IAT location on an NA engine?

[v8zcar]

I have my IAT plumbed into the intake manifold (TPIS MiniRam2). Should it be in the ducting leading to the TB instead?

It seems that the IAT in the intake would soak up more heat than the air passing thru the manifold. My reasoning is, the air is moving and the IAT is not, therefore the IAT should soak up more heat than the air because the IAT is constantly physically touching the manifold. But the air is merely passing thru...

Am I wrong on this?

Thanks,
Owen

 

[AEkrot]

They sell a IAT relocation kit for F and Y bodies - I bought one a long time ago thinking the same thing - then I got a Tech2 and monitored the IAT readings with the sensor installed in both locations and saw no real difference. $40 bucks spent on 5-10% improvement... right... lesson learned.

If your sensor is like mine, the sensor "disc" is held in the air stream by 2 stiff wires that are mounted in plastic which is insulated from the brass sensor mounting "screw/structure". This disc is free to heat up or cool down as the air passes over it. As a result, I don't believe the intake manifold temperature affects the IAT reading significantly.

Alex

 

[bruce]

The more accurate the information is that the ecm has the more accurate the tune can be.
The idea behind using sensors is to gather information.

So, you are wanting to ascertain what is going on in the combustion chamber, and base your tune on that. Which means you want to gather as much data as possible as close to an intake valve as possible.

In low air flow conditions, like idle, the manifold can radiate alot of heat into the intake charge air. Hot air needs more timing. slightly less fuel.

Devil is in the details.
The oems use different locations for various other reasons.

 

[v8zcar]

Thanks to both of you.
That gives me a lot more to think about. Not sure if my IAT is a disc, never really looked at it. My thinking was that right in front of the TB would be the best, but for now, I'll leave it where it is.

Owen

 

[Craig Smith]

Bruce's statement makes the most sense. But I swear that those sensors don't isolate themselves well enough thermally from the part they screw into. Several times we have moved sensors just a foot or so further upstream in the intake tract and saw HUGE differences in IAT along with curing strange drivability problems by doing so. I can't imagine that air would pick up 70 degrees of temperature from the front of the intake to the back while idling, but I've seen that kind of difference.

Any thoughts on this?

 

[v8zcar]

That was my point, no matter how SLOW air is moving at idle, I can't see it absorbing that much heat from the TB to the intake valve vs the sensor which is just sitting there.

BTW, where exactly is this unofficial manual at? I looked everywhere and can't find it. Link???
Thanks,
Owen

 

[bruce]

Originally posted by Craig Smith
Bruce's statement makes the most sense. But I swear that those sensors don't isolate themselves well enough thermally from the part they screw into. Several times we have moved sensors just a foot or so further upstream in the intake tract and saw HUGE differences in IAT along with curing strange drivability problems by doing so. I can't imagine that air would pick up 70 degrees of temperature from the front of the intake to the back while idling, but I've seen that kind of difference.
Any thoughts on this?

I've actually done my homework on this.

You can retap the IAT mount and install a nylon pipe reducer to isolate the sensor from the plenum, and see no change. That's right no change. the disc is the sensor, not the housing. Put an ohmeter across the terminals and then expose the sensor to different temps and note the response, do the same with a coolant temp senor. Then you see the differences in the sensor's element's mounting. then note the sifferences in construction, and you see that the MAT is designed to be IN the air flow.

If you move the sensor further away from the valve, and improve drivibility, then that tells you your original calibration was off.

If you analyse things, they always make sense. It SOUNDS like the way you have the sensor mounted in one position was sheilded from actual air flow in the manifold. There can be relatively stagnate areas within a manifold, especially at low flow conditions.

BTDT

 

[Craig Smith]

Bruce,

I agree 100% with the logic of what you are saying. What I don't understand is how, in the example I mentioned above, we noted a 70 degree air temp change by moving the IAT sensor from the back edge to the front edge of a manifold no longer than a foot or so. Perhaps my misunderstanding stems from my unwillingness to accept that the air truly would pick up that much heat, because it seems impossible to me. I'm no physicist though.

Would you say that a 70 degree increase in air temp from one end of the plenum to the other on an intercooled 4 cylinder engine is abnormal or not? It just seems like a lot to me.

 

[10SV6]

It sounds a lot like the sensor was placed in a "dead" airflow spot in the intake.

 

[bruce]

Originally posted by Craig Smith
Bruce,

Would you say that a 70 degree increase in air temp from one end of the plenum to the other on an intercooled 4 cylinder engine is abnormal or not? It just seems like a lot to me.

4 Cylinder?.
Yep.
If you had the TB on one end and the IAT at the opposite end then easily.

I have yet to see a 4 cyl manifold where they we're thinking right when they designed it.

Look at the Lingenfelter Cavalier in the new Turbo and Hi Tech Perf.. While still not quite the way I'd do it he's real close.