First of all, this forum is primarily to share thoughts and ideas on subjects of mutual interest. Although I sound argumentative, I am really just presenting my point of view on a subject. I know you realize that, but you seem to forget it at times. BTW, what happened to "...I would appreciate any feedback." and "Any other Q's guys shoot them my way." ? Ans this sounded a lot like a sales pitch to me. "...but they usually see at least 3% on hot running engines, and that includes cars like the NSX. Just a little tidbit." But I digress. Surely all such comments are welcome here, but so are rational responses and examination.
Let’s start with "nothing to lose". Even though I do all my own work, this is hardly a case of everything to gain and nothing to lose. The time alone is precious enough, but I’m sure their guarantee does not cover shipping both directions, exhaust gaskets, etc. And then of course there’s the down-time of the car itself. Add that up and it’s not worth doing just so I can brag about my cool (pun intended) exhaust coatings.
The NSX exhaust is not SS for the same reasons you repeat from me, it as SS front to rear so it will look nice and last a very long time as is expected from such a car. My comments about modern cars using SS pre-cat was meant to show that SS is already much better than cheap steel, just as I originally stated, but it’s about cat efficiency not HP. Yes, there is a theoretical HP benefit as well but on a minuscule scale, especially with an already optimally designed exhaust. Furthermore, there is always a point of diminishing returns with such things. Even if the coatings improve heat retention (restrict heat transfer) 100 fold compared to SS, it can’t yield any more HP than the max lost to said transfer. (Again speaking of a non-turbo engine here. The rules change a bit with turbos) In the case of an NSX with SS headers that base loss value is no doubt exceeding small, and therefore so is any gain.
Reliable testing must be performed back to back with minimal time between. The latest tests to which I referred were run on an engine dyno (not a chassis dyno) with just enough delay to swap headers. The base header was cheap steel, not even SS. Care was taken to keep all else equal, and yet the power curve showed zero net gain. In fact, there were more points of marginal loss in power than there were points of gain. A reasonable interpretation of this is that an already efficient system stands to gain very little from the type of mods that may pay significant dividends on other cars. But we NSX owners have known that for a long time. Expensive air intakes for example do little or nothing, but the very well respected makers would gladly have you believe otherwise. (less so these days because we’ve long established the truth) Exhausts and high flow cats are worth at best a very small gain. Even headers are worth only a few ponies, and they generally just shift the powerband around a bit but do little if anything for the all important total area under the curve that counts in real-world performance. (I won’t give up mid range torque where I drive all day for an equal gain in peak HP where I touch often but only for an instant.)
That header manufactures offer it is totally meaningless. To them it’s just an added source of profit and a necessity to stay competitive with what consumers demand. As I said, I would expect high-end manufacturers to use them if they were worth anything like 3% HP compared to the best they can achieve with SS. Come to think of it, I wonder how many racers use coatings these days. I’m just getting back to the track after decades absence and haven’t thought to ask around, but I know most of them would jump at a 1% increase for twice that price. No doubt some have bought into this of course, but have the big-buck professional teams? I think that may take us back to diminishing returns when applied to an otherwise optimal system.
So the bottom line, and my real point here, is that what someone claims to gain from this on their Civic of unknown specifications is almost completely irrelevant to me, particularly compared to scientific tests by a neutral 3rd party.
That may not have covered all your counterpoints, but I think it covers things pretty well. I’ll probably read through it again later when I have more time.
