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Date: Sun, 26 Feb 2012 13:51:03 -0600
From: Dave <david.staten@gmail.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Thermostats.
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On 2/26/2012 11:29 AM, Chris Barber wrote:
> I have been searching the archives but to scant successes regarding thermostats use or lack of use for cooling.
>
> I have been having issue with cooling lately. I use to be able to idle on the ramp for over an hour in the middle of a Houston summer with adequate cooling. However, lately temps are rising faster and higher.
>
> Yesterday, while troubleshooting this issue I noted that after about a ten minute taxi that the mounting location of my coolant temp probes was reading about 220 degrees measured with a handheld thermo gage, close to what was being indicated on the panel  However, the top of the radiator was cool to the touch. The handheld thermo gage read 45 degrees.   Ok. Seems to be a flow/thermostat/pump issue. I will be Looking into this ASAP.
>
> This got me to think about thermostat usage. I have one. I know some do not use them.
>
> It is my understanding that if you remove the thermostat you have to close some passage off. What passage is this and why does this need to be done. Also, what is the accepted method.
>
> While researching I also saw discussion on restrictive plates. While I am not considering a restrictive plate, the thread discussed drilling holes in the thermostat itself. Lynn mentioned do it caught my interest.
>
> It seems this is something I use to know but now forget where I saw it. I just finished reviewing my partial scan of Tracy's conversion manual to no avail and my archive search is giving me hundreds of returns.
>
> Thanks,
>
> Chris
>
> Sent from my iPhone 4
> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/List.html
>

The first engine we built had no thermostat, and had "that" port 
plugged. The thermostat is essentially a Y valve... When cold, it is 
closed, and water is diverted through a bypass hole back to the engine. 
When warm it opens, diverting water from the bypass channel and sending 
it through the radiator.  Of course this is a gradual change from one 
position to the other, as a result of thermal expansion.

If you believe your instrumentation is correct now, and was correct 
then, with regards to temperatures and your idle ability, then what has 
changed?

Has the thermostat failed or become plugged? Has airflow over the 
radiator changed? Is this the same radiator you saw the long low temp 
idles with? (I bought that dual pass cross over radiator for a specific 
reason - to put a cooling fan on one small part of the rad, allowing 
forced airflow to cool ALL of the coolant as it passed through one of 
the pass channels - if you replaced the radiator was it a dual-pass as 
well?) Using the dual pass rad with a fan only over 1/4 of the rad 
surface would provide a large surface for ram air cooling at speed while 
still permitting very effective fan-forced cooling on the ground and at 
idle.

Dave Staten