IAT -- theories, please

[theholycow]

My VW has 100% grille blocking, upper and lower. The air intake opening pulls from the engine bay. I don't have a WAI.

Any ideas why under seemingly equal conditions my IAT isn't approximately equal? It was 70-90 degrees above ambient temp the other day, today it didn't exceed 45 degrees above ambient.

The only difference in condition that I can think of is that it was more windy the other day when my IAT was higher, but that seems counterintuitive.

[JanGeo]

180 engine +50 degree air will result in a higher reading that 180 engine +30 degree air. Also a tail wind will keep you much warmer than a cross wind. Was the higher temperature above ambient on the colder or warmer day?

[theholycow]

I guess I'll have to gather some more data. I thought the ambient temp was pretty close but now I can't remember which days were the nice ones last week.

[dkjones96]

Got an under hood pic?

[theholycow]

I don't have any really good pics, but here's what I do have.

In this pic, you can see a green zip tie behind one of the car's nostrils. Seeing that, you're looking right through the intake mouth.


In this pic, you can see the intake mouth and that same green zip tie:


I've got the whole thing, including the breatin' nostril, blocked.

[dkjones96]

I've got a good idea of what you've done. Makes me wonder if maybe you had a head wind and that upper grille block let more air pass or the opposite is true and the block on there made engine bay temps rise because of the engine working harder.

[theholycow]

The block shouldn't allow any air to pass. It's pretty tight when it's all put together. Engine bay temp should be equal to IAT. Maybe different wind directions changed ventilation from underneath.