I think the new intake plenum and runners should be tac welded up by end of week and hopefully we can get it on and be sure it fits right. Then back for final changes, grinding and a polish, and back again for install and dyno. Here are a few pictures of the progress this week. The throttle body is on, the plenum roughed out, and the runners will be done tomorrow.
We have changed the design of the runners -- again -- because it made no sense to make this and still use the lower intake manifold. Mazda did a great job on the LIM in terms of fitting the turbos and emissions stuff for the Cosmo, but this manifold cannot be modified to flow well. So, we are taking the runners all the way down to just above the base of the LIM -- sort of using it as an extended flange -- and welding the runners to that as a base, so everything bolts up well to the block. We may work on the base of the LIM a bit to smooth the flow into the intake ports. Try to match them as closely as possible by porting the LIM base out. When its all done (welded, ground, and polished), I am going to have them ceramic coated an off white.
I have a real feeling that we are going to see some major horsepower jump here, because the LIM is just such a restriction. We will have increased volume by 4 times and really speeded up velocity at high rpm. This appears to be so critical at higher rpm where the combustion dish is going by so fast.
Gordon
You can see that the primary runners are quite a bit smaller (1x1.25") than the secondaries (1.6x1.6"), so the taper is greater for the primaries. It'll be interesting to see the impact on the primaries.
Here is the revised intake plenum:
And the flange for the Rotary-Works 90mm throttle body being mated to the intake plenum:
