Hi Ed, yes I have doubted the usefulness of a restrictor plate for a long time which is why for the past 2 years with the rotary I had no thermostat nor restrictor.

Anyway, I gave it a try and was prepared for a very short circuit, surprisingly there was no need to reduce power and get back on the ground in a hurry. At this point I can’t guarantee it helps but I’m pretty sure it does no harm in my system … my method of measurement is to check the coolant temperature gauge after a WOT climb to circuit height and compare that to the result last noted on a day with same temperature +/- 1 degree C … the only other variant would be the mixture setting.  I would have to insert/extract the restrictor on the same day with a stable OAT and leave the mixture setting alone to get a more accurate comparison.

 

My next experiment is to switch from 50:50 glycol/water to pure de-ionized water with a touch of water wetter or equivalent … literature supports this giving significant improvement … I’m curious to see for myself.

Jeff

 

From: "Ed Anderson" <eanderson@carolina.rr.com> Subject: Re: [FlyRotary] Coolant Restrictor Plate Date: Thu, 28 Jul 2011 10:50:09 -0400 To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>

More details, Jeff?   From my reading on cooling systems, the only time I have read of an improvement in cooling using a restrictor plate is in the case where the water pump is cavitaing.  The restrictor plate improving cooling in that case because it produces more back pressure around the impeller and eliminates/reduces the air bubble caused by cavitations. This permits the impeller to pump coolant rather than trying to pump air.   Otherwise, the old myth about restrictors/slow water cooling better is just that - a myth.   Now it may well be that a hose size larger than 0.75" dia is unnecessary for some installations and going above size that does not really increase flow rate or cooling, so not saying what you found to be in error, but just didn't want folks to think that restriction = better cooling.   The basic equation for heat removal ('Q') clearly shows that more mass flow ('M') equals more heat removal.  Q = M*Dt/Cp - M being the mass flow  of the coolant.   Here is a link to one of the better non-technical discussion of all aspects of cooling   http://www.stewartcomponents.com/Tech_Tips.htm   read Tech Tip #3 - Thermostats & Restrictors for a discussion about the restriction myth   FWIW   Ed

 

 

 

 

I saw Lynn’s coolant diagram with a restrictor plate in it  …  you guys with evaporator cores and 1” coolant hoses have a 1” restriction, this based on Mazda’s design of 1.5” inlet/outlet on the stock water pump and the stock design includes a thermostat.  With all of that as a background (never had a thermostat), I decided to try a restrictor plate  in my coolant system, using a 0.75” hole in a plate at the water pump outlet into my 1.5” radiator hoses.  I can say that it doesn’t do any harm and may have actually provided about 5% improvement … more testing to follow.

 

Jeff Whaley