Welcome to the Austin Seven Friends web site and forum

As announced earlier, this forum with it's respective web address will go offline within the next days!
Please follow the link to our new forum

http://www.austinsevenfriends.co.uk/forum

and make sure, you readjust your link button to the new address!

Return to Website  > Index
Recent Posts
 
Welcome Austin seven Friends
This Forum is Locked
Author
Comment
View Entire Thread
s
Shuttle
Jan 13, 2017 - 11:13PM
Re: Exhaust pipes.

Chris Farris
To my simple mind it seems illogical to put a restriction in the flow of exhaust gas by narrowing the pipe. After all, the aim of the exhaust system is to get waste products out of the way as quickly as possible and a narrowing could lead to back pressure which would slow things down. Would my exhaust system work better if I opened up the exit end of the silencer to the same as the entry end? Or have I missed a trick?


Whilst I understand 'the best thing to do with the exhaust gas is to get rid of it', back pressure has no benefit whatsoever, except as a fuel saving measure in 2-strokes.

However, The further a gas has to pass down a pipe, the more it cools. Cool exhaust is denser than hot exhaust and causes more 'pumping loss'. By restricting the diameter of the exhaust, the gas is accelerated thus exiting faster and also causing a pressure reduction (think airflow over a wing).

That's what was explained to me. Seems those Austin designers may have known a thing or two.

r
Ruairidh Dunford
Jan 13, 2017 - 11:40PM
Re: Exhaust pipes.

The tailpipe on this car was anything but long and did run pretty hot...

photo IMG_0403_zpsttdssp74.jpg

Made the girls smile though!

https://www.youtube.com/watch?v=de0u8hOdcOU&feature=youtu.be

Email  
Jan 13th, 2017 - 11:40 PM
Jim Holyoake
Jan 14, 2017 - 1:11PM
Re: Exhaust pipes.

When gas is flowing it causes a lot of turbulence if it has to slow down. This means that if the pipe gets bigger at some point there will be a considerable restriction.
Speeding the gas up is not nearly so problematic.

Email  
Jan 14th, 2017 - 1:11 PM
Return to Website  > Index