niner

I tried searching, but did not find anything real helpful.

My question is whether or not it is a good idea to enlarge the exhaust ports on a TII. I've heard that it slows the velocity of the exhaust gas and creates more lag. Is this true? Does it hurt performance more than it helps?
Also, how does it affect cars with upgraded turbos?
I ask b/c I saw the templates on Mazdatrix and was curious if it would be worth it on my next engine, which eventually should get an upgraded turbo.

thanks

RETed

It's always a good thing...



-Ted

NZConvertible

Here's Mazdatrix's porting page, there's a link on exhaust porting at the bottom.

niner

I didnt see any info about how turbo is affected by exhaust porting w/ that link, but maybe I was looking at wrong thing.
I think I'll go w/ Ted's wisdom though and port them.

NZConvertible

Well if you look closely at the photos you’ll see most of the work is actually done on the inside of the port where it exits the chamber. The removal of this restriction allows increased exhaust gas flow. On the outside of the motor the work isn’t so extensive, so velocity doesn’t change that much. In short it is a good thing; go do it!

niner

well thank you for the further explanation

RETed

Sorry I didn't go into detail, I thought you just wanted a yes or no answer.&nbsp Someone recently accused me of not giving them a "yes" or "no" answer...

There is a point about going overly large on the exhaust port.&nbsp You will hit a point where the over-larger will just hinder and decrease exhaust velocities going into the turbo turbine section; a turbo turbine section works best when exhaust gas is at it's hottest and quickest (highest velocity).&nbsp Just as an experiment, I've ported my exhaust port probably the biggest you can go without popping the stock stainless steel sleeve out.&nbsp The port is almost 1" lower and expands at least 1/4" wide on each side.&nbsp Porting it out any larger would just require the port to neck down into the SS sleeve.&nbsp I've been running this port for the past 2 years - the car does not seem to be any slower (significantly) than I can tell on the street.&nbsp A dyno sheet would be a better indicator, but I don't have the money to do that at this time.&nbsp This is all with a stock turbo currently...

With that said and done, I doubt you would run into trouble porting the exhaust port with a stock turbo...



-Ted