I ordered my 2.5 down pipe from bushour racing yesterday but cant decide on weather to buy some heat rap and rap it or just leave it. Besides lowering the under the hood temps at stand still what are the benifits and down falls of doing this. I hear the heat rap will make the DP suseptable to cracking due to the heat being kept inside and not being alowd to escape.

I just needs some feedback and comments on this.

thanks in advance

-chris

 

why 2.5 and not 3 inch?

 

werd y not the 3 inch umm i think if u wrap it..it would be better.

 

its not a noticeable benefit or detriment in my experiance. I have done both and all in all its one more thing to dangle under the car when it starts to fall off.

 

Well I plan on keeping the stolk cat and going from a 3' downpipe to a 2.5 cat then to a 3' cat back is a big bottle neck not to mention big turbulance in the exhaust flow causing a slight loss in power meaning the car will not loose power but if u dont go 3 inch cat u will never get the full benifit of the 3' downpipe. Foy my needs I think the 2.5 is perfect 4 my exhaus IT will be like a horn good flow that just gets faster and faster with little turbulance. Think about it its better to have good flow and open it up rather than have great flow and shove it into a smaller opening.

Chris

 

Its always amusing to listen to the theories people come up with in their heads, isn't it?

 

whats so funny with it. Tell me how raming 3inch in to 2.5 is a good thing? Turbulance is a bad thing in a exhaust system. If your knowlegeable break it down for me. David at bushour seems to aggree with me mabe thats why he makes is 3' downpipe to fit only a 3 inch test pipe or cat hmmmmmmmm.

-chris

 

Dave Buschur himself has stated on this site that if you are keeping your stock cat then a 3" DP is a waste of money.

I tend to think he knows a thing or two on the subject...

 

You're right, if you're keeping the cat, stick with the 2.5. I personally has had experience in this department. I installed a 3" dp with the stock cat and the first thing I noticed was that I was loosing that quick response (low end torque). But since I eliminated the cat and now I have 3" through out, my EVO runs alot better.

 

Thanks mikesevo8

I rest my case.

Back to topic at hand SHould I have my dp heat rapped or jethot coated?

-chris

 

Exhaust shold be free flowing as possible :
2.5" down to 3" remainder of exhaust is no problem.
3" into 2.5" then back to 3" kind defeat the puropse of seeking more free flowing exhaust. Better than a cat yes...but not getting the fulll potential of an 3" piping exhaust. As for the wrapping, tuner here recommen it for circuit racing only...not really for performance gains but the down pipe is just too dam close to the oilpan. Helps limit heat tranfer the pan. Daily, street, auto-x or even drag...the time you actually pushing the car hard is limited compared to endurance, laps or even off-road.

cheers,

 

CA..... this makes scence......I didnt know the cat was 2.5"

It is makes more scence to go small to big if your not going big to big throughout. I see how a botle neck would hurt your flow.

How about taping the down pipe like a candy cane and only doing half of it throughout? ,, that way you have a happy medium?

Just and idea,,,,,, also fishing for a "what a lame idea" response.
LOL,,, but who knows this might work.

 

Ok, I'll bite.

The problem with your 'horn' theory is that you're causing the exhaust pulses to lose energy as the propigate down the pipe. How? Because that pulse has a set amount of energy. Now you're asking it to expend it's energy to fill up a larger and larger space. ( assuming you get a perfect taper like a horn) Not to mention that the exhaust pulse is already losing energy due to transfer of heat to the piping. Basically, by increasing the exhaust diameter as you go further from the turbo, you're actually increasing backpressure as pulse after pulse hits each other as it goes down the piping.

I would rather go from a 3" downpipe, into a 3" cat-con, then into a tapering 2.5" catback.

 

oh yeah, about the topic question. Get it ceramic coated. I found a local coater who charged me only $15 a linear foot to coat my downpipe and midpipe (vishnu signature model)

 

No i was amused becaused going from a smaller to larger exhaust causes the exhaust to slow down, thats all.