Alright. Brand new motor and brand new tune. Built and street/dyno tuned by a reputable shop with plenty of experience doing street & full out race cars.

My AEM WB (installed by previous owner, probably been in the car for 10 years) reads 14.2-15.6 at idle and part throttle. When I make a WOT pull the gauge dips down to 10.8 and then pins at 11.9 or 12.0. Obviously that seems rich to me, but wouldn't I notice it? The car pulls extremely hard, no stumbling or backfires, made good power (467whp through a 9", auto, stock intake). No black smoke that I can see and not really any soot on the bumper or anything, just a few flecks of carbon I've always noticed (white car). It was tuned using a sensor in the tailpipe. I don't have any exhaust leaks.

I'm going to call my tuner on Monday and ask for his advice, but I don't want to sound like an idiot. Wouldn't I know if my car was running rich, or is a 12.0 at WOT not rich enough to notice a difference?

 

"According to Bosch’s published test data, its wideband O2 sensors are accurate to .15 of a point when new, but that margin for error increases to .29 after 500 hours of use, and increases even more to .59 after 2,000 hours. In other words, after 2,000 hours of operation, when an O2 sensor reports an 11.76:1 air/fuel ratio, the actual air/fuel ratio in the engine can be as lean as 12.35:1 or as rich as 11.17:1."

I would take this to be fairly representative of any companies O2 sensors but most of our widebands use a Bosch sender no matter what brand the gauge is.

 

this is an older AEM unit that does use a Bosch sensor. I don’t know if the mileage since install has put me at those levels but I suspect it has degraded to some degree.

 

I would do a free air calibration on it, then see if your numbers change any.

 

So I spoke to my tuner today, who confirmed the car logged 13.0 on the dyno pulls. He said he replaces the dyno wideband every 6-8 months and suggested that my sensor has gone bad. I’m not sure if it’s even worth buying another one and messing with it.

 

Alright well I am stuck again. $95 later for a brand new AEM WB sensor and it reads exactly the same as before. I spoke with my tuner a little bit more in depth about it. When the car was tuned a couple of weeks ago he confirmed that both his software and dyno WB indicated it was at 12.8-13.0 WOT. He is going to hook the car up to his laptop on saturday and see what the car's O2s are reporting.

I am fairly stumped by this. Additional thoughts are appreciated.

I did perform a free air calibration on the new sensor, even though AEM states it is not required.

 

Where did he put his wideband on the car during the dyno session?

 

Tailpipe. But even if there’s some issue with turbulent air or something causing his dyno WB to be off wouldn’t the cars O2s also reflect the rich condition? And at high 11s WOT would I notice the car running rich or nah?

I’m sort of a novice at all of this.

 

What do the plugs look like? That’ll point you in the right direction.

 

Haven’t checked yet. I’ve only put 300 miles on the motor and tune. At these levels assuming it is running at around 12.0 would I notice significant fouling on the plugs?

 

The tailpipe will falsely make the tuner make it run richer at WOT unless the O2 sensor is really tucked up in the tailpipe and you can guarantee there are no leaks upstream. My guess is he didn't do a good job of that and theres nothing wrong with your wideband. High 11's NA won't cause the car to break up at WOT and be noticable other than some power loss. Your tuner should have removed 1 of the front O2 sensors on the dyno and put the wideband in there since he's supposed to tune it in open loop anyways. The stock O2 sensors are narrowband and really only adjust trims at idle and cruise to try to get it close to stoich (14.7:1), they don't do anything at WOT.

 

Seeing what the cars 02 sensors are doing when you are talking about WOT is useless.

 

Thanks. He is taking a look at the car on Saturday morning. I am going to politely insist on having the tune done either off of my WB or the dyno WB in the header bung.

Thanks, makes sense.

 

Got the tune squared away and the car runs great. Makes good power at 12,7 WOT now. Thanks for the replies.

 

cool, congrats.

 

Before/after dyno graph?