Yes I forgot to say except engines with any overlap porting. I'm strictly
talking stock engines, side ported and mildly streetported. That's where all
my experience lies. And yes very extensive testing of all the mufflers out
there. Open exhaust on stock engines deteoriate the torque curve. I've always
been into getting the most out of a stock engine. The guys that are running
the stock 1st gen cars road racing are finding that out. Paul Yaw and I have
talked about it. He is trying to do this with pipe dia. to accomplish this.
Everything is out the window when your talking " P " ported,or turbo and
supercharged engines. John Lauder actually knows the figures for this. He has
done more testing than anybody I know with actual backpressure figures. And
about Mazda, they have learned a couple of things from us. Gee I hope you can
swallow this. When I developed the marine engine we took the '87,'88 turbo
block removed the turbo and fuel injection. Built an intake manifold with a
390 holley and exhaust manifold and made more power than the turbo engine at
factory rated 6500 rpm. Not as much torque of course. 

Not as much torque at what RPM? You CANNOT have less torque at 6500 RPM
and more HP at 6500 RPM. Torque and HP are synonymous at the same RPM.
HP IS torque times RPM times a constant.

This caused many heated debates. 

I can see why!!!

We also changed the oil injection which really sent them into orbit.
In the end Mazda changed their oiling in the future models. I know what your
thinking but this is all stuff that was documented. Skip

Upload your data and documentation here Skip. I am still skeptical. All Mazda engines 
to date have overlap through the combustion chamber recess in the rotor face. 
It is only a matter of degree between the peripheral intake port and the side 
intake port. Only in the new side exhaust port engine is there no overlap. 

There is no doubt in my mind that one can move the torque peak around within the RPM
range at the expense of HP in some other RPM range by adding back pressure but 
that is of no use in an aircraft engines as we are only concerned with HP at a 
narrow range of RPM. These charts well illustrates that point. 
BMEP, volumetric efficiency and torque are synonymous. 

Prop load is at least proportional to the square of RPM so 
HP (hence low RPM torque) is of no use at lower RPM's for aircraft engines.

Moving the torque peak around can be a benefit in road racing if one is limited
to a fixed set of gear ratios in one's transmission which is indeed the case
in amateur road racing. If one had a infinitely variable ratio transmission 
one could operate the engine at peak HP RPM all of the time and one would 
have max available torque all of the time. The fundamental definition of 
HP is a force moving at a given velocity.

One must not only take into consideration the length of a tuned pipe but
it's diameter as well not to mention port timing and port areas. This 
makes the complete characterization of an exhaust and intake system extremely 
time consuming due to the many permutations and combinations.
In fact there are more combinations possible with a rotary than
there are with a piston engine.

Frankly I think this is way beyond the economic capabilities of any
small company Paul Yaw and Racing Beat included. No way is anyone
going to beat Mazda when it comes to rotary engine tuning for a specific
purpose. All you need do is read the many SAE papers and books Mazda has 
published on the subject to come to the same conclusion.

Instrumenting the intake manifold and exhaust manifold for pressure changes
as a function of e-shaft angle would be a step in the right direction as Mazda 
has done but nobody that I know of in the states has done that yet. Certainly 
not any small company tuning Mazda engines.

Paul Lamar
 
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