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Old 02-27-2021, 09:51 AM   #1
VB242
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Default Needing to adjust tune for ambient temp

Car is 242 with a B23ET 8V motor running microsquirt. I'm trying to figure out why I need to fiddle with the tune a little for the different seasons. My coolant temp readings seems normal as do the IAT readings. I'm using the GM IAT sensor DIY auto sells, post intercooler and pre-manifold. Are there any other settings I might have incorrect?
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Old 03-08-2021, 06:04 PM   #2
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You can fiddle with the air temp correction table.
Basically 100% is the temp that you tuned the car at. Then you raise/lower the % modifier on either side of that.
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Old 03-09-2021, 11:23 AM   #3
VB242
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Originally Posted by culberro View Post
You can fiddle with the air temp correction table.
Basically 100% is the temp that you tuned the car at. Then you raise/lower the % modifier on either side of that.
Thanks I'll look into that.
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Old 04-06-2021, 07:33 PM   #4
CFStark77
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I’ve had great luck using the autotune function during weird weather shifts. I use a raspberry pi to power a digital dash that runs tuner studio, so it’s on the fly and removes me from the tuning equation lol. I’m on a very built b230ft and it got me through the weird florida weather shifts, so far. I’m also on micro
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Old 04-07-2021, 12:56 PM   #5
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Coolant temperature effects should be completely out of the picture once the engine is up to normal operating temperature. Make sure that you don't have some coolant temperature based PW adder that is entering into the fuel picture and screwing things up during cooler weather.

I presume that you are adjusting your tune on the basis of the AFR values you are measuring. Are you seeing the need to adjust tune based upon AFR values around idle or low engine outputs or based upon high engine outputs? I have installed temperature measuring probes in both the intake manifold and before the throttle plate. At idle / low engine output the intake manifold air temperature will be higher than the pre throttle plate temperature. Once air flow increases the temperature differential disappears. If you measure pre throttle plate at idle or low engine output this can cause the air temperature correction to be excessive resulting in over fueling which may become more noticeable as ambient air temperatures drop. My preference is to use an air temperature sensor located in the intake manifold so that I don't have to deal with the change in air temperature based upon mass air flow.

Note that the air mass temperature correction factor is determined by the equation n = PV/RT where R is a constant and T is the air temperature. The temperature is specified in absolute degrees (Kelvin or Rankin) so errors in air temperature measurement may not be as significant as you think. If you are measuring an air temperature of 70 C and it is actually 50 C the error is not 70/50 = 40% it is (273+70)/(273+50) = 6%. You can use the equation to work backwards to figure out what air temperature measurements are doing to your AFRs. If you are getting big AFR changes then something else is happening or your calibration curve for your IAT is out of whack.
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Old 04-07-2021, 03:52 PM   #6
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Here's mine. Seems to work okay, even on heat soaked hot starts. Not totally perfect, I more or less set it and forgot it. B230f+t with GM IAT before throttle body, after intercooler.
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