[Diy_efi] Exhaust gas temp

[sc7500]

 > I've got a question about header coatings for you, since you seem to 
be in the know.
 > Is it worth the trouble to coat the inside of the header? 
 > don't think I've ever seen any numbers comparing coated 
inside/outside to outside coated only.

Hello Chris;

Yes, internal coating completes the suite. Remember what is being done - 
in essence, we're sealing the metal tubing from the elements in a 
material that also acts as a thermal barrier.

Headers rust from the inside out; if you don't coat them internally, 
they will deteriorate as if they were not coated at all. but at a 50% 
slower rate. They always die from within...

As for power production, there are gains to be made coating inside and 
out. In dyno tests with 3 sets of identical Sanderson Headers [this was 
done in 1996, before they started coating their own pipes in house] on a 
[what else ?] mild Small Block Chevy,  we found the following:

- Uncoated headers - external temp: 1005* F 2" down from the exhaust 
ports, base HP - 210 @ 4500 RPM / Torque 285 @ 3250
- External coating only - Ex Temp 800* F (same location) , HP - 221 / 
Torque 302
- Internal / External - Temp @ 675* F, HP 228 / Torque 308

So - seems it doesn't hurt to do inside and out. Underhood temps can 
drop nearly 200*, making for cooler intake air; damage from corrosion 
will be cut by a factor of 3 to 10 times; and a smooth internal ceramic 
coating makes for a much hotter exhaust pulse, which virtually 
guarantees better vacuum / scavenge on overlap.

Now don't get all excited about having a pro coater on the board - let 
me explain that I retired in 2003 to heal up from several cancer 
surgeries. Altho I no longer operate a coating service for the general 
public, I _do_ maintain a small R&D lab here at the farm, and I sell our 
materials to those who feel they have the proper equipment and training 
to do their own work. If anyone has any questions regarding the process 
or materials, please visit our website at <www.sonic.net/~sc7500>, and 
then contact me for more info.

Tell you the truth ? Coating isn't as hard as it looks. The challenge is 
in finding and using the correct application equipment., and the right 
ceramic for the particular job.

Best to all
-- 
B.T. Corneto
[The Mad Coater]
Occidental, CA 
 
"United We Stand - Remember 9-11"