I'm thinking about coating the manifold, exhaust housing, and downpipe from my t78 kit before installation. Does anyone here have any recommendations on the different coatings available to help deal with the heat from the rotary? I'm hoping to keep the under hood temps down and corrosion away. Which coatings work best and what are some ball-park figures for pricing? I would prefer to have a shiney finish like the Jet-hot Sterling, but it seems some of the "better" coatings are a matt finish. Any suggestions, ideas, or experiences?

 

Jet-hot 2000 coating seems to work fine on my downpipe but others have reported higher heat coatings which may be better.

 

Although I also want to coat the downpipe, I'm really more concerned with the heat in the manifold and exhaust housing of the turbo. I would imagine 1600oF isn't out of reach for a fourth or fifth gear pull.

Jet-hot 2000 claims:
"When header temperatures exceed 1,250oF for extended periods or spike above 1,300oF, JET-HOT 2000 is the solution. This coating will protect metals up to their melting points or 2,400oF, depending on which limit is reached first."

This seems sufficient, but I don't think they offer the cool sterling finish in the 2000 variety.

 

I recently went from a non coated exhaust housing to one coated with HPC HiPerCoat Extreme coating. The difference is simply staggering.

I have no experience with Jet-Hot... but the HPC stuff is outstanding.

www.hpccoatings.com

 

I just checked out their site. Looks promising. About what did it run to have the housing coated?

 

http://www.performancecoatings.com

 

I thought that coating the exhaust housing is not recommended since it will trap heat in the turbo and cause premature failure.
Is this not correct?

 

My experience is the same as yours, I ran with thermotec wraped headers and insulated exhaust blanket housing, and my turbine section wore out after 25000km, even with water injection for most of those KM. The problem was not releasing enough heat which caused the rear oil seal to fail and also the seal area in the rear part of the bearing cartridge to go oversized, the rear bearing journal on the turbine shaft was discoloured also, I never loss oil pressure and my water and oil temps were OK, it was a localized over heating problem caused by the heat retention of the insulation I was using. The end result was alot of smoke from the turbo especially after a harder run, looked like crop duster !

I will never again insulate my header or turbine housing, the DP I keep insulated to keep heat of the intake manifold, and I used heat shield to stop heat being reflected onto the LIM from the headers.

PS: If I could afford a better turbo, say with a stronger more heat resistant bearing casing, and inconel turbine wheel (my turbine wheel started erroding from the heat) then I may go insulated again, but realy for the couple of 100 rpm earlier spooling the loss in long term reliability is not worth it for me.

 

I've never really heard that... I would assume that the majority of the heat goes out the DP and exhaust... and the extreme heat is only for such short bursts (in my case).

I can tell you that my last turbo (with NO coating) died a pre-mature death (a little over a year)... failed seals and thrust bearing. I know lots of people with this coating and haven't heard of these issues... but the rotary does make significantly more heat than my piston motor... so Rice's input is food for thought.

I primarily wanted the coating to reduce under-hood temps... my turbo/DP is close to my ABS unit... so I'm trying to protect that from the heat. I can tell you that my underhood temps are significantly lower... it's really amazing stuff.

I have no idea what it cost... it was on the turbo when I bought it. So I got mine free

 

Is it ok to coat a tubular ss manifold? Or will it cause it to retain heat and crack?

 

i've done it to my intake manifold and to the touch compared to before is 10X's cooler. up next is the turbo manifold and the turbine housing, w/ the DP.

 

I have been told the you don't want to coat ss in any way since it retains so much heat that the weld joints will break. This is due to the high thermal expansion of stainless steel. The weld joints wouldn't expand much but the pipe will. However I've never tried so I can't back that claim up.

 

I have had my SS dowpipe coated for the past 4 years without any problems.

 

Thats good to know!

 

i've never heard that. then again i've heard that coatings don't work and they're a gimmick, but this person also doesn't believe that we landed on the moon!

 

I talked with a number of the coating companies (JetHot, HPC, Swain) about coating the stock Twins manifold, exhaust housings and downpipe. JetHot and HPC both indicated their 2000 degree coating was needed to withstand the heat of the rotary.

HPCExtreme claims to be a true thermal barrier while JetHot is not. From the HPCoatings website :

"On-track testing has shown as much as a 35% reduction in under hood ambient temperature and more than 50% reduction in component skin temperature. HPC's HiPerCoat Extreme process achieves this by creating a thermal barrier which retains the heat within the exhaust system. In turbocharged applications this coating helps increase turbo boost and spool-up. Independent testing of a turbocharged Mazda engine has shown a 5% increase in horsepower when HiPerCoat Extreme was used on the exhaust manifold, turbo and downpipe."

JetHot had provided data on coating thickness, and while I cannot locate that tech sheet I do remember comparing it to Swain Technology (http://www.swaintech.com) and noticing the Swain Tech White lightning is much thicker (.015-.020" thick ) than JetHot 2000.

It would be interesting to compare notes on the different coatings. I was thinking of having mine coated by Swain this winter.

 

anybody done this.......anybody?

 

You can check my web site...

I have coated the manifold, exhaust side of turbo, and downpipe. All this is to gain more thermal efficiency (keep the heat inside the exhaust for more energy transfer to the turbo). The added effect is to keep the heat down under the hood.

A case in point, I can drive around town all day and come home and open the hood. The motor is not whithering hot like it used to stock. I am running over 400 hp too!

The coatings work!

regards

Rick
1993 RX-7
T04E
403 rwhp

 

what's your website?

 

I had a friend of mine that had HPC coating done to his HKS SS exhaust manifold and loves it, he doesn't have any problems with it, and he's had it for like 4 years now on a daily driven turbo rotary. I'm definately getting it done.

 

Which coating would you recommend for the intake manifolds?

 

Click on the WWW icon at the message border or you can click here:

Rick's web site

Go to pictures and then to the RX-7 area. Lots of pictures of the modifications as well.

regards

Rick

 

Hey Rick,
When you coated the exhaust side of the turbo, did you take it off and send it in to HPC or did you have to send the entire unit?
BTW great website!

 

Hey Rick,
When you coated the exhaust side of the turbo, did you take it off and send it in to HPC or did you have to send the entire unit?
BTW great website!

 

I actually sent the entire unit over. They did a fantastic job! After over 4,000 miles, the coating is still as good as new.

Thanks for the kind remarks on the site. The other areas are quite interesting also (karting, 911, other stuff).

regards

Rick