Now for the coolant pressure steep learning curve. After engine start
> the coolant pressure increased slowly to 12 psi on my Grand Rapids Tech
EIS,
> as usual, and remained there through take-off and climb. Level in the
> traffic pattern it decreased slowly to 8 psi and remained there until
> reducing power for landing. After exiting the runway it was again
reading
> zero.
>
> It is slowly dawning on me that these readings may be quite normal.
The
> only difference from one of my cars is that they don't have a coolant
> pressure readout to confuse the issue. Here is my current thinking: As
the
> engine warms up and coolant expands under pressure, pressure is
regulated
by
> the pressure cap, which sends excess coolant to the recovery tank.
During
> cruise, as the engine cools, pressure decreases to a moderate level and
> maintains that level until power is reduced for landing and the engine
cools
> even more. Now the pressure gradually reduces to below ambient, which
shows
> as "zero" on my EIS (doesn't read negative values), and coolant returns
from
> the recovery tank. Sounds simple enough in the calm of post-flight
> analysis, but I sure didn't expect to see a zero indication on that first
> flight! Am I missing anything here?
>
> To answer a couple questions you people posed. My coolant pressure
> sensor taps into the water pump outlet housing between the thermostat
(yes
> it is still installed even with cowl flaps) and radiator cap--just before
> exiting to the radiator. It is measuring the hottest coolant. The
radiator
> cap is the high point in the system, about level with the recovery tank.
>
> Two flights, no coolant loss, no oil leaks. Yes, except for low rpm
> Ross gear lash, the engine is definitely smooth--:) And with this
Garrett
> turbo pulling 30" MP, it really responds with gusto--:)) My pop-off
valve
> is set for 32", so this is essentially a turbo-normalized system.
I have a RayJay turbo that has never been bolted to anything. So I can
identify one when I see it most of the time, but any advice would be suspect.
There are some things that tend to be true for the rotary. Trying to cool it
by going way rich on the mixture gives you great balls of fire out the back
and not much help with the cooling. But since it is too rich, the burn is
slower and whatever you are using for fuel starts looking like high octane
race gas. (very slow flame speed). We are looking for max power between 1575
and 1625. We don't talk out loud about 1800+. At least not around the engine.
The turbo amplifies any errors in timing or mixture. Best power is just rich
of max EGT. Once leaned out, there is little mixture left burning outside
the engine. Obviously ignition timing has a big roll in that. Earlier timing,
more fuel burned inside the engine, closer to ideal EGT. Later timing, more
fuel left burning in the exhaust system and higher EGTs. Timing adjustments
tend to make a change across the RPM range. Mixture adjustments apply to the
rpm range you are adjusting for. We have the probes 3 inches out from the
port face.
The water system seems to be working just like a street car. The
cap relieves during hydraulic lock when the pressure gets to the caps rated
pressure. Once there just below or at that pressure, any kind of pressure
spike will dump some more water. The radiator is the restrictor in the
system. So the highest coolant pressure will be found between the pump output
and the top of the radiator core. In some cases, the pump output pressure may
be higher than the pressure cap relief pressure and this can cause some
additional coolant dumping. When you take away the revs you instantly get
less than the rated cap relief pressure. You can't get it back until the
engine has cooled and recovered coolant is back inside the engine.
The stock RX-2 and RX-3 pressure bottle system can hold pressure for weeks at
a time.
Lynn
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