AEM Wideband reads leaner than factory widebands during WOT under boost

[rcmikey]

Was ordering an EGT sensor to get an idea where the temps are at the wide band but I can agree I don't believe the exhaust temps would skew the data that much. Who knows? Stranger things have happened. Its only off under boost but at cruise dead on. Going to install a fresh set of widebands before I make anymore changes. Have not had time to make the changes to the exhaust temp table and test yet. I will post when I do.

[rcmikey]

What fuel is this? .715 lambda On gas thats really rich, on E10 even. Little rich even for E85?

Running FTW 99+ Stoich is 8.9 and when I command .715 the AEM reads .78 lambda. Factory will read the same as commanded. Staying on the safe side.

[rcmikey]

If I commanded .78 the factory reads .78 but the AEM and the Dyno would read .85ish. Had been running it for a full season at .715 commanded with no ill effects. plugs looked great. Good power.

[dr.mike]

If the AEM and dyno are post=CAT, then, they would commonly read a bit closer to lambda 1.0, under PE ( If the CAT is working That's what they do. )

At idle to mid-throttle, the values are right at lambda 1.0 which is ZERO to a wideband . Which is why I always say DO NOT JUDGE THE ACCURACY OF YOUR WIDEBAND BY IT READING 14.7 AT IDLE. That is like saying a voltmeter is accurate because it shows 0.0v with the probes shorted together.

[rcmikey]

If the AEM and dyno are post=CAT, then, they would commonly read a bit closer to lambda 1.0, under PE ( If the CAT is working That's what they do. )

At idle to mid-throttle, the values are right at lambda 1.0 which is ZERO to a wideband . Which is why I always say DO NOT JUDGE THE ACCURACY OF YOUR WIDEBAND BY IT READING 14.7 AT IDLE. That is like saying a voltmeter is accurate because it shows 0.0v with the probes shorted together.

No cats.

[GrannySShifting]

Even with cats, its not much different. ive measured wideband readings before cat, after cat, header collector all the way to tailpipe (MIGHT be .5 leaner reading at tailpipe vs all the way forward, not huge differences) and pre and post turbine.

[rcmikey]

I am trying to determine why factory reads richer at WOT under boost. Since AEM and dyno read the same I am wondering what background logic is skewing the factory sensors. Is it blow through? Is it pressure? Is it temp? Don’t know but sure will try to figure it out.

[GrannySShifting]

I dont know but thats prob why guys say Coyotes like to be ran "rich wih timing" vs leaner with less timing. They prob arent really rich

[rcmikey]

I dont know but thats prob why guys say Coyotes like to be ran "rich wih timing" vs leaner with less timing. They prob arent really rich

Thinking the same thing. Seems like once something is posted it becomes the rule of thumb. With the newer logic used in these processors we are all made to look like fools sometimes. I found it difficult but very important to keep an open mind during my years of teaching advanced troubleshooting. Things change fast. We don't like change.

[jsllc]

What I have been saying. The blown motor running the factory tune that the AEM WB said was toooooo lean was enough proof for me.

[rcmikey]

I have seen a few boosted coyotes being remote tuned at the track using factory wide band readings have a bad day.

[bradearlywine]

What fuel is this? .715 lambda On gas thats really rich, on E10 even. Little rich even for E85?

Remember, .715 lamda on gasoline is 28.5% richer than stoich just as .715 lambda on E85 is 28.5% richer than stoich. Lambda reading is based upon the stoich AFR of the fuel. As such, a 1.0 lambda is 14.1 to 1 on E10, and 9.86 to 1 on E85.

For the OP... IMHO Lambse (Commanded lamda) of .715 is very rich and your likely leaving power on the table. You really would want .78-.76 for safe AFR for blown engines. I'd go off the AEM wideband. Its routine that other engines have been off from the factory on the LEAN side. Such as the older 5.4L supercharged Lightnings. A slight lowering of the injector slopes brought the numbers right down to commanded value. There were tables on oxygen sensor that would control bias and the factory had some weird entries. Of course, those didn't have factory widebands that would disagree with you. My guess Ford was more concerned with idle and cruise AFR for fuel mileage.

