Side Pipe SPL

[Rare Iron]

The new page is up - step-by-step on the retrofit with a bunch of photos.

[Richard Hudgins]

Machiavelli

As to the statements about stainless as a header material the following:

The Thermal Conductivity - k - (W/mK) of various materials used in headers are as follows:

Carbon Steel 54
Ceramic coated Carbon steel 2.36
Stainless Steel 16
Inconel 8.4

Note: 1 W/(mK) = 1 W/(m degrees C) = 0.85984 kcal/(hr m degrees C) = 0.5779 Btu/(ft hr degrees F)

It is true that stainless makes a longer lasting header then carbon steel under racing conditions. The life increase is minor in my experience and I have had many problems with cracking at welds due to differential material thermal expansion of the base and filler alloys. (This can be a problem with carbon steel as well if you use a really wrong filler material but this is rare)

I have had the best luck with Inconel for race headers. I have never had a crack or failure of any type using this alloy. It is used by all of the F1 guys and most LeMans Prototype cars as well as the turbocharged engines in many series.


Also you still need a thermal barrier with stainless. They still heat up to match internal temperature it just takes a 3.5X longer than plain carbon steel. Also the lower heat conductivity makes them take much longer to cool down which can give you problems with shutdown heat soak. (This is also true for Inconel and why you see the F1/LeMans headers in a gold foil lined and covered containment.)

Whereas ceramic coated carbon steel takes much longer to achieve 100% heat soak and typically never does due to duty cycle and airflow removing the transferred heat away at almost the same rate as conductivity.


I would still use the ceramic coated carbon steel if I were you. The heat transfer normal to the wall is the lowest of all and will keep under-hood temperatures down. (By a factor of 4 relative to stainless from the above table.)

You must remember that you are normally going to be running at part throttle and your exhaust temps are going to be quite low. (Street use)

For the times that you are going to do track work your full throttle time will seldom be over 60% of a given lap and I doubt that you will be putting in more than 10 lap stints. Overall header temperature or corrosion should not be a real factor in the life span of your system.

But you can make stainless units and then ceramic coat them and have, as Dr. Pangloss in Voltaire's Candide so eloquently stated, the best of all possible worlds.

(The real best would be ceramic coated Inconel $$$$$$$$$)

With any luck this will make some overall sense.

[Machiavelli]

Richard,
Another great post, and it does make perfectly good sense. I hadn't considered the heat soak issue, that alone is a show stopper for me. But as you have said, there is this 2nd "best of all possible worlds" option (leaving Iconel out of it), that being ceramic coated SS. Back on post #12 I mentioned I've been digging more into side pipes, have emails out to some of them. One looks interesting, cutting edge - but we'll see. I actually was going to say "best of both worlds" on that post, looks like it's time to divulge that google hit - http://mastertouch327.com/2.html

I've talked to the owner and he has some technical information about these pipes coming my way. Everything used is SS including the internal baffling which is a perforated SS cone design of some sort, tunable for sound. I'll share the details when I get them, but I do like the ceramic coated inner pipe and the "coolshield" concept. Facing reality, my wife will be with me some of the time - and with her short legs, pipe contact is inevitable. She did "ok" the JBL build, I figure that's the least I can do (not that I'm into burnt calves either - sorry Jay Leno, that's one "badge of honor" I can live without ).

MASTERTOUCH custom builds to your specs and they are performance conscious. You will also note that these pipes are not insanely priced like FireFly's (and without coolshield), so we'll see. In my opinion, that would be a pretty nice marriage with SS ceramic coated headers if his design holds up. (I will email you .pdf files of what he sends me).

One last question, if I were to go with SS ceramic coated headers - would just an outside coat be sufficient? Thinking risk mitigation in case there is some truth to Lelchook's comment re: internal hot spots the coating burns off and rust begins to generate.

Thanks for your assistance Richard, as always - much appreciated!

[Richard Hudgins]

Machiavelli.

The stainless being stainless, (depending on the alloy) would not rust on the inside.

Therefore you could certainly just coat the outside.

The side-pipe design with the dead air space should work fairly well as the thermal conductivity of Air is 0.024 k - (W/mK). However where the outer skin is welded to the inner tube you are going to get significant heat transfer.

In other words hot spots at those locations.

[Machiavelli]

Richard,
I should elaborate on my last post a little -

With regard to the headers only, will just an outside coat be sufficient to alleviate the heat soak concern? I know that typically when you get your headers coated, it's an inside and outside job.

For the side pipes, yes - the inner tube to outer skin would be the thermal conduction path, no doubt why they say Yes, it does get warm, there is no way around that ... But if I were to guess why his design works, I would think because the whole outer skin is one large heat sink relative to the weld area conduction path. Looking forward to seeing the technical details.

[Richard Hudgins]

Originally Posted by Machiavelli

Richard,

With regard to the headers only, will just an outside coat be sufficient to alleviate the heat soak concern? I know that typically when you get your headers coated, it's an inside and outside job.

Yes that should take care of the heat soak issue.

[Machiavelli]

Ok, thanks Richard.

[Machiavelli]

Eric (Rare Iron),
Your chambered flow-thru exhaust makes sense, specifically when dealing with the sound reflection aspect of your "stamped" outer muffler shell to block the leakage from the inner 3" (or 2.5") diameter inner tube. I have also looked at everything on your website, all pictures show a head-on view of this "stamped" muffler concept. Just curious, because sound radiates 360within any chamber, and the annoying higher frequencies like to bounce on metallic surfaces, do you also stamp the opposite sides of your "powersticks" (not visible in the photos)? If not, why not? From where I sit, as long as you maintain that inner 3" (or 2.5") diameter clean flow-thru path, you have double the capacity to block those unwanted higher frequencies by stamping both sides? (Maybe they need to be staggered in some way, but you get the idea)

[Rare Iron]

Originally Posted by Machiavelli

Eric (Rare Iron),
Your chambered flow-thru exhaust makes sense, specifically when dealing with the sound reflection aspect of your "stamped" outer muffler shell to block the leakage from the inner 3" (or 2.5") diameter inner tube. I have also looked at everything on your website, all pictures show a head-on view of this "stamped" muffler concept. Just curious, because sound radiates 360within any chamber, and the annoying higher frequencies like to bounce on metallic surfaces, do you also stamp the opposite sides of your "powersticks" (not visible in the photos)? If not, why not? From where I sit, as long as you maintain that inner 3" (or 2.5") diameter clean flow-thru path, you have double the capacity to block those unwanted higher frequencies by stamping both sides? (Maybe they need to be staggered in some way, but you get the idea)

Machiavelli, the Powerstick muffler is a chambered muffler - Cobrapacks are smooth & not chambered (you probably already know this). The crimps in the outer shell of the chambered mufflers create a soundwave anomaly which "tune" the exhaust - they give the exhaust a very unique sound. I'm not sure what you are asking about my crimp design. I crimp them at 12:00 & 6:00 positions, with relief areas at 9:00 & 3:00. Other chambered designs crimp at all 4 positions. My design pattern gives mine a different sound, as well as my perforation pattern in my cores. All combine to make them what they are.