John Slade wrote:

Paul,
I noticed in an earlier message that you have the same rad as me (Howe
Racing), and you're modifying it to make it perform better. Could you
provide detailed instructions or, better still, do the same mod for me?
Also, my water pump is about an inch too high. What did you do to Bulent's
water pump to shorten it?
Regards,
John Slade, Cozy MKIV #757, progress: http://kgarden.com/cozy
West Palm Beach, FL

My rad modifications are highly experimental as there is no sure way
of sealing the two newly divided chambers after the header tank is welded on.
If mine does not work I will cut the header off completely and re-weld
the whole thing. 

Besides that there is some difference of opinion 
and conflicting reports from the field on the advisability of
running a double pass rad. Power Sport claims it is the root cause
of their cooling trouble but they have made many other changes besides
switching from a double pass to a single pass. Until I see a detailed step
by step report of modifications with data along the way I am a bit skeptical.
Perry Mick runs a very small double pass rad but he is not generating
as much power.

Also Power Sport and Dave Atkins are using the exhaust and the engine 
to heat the air before it goes through the rad. Power Sport is also running the
exhaust pipe behind the rad radiating heat to the back side of the radiator.
I have yet to see their new airplane in a really hot climate like Florida or
Arizona. 

The rad that you and I have, when converted to a double pass, would have little
additional restriction to flow over a stock Mazda single pass radiator.
Some say flow restriction helps as it increases the pressure in the block 
reducing the tendency to have local steam pockets. Other say more
flow is called for. Power Sport and Jeff Spitzer among them.
With the stock pump you can not have it both ways unless you 
increase the overall pressure in the system such as Perry Mick
and Tracy to name just two that are using a 24 psi pressure caps.
Perhaps others are also using high pressure caps. Continental uses
50 psi caps on their water cooled aircraft engines. Ken Welter
on the other hand does not like a 24 psi pressure cap as he feels
it makes the system more likely to leak. Ken uses the stock
16 psi pressure cap.

Tracy Crook has been flying for years with a highly restricted flow
situation as he has only two 5/8 ID heater hoses running from the block
to the water radiators. 

This illustrates the problem with consensus and conflicting opinions 
as it leadsto grid lock :-) Ray Richardson of Power Sport told me one
experiment is worth 1000 opinions based on theory or some such statement.
I say one uncontrolled experiment without detailed record keeping 
is worthless :-) 

Nobody has installed a thermocouple down near the combustion chamber
to really find out what is really going on except Continental,
Mazda and NASA in their experiments with the Mazda engine as
an aircraft engine.

More on the water pump modifications shortly.

Paul Lamar
 
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