Blown Meth Manifold Volume

Any thoughts about the preferred volume of a blown meth intake manifold versus supercharger displacement and engine displacement? Thanks.

 

Distribution is the most important thing. Look at a few & go frome there. In other words I dont know & woud like to see everyones input on this as well. Whatyagot guyz ???

 

Still no proof here, but I'm guessing it doesn't really matter as long as distribution is ok which is hard enough.
Assuming 500ci per revolution for a 14-71 you're pumping over 5 million ci/min at 8000 rpm and 30% over. At that numbers I't hard to believe it will make a difference considering a manifold will be closer to 1500 ci which is just a fraction of 5 million.
On naturally aspirated engines you can achieve gains using pulses from intake runner length and airbox volume, but that's a different story.

Hope this helps and correct me if I'm wrong.

 

Something that is important in manifold confguration is fuel seperation in the air stream.

 

Agreed. For guys with screws, have you tried shoes or deflectors at the outlet side of the screw (inside the manifold) to try to get the supercharger discharge going a little more away from the rear cylinders, and if so how did that work out for you?

Working with a custom built manifold that came from a previous dragster application (nitro). Really tall, which is nice because it gives a lot of distance between the discharge point and the floor, but the volume looks huge versus most manifolds I see out there. Was wondering if too big can be bad, with meth?? There is a lot of opportunity for stuffers inside the manifold.

 

I built one from scratch with this same thing in mind. I'm not done trying things yet, but so far the only thing I can tell different about that engine is that it eats valve guides

 

That's weird. Intake or exhaust? Wonder why?.....

 

examples

We built a hemi manifold that was just a large box above the ports with a radiiused bottom. About 750 ci volume. With about 5 different blowers on that manifold and no port nozzles, plug color was always fairly even. Our last engine had a KB Hemi 10 bolt manifold with lower dams. About 450 ci volume. Fuel distribution was more finicky.

One major consideration: the larger the plenum the higher the blower may go in a backfire. We backfired our first manifold on gas and blew the bottom out of it. In fact it reversed the center high radius and confomed to the contour of the long block.

If the engine is in front, you may want to consider a smaller manifold volume for safety.

bob szabo
author of fuel injection racing secrets
www.racecarbook.com