Hi Frans
My 914 idles smoothly at 1800-2000 and I have it set idle as low as 1500,
which can be helpful in slowing during landing. I try not to idle
continuously below 1800 because it is a little less than smooth and that
roughness is hard on the gearbox. I understand this is normal. When I start
mine up I do not let it run below 2000rpm to keep it smooth and that is a
good minimum taxi speed.
I have not adjusted idle mixture. I am going to a 3 day Rotax maintenance
school next week and hope to learn a lot of this stuff...
My coolant has never gone over about 230 F. I am running Evans, and monitor
CHT as well as coolant temps which are within 10 F of each other.
My oil temp also stays below about 230 F even in a long climb, but I have
not flown in really hot summer conditions yet. Cruise shows around 200 F or
less. Rotax says we should be 250 F max continous I believe.
You may get slightly better cooling on the ground by coarsening your prop to
push more air though the radiators.
I'm no expert. However I am quite sure that your rough idle at 1500 is
normal and not good for your engine. You might check the carb balance again
after all that rough running!
That was cool when it fired right up, eh?
Kevin
914 intercooled, Airmaster prop
----- Original Message -----
From: "Frans Veldman" <frans@paardnatuurlijk.nl>
Sent: Friday, April 24, 2009 1:47 PM
Subject: Europa-List: First engine run; what is normal?
> <frans@paardnatuurlijk.nl>
>
> Hi everyone,
>
> Today I started the engine for the first time. It started right up!
>
> However, not being used to a Rotax 914, it is difficult to tell what
> engine behaviour is normal. There are two things that make me wonder if
> I fall into the normal range:
>
> 1) How rough is normal?
> Ok, I'm spoiled. Have flown most of my hours in a Cessna with diesel
> engine. 4-in-row, 3-blade propeller. These things run as smooth as a car.
> With the Rotax, it is quite different. Vibrations are eminent. Have
> pneumatically balanced the carbs, checked everything, but can't get idle
> reliable and smooth below 1500 rpm. RPM is unstable (varies in a band of
> about 100 RPM above 1500 rpm, more below that), runs relatively smooth
> between 2200 rpm and 3500 rpm, around 4000 rpm vibrations increase,
> didn't go any higher than that. Below 1500 rpm idle is unstable, and
> below 1400 rpm the rpm suddenly drops sharply. Had it for a short while
> running at 800 rpm, but, let's say, 1000 rpm is pretty much impossible
> to get, most of the time it just dies if I try to get below 1400 rpm.
> The vibration is not that bad, it is not as if the machine is going to
> fall apart, but more like you would expect from a motorbike or so, well,
> maybe slightly rougher. I have a two blade prop (Woodcomp SR3000/2W),
> maybe it is normal for a two blade to give some vibrations? Haven't
> balanced it yet, but it is supposed to be balanced from the factory. Is
> this to be expected?
>
> Fuel pressure is 4 psi, RPM drop with both magneto's about 150 rpm
> (although difficult to establish because the rpm varies by itself).
> All 4 EGT's are equal. Checked the plugs, they seem normal as well.
> Front ones appear to receive a slightly richer mixture (see some carbon
> deposites, most likely from starting up with choke), the bottom plugs
> show slight traces of oil on the outer ring. All show a pretty healthy
> tan color on the nose.
>
> Is this RPM instability and roughness normal?
>
> The engine has not been used since delivery around september. Could it
> be that I need to clean the carbs? Another possibility (not yet checked)
> is that I need to change the idle mixture (maybe somewhat enrichen it)?
>
> Oh, I did check the lifters, they appear to be functional, with no air
> trapped inside.
>
> 2) How much heat is normal?
> I knew in advance that the combination Europa-Rotax is somewhat of a
> challenge. Have made some cowling changes with the expectation not to
> experience any heat problems. Alas, this thing heats up quickly. About
> 10 minutes before the coolant (50/50) gets to 130 degrees Celcius.
> Cylinder heads (measured with a ring sensor below the cylinder head
> bolts) about 10 degrees lower (?).
> In fact, I didn't succeed in getting an oil temperature up to the green
> zone (about 90 degrees) without getting into the red zone with the
> coolant. I doubt whether it will be possible to do some serious power
> testing this way.
>
> Is this normal? How long should it be possible to taxi/idle before the
> temps go to high? How should one test higher power settings on the ground?
>
> Get about 750 Celcius on the EGT's at 3500 rpm (fronts a little bit
> lower than the rears). Is that normal?
>
> Have had the prop on fine with all tests.
>
> Any indications of what is normal are appreciated.
>
> Thanks,
> --
> Frans Veldman
>
>
>
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