Chris, as always, the internal combustion
engine is a complex mix of processes. However, my engine can idle all day
without temperature concerns – however, it only takes a minute or so at
WOT and the temps are near their max. However, no problem when flying –
so I wouldn’t be too concerned about temps under those engine run temps
at this point. Yes, you can put larger radiators/oil coolers and get more air
flow and keep the temps lower on the ground, but then you are carrying all that
“surplus” cooling around when you don’t really need it (my
personal opinion of course).
There are two things that come to mind
concerning your rpm drop (You do need to provide more data than rpm, manifold
pressure, fuel pressure (where is it measured?), air/fuel ratio indication
(does it go lean when the rpm drop off or not?), etc.
1st It COULD be a restriction
in your fuel system – running up to 6000 rpm the first time – there
is “surplus” fuel that permits you to get there – but a
restriction could then preclude you from maintaining that rpm for more than a
short time because a fuel restriction inhibits fuel flow. But, if this is the
case then you should see your air/fuel ratio indicator start to show a lean
mixture.
2nd A second possibility is
that as the engine heats up you could be loosing compression and that results
in a loss of some power and the rpm drop back down – however, the fact
that you can then run the engine back up to (almost) 6000 rpm tends to indicate
this is probably not your problem.
I would suspect a fuel flow restriction
myself – you can “zoom” up to 6000 rpm but then the
restricted fuel flow causes engine to drop back to an rpm sustainable by the
restricted flow.
That’s my $0.02 based on the
information you have provide thus far.
Ed
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Chris Barber
Sent: Saturday, October 24, 2009
3:23 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] RPM drop
I hooked up my front oil cooler, the aviation one that was causing a
restriction in the system and leakage past the oil filter seal,
in parallel today with the standard Mazda stock radiator. I cranked
her up and the oil flowed and heated all parts of the system and after only
one snugging of a fixture, no leaks. Temps still were about the
same. I took the engine to full power. It does not like full power
on the ramp. The temps raise really quickly and even after 60 seconds, I
am at limits I am uncomfortable with. I can have it sit at idle
for over an hour with no problem. I have fans mounted, but they do not
seem to help much at high RPM's. The weather was quite cool for Houston at about 70
degrees today.
On a related note. As I have mentioned I am getting just over
6000 rpm at full throttle when I enrich the mixture. HOWEVER, once at
full throttle the rpm is dropping off a few hundred rpm....maybe down to 5400
rpm. If I throttle back and go back to WOT it can get to just about
6000 again....maybe not quite 6000. I can't play with it too long like
this as the temps raise so quickly.
Is this something obvious that I can check? Thoughts????
__________ Information from ESET NOD32 Antivirus, version of virus signature
database 3267 (20080714) __________
The message was checked by ESET NOD32 Antivirus.
http://www.eset.com