Dmak

Found this ad for evoheatshield in the back of European car magazine and it looks very interesting..

<img src="http://evolutiontuning.com/evoheatshieldmain.jpg">

What it is, is a .25" thick insulating spacers which thermally separate the intake manifold from the cylinder head. This reduces the transfer of heat from the cylinder head to the intake manifold.. This better performance..

What do you guys think of this? I think I'm going to try it out..

<a href="http://evolutiontuning.com/evolution.html">evotuning</a>

Žob

Couldn't hurt could could it

Bollinger

First problem is that the heat will find its way across anyway. Either out into the air then the air heats the intake, or just plain radiant heat to the intake. So in short bursts it could have quite an effect, but if your engine stays hot for a period of time, it will eventually heat up the intake manifold anyway.

That's one problem, and not necessarily a bad one. What I am more concerned about is whether any difference in temp between the intake and block will lead to a mismatch between the ports and the intake runners due to differing expansion rates. Maybe I'm crazy here. Someone clue me in better.

Here's a good test: do racers use this? If it is really an advantage to put an insulator in, then racers would already use it. Do top-end ($$$ is no object) cars already use it like Ferrari and Lambo. Do they? I don't think so, but I'm not sure.

Finally, an insulator is basically created by having lots of air bubbles in a medium, these are actually the insulation. Thus, insulators are typically soft and spongy. The way the intake manifold attaches to the block is by bolts straight through the gasket. Thus, when tightening the manifold to the block, you are compressing the insulator, forcing the bubbles to close and thus ruining it's insulating properties. These gaskets will need some kind of rigid spacer to take the stress of the bolts being tightened and keep the insulator from being compressed. This could take the form of a metal sleeve around the bolt holes and hopefully around the intake port holes also.

Nogaro

more imporent parts on the car that needs you and your wallet's attention. But thanks for bring it up, a cool thing anyway.

MikTip

The bolts will still transfer heat.

DrHandball

I agree with several of your points mostly that the intake will eventually heat up. Someone else mentioned that the bolts will still transfer heat. You also mentioned that these insulators probably have air spaces in them and that that is how you get the insulating effect. You also mentioned differing expansion rates between ports.

First: Yes, the bolts will still transfer heat to the manifold. However, with the use of an insulating material between the two pieces you have reduced the effective area through which the heat is transferred.

Second: Not all insulators contain air spaces to achieve their insulating properties. Many materials have properties of low thermal conductivity that make them good insulators. These could be made for those materials. There is nothing in Dmak's post to indicate what the materials of construction are.

Third: Differing rates of expansion between ports will probably not be any worse with these insulators than without. The rate of expansion will be affected on the intake by the presence of the insulator. This is probably not enough to be concerned about.

Finally one point to consider is that eventually with these gaskets being .25" thick, an equilibrium state will be reached. One could argue that the insulating material and the parts it is seperating will eventually all reach the same temperature.

One other consideration would be that with air/fuel moving through the intake, heat should flow from the cylinder head to the intake and the intake should always be cooler that the head. Having said that using an insulator to help reduce heat transfer to the intake manifold could have adverse effects on head temperatures. This may or may not be serious.

All in all keeping the intake manifold as cool as possible is a good thing as air/fuel mix density is increased. You do want a vapor in the engine's combustion chamber, not a mist.

Audiboy

But heat conduction is a function of surface area

Audiboy

oops, should have read DRHandballs post below. answered this already

RangeR BoB

You must be in F1 or some exotic racing series where every last erg counts.

The amount of heating the metal of the intake can make on the air as it is rushing in at 300 feet per second is negligable. Think of it, you are talking 1/300th of a second, if the runner is a foot long. Or 1/150th if it is a massively long 2 feet (not comon at all). How much heat can get transferred to the incoming air at this point?

What's that you say? Oh sure, an intercooler works to cool air at the same velocity, but the ratio of surface area to volume is MUCH different than a stream of air in a intake manifold. The boundary layer of air makes a nifty insulator and keeps the moving stream quite well insulated from heat transfer from the warm metal. Granted, not all flow thru an intake manifold is laminar, but good enough for this discussion.

Low thermal conductivity spacers made sense on carburetted V-8s because they had a ton of hot oil splashing up on them from the lifter/pushrod/cam area and many featured a EGR (Exhaust Gas Recirculation) passage or water passage below the carb base (all of which belong to us) for emissions reasons. It helped warm the carb to keep it from frosting up on cold/humid days and reduced the need for choke and thus unburned hydrocarbon emissions. For racing, this heat is not needed. Keeping the carb cool was mostly a matter of reducing vapor lock and float bowl venting problems, but cool air is indeed dense air. Note that heat soaking a zinc casting bolted to a hot manifold is much different than reducing the thermal transfer of heat to a moving column of air.

Heat comes from many places, and while these spacers may slow down the initial heat up of the manifold from heat transferred from the head, there is already a great mechanism in place: The intake manifold gasket. Most are a fiber composition and conduct heat poorly.

Even with the insulators, the manifold will still pick up radiant heat and be warmed by Radiator & Intercooler discharge air.

If you get even a single horsepower out of those spacers, I'll be surprised. Prove it to me with back to back runs, same day, same dyno.

They are a waste of time. (great for lining the pockets of the designers, tho)