James Phillips wrote:

I was wondering if anyone knows how much less power to expect from an

engine with

86 n.a. rotors as opposed to one with the later, lighter, higher

compression

rotors.
I have a set of 4 port end-housings that I will run with n.a. rotors like

Tracy's

latest motor built by Bruce T. The thing is that I have a good set of 86

n.a rotors

on hand and would have to purchase a set of later rotors and they aren't

exactly

cheap. I'm wondering if the increase in power would be enough to make it

worth it.

If they are the same compression ratio and you are running the engine at
the
same RPM there will be no power differences. Light weight rotors allow the
engine
to rev higher but if you have a fixed pitch prop you will not be able to
take advantage of this.


Paul,

John.P.Vitamvas wrote:

The 89-91 13B NA rotors are a higher compression ratio than the '86-88
rotors as well as being lighter in weight:

Motor          Year      Compression ratio         Weight (lb)
13B       74-78          9.2                  11.58
13B       84-85          9.4                  11.58
13B NA    86-88          9.4                  10.04
13BT      87-88          8.5                  10.04
13B NA    89-91          9.7                  9.54
13BT      89-91          9.0                  9.54
13B REW   93+            9.0                  9.54

John Vitamvas

Thanks John. I mis-read the message. I have a chart from an SAE paper
by Mazda around showing HP verses compression ratio. I will look it up
when I get the chance.

Paul Lamar
 
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