I was just wondering if anyone has used a wideband on the dyno and then tried it on the street to see what the difference was in the af ratio.I would imagine that the car would run richer on the street than on the dyno.

 

Other way around. To obtain optimal fuel efficiency engine management attempts to maintain a stoimetric fuel mixture. The objective at partial throttle (street driving) it to obtain optimal fuel efficiency, not performance. The ECU will incorporate sensor readings and make dynamic adjustments to injector duration and ingnition timing.

At wide open throttle (WOT) the ECU uses a static fuel map that is a rich mixture. This is more of a compromise. A rich fuel mixture may not make the most power, but the additional fuel will help keep temperatures in the combustion chamber from getting too hot. Why does heat matter? Heat can be a factor in pre-detonation of the fuel mixture which may impact the longevity of the engine.

In short, our engine run richer on the dyno, not in 'street' conditions.

Final note: our ECU isn't too happy with a wideband O2 sensor. The easiest way to install a wideband would be to weld a bung into the exhaust and isolate the sensor from the ECU.

 

^ no, you can install a PLX devices wideband in the stock port. It will output a simulated narrowband signal and keep the ECU perfectly happy.

http://www.plxdevices.com

 

Welding a bung or wiring in a simulator. I suppose electrical is easier. There are widebands available with a narrowband output and that would eliminate the need to use a simulator. It just might cost a few bones more though.

 

In fact, any of the PLX widebands include this functionality without the simulator. Sweet.

 

Perhaps he was asking if there would be differences in street vs dyno readings for WOT?

If so, yes there would be differences but mostly because of the location of the sensor. My understanding is that a sensor sitting at the tailpipe exit will read somewhat leaner than one installed in the stock O2 sensor location. Is that correct?

 

I wanted to know if someone had a wideband in there car and compared the street driving results to the dyno results at wot.I would have thought that the car would run slightly richer under a harder load(the street in this case).I know the readings before and after the cat are different,but thats not what im looking for here.Thanks for all youre responses!!!

 

At wide open throttle the ECU uses a static fuel map. There should be no difference between street driving or rolling a dyno if atmoshperic conditions are identical.

 

It's not static. It applies the long term fuel trims to it, that's why it's so dangerous to tune with a VAFC. It's static in that it's not looking at MAP sensor Data, but it is applying long term trims.

 

I would see Identical AF#'s at WOT on the dyno and the track/street. 12-12.5's with a Vortech/Emanage/440cc injectors.