----- Original Message -----
Sent: Monday, July 10, 2006 1:28 PM
Subject: [FlyRotary] Temperature
control
The setup:
·
Engine/Model/Year: 13B 6 port NA mixed
·
Source Condition: David Atkins Rebuilt for
Aviation Application
·
Modifications: Ported intakes and cooling for
180HP
·
Intake: Atkins short manifold w/TWM 48mm
Throttle body
·
Exhaust: 321 SS tangential muffler
·
Engine Control: RWS EC2
·
Fuel Control: 4 Mazda 460cc Injectors, pri. in
block & sec in manifold
·
Fuel Pumps: RWS
·
Cooling System: 2 – 9”x13”GM evaporator cores
with 0.75” auto hose, stock water pump with 180F deg.-thermostat, 50/50
glycol\water mix.
·
Oil System: stock 1986 oil cooler
·
Installation: conventional – self built
mount
·
PSRU/Re-Drive: Ross 2.85:1
·
Prop: IVO Magnum 74" 45-105”pitch in-flight
adjustable
·
Power: 180HP?
The issue:
On the ground, cooling stabilizes at 180-190F deg and oil is usually 10
degrees below the cooling with an OAT of 65-70F deg.
When running with higher OAT (75-85F deg) after about 0.5 hours of
moderate taxi runs (up to 4300RPM) the cooling temps reach 212Fdeg with the
oil about 200F deg.
The question:
Can something be done to get lower operating temperatures without
redesigning the system?
Would switching to pure water help and if so by how much?
Would removing the thermostat help and if so by how much?
How much change should I expect if I were to do both?
You guys down south should have a good idea of how best to enhance
cooling.
What are your suggestions?
Thanks,
Jim Maher(Dyke Delta)
Hi James,
Welcome to the club, cooling appears to always be the
first item of business. I can not quantify the differences those
changes you propose would make.
However, a 50/50 coolant mixture has a 40% lower
specific heat than pure water alone. Meaning it will not carry as much
heat away at the same coolant temperature. Would pure water give you 40%
more cooling - I personally doubt it, would it help, I believe it certainly
would.
I fly without a thermostat and my normal (60-70 F OAT)
temps are 160F for coolant and oil at cruise. On a hot day, right after
take off, I may hit 200F on the oil and 220F on the coolant for a short
duration. With a thermostat, your coolant temps are going to
go right up to the thermostat limits shortly after starting your engine -
after all that is what a thermostat does. But, still at moderate rpm of
4300 on a 60-70F day, I would like for the coolant and oil not to exceed
200F.
I fly without a thermostat to remove any flow
restriction as well as permitting my temps to stay below any thermostat limit
if conditions permit. Since I get acceptable temperatures when flying I
am satisfied without a thermostat. In winter, the temps do run a bit
cool, but then I can tape off a bit of the core and get higher
temps.
Ed
That's my 0.02 worth
Ed