Tuning accuracy without AFR??

[auspeed]

Hi I am wondering if it is possible to inidicate if you are close to fuel AFR's when using the O2 sensor voltages as a reference for either being rich or lean @ WOT?.

Does anyone use any kind of relationship that is a rule of thumb as to what O2 sensor milli volts refences to AFR?s

WHen people tune who dont have access to wideband can/have you also use STFT to estimate AFR'S??

THanks

[eficalibrator]

Absolutely not. Trying to tune WOT AFR by narrowband voltage is a great way to damage your engine. Narrowband HEGO voltage changes with temperature as well as AFR. They're only meant to show a change around stoich. If you want an accurate number for how rich of stoich you are at WOT, a wideband is required.

[joecar]

+1 wideband is required...

try to get one that has serial comms output (e.g. if it can drive a serial gauge, then EFILive FSV2 can probably read it).

[joecar]

Motor: $6000+.
Wideband: $200.

[auspeed]

Yes I use an LM-2 with FSv2 with serial connection setup.
I have seen others tune with only onboard PID's and wondering if there was anyway to achieve some accuracy by doing this??

[joecar]

You can tune part throttle where the commanded AFR is stoichiometric or very close to it.

[n8dogg]

I think as a general rule of thumb if your part throttle AFR is spot on then your WOT should be fairly accurate correct? All I know is after tuning my car with out a WB my WOT AFR checked spot on once I installed my LC-1. Then again my car is fairly stock and has low miles.

[WeathermanShawn]

I think as a general rule of thumb if your part throttle AFR is spot on then your WOT should be fairly accurate correct? All I know is after tuning my car with out a WB my WOT AFR checked spot on once I installed my LC-1. Then again my car is fairly stock and has low miles.

It would seem to be that way if your car is mechanically healthy and 'stock'. But here is a good example of a tune where closed-loop has been 'normal' and WOT has been extremely lean. Without a wideband you might not have known..http://forum.efilive.com/showthread.php?15813-Noob-needs-help-with-Roadrunner/page21

[n8dogg]

It would seem to be that way if your car is mechanically healthy and 'stock'. But here is a good example of a tune where closed-loop has been 'normal' and WOT has been extremely lean. Without a wideband you might not have known..http://forum.efilive.com/showthread.php?15813-Noob-needs-help-with-Roadrunner/page21

I agree that with out a wideband one may not know. But you can see in his log the PCM seems to be commanding the lean A/F ratio. I'm not trying to argue that widebands are not important, I think anyone doing tuning should use one. I do believe that your chances of running lean on a fairly stock car with the VE nailed down at WOT are about as high as a completely factory car on a factory tune running lean at WOT.

[WeathermanShawn]

I understand your point. With a healthy MAF and injectors, if you have closed-loop nailed down +/- (0 )Trims..normally the rest of the MAF scale and resultant injector slope stays relatively the same.

Its only when things go wrong that the rules go out the door. But, you are right..monitoring the NB's even during PE Mode/WOT can be useful.

Its all a system. I agree NB's can be an important tool..:)

Edit: By the way, we have not heard from you in awhile. Hows it going? Did you ever give your talk?

[joecar]

Shawn's right, how's it going n8...:cheers: