chimchim

Everyone has read about why CAI's work - lower temperature air means higher density of O2 which means more fuel can be burned. Blah blah blah, yeah everyone is so smart.

But what exactly going on under the hood? I can't be just a constant "hot" temperature? Turns out, of course it's not. In fact, sometimes, it cools down under there to outside temperature. And some times it gets searingly hot. Pretty much when you're sitting idle at a redlight, it gets hot. But when you're driving at speed, the air flow (depending upon the design of the car) can significantly cool down the under hood temperatures.

Anyways, here's some links to tests I found:

http://www.318ti.org/notebook/under_hood_temp/
http://www.318ti.org/notebook/under_...emp/page2.html

So... does this say something for adding exit vents on the hood and/or fenders?

j87w

The other day I just started my car and brang it into the shop. We just got a new temperature gun. I drove it for about 20 min, let it sit for 10 min, then drove it for about 2 more. My intake manifold was reading about 105 to 110 degrees, the header was reading about 90 or so, then the intake pipe was reading in the 85 range. I didnt know that the IM go so hot.

Provocateur

That is why they make Hondata type gaskets so that the heat transfer doesn't affect the intake manifold and heat up the incoming air.

The reading for the header seem awfully low...don't they get to be over 800 degrees?

chimchim

Has anyone done a study on just HOW MUCH a "hot" intake manifold actually transfers that heat to the air?

Oh... can you easily change the manifold gasket without totally taking a lot of things apart? Like can you just un bolt the manifold, peel off the gasket, put on the new one, and replace the manifold?

j87w

It was probably low for a header. The car sat but im not sure how much it dropped down.

Kai

Well, once upon a time on a dyno, I discovered my car runs a full 5 wheel horsepower better at 180*F versus 220*F indicated coolant temp. Don't ask how I know that.

chimchim

Ack... Hondata doesn't make a heatshield intake gasket for the D16Y8. Mostly just B and K series, plus a D16Z

JimBlake

That's pretty much like a 1st-semester heat transfer homework problem... Not very effective.

If the intake manifold were an effective heat exchanger, there wouldn't be any need for intercoolers.

chimchim

So what you're saying is that the Hondata intake gasket, while it may insulate the intake manifold from heating up as much from engine, a hot intake manifold isn't going to heat up the air that much. Thus rendering the purpose of the insulating intake manifold gasket not very useful for its intended purpose.

Eddiebx

a hondata gasket helps to some extent, probably like when you are constantly moving and sucking up air. but i can tell you that it doesnt do shit to prevent heatsoak of the manifold. when your sitting idle the IAT reaches temps as high as 120-130s on a hot summer day. i forget exactly how high it hit, its been ages since i went to the track and datalogged,