Intake design part 1: Pressure resonance in the plenum with forced induction???
#17
Three Wheelin'
I'll chime in, for once I actually know something about a topic. Believe it or not, I work on this stuff all day. Engine induction systems product development engineer.
The shape/angle of the wall opposite the runner opening are not whats critical for these pressure waves. The critical dimension for runner tuning is length, and this length is simply from the intake valve to the opening at the plenum. The opposite wall on the plenum has no real effects here, although its certainly still important, mainly its contribution to consistent flow through each runner on an asymmetric manifold.
I could try to explain the whole wave phenomenon it a little more detail, but howstuffworks probably does it better...
http://auto.howstuffworks.com/question517.htm
However, on a turbo car, our efforts are better spent elsewhere. Decreasing restriction/increasing flow and dropping charged air temps is the thing to work on.
The shape/angle of the wall opposite the runner opening are not whats critical for these pressure waves. The critical dimension for runner tuning is length, and this length is simply from the intake valve to the opening at the plenum. The opposite wall on the plenum has no real effects here, although its certainly still important, mainly its contribution to consistent flow through each runner on an asymmetric manifold.
I could try to explain the whole wave phenomenon it a little more detail, but howstuffworks probably does it better...
http://auto.howstuffworks.com/question517.htm
However, on a turbo car, our efforts are better spent elsewhere. Decreasing restriction/increasing flow and dropping charged air temps is the thing to work on.
#20
Race Director
Thread Starter
I am trying to "tune" the runner lengths, not just make the as long as possible. It will either be 9 inches or 11 inches, hopefully 11 as that means 4 reflective waves. If I can fit 10 inches, I will be making it 9 for example. Unless I change the tune target!
#21
Three Wheelin'
The engineer in me wants to say you should at least try to run some tests on a flowbench if you're going to start buildin your own manifold. If things conspire against you, you could see 5-10% differences between runners, most likely makeing some run too rich, while others run too lean. (Unless you've got four WBO2s and stand-alone EMS with individual cylinder control).
Here's some links to get you started...
http://www.speakeasy.org/~synchris/e...flowbench.html
http://tractorsport.com/flowbenchparts.htm
I'm lucky, I've got a few flowbenches at work that I can use whenever. I just don't have the desire to uild my own manifold just yet. Maybe once I start running out of things to tweak on my new car.
Here's some links to get you started...
http://www.speakeasy.org/~synchris/e...flowbench.html
http://tractorsport.com/flowbenchparts.htm
I'm lucky, I've got a few flowbenches at work that I can use whenever. I just don't have the desire to uild my own manifold just yet. Maybe once I start running out of things to tweak on my new car.
#22
Is there space for 11 inch runners. A friend of mine did
some calculation sometime back & it seems that the ideal
would be 15-16 inches measured from the valve seat but
where to find the space.
some calculation sometime back & it seems that the ideal
would be 15-16 inches measured from the valve seat but
where to find the space.
#23
Race Director
Thread Starter
Funny you should say, it will be flow tested by runner, unlike some, and it will be used in conjunction with individual WBO2 and EGT
Are you sure there is 11 inches space there including the required distance from the velocity stack to the pelnum face? I am thinking AOS would be in the way...
Dan, velocity stacks in a turbo application or not?
Are you sure there is 11 inches space there including the required distance from the velocity stack to the pelnum face? I am thinking AOS would be in the way...
Dan, velocity stacks in a turbo application or not?
#25
Race Director
Thread Starter
Yeah I got it, I meant 11, You need 11 plus twice the diameter of the runner (2 inches for me), in distance from the end of the stack to the plenum...
#28
Three Wheelin'
Originally Posted by NZ951
Dan, velocity stacks in a turbo application or not?
This is a pretty good discussion about it, except his design for the "180 deg." bellmouth is flawed, the bell radius should be about half the tube radius, his looks to be closer to 1/4 or so. If he bumped that bell radius up to around 1/2 tube radius, the CFD results should show it flows the best.
http://www.gt40s.com/ubbthreads/show...p?Number=29735
#29
Race Director
Thread Starter
Originally Posted by fortysixandtwo
Why would getting 11" of runner be difficult? The factory ones are about 15".
#30
Race Director
Thread Starter
Originally Posted by DanG
DEFINITELY. If you're going through the efforts of building your own manifold, this part is a no brainer. It should also help you with packaging, since your runner lengths extend into the plenum a bit.
This is a pretty good discussion about it, except his design for the "180 deg." bellmouth is flawed, the bell radius should be about half the tube radius, his looks to be closer to 1/4 or so. If he bumped that bell radius up to around 1/2 tube radius, the CFD results should show it flows the best.
http://www.gt40s.com/ubbthreads/show...p?Number=29735
This is a pretty good discussion about it, except his design for the "180 deg." bellmouth is flawed, the bell radius should be about half the tube radius, his looks to be closer to 1/4 or so. If he bumped that bell radius up to around 1/2 tube radius, the CFD results should show it flows the best.
http://www.gt40s.com/ubbthreads/show...p?Number=29735