AUTOMOTIVE EXHAUST FLOW AND TEMPERATURE 2

[PINNEY]

I need to design an exhaust extraction fan system.
What is the temperature and flow rate exiting the exhaust pipe? Where could I find this information??
Thanks

 

[btrueblood]

Search this forum, the subject has come up a few times.

 

[BarneyD]

What kind of car (or whatever your working on) are you asking about? It depends on how lean/rich the engine your working on.....if we're even talking about a car here. I think 900 degrees at the header sounds familiar. Of course it would be less at the rear of the car.


Barney Demonbreun
Technician for Gary Force Acura, and owner of;
Ashland Motorsports
1304 Big Marrowbone Rd.
Ashland City, Tn. 37015

 

[Rob45]

The answer to your question involves so many different variables it's impossible to answer with no more information than you've stated: Diesel or gasoline?
Nat. aspirated or blown?
RPM?
Load?
and the list goes on.

Here's your best bet:
run a test. Get a thermocouple and a reader; you can even use one like the Sears DVOM that has a thermocouple reader function.

"One test is worth a thousand expert opinions."

 

[GregLocock]

Rob, You forgot - publish your results here and we'll pull them apart.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Warpspeed]

Pinney, temperature could be just about anything.

I believe flow usually works out around 2.2 CFM per horsepower when the exhaust has expanded back to atmospheric pressure. That will be a very rough starting point only. It is usual to have a much larger extraction system than that, and allow plenty of ambient air to bleed into it right at the header discharge point.

 

[patprimmer]

Is the question about exhaust extraction from a dyno room, or about exhaust scavenging an engine

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Rob45]

Greg:
"Rob, You forgot - publish your results here and we'll pull them apart."
LOL!
Yes, there's always that!

But to geet back to Pinney's question:
You could always assume 100% volumetric efficiency and sufficient length of pipe to drop the gas temperature to 500 F or so.
E.g., 300 cubic inch engine running 4000 rpm would produce 600,000 cubic inches of exhaust per minute x 1160/560 = 719 cfm.
call it 800 cfm and you should have your dyno room (if that's what it is) covered.

 

[evelrod]

PINNEY, have a look at this mpeg.

http://www.zoominternet.net/~jonlauer/f1fireup.mpeg

I am not sure what fan would handle that.

Rod

 

[EngJW]

The equation in our handbook is to take the cfm of intake air (which includes the volumetric efficiency) and multiply it by 2.4 for a gasoline engine or 2.0 for a diesel.

This is probably more of a rule of thumb type of equation but it has been used longer than I've been around, so it would have been thrown out long ago if it didn't work.

 

[Rob45]

That equation sounds like it would work just fine.