912UL runs hot?

[turboturner]

hi all;
since I've had it my 912UL (in a KF Classic IV) EGT runs at 1600 deg F in cruise. In a full pwr climb at 60mph it drops to 1540 deg. On T/O it's near the top limit (1652). Can't get it below these values (unless I throttle back for descent/landing). OAT has no effect. Oil level is fine & all other eng parameters are fine too (oil temp, coolant temp...). I don't have a CHT gauge.
Any ideas on how to bring this down? Thnx for your input.
PS: I ask here vs Rotax forum wondering if this is peculiar to KF cowl design.

[Dave S]

Turboturner,

Not sure if this will help any; however, the first thing I would check is the location of the EGT probe. A person will get radically different temp readings if the probe is close to the exhaust port vs much further downstream in the pipe...the exhaust gasses cool as they flow down the pipe. There should be a design location on the exhaust stack for the probe......I am not sure what that is for the UL

Second thing I would check is trying to figure out if the EGT system is calibrated......Not real sure how to do that at these temps.

Consider the EGT reading may not necessarily be telling you the truth.

Not real sure that a EGT tells a person much on a 4 stroke unless there is a manual mixture control & constant speed prop.

I'd certainly consider opting for a CHT probe/gauge as that is much more significant than an EGT regarding the temp stability of the engine on a 4 stroke without a manual mixture control or CS prop...although if your coolant temp is fine that is telling you things can't be far off.

Sincerely,

Dave S
KF7 Trigear
912ULS Warp Drive

[turboturner]

Thnx for that thorough & reasoned reply Dave. I'll check the probe's location & may well opt for a CHT.
Carl

[avidflyer]

Don't have any experience with a 912, but put around 400 hrs on a Jabiru with EGT gauge for all 4 cylinders. Prop load and fuel mixture effect the EGT temp. Richer mixture and/or increased prop load lower the EGT temp. Can you hit RPM redline fairly easy? (lightly loaded prop) and/or do the spark plugs look like you are running very lean? That's what I would look at first if you are sure the EGT probe is in the right place and reading correctly. Jim Chuk

[kmach]

Hi,

I agree with Dave, the distance of the egt probe from the exhaust port is real important . there is a spec for it, I believe its something around 110 mm , this is going off my memory so please look it up !

I also think the CHT is more important and is required , its a should have item!

The coolant temp on my ULS is usually within 15* F of the cht readings , but this would depend on where the coolant probe is located .

What cowling do you have ? smooth cowl or round cowl ? picture might help.

[turboturner]

Jim, mixture is rich (dark spark plugs). No problem hitting max RPM.
kmach: round cowl.
Am starting to wonder if the carb needles are set for the wrong alt.
TY both for that info.

[Av8r3400]

The plugs should not be black or dark. They should be a nice light tan color. If your plugs are black, I would suggest that you are running too rich.

What altitude are you at? The OEM position of the needles is usually pretty universal in position #3 (second from the bottom).

[BigJohn]

Sounds like you are running to lean, ck EGT probe locations and if they are correct check size of main jets, A easy check is check EGT's on hard full throttle climb then keep in climb and reduce RPM approx 300 and see if EGT Temps increase, If not you most likely have to small main Jets. You could have a CHT probe a swell as Water, They should be close usually within 10-15 degrees.

[avidflyer]

If you look at the plugs after it's been idled for a while, (especially if it's rich at idle) you wont see what the plugs look like at full or 3/4 power as they will be showing the idle condition. So you might look rich, and still be lean at high power settings. I always tied the plane off, ran it for a while at the rpm I was concerned about, and shut it down as quickly as possible, then pull the plugs and look at them. Jim Chuk

[JimS]

When you say "no problem hitting max rpm" do you mean it is easy to blow right past it or it is attainable in level flight? If you have no problem running up past it in level flight than adding a bit of pitch would bring those EGTs down. On the other hand maybe you really like the takeoff performance of a prop that is a bit under-pitched? (which would give you elevated EGTs).