My AEM wideband is oscillating pretty bad during cruising speed. Is this normal? This has been happening since I've installed it but never said anything and I'm just wondering if its normal. It oscillates between 14.2:1 to 16:1 very quickly and often. In PE it nails the proper AFR so I think the gauge is reading right. Is it maybe the raised fuel pressure without tuning the fuel in there. I just took the AFR form stock pressure (43) to 50 psi. No real reason why, just cause I could when I installed the AFR. What do you guys think, this is the only thing I can think of, I haven't tried putting it back to stock just wondering what you guys think.


"Never argue with an idiot. They'll drag you down to their level, then beat you with experience!" -Anonymous

it does that. no worries.

Yes that is normal. During cruising speed, or closed loop the ECU is trying to get perfect 14:7:1, and goes from side to side of that.



FU Tuning

closed loop operation. normal

14.82 @ 97 mph

^Right that's why I never bothered to return my fuel to stock pressure since the 2nd O2 should correct for the fuel add. But I was wondering if maybe the higher fuel pressure could be increasing the magnitude of the swing......don't really care. Car runs fine the way it is.


"Never argue with an idiot. They'll drag you down to their level, then beat you with experience!" -Anonymous

adding unneeded fuel pressure without tuning for it is like throwing in larger injectors and not tuning for them.

cars dont really know what they are doing... they just do as told and follow orders blindly. they follow the program of your tune, and then listen to the sensors to tell it if that is ok or how to adjust it...

your car is "programmed" to run on the old setup.... so if you throw in a variable like higher fuel pressure, it throws everything off a tad, and then the computer has to compensate for that. In the case of fuel pressure/injector size changes... The more it compensates, the more it overshoots... the car thinks it is getting 100 units of fuel per second... but since you changed it and didnt tell the car... anytime it asks for 100 units, it gets 110 units... or whatever...

so now imagine trying to balence that...
"we are getting too lean... give me 110 units" but it gets 122...
"whoa!! i said 110!! too much! we are too rich.. back us down to 90 units..." but it gets 92
"ok come down 5 more still... ok.. getting lean, bump her back to to 110..." but it gets 122 again...

and it happens over and over. the further off your tune is from the actual setup, the more swing you will have as it is always getting more than it expects, and has to overcompensate. but yes... even a perfect tune will oscillate.. it should swing steadily within the NB range... so from like low 14 to high 15 or so... peaks into 13 and 16 are even common.

Cold starts and Full Throttle are the exception to this... as those are outside the scope of the stock O2 sensor... so it has to rely entirely on your program... and since it doesnt know how it is running, it cant compensate... so it stays flat and steady... and just hopes that is what you asked for is what you really wanted.

Quote:

since the 2nd O2 should correct for the fuel

actually.... the "2nd" or downstream O2 sensor has nothing to do with fuel mix at all... it simply monitors converter effeciency. all fuel mods are based off the upstream sensor (in manifold)
(unless you were refering to your WB as 1st O2 and the stock NB O2 as the second, in which case i guess the downstream would be the third...)

^yup, I figured I'm using my 1st(sorry I meant the 1st, I'm not even running the second.....I dont know why I said that) O2 sensor to constantly adjust the fuel input using it's PID adjustments which is obviously going to enhance the swing..yes...obvious. I like the added throttle response the higher pressure gives, although the ECU has to correct for it during crusing, just wondering "how much is normal" which sounds like I'm barely off normal so I'll leave it.

Thanks for the info guys.


"Never argue with an idiot. They'll drag you down to their level, then beat you with experience!" -Anonymous

Hey Joshua, got a question for you.
Did you still keep the original narrow band in the exhaust for the ecu or have you eliminated it for the use of the wideband?
I'm in a similar situation with a newly purchased AEM Uego along with HPT Pro that will be hooking up with the Atomic exhaust that is on it's way.
So this has my curiousity up. I'm pretty sure we keep the narrow band in while the wide band is used strictly for tuning, yes?

Thanks man.



Misnblu.com
Newbie member since 1999
Thank you Dave and JBO!

Yeah, I just welded in another O2 bung into the line below the stock narrow, I think the AEM wants 36"? I think I ended up like 30 or so...or rather like 6 inches short of what it was requesting. I'm not sure the exact number now. So the ECU still has it's own O2 and I have the AEM straight to the gauge.


"Never argue with an idiot. They'll drag you down to their level, then beat you with experience!" -Anonymous

Thanks Joshua.
I can't wait to get it all together, tune it, and hit the track for some personal bests before the rebuild.and 5 speed swap.


Misnblu.com
Newbie member since 1999
Thank you Dave and JBO!