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What actually is it there for.

 
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What heat sheild are you talking about?

 
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(in game show host voice) to protect other parts of the engine bay from....... Drumrole please........ You guessed it it protects the engine bay from HEAT.

We would have also accepted it protects the filter from heat if it was the heat sheild for a filter.


What does win Johnny?



I year supply for being flamed because he is a noooooooooooooooooooooooooob

 
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Exhaust heat shield?

 
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(back in game show host voice) Does the same damn thing!!!!! Protects things from HEAT!!!!!!

 
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It could also protect the headers from rusting when you pee on the engine. But I don't recommend peeing on the engine while it's hot... steam burns, you know.

 
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And peeing on something hot, like your exhaust for instance, causes an extremely foul odor. Uh.. not that I'd know anything about that. Yeah. Someone told me, that's right.

 
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1. I meant was he talking about the exhaust heat shield, not asking what it does.

2. It probably keeps the exhaust hotter than it cools down the engine bay wise guy. Heat = less pollution.

 
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Irregardless of what the original question was, a heat shield is a heat shield. It doesnt matter where the heat shield is at, simple as that. So your question "Exhaust heat shield?" doesnt help adressing the original question and is pointless.

 
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actually the heat sheild on the header is to keep things from getting hotter in the engine bay. The one on the underside of your car between the exhuast piping and the car is to protect the car.

 
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and yes I am wiser than you, if you actually believe it is to keep the exhuast gasses hotter. Come on heat in the engine bay will screw you.

 
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Actually theya re there for two reason:

1. protect the engine from heat (which is by far the least important).

(in game show host voice)and 2. (dramatic pause)

keep heat in (applause)

why keep heat in?

Well catalytic converters run better hot (especially in the CO oxidation step, which is what the primary cat does). So how do keep them hot, don't let the heat in the first place. What happens if you take them off, you emisions of CO, NOx, and SOx will go up. How do I know this, I desinged a the catalyst that goes in them for Toyota.

Noob

 
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Asking which shield the original poster meant is pointless?
And, a heat shield is not just a heat shield. How many engine bays have you seen? How much engine bay customization have you done to keep a bay from overheating?

 
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Infact the primary catalyst need to run around 900C (or 1600+F), so it need all the help it can get.

 
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Actually, heat can be a good thing. Controlled heat even better. I know racers who have to partially block air scoops because their cars run too cold. Metal expands and part's tolerances are set for certain temperatures. Go run your car hard while it's cold and see what happens.

 
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does anyone here not freaking understand that if it keeping heat out of the engine bay then of course it is keeping the exhuast piping hotter. I never said it wasn't for the purpose to keep the exhuast gasses for hotter.

 
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oh yeah and do u not understand that shield can mean keep in or keep out? wow it has more than one meaning. hmmmmm thats weird.

 
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I highly doubt this "heat shield" keeps the engine bay any cooler. If you have the time, take some bay readings and prove it to me. It looks like it does a good job deflecting incoming air away from the exhaust though.

 
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You can always cook eggs on it, too.

 
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You never stated that above. Infact you didn't say anything about the catalytic converters? Yes of course I know if it keep heat from getting out it is keeping heat in. I've got a MS in cheical engineering and am working on a PhD. Do you know what a chemical engineer does, we have three main things we specialize in, one of them being heat transfer, I've take 4 classes called heat transfer. Do you under stand q=Z(1/2 mu^2 int(y-a) -1/2 mu^2 int(y+a)? It's the equation for thermal conductivity of gas. I won't eve try to put the thermal condution and convection equtions for solids on here.

 
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It will keep cooler if the car is only moving slowly, but during normal driviing, the air passing through the engine bay is more than sufficent. If you need proof look at older cars (like the '60's and '70's camaro's). See what kind of heat shield they had, not to metion the heat a big block makes.

 
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They're high in Iron when cooked with this method too!!!

 
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http://www.lytron.com/support/heat_transfer.htm

 
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It's cooling effect isn't nearly its heat retention effect, that was my point. My experience has been mostly 70s RWD I4 and I6, and exhaust "shields" did practically nothing.

 
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Yes, that's a VERY general crash course in Thermo and a little bit transport. Now, I'll set some equation up for all those cases and we can all solve them and find out exactly how much heat is being saved and lost with and without the heat shields, but I don't think that neccassary, unless you really want to...

 
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Yes, I agree with you, it's just if you're sitting still, it will make the engine bay hot, enough to do any damage, probably not.

 
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Just let it die. It wouldn't be a real world test anyways.

 
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Let me get my graphing calculator out and blow the dust off of it.

 
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thats heat shield doesnt do sheit. Ever put your hand near it after driving around? It's almost as hot as the header. The reason its there is to keep your fingers of the header and other things too. That metal plate is useless.

 
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The heat shield protects the header from all the heat the radiator puts out! If you don't belive me, take it off, drive around, and put your hand on the header. It will be really hot.