[Ravan17]

hey guys, for the longest time ive been trying to log some runs to see how the AFR is during runs..... but here is the problem.... no mater what i se tthe GAIN value on the EMS....... it will only match what the gauge reads AT THAT certain time, anything higher or lower is wayyyy off....... the gauge was checked by AEM and they sent it back saying ti was perfectly fine...and honestly, i think it is b/c it reads right where it should, just doesnt read that \value into the EMS..... some one suggested running a thicker gauge wire to the signal wire from the gauge to the EMS since i have the gauge mounted in the Apillar....


i am STUMPEDDDD and have NOOO IDEA wat could be causing this...... does anyone have any kind of suggestions? b/c i want to try to get this problem fixed tmrw so that i can log some runs on the 16th at the track........


thank you.

 

[93 twintrbo]

I was having the same problem. I just re-adjusted the Cal table untill all Afr's were within range according to the gauge. From day to day, its off slightly but I have learned to work around it.

 

[chevyeater-on-sf]

Sounds like the voltage vs. value table is off. I.E. check on the O2 sensor wizard...

 

[Adr3naline]

I have had this problem several times with the AEM and various widebands. Tried everything from .1-2.0 gain settings, manually moved over the voltages into the chart, and spent forever trying to get the gain to match voltages on the AEM and the W/B. First thing you do is make sure you are using Gasoline AFR units. Then make sure you have loaded the correct preset voltage maps in the wizard. If you haven't it doesn't really matter b/c you can set w/e voltages to w/e AFRs you want manually. What usually works the best is to use the +12 switched and the ground off the engine harness right by the AEM. What that does is the Wideband is now using the same ground as the ECU. That is a critical to get it working properly. I have messed with every possible way to ground the LC-1, Uegos, etc. Wired them directly from battery, bolted close the ECU, bolted off chassis, and various combinations. As soon as the wideband sees the same ground and voltage as the AEM, bam, usually works.

 

[Ravan17]

THANK YOU for all the suggestions guys, i have to work with my cooling system today, i think i have an air bubble, but hopefully i get around to rewiring it today, but probably tmrw.

if i dont get to change the ground today i'll atleast make sure that all of the other settings on the EMS are appropriate.


so basically just run the power and ground to the wideband gauge from the EMS, correct?

 

[Adr3naline]

THANK YOU for all the suggestions guys, i have to work with my cooling system today, i think i have an air bubble, but hopefully i get around to rewiring it today, but probably tmrw.

if i dont get to change the ground today i'll atleast make sure that all of the other settings on the EMS are appropriate.


so basically just run the power and ground to the wideband gauge from the EMS, correct?

Yes. That way the wideband sees the exact same voltage and ground that the AEM does. Most of the time what people do is run it off of a switched +12V and good chassis ground. Which if you're running the guage by itself just to monitor is perfectly fine. But when you're trying to match what the EMS sees with what the W/B is seeing, it creates that discrepency that so many people have a problem with.

 

[BlueSteel]

^^^^Can somebody else confirm this. That doesn't sound right. A ground is a ground, the whole car is ground as one. Similar to the 12v supply, its all coming from one source. Chevyeater's response sounds more logical.

Could you elaborate on this more Adr3naline

 

[Adr3naline]

^^^^ A ground is a ground, the whole car is ground as one. Similar to the 12v supply, its all coming from one source.

Could you elaborate on this more Adr3naline

That's where you're misinformed. That isn't how it works. "Positive currents" are more or less as you described, "negative currents" are not. Grounding can get pretty in depth and can have a drastic effect on how the AEM interprets the signal.

 

[Ravan17]

yea i'll agree with that...i just never thought about it. but taking basic electrical engineering last year i found out that even the "simple" current and all that really arent simple and intuitive like they seem

 

[chevyeater-on-sf]

Don't use ECU power to power the wideband as Adr3naline posted. That is a bad idea.

 

[Adr3naline]

Don't use ECU power to power the wideband as Adr3naline posted. That is a bad idea.

It's optimal for signal, but yes there are risks involved with it.

 

[chevyeater-on-sf]

It's optimal for signal, but yes there are risks involved with it.

Powering the wideband sensor heater (several amps) off an ecu power feed is less than optimal for anything.

 

[BlueSteel]

^^^Thanks chevyeater, thats what I thought. I'm going to leave my wiring the way it is and use the tables in the AEM.

 

[Ravan17]

uh..... what?

 

[Ravan17]

how do i change the values to gasoline values? i thin those might be wrong, the highes AFR on the table is only 9.... thats at like 3 volts

 

[Adr3naline]

Configure>Units>AFR>Gasoline>Apply>OK

 

[Ravan17]

nvm, i got that, and the table is calibrated just like the manual says. i got the ems to read exactly 14.7 with the gauge disconected running 2.35 volts like it should. as soon as i connect the damn gauge back up, it goes fucking crazy and starts reading 14 instead of 12.7, and 15.9 instead of 14.7.


so could the voltage be messing it up?


let me ask you this also.... i am running the power to the gauge from a source that also powers a bunch of other guages, boost controller, ect. could that effect it at all?

 

[Ravan17]

update... so after i set the tables and stuff. i got the gain to match.... but as soon as i hooked it back up, it was off by a little bit, seems like the voltage has something to do with it. but what i did was re adjust the gain a little bit to match the two AFR's, now, so far it looks pretty good, not 100% dead on, but only off by a few values, untill it gets above 12.... but i figured i dont need that are anyways since im more interestd in the lower portion, so now im going to get out and make a few pulls to see if the values i see on the gauge are recorded on the EMS.... im praying to god that its going to be good.



what is an ideal AFR under boosted pulls? some where between 11 and 12? and what is the maximum after i should be comfortable with since its boosting 2 more psi then im tuned for?

 

[Adr3naline]

The problem with only having that little bit of accuracy is that for one you are always going to be guessing what it actually is compared to the gauge. The second is that you will never be able to utilize 02 FB. it is a grounding issue. It almost always is. The problem with changing the voltages on the tables like people are saying is that you should never have to. The preset values should work just fine. To answer your question about AFRs, if you're running pump gas with no methanol or anything, tune to about 11.3-11.5 That's a bit on the safe side.

 

[Ravan17]

ok, i'll just re wire all of the power and ground calbes running to the gauge, i'll try to get it its own independent source. and then see how it reads. i didnt change any of values, i simply got them to show, the values i had on there before went only up to 9 for some reason....4-9 over the 5 volts.... ti was weird b/c it was set to gasoline, but hwne i reset it , it showed back up.


so 11.3-11.5 is "safe" but what would start becoming unsafe? i am running a 2.5mm hg so im running supper low compression....but ofcourse that has nothing to do with how lean it gets.... i think i saw my guage jump up to the 12.2 region during a pull when it spiked ot 19 psi (the highest it ever goes untill settling down to between 17 and 18) that wouldnt be too lean would it?