Questionning Jennings! - Slanted Ports VS Straight-In Ports!

Thanks

Lohring Miller

Marc wrote: So in short, I still feel he didn't explain it clearly enough...it really leads to misinterpretation when he says that "effective area of straight in ports are greater than those entering the cylinder at an angle". This is only true if you are matching window sizes!

Hi Marc, Jennings is correct and you explained it perfectly with you slant cut tube but in reverse. When you measure the slant cut of your tube then you have .559 sqin whereas the actual port area is .442 sqin based on the diameter of the tube. Clearly a port cannot flow more than its actual diameter allows. This is why you have to measure a slanted port in the way that he shows on the middle pic on his diagram.
I hope that's clear .
Dave

Dave Marles wrote:

Marc wrote: So in short, I still feel he didn't explain it clearly enough...it really leads to misinterpretation when he says that "effective area of straight in ports are greater than those entering the cylinder at an angle". This is only true if you are matching window sizes!

Hi Marc, Jennings is correct and you explained it perfectly with you slant cut tube but in reverse. When you measure the slant cut of your tube then you have .559 sqin whereas the actual port area is .442 sqin based on the diameter of the tube. Clearly a port cannot flow more than its actual diameter allows. This is why you have to measure a slanted port in the way that he shows on the middle pic on his diagram.
I hope that's clear .
Dave

Yep...at first I really didn't get it... I didn't like the fact that it was presented as a slanted port flowing less... that's not the case... it just means that you can't rely on the measurements at the port's mouth in the cylinder, for the reasons shown above. The port itself, whether slanted or not flow the same if the internal area is the same. I just had to bounce it around a few times to really get what he was trying to say. He obviously knew what he was saying and thinking, just wasn't explained as clearly as could be I thought! That's why I started this thread after a private discussion with Scott. I thought it would be cool to discuss these concepts openly with all the readers. Thanks for chipping in. Nice to see you on here Dave! There are some great minds reading on here, I really like it when you guys join in. We need to get more of these technical discussions going! BTW, thank you very much for the donation also.