bcgardner wrote:

Paul,

You wrote: "Mazda felt it was important to have a tuned intake system with
their turbo cars so I guess it works."

I think that's a fair observation but remember, as you have pointed out many
times, most cars spend the vast majority of their lives putting out
substantially less than rated horsepower. My 87 Turbo that I drive can be
off the boost at highway speeds (about 3200 rpm) but I'm a lot less sure
that I could be off the boost and running at 6000 rpm  unless I were going
downhill. I'm also certain that to generate the factory stock rating of 182
HP (86-88) or 200 HP (89-91) fully utilized the 5.5 lbs boost (86-88) or
somewhat higher boost (7 lbs?) on tap in the 89-91.

The fact that the car ran a lot at unboosted rpms at cruise speed could
explain the need to tune the intake, even on turbo cars. But I think that at
6000 rpm, as we plan to run this engine, we almost surely would be
positively pressurizing the intake with turbo to get the horsepower
required.

On the other hand, I certainly don't think it hurts anything to tune the
intake if one has the room, on the off-chance that it still can help.

You didn't comment on my notion that the turbo on the exhaust side
effectively nullifies any exhaust scavenging that one is trying to get with
the 32" exhaust pipe length. True or not?

Barry Gardner
Wheaton, IL

Yes that is true in most cases. However Paul Yaw built a turbo aircraft engine
with a tuned exhaust manifold. It appears to me to be tuned for higher than
6000 RPM with rather short pipes. On the other hand it generates plenty of HP 
at 6000 RPM. 265 as I recall.

Paul Lamar
 
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