Subject: Gas mileage
From: ACRE NL
Date: 12/4/2002, 7:23 AM


Anybody  remember what the 3rd gen RX7 EPA mileage rating
was? Mazda is claiming the RX8 will come in at 18-19
city and 23-24 highway according to the Jan Motor Trend article.

Is this the 40% they claim?

Paul Lamar

Marc Wiese wrote:

That is almost exactly what my 94 twin turbo gets!! The city is a bit
higher than mine. (driven conservatory-little boost).

Marc Wiese

As Jeff Spitzer pointed out several years ago and Mazda mentioned
in their tech papers a turbo charger can improve the compression
ratio in effect. Jeff called it the overall pressure ratio.
The Wankel configuration is not amiable to high compression
by mechanical means because the combustion chamber is in the 
rotor. The shallower the combustion chamber the higher the compression 
but the worse the combustion chamber shape diverging further from the 
ideal spherical shape. Therefor the turbo charger can boost the 
overall compression ratio leading to lower fuel burn per HP 
generated.

I don't know if Jon Lauter noticed this effect in his
supercharged rotary boat engines. 

It will be interesting to see what a turbo charged RX8 engine
does as far as fuel consumption is concerned.

Paul Lamar
 
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