C M Smith wrote:

Paul,
The table looks good. For quick pump work I use one atmosphere as 15

psi and 30 feet of

water; 2 feet per psi. Plenty good enough for small sizes of pump.

The efficiency of the cast impeller in an automotive paddle pump is

abysmal but it is easy

to cast and there is plenty of HP availble.

C M,

  Is there something that could be done to improve the design of the

pump

impeller and possibly the housing to significantly improve this

"abysmal"

factory design? We are far less cost driven than the factory is and

I think

many of us would be willing to invest in an improved design that

yielded a

significant increase in flow and cooling potential. Its been pointed

out by

several people here over the years that the stock pump flow appears

to be

marginal and that the cooling situation could be helped by improving the
flow potential of the pump.

  A couple of years ago Jeff Spitzer proposed to do just that and
supposedly  was prototyping and testing an improved design which he was
then going to make available to us. Unfortunately, nothing ever came

of it.

I havent seen anything posted on here by Jeff in years. Is he even

still on

here Paul?

Mike Wills

Most of the cast impellers in the  Mazda pumps look very good
compared to the sheet metal impellers I have seen in other brands.
Here is a picture of one of the worst Mazda ones. The Cosmo is better.
I think one would be lucky to get a single digit improvements
in the efficiency. After all, centrifugal pumps have probably
been around for at least 200 years.

I think the most important thing is matching the radiator resistance
the the characteristics of the water pump. The block does not
seem to be that big of a retarding force.

Paul Lamar

Hi Paul,

The later model pump has a pressed steel impeller and the diameter is

reduced. the belt ratio is now 1.43 to 1.

Don Dunbar

There's that penny again. A penny saved is $10,000 earned.
Out here in So Cal the third gen's over heated.

Paul Lamar

I have compared the water pump off my 20B to a pump from an '89 n/a 13b and
the 20b impeller is slightly larger, about 1/8".  Seems logical that the
20b pump would have a higher capacity than the 13b pump since you're
cooling 50% more.  If that's the case, it seems like a simple matter for
the 13b folks to change out the stock front housing and pump for a 20b
version.  Does the third gen 13b-REW use the same pump as the 20B?  Or at
least the same size impeller?  Now for my 20B, if I could just locate a 26B
front cover and pump.

Mark

You are not necessarily cooling significantly more in a car. For example
a Corvette engine is about the lightest duty engine around.
400 HP rated and 25 HP to get it down the road at 65 MPH.
The three rotor is called on for lighter duty than the two rotor.
They both use about the same HP going down the road. Only
climbing a hill is the three rotor called on for significantly 
more HP. In the ratio of the gross weights of the cars they are
installed in.

Jim Mederer uses a much bigger pump to cool his high HP
three rotor in continuos high HP output. You three rotor
guys may run into the same phenomenon.
 
Paul Lamar
 
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