If you are logging the readings, just be sure logged reading matches what is displayed on the wideband unit. If you are commanding .715, the car reads .715, but the AEM reads .77, your right where you want to be.

[caged]

Lol i should of looked harder before i asked the same question. Yeah it gets worse as power goes up/on a restrictive exhaust. I asume its the back pressure on the widebands with no compensation. So the correct way is just to eat it up in target lambda? Some of the whipple cars on std exhaust get pretty hairy before you rape the target.

[GrannySShifting]

Lol i should of looked harder before i asked the same question. Yeah it gets worse as power goes up/on a restrictive exhaust. I asume its the back pressure on the widebands with no compensation. So the correct way is just to eat it up in target lambda? Some of the whipple cars on std exhaust get pretty hairy before you rape the target.

Back pressure in a longtube header on a 750hp blower car is NOTHING compared to the backpressure in a 1000hp turbo car with the 02 between exh valve and turbine and i havent seen 1.5 point difference

[GrannySShifting]

Remember, .715 lamda on gasoline is 28.5% richer than stoich just as .715 lambda on E85 is 28.5% richer than stoich. Lambda reading is based upon the stoich AFR of the fuel. As such, a 1.0 lambda is 14.1 to 1 on E10, and 9.86 to 1 on E85.

I know how lambda works, but ethanol might tolerate 28.5% richer than stoich while gasoline will not it can run richer than stoich usually and still make power as most alcohols will is what I was saying. He is running an ethanol based fuel at a true AEM read .77 lambda which makes perfect sense for E

[murfie]

I am trying to determine why factory reads richer at WOT under boost. Since AEM and dyno read the same I am wondering what background logic is skewing the factory sensors. Is it blow through? Is it pressure? Is it temp? Don’t know but sure will try to figure it out.

Have you compared your calculated MAP and an actual MAP sensor? The MAF adaption may be skewing airmass values for your commanded lambda and therefore causing your enrichment fuel trims to be wrong getting you to the wrong lambda reading on the factory O2s.

[rcmikey]

That was the plan for this last weekend. Was going to make some passes and work on speed density but didn’t go as planned. Broke the rear on the first launch. To top that off bank 1 wide band decided it wanted to fail during warm up.

[rcmikey]

This is the third wide band in two years that failed. I believe it’s mostly caused by the fuel I’m running along with the location of the sensor in the long tubes. They are at 9 o’clock. No way to let the condensation run out.

[GrannySShifting]

I can agree there are many factors that can and will effect the accuracy of different wideband sensors. 1. Back pressure: tested with and without cut outs open with the same results. 2. Speed type and position of sensors/polling: this should not make an 8% error between the two because they are dead on at cruise. I could see if they were different all the time. During a dyno pull the entire time under boost the AEM is reading lean. Sensor is located same as stock sensor just 180 degrees out. Dyno sensor reads 8% lean also. Not to say you are wrong. I appreciate the input.

With the same sensor setup on a non boosted coyote the sensors are dead on for the entire WOT pull to include the dyno wideband.

Do you think I could be experiencing blowthough at that boost level and cam timing? I know that the copperhead will calculate within the speed density logic to compensate for blowthrough. So the factory wideband reading would be compensated for this. Any instance of blowthrough will create a lean condition post combustion than actually occurs in the cylinder. My thoughts are the AEM has no input of correction therefore will read leaner than the factory corrected sensors. The dyno sensor has no logic to compensate so it would read the same as the AEM. Thoughts????

If my thought process is correct this may be a solid indicator of blowthrough for boosted coyotes. Maybe help in speed density tuning?

https://www.hptuners.com/forum/showt...ity-Calculator

I had not seen this before. If thats accurate than alot of people have been running much richer mixtures than theyd think, because most of the coyote guys have VERY little overlap I dont see there being much blowthrough... unless the factory stuff over compensates ALOT

[txcharlie]

If you are running altered VCT, then you may have increased your overlap, which may help account for the lean reading.