|
|
I fly and maintain two TU206 Cessnas. Both planes have EGT probes at
each cylinder and one TIT (turbine inlet temp) probe just before the
turbo. The reason we want to know TIT is that our turbos have a max
TIT of 1650F. I would guess the Mazda turbo would be around that same
max TIT temp. We climb at 1450F and cruise at 1550F and we sometimes
make it to engine TBO with the same turbo and sometimes not. Our
problem is the hot section cast iron housing tends to crack beyond
limits so we end up changing it out. You would want TIT to make sure
you don't overtemp your turbo. On the 206 we can lean much more than
what the turbo can handle so we use TIT to know that we don't overtemp
the turbo. We have 6 EGT and 1 TIT probes pre turbo and in about 5,000
hours of operation we have had no damage to the turbines nor a broken
probe. They fail on us because the wires get brittle and when you move
them around during an inspection the wires break but not the probes
themselves. My advice would be to use good quality probes, and stay
away from Westach kind of probes that do tend to break off. Our engine
monitors are the Insight brand. Two bad they don't make one for 2
rotors! Maybe it's good though because we wouldn't want to pay their
prices.
The for our planes the TIT is always higher than any one EGT (even
though our EGT probes are a lot closer to the cylinder). This, I was
told, is because an EGT probe gets a blast of hot air 1/4 of the time
(1 cycle out of 4 cycles). There is a time of cooling between hot
blasts of exhaust for an EGT probe. The turbo sees a constant steady
blast from all the cylinders hence the TIT temps are always higher.
That might be the reason on a 2 rotor is hotter downstream too as the
output of 2 rotors combine to make a more solid flow with no cooling
between blasts. You would think this would be less though with a
rotary because the blasts are a lot closer together and not just 1/4 of
the time.
My $.02 and you get what you pay for.
Jeff
cardmarc@charter.net wrote:
Only problem is that if a tip piece of the probe breaks off, it will go thru the turbine and make a mess. Just a thought. Many people only put one probe after the turbine because of this possibility. I do not have any firsthand experience with this happening but have heard of it.
Marc W
From: Bulent Aliev <atlasyts@bellsouth.net>
Date: 2005/01/10 Mon AM 01:51:58 GMT
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: [FlyRotary] EGT probes
Hi Guys,
I removed my turbo manifold today for ceramic coating, so I want to install
two EGT probes, one for each rotor. I want to drill and tap into the cast
iron manifold about 1" away from the exhaust ports. My questions are:
1. Any draw backs?
2. Recommendations for probes that will stand up to the heat in this
location and will work with the EM2.
My engine starts instantly every time. At the beginning I kept the mixture
knob to the center position. Any movement to the left and the engine would
stumble. Now I'm noticing the knob is fully to the left and it is rich. Not
too rich but more than before? I guess it is time to get into the
programming stuff?
I'm drawing big crowds at the airport with this engine. Today I had to put a
yellow rope on the hangar doors so I can work. Handed chairs to the old
timers, the youngins had standing room only :)
Buly
Homepage: http://www.flyrotary.com/
Archive: http://lancaironline.net/lists/flyrotary/List.html
Homepage: http://www.flyrotary.com/
Archive: http://lancaironline.net/lists/flyrotary/List.html
.
|
|