AEM Wideband / Megasquirt Problem
 

Hey Everyone!

I just installed my MegasquirtPNP, adjusted my idle, timing etc.

The only problem I have is that the Virtual Air/Fuel Gauge does not agree with my AEM Wideband.

At idle they will stay pretty close but when I drive the car the real gauge will say -- -- while the virtual gauge on Megatune will read a normal 12-15.

I've selected the proper gauge from the configurator, set Megatune to wideband and adjusted the voltage to 2.34. I then made sure that the power and ground went to the ecu's power and ground and disconnected the stock O2. I'm now officially out of ideas. Anyone have any suggestions?

https://www.miataturbo.net/forum/t28005/?highlight=aem

/hand holding ;)

Thanks for the link!

If I use that adjustment will I have to convert all my tuning to AFM instead of AFR or can I just use it to calibrate the gauge to match the virtual gauge?

Also, in the link he talks about changing tenths of a point, will this fix work when it's 2-3 whole points?

we tried doing this, and have tried pretty much everything to get his AFR's to match up and nothing.....they got closer!

at idle they match up and when you first start out driving they match up, but as you proceed with running the car they begin to venture apart! that and a couple other things that are happening iss we put green top supra injectors in his car witch i belive are 320cc and tried setting up in MT for the injectors and the car started really really bad.........

we are out of ideas.....

I did some more test tonight and it seems that they really start to separate around 25K RPM in third gear, at the same RPM in fourth gear they're approx 3-4 off, and by the time I'm in fifth they're completely separated with the physical gauge reading 18+ and the Megatune Gauge reading 11-13.

When I bring the car to a stop they slowly start to line up again. And he's right, we've tried everything in that post but it doesn't seem to help this particular problem. I can change the lambda sensor file and change the reading in Megatune but once I hit that spot where they separate it does nothing.

What motor are you running that allows you to spin 25,000 revolutions per minuet?

Wow, looks like I missed some decimal points, sorry about that.

So I just switched the MT software to read "Unknown Wideband" which essentially converts it into a simple volt meter. It looks like at low speeds/rpms the volts are right where they should be but as I gain speed the volts just start to drop regardless of what the gauge is showing. Could this be something wrong within my Megasquirt? It doesn't make sense that the sensor reads fine and gives a good voltage signal at idle and slow speeds, then get's really skewed when it's going along.

i hope its not the unit!

it was fine when i parked my car and pulled it! i had the same set up minus what you have under the hood!

This problem occurs because the AEM's actual output curve does not match its published output curve. To fix it, you would need to map out the unit's voltage output vs AFR at several points and build your own calibration table. I think Joe Perez did this for his.

I've also heard reports that the AEM's error also can drift over time. I don't know if that's true or not.

at first we had his Bank 2 O2 censor disconnected, he disconnected the bank 1 in the bay this morning and everything is good now! they match up great!

Are you saying that the narrowband sensor was still installed along side the wideband? Yes, that would be the problem. ;)

yeh! at first both were plugged up, then we disconnected the rear and still the prob existed, then he unplugged the front one and now all is well!