Supercharged IAT location

[Fueler]

Roots supercharged Chevy with Enderle throttle body/hat, 8 injectors above blower.
What is the consensus on the IAT location, Above or below the blower?
Pros and cons of each?

[dontz125]

The IAT has to report the air temperature actually entering the cylinders. In a situation like this, with or without coolers, you want it to be after the last heat-transferring device.

[Fueler]

That would be the logical location I agree.
I have also seen several similar setups with the IAT above the blower with the injectors.
These usually were tied into some kind of plug and play non tunable ecu.
Wonder what their thinking was as to why that location?
Was it just to make a "package" or was there a tuning reason?

[elutionsdesign]

If it was a MAF (mass air flow) based system the IAT placement is much less critical, once you know the mass of air moving through you're no longer using the ideal gas law to make fuel calculations.

[Fueler]

Not a MAF application. The best example I can think of is here.
http://www.force-efi.com/specials.htm

[elutionsdesign]

Hmmm, I'd guess it is a packaging issue, meaning they can package it there and you don't have to be drilling holes on the pressure side of the manifold.

[slow_hemi6]

They probably just don't want to/ can't deal with heat soak start up issues. If you have the sensor down there in the oven then you will have heat soak but under boost you do need to know the true temperature of that intake charge. I have seen guys run a second ambient IAT temp sensor for start up and change to the MAT sensor after start. Mine being N/A, I just fudge the curve. lol.

[Fueler]

That sounds like a good possibility of what probably happens there.
Any idea of how one would go about getting an MS2 extra to see the 2 different IATs? 1 at start/warmup and the other at Run.

[slow_hemi6]

IIRC the guy had a change over relay driven by a programmable output. Probably used the "seconds" output channel to switch over after a given elapsed time. That's probably what I would try if I needed it.

[knightrous]

They probably just don't want to/ can't deal with heat soak start up issues. If you have the sensor down there in the oven then you will have heat soak but under boost you do need to know the true temperature of that intake charge. I have seen guys run a second ambient IAT temp sensor for start up and change to the MAT sensor after start. Mine being N/A, I just fudge the curve. lol.

This isn't a bad idea, however I reckon it could be implemented a bit better.
Run two temp sensors, one as a Intake Air Temp (IAT) sensor and another as a Manifold Air Temp (MAT) sensor.
Always use the IAT sensor until you exceed 100kpa (or based on a curve) then begin using the MAT sensor.
This would allow you to avoid any heat soak issues and still be able to run Speed Density correctly.
As a bonus, you would also have the ability to see the difference between the IAT and MAT temps side by side in logs.

[Fueler]

I have been looking around TS to see how to implement this dual temp scheme and am failing to see the light.
Is this possible to pull off?

[elutionsdesign]

As mentioned, use a programmable output to drive a relay that switches from one sensor to the other. Go to "Boost/Advanced" and then down to "Programmable On/Off outputs".

[sdtib]

This sounds like it might be a great (but complicated) solution to my problem.

http://www.msextra.com/forums/viewtopic ... 34&t=56915

@fueler...pros and cons of IAT location from my perspective are in that post

[megaman3]

knightrous,

you had mentioned that you posted some Eagle files for the megasquirt. I cannot find them anywhere. can you repost or send a link to them? Thanks.