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Is it possible to monitor IAT's with MJLJ?

Posted: Wed May 06, 2009 3:35 am
by BoostedE21
Hey guys,

I'm pulling together a turbo project, and I'm a bit concerned about my air intake temperatures. Is there a way to monitor those temperatures and retard timing accordingly automatically with MJLJ? Without the ability to change the timing when temps start do their unwanted climb, I can only run a pretty poor spark table to remain safe.

Basically need to find out if the MJLJ configuration allows me to wire in an IAT sensor, be it from GM or just a sender for a gage, and then use timing retard/IAT subsection. It's under the Spark header in megatune, IAT/Clt related ignition. I would rather just let the computer take care of altering timing based on IAT it instead of having 4 different files I run depending on outside temps, etc - and it would be a nice failsafe for my motor if my Meth/Water injection pump fails of if I accidently let the tank run dry. If MJLJ can't do it, would it be possible to buy a MS computer and have it just managing ignition for now? I'm not sure what the compatibility is between MJLJ and MS, and how much re-wiring would be necessary to switch between the two for just the ignition system.

Posted: Wed May 06, 2009 7:21 am
by brentp
Hello,

Yes- you can accomplish this using the Auxiliary input of the MJLJ. The process comprises a few steps:

1. calibrate the aux input channel for your sensor. This involves scaling the raw "ADC" values to something useful, like degrees F or degrees C.
http://www.autosportlabs.net/MJLJ_V4_Op ... figuration

2. Edit the advance correction table to apply a correction factor based on the measured value on the aux input.
http://www.autosportlabs.net/MJLJ_V4_Op ... rrection_2

3. Wire up the sensor according to this guide:
http://www.autosportlabs.net/MJLJ_V4_ve ... iary_Input

Hope this helps, and let us know how your implementation works out.

Posted: Thu May 07, 2009 6:32 am
by BoostedE21
Thanks for the help! I should have mentioned, I have V3 not V4. Is it still capable of that?

Edit: A quick search indicated that it's not. Looks like it's time to upgrade!

Posted: Thu May 07, 2009 3:19 pm
by brentp
Actually, our beta 3.3.x firmware adds this capability to the V3 controller, with some limitations. It will require hardware modifications, whereas it's built-in on the V4 controller.
http://www.autosportlabs.org/viewtopic.php?t=2100