[oldman]

I view the exhaust system as a heat sink.

Race engine open header, yep the more heat retained before ejection to the atm, the more HP is to be found, in general of course.

For a street car, especially one with headers hooked up to the factory cat back, to my mind the question is moot, does a coated header which has more retained heat and energy at the header exit point into a muffled exhaust system yield more engine power? I HIGHLY doubt it.

Will my engine compartment be slightly hotter when I'm in grid lock with non-coated headers? Yep.. don't get into a 1/4 mile throw down in the center of Austin at 7:30 in the morning.

[TJay74]

There have been several coated header test over the years, all of them have shown on a street engine to produce 5-10 hp more than a non-coated header.

Remember, it is not always one mod that makes the increase, it is the sum of all of the mods that make the increase.

[aka Reckless]

LOL, driven through Austin many times, not just 7:30 haha, it's a mess any time between 6am and 9pm

[JANNETTYRACING]

Originally Posted by oldman

I view the exhaust system as a heat sink.

Race engine open header, yep the more heat retained before ejection to the atm, the more HP is to be found, in general of course.

For a street car, especially one with headers hooked up to the factory cat back, to my mind the question is moot, does a coated header which has more retained heat and energy at the header exit point into a muffled exhaust system yield more engine power? I HIGHLY doubt it.

Will my engine compartment be slightly hotter when I'm in grid lock with non-coated headers? Yep.. don't get into a 1/4 mile throw down in the center of Austin at 7:30 in the morning.

Temps around the headers coated vs non coated can be up to 400 degrees different depending on how close you get to the tubes.

Best investment you can make when it comes to performance exhaust mods.

There is a lot more to it than Dyno numbers.

Ted.

[oldman]

Originally Posted by TJay74

There have been several coated header test over the years, all of them have shown on a street engine to produce 5-10 hp more than a non-coated header.

Remember, it is not always one mod that makes the increase, it is the sum of all of the mods that make the increase.

love to learn, please post a few. thanks, I mean since full LT and off road plus tune yields 15 hp, um how many more with coated headers..

[Fraxum]

Originally Posted by oldman

love to learn, please post a few. thanks, I mean since full LT and off road plus tune yields 15 hp, um how many more with coated headers..

LOL. I have to agree with you there and Ted. Having had both uncoated and coated LTs.

But doesn't holding down underhood temps help preserve HP? And of course makes thing easier to work on when warm. I'm sold on coating.

[2000form]

I did a search and saw hot rod did a test of coated versus non coated. It was on an engine stand so there was a variation. They clearly saw a huge increase in pipe temperature and cool down but no hp difference. I would think at very low speeds or on launch there would be a hp difference due to the under hood temperatures but I would think once you start moving and there was air circulation that difference would go away as well. I have never had coated headers and they have done pretty well.

[2000form]

But if someone showed me I could get an additional 10 hp by coating the headers after there is some air circulation, I would make the change.

[Fraxum]

Originally Posted by 2000form

But if someone showed me I could get an additional 10 hp by coating the headers after there is some air circulation, I would make the change.

As for me I agree with the OP. No HP gain, just lower underhood temps.

[Burly]

The local speed shop guys made the comment that there was a lot plastic under the hood and header coating would help longevity of those plastic parts. Another agreed, while looking under hood, you can't even see the headers from all plastic stuff.
I have no experience with either, but the googling I've done seems to agree the coatings inside and out are a good idea. Many things I've read claimed a very small increase in HP...

[PRAY]

How much extra is the coating from say Kook's or ARH? Or do you have to send them out after you get them. I would just call Kook's but it is Saturday. Headers for these cars are already extremely expensive. Adding say $500 for coating to a system that is already over $1,500 just makes it more prohibitive for the average guy. Thanks.

[oldman]

Originally Posted by 2000form

I did a search and saw hot rod did a test of coated versus non coated. It was on an engine stand so there was a variation. They clearly saw a huge increase in pipe temperature and cool down but no hp difference. I would think at very low speeds or on launch there would be a hp difference due to the under hood temperatures but I would think once you start moving and there was air circulation that difference would go away as well. I have never had coated headers and they have done pretty well.

please post link, was this an open system, header to atm?

[oldman]

Originally Posted by PRAY

How much extra is the coating from say Kook's or ARH? Or do you have to send them out after you get them. I would just call Kook's but it is Saturday. Headers for these cars are already extremely expensive. Adding say $500 for coating to a system that is already over $1,500 just makes it more prohibitive for the average guy. Thanks.

The coating prices were reasonable, I did not see the price vs actual performance as benefit. On turbo setup with a $1200 Honda ram horn and a $350 swain white lightning coating yep worth every penny.

As I've speculated on even if there is that much more heat retention within the header pipe, it just means more back pressure post header in a closed system at the "expense" of a slightly hotter engine compartment which realistically on my DD is nothing as the average speed on a drive is MORE than enough air flow to render any potential heat injection into the engine compartment moot. Any one want to even debate how much cubic feet of air is moving thru the compartment at say 10 MPH much less 60 MPH... I think not.

http://nitroplate.com/dyno-performance/
Here 10 HP for an open header, which I don't doubt. 200 degree reduction of radiate heat in a dyno room. If air was moving over the headers during the dyno run there would be substantially less.

So my question is the header is radiating less heat, great, open header you are maintaining more energy and the header is going to be working at a higher heat delta and by thermodynamics we know that it can do more work period. But that is not my contention. On a DD it is bolted to an exhaust system that is functioning as a heat sink, a higher energy flow entering the stock cat back will cause more back pressure, the coating is mere moving the heat dissipation further down the line. Negative pressure savaging waves in a closed system emanate from the tail pipe on the "sink". All this to my mind goes to angles dancing on pins. In a closed exhaust system does a reduction of say 2400 watts of radiate heat at the header mean anything in terms of performance? So is this a performance thing or is it a "heat reduction" thing? closed system?

Heat reduction, 200 degrees of delta of radiated heat is nothing until we can look at what 10 MPH of air would do, gut feeling the radiated heat would go to like 20 degrees delta. So yea I'd like to see a dyno of a closed system with some fans to simulate air movement and cause these are full WOT pulls to 6500 RPM, I think at least 70 mph of wind would be minimal to replicate an actual car.

[LibertyHill]

I went uncoated and now wish I had given it more thought. Wraps seems like a bad idea even on SS, but the semi-rigid insulating blankets over the top seems like they may be worthy of consideration to insulate from some of the radiating heat. Any thoughts on those?