Composite intake manifold 951
01-09-2008 | 09:19 PM
#16
Banned
Joined: Apr 2002
Posts: 8,599
Likes: 1
From: limbo....
What are the drawbacks to a large plenum volume? The plenum doesn't seem that big. Besides, without knowing more about the internal construction, all we can do is speculate. Looks like about 3 liters. Corky Bell says a good rule of thumb plenum volume = 1/2 engine displacement ...in which case that thing is huge! I have heard other theories relating ideal plenum volume to runner volume. What factors did you take into consideration on your own engine and have you experimented with anything else?
BUT, then he went and used a 52mm TB flange.
So, basicly, its a totaly useless piece of ****.
My plenum is very big for a 7,000 RPM engine, but Tim gave me a 8-8500 RPM plenum because I asked him to - as that is where the engine will soon be.
My plenum is much smaller than this one.
The carbon work is very pretty, however.
My opinion, of course.
01-09-2008 | 10:31 PM
#18
Three Wheelin'
Joined: Nov 2001
Posts: 1,594
Likes: 1
From: Costa Mesa, CA
With due respect to the almighty tool, plenum volume is not nearly as big of a factor in power level and tuned RPM as its being made out to be. Runner length, diameter, and entrance shape have a much bigger influence on those characteristics.
I'm not saying you can disregard plenum volume, or the above plenum is "good", but it would be foolish to disqualify it based simply on saying it "looks too big". CFD is a big nasty can of worms, and it doesn't boil down to black and white rules very often. Even with your data-based experience of smaller plenum = more power at a lower RPM, that doesn't mean the same would hold true for this manifold. Change the plenum shape, thickness, entrance angle,... any of those parameters even just a bit, and you have to start your testing from scratch.
I'm not saying you can disregard plenum volume, or the above plenum is "good", but it would be foolish to disqualify it based simply on saying it "looks too big". CFD is a big nasty can of worms, and it doesn't boil down to black and white rules very often. Even with your data-based experience of smaller plenum = more power at a lower RPM, that doesn't mean the same would hold true for this manifold. Change the plenum shape, thickness, entrance angle,... any of those parameters even just a bit, and you have to start your testing from scratch.
