Upright or side Plenum?!

[Mohamed Aziz]

Hello,
I'm involved in designing our intake system for a single cylinder engine. I have been searching about plenum volume and shape. Of course there are a lot of designs, but I was wondering why I may think of using a side plenum in case of a single cylinder engine. I knew that more bends make more friction losses in the flow and thus lower VE. So, I think it's better to use the upright plenum but I wanted to know if the side plenum has more advantages.
Please tell me whether my thinking is right or not.
Also is it convenient to start the design with a 8× engine displacement plenum volume for a single cylinder engine?
Thanks in advance.

[MCoach]

8x engine displacement plenum volume may not be very convenient for your chassis designer, but you are certainly on the right track.

Isn't it still a single bend whether it bends up or bends to the side?

[Mohamed Aziz]

Thanks MCoach.
But I think the bend angle in case of side plenum is bigger than when it bends up, is this right or it depends on other variables?

[Bemo]

If you build it on the side of the engine be aware that if any portion of your intake manifold is below 350mm from ground (not absolutely sure about the number, but should be in that ballpark), it has to be protected by tubes according to side impact protection dimensions. As this is insanely heavy you obviously don't want that ;-)

[apalrd]

There are a lot of variables to consider when designing a plenum. IMHO, the first things you should focus on are:

-Geometry of the port, runner, bell mouth, and runner length
-Total volume of the plenum
-Maximum taper rate of the tubes, especially near the restrictor
-Location and placement of anything on the plenum, fuel injector location, and MAP sensor location

These will have a far greater effect on the engine performance than the angle which the intake tube enters the plenum. If your plenum is massive, then the engine will not be drawing pulsed air through the intake tube. Air will be flowing at a relatively constant rate through the intake tube into the plenum volume, and pulses of air will leave via the runner, but the large air mass in the plenum will dampen the airflow through the intake tube, so the angle shouldn't matter at all.