Al Gietzen wrote:

> 
> From what little data I was able to find for the water pump on the
> 20B, it will pump about 35 gpm at engine RPM of 6000.  Marginal, at
> best, for that climbout on a 90 degree day.  At altitude, at cruise;
> the EWP may be able to handle it.
> 
Mike Robert wrote:

Gentlemen: as a data point I have in front of me the factory service
manual for the 1985 RX-7. The Technical Data section lists the water
pump capacity as 150-160 liters per minute/39.6-42.3 U.S. gpm/33.0-35.2
Imp. gpm at 6500 rpm of engine. They list a 1:1.18 eshaft/pump pulley
ratio. Given that these numbers are for both the NA 12A and 13B models
I'd definitely check to see if maybe that 20B might require a tad more
flow especially running at 6K rpm at a relatively high power setting.

 It wouldn't surprise me at all that Mazda used the same pump on the 13B and the 20B; and that the one data point that I have may be for the 13B.  It is reasonably consistent with the data you give.  The V-belt pulleys (o.d.) on my 20B are 4.5 eshaft and 3.75 pump (belt efffective diameters about 3.75/3) or a ratio of 1.25.  These may not be stock - were installed by David Atkins.  This may give a bit more flow than the 13B spec.  Not sure what pump is on my engine, but the 13Brew may have slightly higher flow as well.  I hope to eventually measure the flow I get.

 

Al