Exhaust flow talk

[Bean]

NoHachi Wrote:I have read Bell and about every other book out there..

Lets tackle this thing step by step and see if you lot can figure it out by yourself.

Quote:EDIT: don't forget that exhaust gas does also cools down on the way out (volume decreases) so to keep gas velocity level it would need to get smaller further too the back (this goes for turbo as well)

Why do you want to keep up velocity? Massflow stays the same.. In the end u need to dump your gass in 0,0 velocity air at ambient pressure..think about that and then about the "steps" that you siad you believed in..

Maybe I should have been clearer about my formulations...but I still stand by my case..the best exhaust has the biggest diameter possible as soon and smooth as possible...what does this exhaust look like? Weeeelll it would be a trumpet shape right behind the header..Take a look at whats dangling behind an F1 car and then think again abot your "reduce diameter" theory.

The point all of you are missing and the one I should have emphasized is that you have to make the change GRADUAL. Make too abrupt a change and the flow seperates from the walls and creates drag. That what happens in exhausts..the change in diameter is too fast...but the big diameter itself is not the problem.

my last phyics lesson quite a while ago but I'll try to formulate my thoughts/thinking as good as possible...I'm just an enthusiast not a pro

if you read all of it your probably right but IMHO this goes for the case to achieve max power... and thats nothing to do with driveability - this is also were I think (haven't looked at it from a physics point, more of a feeling ) that velocity comes into play as while driving you don't get constant airflow as your revs change continously in contrast for a helicopter turbine where rpm is constant (while flying) and you just change the angle of the blades... what I desire is a useable torqueband with 'enough' power... with good emissions as a bonus
PS: with te steps i ment what you called GRADUAL above, miss-understanding but I do occasional shovel my own grave