The rear pipe is really close in one spot. I know the exhaust gasses get up to 2000*, but how hot do the headers get on the surface, with air around them and the radiator fan blowing across them? Anyone know? I have the RB headers, btw.

I imagine the intake manifold heats up from that stuff quite a bit, which is not good for the intake charge, nor is it good for the powdercoat I have on the intake, probably should've have done the lower manifold. I think the powdercoat is going to melt sitting that close to exhaust, so I really need a way to reduce the temperature there or at least reduce the heat transfer. I'm making a heat shield, but I have a stock GSL-SE intake, and so there's barely any room at all, because of the actuators and their piping. I'd be lucky to have a few millimeters of air between the surfaces, maybe it'll help a bit, maybe it won't. I'm seriously contemplating getting the headers high-heat ceramic-coated, but I don't know how much that's going to reduce the temperature. Anyone know actual temperature reduction with ceramic coating?

 

An aluminum heat shield does wonders. I got one for my dellorto intake, and there was a sizable difference in intake temps. It'd probably be pretty easy to fab a shield to fit a GSL-SE intake imo. The other thing you could consider is wrapping the headers.

 

You can also install the stock exhaust heat shield around the headers.

 

are sure egt's hit 2000*. i find that hard to believe.

 

you can wrap the headers too. it will shorten their life, but my UNwrapped header is old enough to go drinking, so if it lasts half as long that's still a could of decades

 

I donno about reaching 2000* in my particular case, I'm not gonna be making a lot of power, but I'm going to be racing the car, so it's gonna get hot. Even if it's 1700*, that's still pretty fuggin hot, I imagine header surface will be easily over 1000* and depending on ambient temperatures and how much air flows over the exhaust, there'll be several hundred degrees of radiant heat. It's my understanding powder coat doesn't hold up well to temperatures much over 200* and will ignite at 500*, and I definitely want to avoid fire, so ideally keeping the intake at 200* or less is the goal, not to mention keeping the intake charge nice and cool, which is good for HP.

Some ceramic coating places claim header surface temperature reduction of 400* or so, and reduction of radiant heat by like 50%, which is probably optimistic, but even if it's somewhat close to that, it's probably worth it and I'll try it. In addition, I've ordered some adhesive heat insulation, which I'm going to put on my heat shield. Hopefully the combo of ceramic coat and insulated heat shield will get me to where I need to be. If it's still too hot, I'll sand off the powder from the bottom of the intake or something... At least from the spot that's close to the header.

I'd wrap the headers if I didn't plan to track the car, but with sustained high temperatures the header is going to rot a lot quicker... I'll think about it, but that's more of a last resort.

 

Sounds like you need more airflow over the headers to keep air temps reasonable between the intake and exhaust. If you use the "high flow" taurus e-fan, it sucks so much air through that you can actually feel it blowing when you open the hood. It might be worth the time to try. It's fairly easy and reasonably priced (can pull at a junk yard for about 25 bucks) Combine that with a heat shield around the intake and you will probably be good, but if you are really worried, also wrap the headers.

 

Wrap the header. It makes a huge difference.

 

I don't think the fan matters, because at driving speeds the natural airflow is greater than anything a fan can produce, anyway. And the stock shroud funnels the air towards the engine and headers a lot better. At idling and crawl speeds the exhaust isn't as hot as at WOT and high RPMs.

I'm thinking in addition to the heat shield, I'll use the insulation on the bottom of the intake as well. 4 layers (inner ceramic, outer ceramic, heat shield, and insulation) seem reasonable to keep block most of the heat.

Although it's all speculation. I actually wanted to see some temperature numbers with the headers and heat shield. Or if anyone knows how hot the lower intake gets with headers below it, that would work too. Maybe someone has a thermometer and can measure? Some kind of more or less scientific input would be good.

 

my last gsl-se melted the passengers shoes after a track session...

 

WTF. Seriously? That doesn't sound right. Did you not have any heat shielding under there?

 

At the end of three back to back 10,000rpm dyno runs I used my digital pyrometer and the bottom of the intake manifold was 110*F.

Of course I have a ceramic coated header, and the stock heat shield wrapped around the header. And the stock heat shield is double layer with a 1/8" aluminum plate riveted inside it. But this will give you an idea of what you need to do to get that temp.

 

car came without the big upper heat shield and no carpet. so it was exhaust -> floor -> shoes, in the summer

on a stock car, its exhaust -> shield -> floor -> carpet -> shoes

 

Theres some quoted temps from RB in this thread:

https://www.rx7club.com/showthread.p...ght=egt+header

 

On the track I've seen 1850*F max. On the street the repu has gotten up to 1700*F when flogging it good. All of this measured inside the header, 22" from port face.

If you buy paint or ceramic coating, make sure it is designed to take 2000*F.

 

Cool. I dropped the headers off today to get ceramic coated with the 2000* stuff, and will also get the powder coat removed from the bottom of the LIM, just to eliminate any possibility of heat damage. I'm still working on the heat shield, the fitment's a bit tricky, but with all of those elements working together I believe I should be golden and will have the peace of mind I need.