Correction factors AT and IT
Thread Starter
TECH Fanatic
Joined: Aug 2005
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From: Sunny London, UK
Correction factors AT and IT Hi all,
Ive been searching here and google for info on this.
I understand correcting to STP, but figuring out where the probes should go any why has been hard to track down. Can anyone refer me to a dyno users manual or doc or just plain old tell me how it should work.
I mean should IT be the same as IAT, ie measured in the intake of the vehicle? What about forced induction? Should this be the air temp entering the TB or the air temp in front of the air filter? And why?
AT is a bit easier to understand. I guess its the outside Ambient temp.
Ive been searching here and google for info on this.
I understand correcting to STP, but figuring out where the probes should go any why has been hard to track down. Can anyone refer me to a dyno users manual or doc or just plain old tell me how it should work.
I mean should IT be the same as IAT, ie measured in the intake of the vehicle? What about forced induction? Should this be the air temp entering the TB or the air temp in front of the air filter? And why?
AT is a bit easier to understand. I guess its the outside Ambient temp.
Thread Starter
TECH Fanatic
Joined: Aug 2005
Posts: 1,691
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From: Sunny London, UK
So IT and AT should match?
Are you then saying that there is no valid reason for them to be different even with forced induction (turbo etc) where actual intake temps can be a lot higher?
Are you then saying that there is no valid reason for them to be different even with forced induction (turbo etc) where actual intake temps can be a lot higher?
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Joined: Sep 2004
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From: Omaha, NE
Originally Posted by ringram
So IT and AT should match?
Are you then saying that there is no valid reason for them to be different even with forced induction (turbo etc) where actual intake temps can be a lot higher?
Are you then saying that there is no valid reason for them to be different even with forced induction (turbo etc) where actual intake temps can be a lot higher?
No, I did not state IT and AT should match, etc, I just basically stated how dynos shops do it. I think I know where you are going with this and wish I had more time to explain why we do it this way. Basically what is different yet is the IVAT (intake valve air temp) which is different then IT or AT. Our current system seems to work well for NA but leaves some to be desired for FI applications. One example, if we corrected to IT or IVAT, a customer that baselined without an intercooler (correctly called aftercooler), then came back with one, would never show a HP/TQ increase, bad for IC sales.
Thread Starter
TECH Fanatic
Joined: Aug 2005
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From: Sunny London, UK
Yeah, exactly what I couldnt figure out. Which is why I was asking what the "correct" method is. In my mind IVAT must be the ideal temperature to measure as thats what the engine see's. Of course getting the probe there to measure is hard, the closest compromise seems to be to sit it in front of the intake filter.
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Joined: Jan 2006
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Originally Posted by ringram
Yeah, exactly what I couldnt figure out. Which is why I was asking what the "correct" method is. In my mind IVAT must be the ideal temperature to measure as thats what the engine see's. Of course getting the probe there to measure is hard, the closest compromise seems to be to sit it in front of the intake filter.
I tell people if your Intake Air Temp (as measured before entering the engine) is way higher than Ambient Temp, then they need a better vehicle cooling fan, ie. don't skimp on necessities.
