Tractorsport Flowbench Forum Archive

Posted: **Fri Feb 23, 2007 4:15 pm**

I just read a bit about an F1 engine... they state that the exhaust goes sonic for 50 CRA after EVO in it,and that the port therefore have to be modeled with both super- and sub-sonic flow in mind..

Posted: **Fri Feb 23, 2007 7:00 pm**

Posted: **Fri Feb 23, 2007 7:09 pm**

Posted: **Fri Feb 23, 2007 8:37 pm**

Larry, I had to go back and edit the post,I took it from memory and had mixed the EVO point (95 degrees ATDC) with the crank movement. It's sonic for the first 50 degrees of crank rotation after EVO,that was said to happen with an in-cylinder pressure of 147 psi (10 Bar) in their example. SAE 2002-01-3359 is the one,I got it from Erland Cox on Speedtalk,he said they were available on G.P. Blair's site.

Posted: **Sat Feb 24, 2007 12:39 pm**

On the same tack, pre WWII Harley flattrack racers drilled holes in the cylinders near BDC, open to atmosphere, to facilitate blowdown/inrush, and it actually helped. Very messy, though. Today the EPA and CARB would love it!

Edited By gofaster on 1172335216

Posted: **Sat Feb 24, 2007 11:31 pm**

Posted: **Sat Feb 24, 2007 11:36 pm**

Posted: **Sun Feb 25, 2007 10:55 am**

Posted: **Mon Feb 26, 2007 12:03 pm**

Larry,
as you said:

"I'll bet that was messy! As if enough oil wasn't already escaping on early HD stuff!"

That's especially true as those were the days of total loss oil systems. I enjoyed looking at the article you posted. The author has some great material. I own a book he published on Linkert carbs. A few years back I was swamped with side valve and Knucklehead work and his references were invaluable. (I probably oughta told him that!)

Posted: **Mon Feb 26, 2007 10:27 pm**

Posted: **Tue Feb 27, 2007 11:58 pm**

Tractorsport Flowbench Forum Archive

Flow depresion - Effect on velocity