</font><blockquote><font class="small">Quoting GSTwithPSI:</font><hr />
Not to thread jack, but feel like this is one of many posts in the last week or so that have mentioned how under hood temps would greatly suffer from running a FP manifold (or fill in the blank with X exhaust manifold) without a heat shield. In theory, I could see how this would be detrimental, but in practice, I’m skeptical about the real world measurable effects. It seems to me that at speed, the engine bay would see enough airflow to negate the effects? I’m talking about street cars here, not race machines designed to squeeze every last HP out of a setup. I know there are a million factors which may improve or hinder performance in regard to under hood temps and how they actually equate to HP loss or gain. But, it seems to me that in regard to an unshielded exhaust manifold, the effects would be negligible in most cases. I see a bunch of guys on T00ners wrapping their intake manifolds and such in that golden Mylar looking sh*t, alleging it improved performance by a ridiculous amount without any real numbers to back up their claims. This lack of data makes me wonder; do heat shielded exhaust manifolds and Mylar wrapped intake bits really yield enough of an improvment to make them worthwhile in street car? Although I’m sure precautions like this do help in some cases, I’m wondering if anyone has some REAL data or testing where they manipulated some of these factors and logged a measurable difference in IAT, or some other related parameter? I realize that the “measureable effects” extend past under hood temps alone, and other things such as turbine efficiency could stand to benefit from a insulated manifold. To be clear, I’m not talking about these. I’m talking strictly about under hood temperature, and the real world effect it has on performance (mainly IATs).
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The results of not having a heat shield on an exhaust manifold and dp are not negligible in the slightest form. Why do you think so many people kill their alternator after they ditch the stock exhaust with the shields and then install a giant exhaust system with no shields. How hot do turbos get under boost? 650f? 700f? And when it's 110 out like in the southwest like phoenix which sees 110*+ temps in june through august. Heat is an engines biggest enemy.
Op would be wise to use some sort of ex mani shield or wrap. A air intake box is nice but not if your ex mani is cooking the sheet metal and intake pipe.
The gold foil ellegedly reflects 78% radiant heat according to the manufacture and dealers. I use it on the under side of my hood to try and preserve the resin, to prolong the negative affect of heat from the exhaust mani (and wastegate). Many racers use it however I think wrapping the entire intake mani is excessive. No I have not done tests on how much heat it reflects.
A "cold air" intake box would be beneficial the most if other heat sources are addressed at the same time. The best cold air intake box for a gvr4 Ive seen is I think Terry Postens. Here:
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With a nice box the next best solution for cold air is to put a vent in the hood like the jdm spec evo iii or iv style where the vent is in the corner near the headlight.
As for heat build up in daily drive use, heat would actually be worse I imgaine than in a race car. Daily driving in most cities people are sitting in rush hour traffic going no where with no air to move through the engine bay for twenty minutes, or longer. Not to mention, most people don't have vented hoods so all that heat is being trapped. Living in the hottest part of the country, I have tried many tricks in the book for heat control.
Also think about this, heat shields make enough difference in blocking (or absorbing) heat that they come on cars from toyota/lexus, mb, bmw, porsche, etc etc. They use heat shields because they work.