Ceramic coating the exhaust

[LimaXray]

you honda guys

You know what, you're right, turbo lag is reduced by reducing restrictions.  Duh.  I don't know what I was thinking, I must have been away from the turbo too long.  My turbo spools slightly faster without a cat then with a cat.  But, it also has better off boost performance with the cat.  I don't have the most street friendly turbo, and added restrictions do make a difference for that <3k NA torque in stop and go traffic.  I'll have to try running an open downpipe and see what that does. 

Nevertheless, I'm sure ceramic coating the primary on the GS will do more then just look cool.  Looking around it seems ceramic coating MC exhausts is a somewhat common performance mod.

If you don't believe me about the header wrap thing, go down to a good speed shop and talk to the guys there.  Every person I've talked to in the racing biz has had nothing good to say about it.  Or do a google search for header wrap, you'll finds loads of sites and forums saying don't use it.  It's just one of those things that's been beaten into me.

[denman]

my virago had MAC ceramic coated headers in glos black.  they looked great the nine years i had them.   sounds like a good idea go for it.   see ya.

[CRXDrew]

  you love us Honda guys. (lol, funny because... i hate most Honda guys  )

[Turd Ferguson]

Good thread here guys!  And it turned into a turbocharger conversation which is near and dear to my heart!

Unfortunately, too many people seem misinformed about "back pressure" in regards to IC engines.  Not only is back pressure a bad thing for a turbocharged application, but there is no case where back pressure can positively influence the performance of an internal combustion engine.  When discussing a large diameter exhaust, many people claim that "you will loose too much back pressure".  This is usually thought to hurt the low-mid RPM range of an engines performance and help the high RPM range.  In fact, switching to an overly large diameter exhaust pipe will lower the exhaust gas velocity.  This is where your low-mid RPM performance is lost.  The higher velocity exhaust gasses produce a "scavenging" effect in the cylinder which aids in the evacuation of exhaust gasses at these lower RPM's.  If the diameter of the exhaust pipe is enlarged beyond a certain point, this scavenging effect will be deminished or lost, thus hurting low end power.  Scavenging effects are non-existant in higher RPM ranges, so in this instance, the more air you can flow...the better. 

Remember high school physics class?  If you keep the volumetric flow rate the same through a peice of pipe and somehow enlarge its diameter (and thus cross-sectional area), the velocity will slow.  The flow rate near the exhaust valve pulses (as the valve opens and closes).  The exhaust gasses further down the exhaust pipe do not pulse as much mainly due to pressure gradients in the exhaust pipe.  When the exhaust valve closes, the exhaust gasses further down the pipe are still flowing.  This causes a slight pressure drop near the valve and the faster the exhaust gasses are flowing in the exhaust, the greater this pressure drop will be.  Once the valve opens again, the exhaust gasses in the cylinder are generally at a higher pressure and will be scavenged (or "pulled") out of the cylinder at a slightly faster rate than they would be of only pushed out by the piston.

Alright, I'll shut up.  Horray for geeks like us!

-Turd

[CRXDrew]

  not a bad writeup Mr. Ferguson. 

[galahs]

Alot of exhaust wraps, accelerate corrosion of the pipe.


The advantage of ceramic coating:

- reduces chances of corrossion
- helps chanel heat out the tail pipe. Hotter gases flow better meaning better performance, keeps your faring (if you have one) from getting too hot, and (especially if its not black) less heat will radiate from the exhaust piping heating the oil pan more.