Ideal Air Temp Sensor Location With Supercharger

[1herrick1]

The engine and manifold system I'm setting up with my MSII originally ran a speed density ECM and had the IAT sensor screwed into one of the intake runners near the cylinder head. In later years, the switch was made to mass air and the IAT sensor was relocated to the air cleaner duct upstream of the throttle body. I've got the parts to put it in either place. My concern is that I intend to run a twin screw Roots-type supercharger designed to fit my lower intake. I realize that the blower will raise the temperature of the incoming air as it compressed it. Where would be the ideal location - ahead of the throttle body and supercharger measuring ambient incoming air or in the runner after the supercharger measuring air temp immediately before it hits the cylinder?

[Bernard Fife]

1h1,

The IAT must be sampled where it will reflect the temperature of the air that the MAP sensor is sampling, i.e. after the supercharger. It has to be done this a way so that the density of the air can be corectly calculated.

Lance.

[1herrick1]

Thanks for the reply, Lance. That's the location that made the most sense to me, but I thought I'd better ask rather than ASSume. The reasoning behind it makes perfect sense, too - and also explains why they moved it ahead of the throttle body when they changed to mass air. I would imagine the same principle applies there with the MAF sensor.

[trakkies]

1h1,

The IAT must be sampled where it will reflect the temperature of the air that the MAP sensor is sampling, i.e. after the supercharger. It has to be done this a way so that the density of the air can be corectly calculated.

Lance.

Interesting. My car originally had Lucas flapper injection with the IAT in the flapper. So I put the MS one in the trunking I replaced the flapper with. Are you saying it would be better in the plenum? And does it matter much where? I have a convenient hole where the cold start injector used to be. Or would it be better closer to the throttle?

I've seen them mounted in the plenum, but reasoned it would be too much effected by the temperature of the plenum body.

[Matt Cramer]

Trakkies - is your engine supercharged or naturally aspirated?

[trakkies]

Trakkies - is your engine supercharged or naturally aspirated?

No blower. Naturally aspirated.

[Matt Cramer]

In that case, putting it in the MAF location should be fine. You just want it after any device that adds or subtracts a large quantity of heat from the air.

[trakkies]

In that case, putting it in the MAF location should be fine. You just want it after any device that adds or subtracts a large quantity of heat from the air.

Thanks for clearing that up.

[Matt Cramer]

You're welcome. I've seen naturally aspirated engines run the IAT in the air cleaner without any trouble.