Hot running engine

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antonvalks
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Hot running engine

Unread post by antonvalks » Sun Nov 05, 2017 7:21 am

Need some advice please. Since the rebuilt after our hangar door incident, ESS has been running hot. On a flight back from George to Plett (after the 10 hr head torque), I recorded the following:
EGT: 737, 724, 675, 689, 705, 748
CHT: 168, 182, 162, 181, 169, 179
(Please note: much higher temperatures were recorded by my partner but I do not have them available)

I mentioned it to the factory and Len's opinion was it is not excessive. However, keep in mind this was after I had to nurse her and fly with carb heat out for almost the duration of the flight. Had I not done that, who knows how hot she would have run? Temperatures came down when carb heat was applied. This could be an indication that she is running too lean, or not? But, the carburettor was not changed or adjusted after the rebuilt. Why now, when I never had issues before?

What further puzzles me is the fact that there is no common pattern when compaing cht and egt for each cylinder, eg. No 1 and 5 is hot on egt but ok on cht. No. 4 is ok on egt but hot on cht. No. 2 and 6 is hot both sides. No. 3 is ok on both sides. Is this even possible or an indication of faulty instruments? Is there no relation between cht and egt on each cylinder? I would expect to find a hot egt for every hot cht.

I found the following article interesting: http://www.jabiru430.com/EngineCoolingimages.html Anyone care to comment?
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Marius Schrenk
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Re: Hot running engine

Unread post by Marius Schrenk » Thu Nov 09, 2017 5:20 pm

antonvalks wrote:Need some advice please. Since the rebuilt after our hangar door incident, ESS has been running hot. On a flight back from George to Plett (after the 10 hr head torque), I recorded the following:
EGT: 737, 724, 675, 689, 705, 748
CHT: 168, 182, 162, 181, 169, 179
(Please note: much higher temperatures were recorded by my partner but I do not have them available)

I mentioned it to the factory and Len's opinion was it is not excessive. However, keep in mind this was after I had to nurse her and fly with carb heat out for almost the duration of the flight. Had I not done that, who knows how hot she would have run? Temperatures came down when carb heat was applied. This could be an indication that she is running too lean, or not? But, the carburettor was not changed or adjusted after the rebuilt. Why now, when I never had issues before?

What further puzzles me is the fact that there is no common pattern when compaing cht and egt for each cylinder, eg. No 1 and 5 is hot on egt but ok on cht. No. 4 is ok on egt but hot on cht. No. 2 and 6 is hot both sides. No. 3 is ok on both sides. Is this even possible or an indication of faulty instruments? Is there no relation between cht and egt on each cylinder? I would expect to find a hot egt for every hot cht.

I found the following article interesting: http://www.jabiru430.com/EngineCoolingimages.html Anyone care to comment?
Hi Anton what was done to the engine ?.....is it running in again ? (new rings ?)
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Re: Hot running engine

Unread post by buffet » Tue Nov 14, 2017 8:00 am

Anton give me a call 0833742426.
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Re: Hot running engine

Unread post by antonvalks » Tue Nov 14, 2017 8:41 pm

Marius Schrenk wrote: Hi Anton what was done to the engine ?.....is it running in again ? (new rings ?)
She had a complete rebuilt, new crank, new cam, new rings, new bearings. Not sure about the pistons, but suspect the old ones were used.
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Re: Hot running engine

Unread post by Jay-Jay Jordaan » Tue Nov 21, 2017 8:07 pm

Well good luck with your over heating problem Anton.I had to sell my Jabiru because of the same problem. After 200 hrs nr 4 and 6 cylinders ran up to 180 and will keep on climbing until I fly with carb heat. My flights became engine management instead of enjoying the flight. What baffles me is that I was told to close the opening around the oil cooler witch did not help. I then had to extend the lip under the cowl opening to extract more air. Now all this was ok for the first 220 hrs. I then decided to put her in the market, lost a lot of moola and wished the new owner well to have it sorted out. I hear from him that even today it is still not sorted. My Bat Hawk with the Camit up front is doing well with no problems but then it sits nicely open in the fresh air all the time.
I spoke with a Doctor closeby and he had the same problem on his RV. he told me that according to his AMO the two overheating cylinders "Glazed" witch caused the overheating issue. It was 100% after the overhaul.
Hope you win with your Jabbi. :( :(
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Re: Hot running engine

Unread post by Flooi » Wed Nov 22, 2017 5:45 am

After listening... and learning from many Jab owners, it seems that if installation is not 100% correct
with correct cooling in mind: Once it runs too hot for some time, only a overhaul will correct the
problem. I know of some Jabi's working hard, many running on mogas, BUT running cool from day one...
have reached the 1000hr top overhaul period. Cooling is major recipe for Jab!
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Re: Hot running engine

