Author Topic: Air temp sensor location.  (Read 8915 times)

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Offline javajoe79

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Air temp sensor location.
« on: August 13, 2008, 10:50:03 PM »
  So I know you want the IAT sensor as close to the engine/throttle as possible, so as to have the most accurate temps. My boss always makes a big deal about IAT placement. Just recently and in other cases, I put it in the intake pipe, just before the silicone coupler to the throttle body. He insists that the engine will make more power if it is even closer, as in, stuck in the silicone coupler, no more than two or three inches closer inside of a 4" intake. Anyone else want to back me up or side with my boss? I would just like to add up some opinions. By the way, this is on a Motec M800 on an LS1.

 Thanks
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Offline dieselgeek

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Re: Air temp sensor location.
« Reply #1 on: August 14, 2008, 03:52:27 PM »
well, he's wrong about "more power" for sure.   The positioning isn't that important, so long as the EMS is programmed to adjust fuel delivery properly based on the temp it sees...


Offline javajoe79

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Re: Air temp sensor location.
« Reply #2 on: August 14, 2008, 11:14:22 PM »
Yeah see that is what I told him.
Coffey Fabrication and Race Prep
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Offline FoundSoul

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Re: Air temp sensor location.
« Reply #3 on: August 24, 2008, 04:35:47 PM »
Backing the 'geek on this one-- closer/further doesn't matter power-wise, the only benefit to getting it closer is your reading a truer to life temp reading of the air as it enters the engine, but a couple inches aren't going to matter here....  Just put it in the intake tube after anything that heats the air up (turbo/sc) and after anything that cools it back down (intercooler).  Basically just before the throttle body.  Some have even put them in the intake itself, the only problem with this is potential heatsoak from the manifold. 

Jerry a.k.a. 'FoundSoul'
http://www.DIYAutoTune.com and http://AMPEFI.com
13 Records total held at the ECTA Ohio Mile (as of 9/2015)
Fastest so far-- AA/BGC Record @ 217.3913mph September 2015  -- MS3Pro Engine Management and a little 3.0 liter

Congrats to our customers:
Lee Sicilio - 1969 Daytona Charger #97 - Bonneville A/BGALT Record Holder - 273.514mph - MegaSquirt-3 EFI and Ignition Control
Gary Hart - 1953 Studebaker #787 - Bonneville AA/BGALT Record Holder - 240.984mph - MegaSquirt-1 EFI and Ignition Control
Frank Kinney - Black Opel Racing #6666 - Bonneville E/GMS Recond Holder - 208.974mph - MegaSquirt-3 EFI and Ignition Control

Offline GH

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Re: Air temp sensor location.
« Reply #4 on: August 24, 2008, 08:30:18 PM »
Jerry, we had an adapter made out of UHMW, then screwed the IAT sensor into it, we did it to isolate the heat from the stainless steel plenum to the sensor.

Offline FoundSoul

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Re: Air temp sensor location.
« Reply #5 on: August 24, 2008, 09:38:19 PM »
I noticed that on your plenum last week Gary-- should do the trick just fine, and from looking over your datalogs I don't see any reason to think your heat soaking your sensor...

Jerry a.k.a. 'FoundSoul'
http://www.DIYAutoTune.com and http://AMPEFI.com
13 Records total held at the ECTA Ohio Mile (as of 9/2015)
Fastest so far-- AA/BGC Record @ 217.3913mph September 2015  -- MS3Pro Engine Management and a little 3.0 liter

Congrats to our customers:
Lee Sicilio - 1969 Daytona Charger #97 - Bonneville A/BGALT Record Holder - 273.514mph - MegaSquirt-3 EFI and Ignition Control
Gary Hart - 1953 Studebaker #787 - Bonneville AA/BGALT Record Holder - 240.984mph - MegaSquirt-1 EFI and Ignition Control
Frank Kinney - Black Opel Racing #6666 - Bonneville E/GMS Recond Holder - 208.974mph - MegaSquirt-3 EFI and Ignition Control

McRat

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Re: Air temp sensor location.
« Reply #6 on: August 24, 2008, 09:46:20 PM »
Here's the problem on engines like the LSx:

Often the IAT sensor is put into an area that is subject to radiant heat.  This gives a false high reading which can cause spark retard.
My philosophy is to run it in the area of the air filter if NA, and run it in a plastic area if running boost.  Do not even use it with nitrous as it will advance timing when the bottle goes active if downstream of the jet.

For hardcore racing of just a few minutes or less of duration, I'd rather just zero out the IAT tables and adjust to the track.

Zero'g the IAT will drop the ET on a 2002 Z06 (LS6) 0.4 seconds and improve the traps 4mph in the quarter.  Nothing to sneeze at.

Offline FoundSoul

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Re: Air temp sensor location.
« Reply #7 on: August 24, 2008, 10:23:59 PM »
The way I see it, an engine's an engine.  LSx or JDM import...

If I understand you though, it sounds like you're referring to zeroing out an IAT based correction table on a particular EMS or hack of the OEM EMS.  If that's what you're talking about, then sure-- zeroing out a correction table that for instance, pulls timing at higher IATs, could in theory boost performance, so long as the fuel is adequate to prevent detonation under the conditions, and since the OEMs generally tune on the conservative side, I'm not surprised at all. 

But I think we're talking about something else here.

