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Wrapping entire exhaust
Furyous - 22/9/15 at 02:47 AM

Is there a disadvantage to wrapping an entire exhaust from the head to the tip? I gather hot headers aid gas flow but would it matter if the heat is kept in the whole exhaust system? Does it make much difference when the exhaust is only a few feet long?

Just having some idle thoughts about the exhaust on the Fury inside the pods...

matt5964 - 22/9/15 at 06:04 AM

How about ceramic coating

http://www.zircotec.com

Wrapping would need replacing over time and you need to be careful not to create any hotspots with uneven reaping which will fate argue the exhaust.

jeffw - 22/9/15 at 06:52 AM

You don't need to wrap the silencer as it is already insulated internally. Always remember the heat has to go somewhere, if you are containing it by ceramic coating/wrapping etc it will heat up the next plain piece of metal, whatever that is.

coyoteboy - 22/9/15 at 07:18 AM

Works fine, keeps the exhaust gases hot and lower density, therefore fast moving, but will mean your silencer will run notably hotter. I've done it on my tin top, changes the exhaust note too

Mr Whippy - 22/9/15 at 11:28 AM

quote:
Originally posted by coyoteboy
Works fine, keeps the exhaust gases hot and lower density, therefore fast moving, but will mean your silencer will run notably hotter. I've done it on my tin top, changes the exhaust note too


Surprising

cliftyhanger - 22/9/15 at 04:47 PM

quote:
Originally posted by coyoteboy
Works fine, keeps the exhaust gases hot and lower density, therefore fast moving, but will mean your silencer will run notably hotter. I've done it on my tin top, changes the exhaust note too

Ah, but higher temp increases either volume or pressure. Or both. Neither of which are good news.

All this exhaust stuff is never as easy as it sounds. I am very undecided about the science of it all.
I was told by a guy who was once involved in F1 exhausts that a chamber after the manifold allows the gasses to expand and therefore cool rapidly. This causes them to contract, and so easier to shove along the exhaust. Makes sense, until you start thinking the gas has to recompress a bit to go along the exhaust system. And that the heat from the expansion needs to go somewhere.

Badger_McLetcher - 22/9/15 at 05:00 PM

Guess it may make it slightly higher? If the gas stays hotter therefore lower density and faster flow. TBH I'm surprised it makes a noticeable difference though!

snapper - 22/9/15 at 05:21 PM

The side pods on a Fury need protection both on the inside of the area that meets the interior ( your passenger or you will fry) and the inside of the exterior face or tell coat will suffer.
You need to protect against radiated and converted heat so multiple solutions are required

coyoteboy - 23/9/15 at 08:21 PM

quote:

Ah, but higher temp increases either volume or pressure. Or both. Neither of which are good news


You're viewing it the wrong way.

1) Exhaust isn't a closed system in which increase in T increases P. It does increase volume, and that's why it expands out of the tailpipe faster and with lower density.
2) Pressure and temperature are at their maximum at the header and only drop from there on as the gas expands from the valve area. If you allow the gas to cool too much before the end of the pipe you build up a cold "dam" of gas (exaggeration) so the higher pressure gas behind cannot expand from the port as easily.

It is ALWAYS better to have the least static restriction possible on exhausts - be they turbo or NA. That's best achieved by higher temperature gases. Naturally you can change scavenging effects by changing the density enough to bugger up your header length calcs but by the time you're down to your mid/tail areas you're making zero effect to that particular tuning method.

As for change of note: - I think the theory states it should get higher pitched due to the change in speed of sound in air, but it actually seems a LOT lower and to lose the higher pitch notes - I've not thought about why that might be.

[Edited on 23/9/15 by coyoteboy]

cliftyhanger - 23/9/15 at 08:41 PM

I realise it is not a closed system, however a hot gas, sealed/closed or not has higher volume for any given mass (or no. of moles if you want to be scientific) entirely dependant on temp. So a larger volume of gas to shift albeit at lower density. But that means it has to move faster. And faster moving suffers from more resistance.

All this exhaust stuff is difficult, theories seem to oppose each other. I guess the only way to tell for sure is back to back testing. And I wonder if anybody has actually done that? (apart from companies selling stuff, wouldn't trust their results)

coyoteboy - 23/9/15 at 09:27 PM

Your exhaust is only a set length, larger volume but lower density means fewer grams of gas in the exhaust at any one moment and the lower density means less resistance from the higher speed flow.

David Jenkins - 23/9/15 at 09:36 PM

My exhaust was originally wrapped within the engine bay - manifold and about 3 or 4 foot of pipe - and every time I stopped the engine I was rewarded with a loud backfire! Took the wrapping off when I did some maintenance on the engine and the backfire went away...

...I have no idea why!