IAT placement NA
 

Where is the optimum area to place the IAT sensor on a normal aspirated car? The stock location is in the air box, would this same area be the same for the GM sensor and a MS? I am completely redoing my CSP Miata's intake so now is the time to put it the correct place.

it's conveniently close to the wiring harness

So your saying it doesn't matter?

I don't think so, but I'm sure Brain will come along and tell me I am wrong again.

I've been told tube and filter size are more important.

Unless you suspect that the temperature of the air entering the manifold is going to be radically different from the ambient under-hood temperature (eg: if you have an effective CAI system) then you can pretty much just hang the sensor anyplace that puts it out of harm's way and away from any sources of radiant heat (exhaust manifold, radiator, etc.)

It will have a very effective CAI due to a rules change for 2011. There will be a box with a velocity stack in it and I was thinking in the side of that box. Ideas?

what kind of temp change do you think you'll see between the velocity stack and the throttle body?

There is my problem, I don't know what the MS needs to see. The intake tube between the insulated airbox and the TB will be insulated as well. If the MS needs to see actual intake temps I need to drill and thread my intake manifold and put the IAT sensor there. I guess my question should have been where does the MS need to see the air temp.

With an autocross car you generate a lot of heat quickly over 60 seconds or so and then have a 5 to 10 minute cool down. You will generally leave the engine running and pop the hood between runs to minimize heat soak.

The MS needs to se the real air temp entering the engine. Keep it away from radiant heat as much as possible or else it will heat soak and report temperature that's much higher than reality. Mine is right behind the air filter, which is in the left rear corner of the bay behind a heat shield. I did have it and the filter near the headlight, but it heat soaked badly from the hot air coming off of the radiator.

My €0.015:

If you drill and tap a hole into the intake manifold and screw the IAT sensor into that, heat which is conductively coupled from the head into the manifold will then be conductively coupled into the body of the IAT sensor, and this may artificially raise the reported temperature by a greater amount than the amount by which heat is transferred from the intake manifold into the intake airstream.

[science]
If the rate of heat transfer from the intake manifold casting into the intake airstream were very high at all, then the manifold would run cool to the touch, because most of the heat which is conducted into it from the head would be drawn right back out again by the air flowing through it.

Press your cheek against the intake manifold after driving on the freeway for a while. Then apply burn ointment and cover with a sterile gauze bandage.
[/science]

Measuring IAT is an inexact science at best. My vote would be simply to put the sensor either in the airbox or somewhere in the insulated tube which conjoins the airbox to the throttle body. I'm more worried about heatsoak of the IAT sensor due to external influences than failing to account for some trivial rise in temperature that's going to occur between the airbox and the combustion chamber. If you really wanted to get an accurate reading, you'd need to have the IAT sensor located inside the intake port just behind the valve. And that's just not a practical thing to do.

That was my train of thought when this came up last night during the build but I wasn't sure just how accurate it needed to be. So the lack of heat soak at the air box out weighs the temp difference at the actual manifold or port for that matter.

Thanks.

My car still has the stock intake box & snorkel, and I have the sensor zip tied up close to the fender so the tip is kind of in the flow of air entering the snorkel. The intake air will certainly be a bit warmer by the time it reaches the TB, but in reality the deltaT must be pretty consistent because it has not caused any problems. I agree with Joe that avoiding heat soak of the sensor body is probably the bigger concern. Don't screw it into anything that gets hot, don't locate it too close to exhaust parts, and don't put it directly in the path of hot air coming through the radiator. Beyond that, you just tune the MS with the sensor wherever it is, and you will be fine.

If your putting the filter in a ram air box. Put the sensor in their too.

As Joe says, just put it where there's no radiant heat.

If it reads over or under a few degrees it really doesn't matter, you'll tune the car for the temp sensors location (and over/under reading), this over/under-reading will be consistent so the fact that it might read 3deg over than the true temp is pretty irellevant.

I don't understand why people don't just run better IAT sensors. I've been using these VW/Audi sensors and they work great, with no detectable heat soak:

http://www.mjmautohaus.com/catalog/images/058905379.jpg

It's used on the 1.8t and 2.7t engines among others. It costs about $25. Mine is now mounted in a machined port on the cast aluminum pipe just before the throttle body, but when I was NA I made a seat for it on the piece of exhaust tube I had my K&N attached to out of JB weld.

Where are you buying the sensor from? Rockauto?

You can get them here: http://www.efiexpress.com/catalog/pr...products_id=39 -- they have the connector and pins too, but you might have to email about it (I don't see it in the catalog).

Inbreeding.

Where and how did you mount it and seal it against boost leak?

-Raj

I have a cast intake elbow that I machined to take the sensor and O-ring. I had to build up a bit of it with epoxy to keep the sensor square with the offset bolt.

http://www.boost-instruments.com/miata/iat.jpg

(The copper pipe is temporary until I get someone to TIG an AN-20 fitting on my radiator.)