Mine is rusted to ****, and I needed to use my air chisel to get it off. Do I really need to replace it? I'm running the RB streetport exhaust system.

 

I wouldn't think it is mandatory, but would be good to have. Even the muffler gets pretty warm, specially the RB or any reverse flow type.

 

I belive that the Rx8 had a recall because the head from the exhaust had caused a fire and I think it had to do with a similar type of heat shield.

 

****, I guess I'll have to make a new one.

 

It'll keep yo gas colder and give you mad mo powwwwaaaaahhhh!

 

I would recommend keeping it, or replacing it with something else. As others have said, if the thing heats up, gas will evaporate more, your fuel economy will go WAY down (even worse... than it is now...), and in a extreme case you could have a serious fire. Its just not worth removing it, it was there for a reason.

 

Some aluminum flashing could be made into a good heat shield. I use it all the time. Nice and lightweight, easy to bend and shiny.

 

I agree, in the rare case that you get a small hole in your exhaust and your gastank at the same time, you would be up in flames. 15 minutes or 1500 dollars worth of damages.

 

When I installed my SE tank, there was no heat shield, nor were there attach points for the heat shield. The carb tank that I replaced had one. Did they not have it on the SE?

 

Aluminum isn't very good as a heat shield because it transfers heat relatively quickly. Steel is better.

 

Yes. And the shiney-er the better. Radiation absorbtion is reduced dramatically on a highly polished surface as compared to a rough or painted one.

 

I disagree with some of the statements here. Aluminum will conduct heat better. If the muffler or exhaust is to close in a particular area, or if there is a small leak impinging exhaust gas locally on the heat shield, the aluminum will spread the heat better, meaning the heat shield will be more uniformly hot all over. It is highly unlikely the aluminum will get hot enough to melt. You might be able to attach a flat sheet to some remnant of the original steel heat shield, depending on what is left of it. You may need a large washer to spread the load wherever you attach it. The disadvantage of aluminum is it is more prone to fatigue if it vibrates. But it won't rust!

I used aluminum to make a heat shield around my RB header to keep the heat off my carb. That has worked well.

 

So if I go and get a sheet of stainless steel at Home Depot, cut it to roughly the same size as the old one, and pound it into roughly the same shape, I should be good to go?

 

That'd do it... if you want to get crazy paranoid you could wrap the exhaust with header wrap where it passes under the gas tank, but the stainless steel (or slightly thicker gauge aluminum) will do it

 

Just to give my view a perspective for you, I'm a mechanical engineer with a masters degree in heat transfer and airflow.

The main purpose of a heat shield is to keep heat from transfering from a hot component to a cooler one, obviously. The main mechanism for this kind of heat transfer is referred to as radiation. This means that the heat travels from the hot surface to the cold through electromagnetic waves. In general, it's safe to consider the entire surface of a heat shield as being evenly radiated by the exhaust component. This radiation is best reflected back to the hot component by using a shiney surface, it absorbs less of the radiation. This part of the story can be handled almost equally between aluminum and steel if they are both equally finished on their surfaces.

Once heat is absorbed at the surface of the heat shield, it will try to make it's way through the sheild to the cold side through another mechanism known as conduction. This is where the material differences come into play. Because aluminum is about 5 times more conductive than steel, the heat has a much easier time making it to the back side of the shield. The temperature on the cold side of the sheild will be much hotter with an aluminum piece than a steel one. Because of this, there will be more heat transferred, again by radiation, to the components on the cold side of the shield.

Hopefully that's understandable. Ideally, you'd use a very low conductivity material for a heat shield, that's why the space shuttle uses ceramics, they have significantly lower conductivity than metals.

 

One time my muffler exploded (no, really...) and in the 1/4 mile on the highway it took for me to decide to pull over, the undercoating on the fuel tank was smoking.

That was *with* the heat shield.