs them where as after a proper tune like mine if i was using the 02's and disconnect them mine will still run the same no issues, even without the 02's i can still dial in stoich fueling and only use enrichment when power is needed so economy is better then factory (i have a wideband also for tuning), its why so many people do there own tuning as u can get it to run so much better then factory even using the 02's as factory has to suit hundreds of thousands of vehicles where as tuning can refine it to what your engine likes

Yea I run a wideband on my carby work ute. My VS will be getting two so I can see if the ECU is working how it should.
They're not as accurate as a gas analyser but they don't need a new cell every 12 months at $600 a pop.

 

[mechanic]

Ok. I haven't used your tuning program so I can't comment on that.

I agree that the OEM introduces a factor of safety into the fuel map to ensure serviceability, longevity, emissions etc are balanced and within spec. This factory is easy to remove to achieve immediate results. There is always a trade-off between efficiency and emissions (VW dieselgate etc but the same theory applies for petrol engines).

Do you incorporate these considerations into your adjustments?

 

[07GTS]

As long as the CPU still has the ability to process the required calculations in a given time frame, then I’d think the engine will still run sweet...

I’d thing if the O2 sensors have some large offset error that results in too large a LTFT’s being required, then there would be any issue to resolve. I’d think the correct way to resolve such would be to replace the O2 sensors so they read within the required spec and accuracy, not by reprogramming the fuel maps. LTFT is doing just as it is supposed to do (adjust fuelling for variations in hardware).

Obviously you can change the characteristics of the engine and make it burp and fart in different ways, or produce more power, all by playing with fuel maps. But all you’re doing is changing the factory compromises made to balance consumption agains pollution and power, given the standard tolerances of the hardware put into these engines. If in the process you set up the table to narrower equipment tolerances within your specific car that doesn’t make it run sweeter as such.

Put another way, if O2 sensors are reading correctly and within the limits designed within the ECU, the fact LTFT is not zero doesn’t really matter. The engine should still run sweet. It’s only when you have conditions which are due to a hardware fault (leaky or part blocked injectors, faulty O2 sensors) where the ECU can’t compensate enough to resolve the fuelling, then action is then needed. That action is repairing the faulty parts (not changing fuel maps).

The fact an engine may run better with O2 disconnected is somewhat irrelevant as that's the normal running mode but rather a fault situation. Still, it’s admirable but somewhat irrelevant

Don’t get me wrong, I’m not criticising, it’s either I haven’t understood what you’ve said or it seems what you’ve said is a little wrong (w.r.t the little this layman, me, knows about ECU’s and how they control engines).

Playing with ECU mapping is something that I’d be interested in once my car is out of warranty, so guess I have to increase my knowledge somehow

all good my end, what i have said so far as requested was a simplified version of what im explaining so that is prob why it leaves some holes in it as its a much more involved process as u will find out if u get into tuning and then u will understand what im on about, LTFT are not a cell by cell correction they are a zone area of MAP v RPM in a low, middle, high zones so basically 3 zones to correct for all close loop fueling so the LTFT is the average of that zone, the STFT are instantly always adjusting to give the LTFT its average so a zone may have some cells as a -10 and some a +15 but u only see the LTFT average as say +2.5 thinking its good as its for the whole zone and this is where im adjusting mine so ALL CELLS are as close as possible which makes it all a better tune,

im not against 02's they work well when they are operating as they should and i keep mine in as they are a tuning tool as they can show up spikes faster then a wideband can, ur not using the 02's every time u go WOT u go open loop and ur only using the base fueling tables with no feedback, all tuners that dial in fuel tables disable the 02's so u go open loop all the time then dial in the fueling with a wideband and then re enable closed loop to use the 02's again and its a much closer/better fueling so all im doing is what every tuner does with every car they tune just some keep the STFT+LTFT and some just use STFT or like me as i can keep an eye on fueling all the time i have stayed OL for a while but my new build ill prob use them and dial them in properly as camshafts/aftermarket exhausts play with the feedback, this balance of consumption, emissions and power my engine can still run exactly as it does from factory just because ur OL dosnt mean ur using more fuel

 

[07GTS]

Ok. I haven't used your tuning program so I can't comment on that.

I agree that the OEM introduces a factor of safety into the fuel map to ensure serviceability, longevity, emissions etc are balanced and within spec. This factory is easy to remove to achieve immediate results. There is always a trade-off between efficiency and emissions (VW dieselgate etc but the same theory applies for petrol engines).

Do you incorporate these considerations into your adjustments?

the aem widebands are prob the best/fastest acting before u get the proper full on widebands as u mentioned, im using one in each bank of my new build and they work on the factory canbus so i see them as a pid and with no offsets they are accurate as u can get till they wear out eventually as the new bosch 4.9 is ment to be able to be used full time unlike earlier sensors that need constant calibration, my adjustments are good for cruise and mild use i keep stoich (could go leaner at cruise for ethanol to save fuel but havnt played with that much yet) and PE i tune for best power/torque (engine is well past thinking about emissions at this stage )

 

[Immortality]

Hello. After getting a random DTC76 code, I've been looking into checking the O2 sensors of my '99 VT L67. Today I cleaned the ground connections for the sensors, reset the PCM and went for a drive.

When I got back I checked for codes (all good) and then logged the voltage of each sensor while holding the engine at 2k rpm. I've read that the sensors should contantly alternate between 100mv and 900mv, which it seems they do. At idle however, they both stay steady at around 800mv.

As I don't know much about these sensors, I was just wondering if someone else could have a look at the graph to see if all is good. I can provide more readings if needed. Thank you for any help.

XDL log download: here.


Side note: My long term fuel trim is at -11 for both banks. Is this within a normal range? Car feels like it runs fine and I get around 10L/100km.

Graph looks normal.

On the L67 the idle is set to open loop and at engine operating temp it is set slightly rich. I haven't checked the log but it should show rich after about 10 seconds.