What the OP asked about if I understood correctly though, was physical sensor placement to make sure it gets an accurate reading of incoming air temps as the air enters the intake.  On a Speed Density based EFI system the IAT sensor is a critical measurement.  You can zero out the correction table, that's just a correction table though, but try to flatten out or fake out the IAT reading to the ECU and the ECU has lost a huge piece of the equation it uses to calculate the proper base pulsewidth (that that correction table would be correction, if the base PW is wrong it doesn't matter what you do in the corrections, it will never be right).  I've done testing on my dyno at different intake temps (easy to do, open and close the hood while drawing air from the engine bay for the engine) with a improperly calibrated IAT sensor and then properly calibrated the IAT sensor to see the difference in real time.  I could easily see a 1.5-2 point difference in the AFR when the IAT sensor was miscalibrated (and reporting slightly off-base temps to the ECU, which it then used to calculate fuel pulsewidth incorrectly).  If the IAT was gone altogether, then the ECU has no way to properly calculate fuel PW on a speed density system.



Jerry a.k.a. 'FoundSoul'
http://www.DIYAutoTune.com and http://AMPEFI.com
13 Records total held at the ECTA Ohio Mile (as of 9/2015)
Fastest so far-- AA/BGC Record @ 217.3913mph September 2015  -- MS3Pro Engine Management and a little 3.0 liter

Congrats to our customers:
Lee Sicilio - 1969 Daytona Charger #97 - Bonneville A/BGALT Record Holder - 273.514mph - MegaSquirt-3 EFI and Ignition Control
Gary Hart - 1953 Studebaker #787 - Bonneville AA/BGALT Record Holder - 240.984mph - MegaSquirt-1 EFI and Ignition Control
Frank Kinney - Black Opel Racing #6666 - Bonneville E/GMS Recond Holder - 208.974mph - MegaSquirt-3 EFI and Ignition Control

McRat

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Re: Air temp sensor location.
« Reply #8 on: August 24, 2008, 11:06:50 PM »
I was talking both the necessity of IAT correction and placement.

If you place it near a heat generating metal surface, like an aluminum manifold, throttle body, MAF, etc, it will pick up some temp from it.  Radiant heat travels through air.

Try this:

Put a IAT in your inlet hsg (assuming CAI) and put one in your aluminum intake manifold and datalog.

You will see the IAT in the CAI will be lower (yet still often higher than true air temp) than one in the manifold, and it will be "laggy"; not respond well to changes in temp in a timely fashion.

If the IAT is active, you want it to react fast when the temp changes.  You will see changes in IAT from the start line to the traps due to the hot air coming up.

But your timing is mostly critical at WOT under max load, or highest gear.  This is where detonation is most likely to hit.  So putting 0's in the IAT correction table will cause retarded timing at first, where you have surplus HP and light load, and then you tune for traps.

Granted my experience is based on autoX and drag racing tuning with LS1's vs. dyno tuning, but it might hold true to LSR as well.  Just my experience playing with IAT tweaks over the years.


Offline FoundSoul

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Re: Air temp sensor location.
« Reply #9 on: August 25, 2008, 09:56:58 AM »
True enough if you place the IAT in a heated metal surface, you'll pick up some radiant heat from it. 

Sounds like we agree?  That the IAT must be in a location where it gets true engine temp and reacts fast...

----

Typically though, if at all possible, I try to keep my IAT corrections to the ignition from even being needed. IE I'll try and design the car so that the IATs don't get over 130degF or so.  For example on GH's car, we'd start a long course run at 95degF IAT and end it the run at 104-108degF.  There's no need for ignition retard there based on the IAT so yes it's essentially flat.  When building the table though I'd probably put some in there as a safeguard for 'just in case' things went wrong and IATs went up.  For instance I might have it start pulling 1 degree of timing for each 12-15degF of temp increase above 130degF IAT to help save the motor just in case something went wrong.  (Like a IC pump failure, or worse, some goofball forgetting to put ice in the chest).

Jerry a.k.a. 'FoundSoul'
http://www.DIYAutoTune.com and http://AMPEFI.com
13 Records total held at the ECTA Ohio Mile (as of 9/2015)
Fastest so far-- AA/BGC Record @ 217.3913mph September 2015  -- MS3Pro Engine Management and a little 3.0 liter

Congrats to our customers:
Lee Sicilio - 1969 Daytona Charger #97 - Bonneville A/BGALT Record Holder - 273.514mph - MegaSquirt-3 EFI and Ignition Control
Gary Hart - 1953 Studebaker #787 - Bonneville AA/BGALT Record Holder - 240.984mph - MegaSquirt-1 EFI and Ignition Control
Frank Kinney - Black Opel Racing #6666 - Bonneville E/GMS Recond Holder - 208.974mph - MegaSquirt-3 EFI and Ignition Control

Offline javajoe79

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Re: Air temp sensor location.
« Reply #10 on: October 15, 2008, 11:58:24 AM »
 Too add to this. We have since been to the track with this car and dynoed it. The tuner was Shane T and the ecu is a motec m800. Shane said that it should be further away from the engine, to lessen heat soak, if you can do that but ultimately it doesn't matter. If the tuning is done considering the placement of the sensor, then the same outcome can be reached.
Coffey Fabrication and Race Prep
313 Wilhagan Rd Nashville, TN 37217
615-210-1605

https://www.facebook.com/CoffeyFabrication