Unread post by Marius Schrenk » Wed Nov 22, 2017 6:50 am

About 5 years ago Len at the factory had a mod on the cylinder heads that increased the return flow of oil (that build up in the tappet covers)since that was done to my engine.....it's over cooling. :D
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Re: Hot running engine

Unread post by dak » Wed Nov 22, 2017 10:07 pm

Hi Anton
Was wondering how your Jabi was doing, sorry to hear about the grey hair 8-[
Too lean and overheating after a rebuild may indicate a leak in the induction system ?
A Jabi has a lot of joints in it's induction system, plenty opportunity for a leak.
Found a leak on my old Jabi (2200) by pressurizing the induction system and spraying soapy water
on every joint. Not sure if the pressurization trick will work on a 3300 ? (need to find a spot where all
exhaust valves are closed at the same time and pump air into the cylinder with an inlet valve open.
Remove the scat hose from the carb and block with your hand ... pressure will build.

I've seen a number of Jabi's that just overheat for no obvious reason, poor owner spends a fortune chasing down the problem ?
My Jabi engine was rebuild after prop strike but crank was deemed ok and left alone. Runs as cool as a cucumber 8)
Along the coast it ran a lot hotter than it does in JHB.
I looked at a few Jabi's before buying my J430 and just steared clear of the ones with overheating issues because it does not appear
fixable. Buying a brand new one involves some risks.
I was trying to buy a new one , maybe a good thing the salesman was not big on negotiation.
I have a great J430.
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Re: Hot running engine

Unread post by antonvalks » Fri Feb 09, 2018 6:17 am

Just a quick report back. I followed Buffet's telephonic advice who suggested I have the carb needle polished. Took it to the factory as I was a bit scared of doing it myself. All I can say: best advice and best job I have ever seen. Totally cured my heating problem. And the bonus is: she is even more frugal on juice!!! =D> =D> Don't ask me why, as I expected a richer running engine consuming more fuel. The return flight from George to Plett consumed only 9 liters of fuel. \:D/ \:D/ \:D/
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Re: Hot running engine

Unread post by J430 » Fri Feb 09, 2018 9:49 am

That's interesting as it goes against my mixture alteration findings. If you watch my Hacman video you'll see that making the mixture lean, doesn't affect CHT other than a degree or two at the most. I wonder why the difference....
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Re: Hot running engine

Unread post by Marius Schrenk » Sun Feb 11, 2018 9:57 am

If I read between the lines it seems Anton took the plane to George (not just the needle)....I suspect they gave him a "tune" on top of the needle polish. :wink:
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Re: Hot running engine

Unread post by ZuluBen » Sun Feb 11, 2018 10:22 am

Glad you got that sorted!
The explanation is actually very simple.
When your EGT's is not correct, your engine is simply not producing optimum power, leading to the engine having to work too hard, hence the higher CHT's and higher fuel consumption.

If you are running in the 740 range on EGT's, you are actually running "Lean of Peak". Books have been written on that subject, but is is not good for making power, and should only be considered at altitude and at cruising power.

Optimum EGT for a Jab is 680. Yesterday, coming back from Nata, I had to climb to get over some uncomfortable weather, and at FL145 my EGT's were down to 610 ....

I am looking at the Hacman thing, but to get it landed here will costs a bundle .... Anybody going overseas any time soon?
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Re: Hot running engine

Unread post by CJW » Sun Feb 11, 2018 3:43 pm

What is the optimum cht’s and egt’s at different altitudes and during the different phases of flight? We all know what the manuals say, but I think those numbers are purely indicative of what is acceptable and not the optimum, or am I missing something?
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Re: Hot running engine

Unread post by ZuluBen » Mon Feb 12, 2018 10:04 pm

The ideal EGT would be 680 deg C under all conditions and altitudes.

And ideally all the cylinders should have the same or as close as possible readings. Very hard to obtain without fuel injection ...

CHT, the cooler the better. In reality, somewhere between 140 and 150, again an even a spread the better.
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Re: Hot running engine

Unread post by J430 » Tue Feb 13, 2018 12:57 pm

If you can't afford a HacMan, you could make your own. Buying their unit will be quick and easy with zero stuffing around. If you have a little more time to spend by sourcing the parts you could definitely do it yourself.


As for temps - I was advised by the owner of CAMIT before their demise that EGT temps should be 640-680 at above 75% power (just past the step in the needle), and below 75% power (when the egt's go up because of the needle step), temps should be 680-720, or what I do is to ensure my highest EGT is 720. Higher temps are ok if operating at reduced power settings.

680 is probably safe for the engine but would waste a lot of fuel, however it also means that at full power settings the mixture will be very rich which is not great for a number of reasons which include fouling plugs.

CHT maximum for the CAMIT engine is 180 for takeoff only. For Jabiru build engines, you'd need to keep it below 160, as they are not built using the same grade of alloy as the CAMIT engine. My all time hottest temp was 165 on climb-out on a 38 degree day (CAMIT engine).

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