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Old 02-13-2009, 02:32 PM   #1
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Default AEM switched Megatune to AFR's - what happened?

Went through last night and did the mod to the ini code to have megatune show AFR's instead of volts. I knew that a lot of guys have things display a few tenths off. In Volts I had the equivilent of 12 to 15 as the range it now shows 11.1 to 12.5 across the scale in AFR's!

Any ideas what might have happened? I only changed the settings in the 94/95 file I'm using. Didn't mess with anything but the AEM Linear settings.

Computer illiterate so I don't know how to save or post a screen shot.

Last edited by cueball1; 02-13-2009 at 02:43 PM.
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Old 02-13-2009, 02:38 PM   #2
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I noticed my voltages were off as well, but I adjusted the lambdasensor.ini file to compensate. I had to adjust the AEM WB from 9.78 down to 9.15 in order for MS to get really, really close to what the AEM gauge read.

Now all is well.
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Old 02-13-2009, 02:46 PM   #3
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When I was using Voltage it was pretty darn close. Now that it's showing AFR's it's off by 2-3 points not a few 10ths.

Would the voltages I was using in my maps not translate into AFR's when I made the change? If they do why would they translate so far off?
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Old 02-13-2009, 02:47 PM   #4
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Verify to make sure you entered all of the values in the .ini file - if any of the numbers you altered are not exactly correct it will throw it off. Post the site you got your instructions from just so we can verify that you are using the same numbers we are. And verify that you did make the changes to the AEM_LINEAR.
Then, make sure you selected AEM_LINEAR in the configurations for megatune. NOT AEM NON-LINEAR even though this is the one that many instructions say to use. The non-linear has different voltage max/mins than the AEM UEGO and will throw off the readings.
-Ryan
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Old 02-13-2009, 03:07 PM   #5
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Definetely using the AEM Linear. I made the changes per the Joe Perez thread about doing this in the "super important ms" sticky. I have since made the change in the ms files to every page 7 AEM linear I could find. It didn't change how it reads.

It shows AFR's but they are still WAY off from what I was using when it read voltage. It was working fine using voltage and was off just a couple 10ths from what the gauge read like most people find. I made the change to AFR's just so it's easier to work with.

Eeek. This isn't easier!

(yes, I said eeek! I drive a Miata. What do you expect?)
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Old 02-13-2009, 03:30 PM   #6
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F me running. I reread Joes thread and found this...

Quote:
The next time you open MegaTune and look at your AFR Targets table, you'll find that it is scaled in AFR rather than Volts. The contents of the table will be garbage so if you already had values in here you'll need to re-create them, but from now on you can work in meaningful units.

AAAck. I assumed the voltages in my settings would have translated into semi accurate AFR's. A little knowledge is a dangerous thing in my hands. Now back to your regularly scheduled programming.

Last edited by cueball1; 02-13-2009 at 03:43 PM.
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Old 02-13-2009, 03:33 PM   #7
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I followed these instructions. I have mine set at 8.10 and its close but not perfect.

Quote:
Now, a lot of folks have reported problems with the default calibration, in that it can be a few tenths out in terms of the MS agreeing with the AEM. It seems that there is some variance from one AEM unit to the next. If you find yourself in this group, you can correct it by opening up the file file "lambdasensors.ini" which you'll find in the same directory as before. Locate the following section, and note that I've highlighted a certain pair of values in red:

#elif AEM_LINEAR
afr = { 9.72 + egoADC * 0.038666 }
lambda = { afr / 14.7 }
TargetAFR = { 9.72 + afrtarget * 0.038666 }
TargetLambda = { TargetAFR / 14.7 }

To alter the calibration, you need to change the 9.72s to something else. And this, sadly, is where the fudge factor comes into play. Some people have reported success in scaling the value up (to 10, for example) others report needing to insert lower values (9.5, in one instance). You're going to have to play with it and see what works. Just turn off EGO correction and eyeball the laptop display vs. the gauge at idle. Find a value that works for you.
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Old 02-13-2009, 09:55 PM   #8
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On the MS forum it looks like you not only have to change that starting number but might also have to fiddle with the .038666 to get the proper scaling. You might change the 1st number and be dead on at say 14 but as you move away from 14 it's not in sync. Looks like Cjernigan was over there with this issue. He ended up at something like .035XXX .

Got my new AFR's in and tweaked the 1st number to get the gauge close. I'll watch to see if the other number needs some fiddling with so the scaling matches too.
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Old 02-13-2009, 11:26 PM   #9
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Quote:
Originally Posted by cueball1 View Post
Computer illiterate so I don't know how to save or post a screen shot.
Easy - find the "print screen" button on your keyboard, it usually requires you to hold "shift" or "Fn" to use. Print screen takes a snapshot of your monitor and saves it to the clipboard just like copied text.

So, open MS paint or other photo editor, and paste it into a blank doc. Crop as necessary, save as JPG or GIF or whatever, and either host it online or upload it to the mt.net server.

Viola!
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Old 02-14-2009, 01:46 PM   #10
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Koto!!!

THANK YOU!!!!

You really can learn something new every day if you pay attention. That was truly useful information. I've always wondered how and had never taken the time to figure it out. I'm one step closer to being a functional human being in a computer driven world.
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Old 02-16-2009, 02:52 PM   #11
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No problem, glad I could help, even if it wasn't help about the MS situation.
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Old 02-16-2009, 03:08 PM   #12
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Quote:
Originally Posted by cueball1 View Post
On the MS forum it looks like you not only have to change that starting number but might also have to fiddle with the .038666 to get the proper scaling. You might change the 1st number and be dead on at say 14 but as you move away from 14 it's not in sync. Looks like Cjernigan was over there with this issue. He ended up at something like .035XXX .

Got my new AFR's in and tweaked the 1st number to get the gauge close. I'll watch to see if the other number needs some fiddling with so the scaling matches too.


Link to thread please.
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Old 02-21-2009, 06:09 PM   #13
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Sorry. I missed this request. Here is the link discussing the change to AFR's for people using AEM Uego. Cjernigan jumps in on the 2nd page. Good info in this thread as they work out what needs to be done!

MSx/Extra EFI • View topic - AEM_LINEAR sensor values
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