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Paul R

Over heating on 2200 Gen 4 Jabiru 170

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We had a new Jabiru Gen 4 2200 engine fitted to out J170 C along with CHT and EGT new AGL gauges, I have just completed the run in period on the aircraft , we have now gone to standard W100 Plus Aero shell oil. The aircraft flys well but consistently shows high temps on 1 and 3 cylinders. In climb both reach over well 200 degrees Celsius. Also in cruise 1 and 3 are at 202 C and 192 C respectively. Cylinders 2 and 4 hover around 165/173 respectively. Ram air ducts and fitted correctly and I am now running on Avgas 100. I am seeking information from any other Jabiru Gen 4 2200 engines owners who may be experiencing similar issues. Ambient temp for all these flights has been 10 to 12 deg.

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We had a new Jabiru Gen 4 2200 engine fitted to out J170 C along with CHT and EGT new AGL gauges, I have just completed the run in period on the aircraft , we have now gone to standard W100 Plus Aero shell oil. The aircraft flys well but consistently shows high temps on 1 and 3 cylinders. In climb both reach over well 200 degrees Celsius. Also in cruise 1 and 3 are at 202 C and 192 C respectively. Cylinders 2 and 4 hover around 165/173 respectively. Ram air ducts and fitted correctly and I am now running on Avgas 100. I am seeking information from any other Jabiru Gen 4 2200 engines owners who may be experiencing similar issues. Ambient temp for all these flights has been 10 to 12 deg.

 

What is the factory saying?

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I would not be flying it at those temps far too high. On our club jab with older engine I have the alarm set at 155’C it gives pilots early warning to do something about it. Something is quite amiss there. Was it running that hot during breakin?

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155 sounds where we should be. From the get go the EGT were a problem also being too high, they have now settled within tolerance, CHT's are obviously well over same. Our next move is back to Bundy. Is your club aircraft a Gen 4, 2200 and if so has it exhibited similar problems.

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Posted (edited)

Not gen 4 ours only goes over on climb. in cruise we have a spread of 135 to 150. I would not be flying it, it’s definitely not good for the engine. What have jabiru got to say about it? did they fit it?

Edited by Guest

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Are the senders suitable/matched for the installed instruments?

Years ago, a mate's VW oil temp went thru the roof on the first flight. Oil temp sender was a different brand to the guage, totally wrong. He got the correct sender to match the guage, then all good. The clue was that the oil was actually still cool so clearly it was not a cooling problem at all.

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Best to increase climb speed when running in or any time the temps go up a bit. Unless there's a hill in the way. Nev

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Just throwing it out there, but I imagine the prop pitch is set correctly?

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Posted (edited)

The Jabiru 2200 installation manual states the following, as regards CHT's ...

 

1868425401_JABCHT.jpg.13d3242b82d6e324e5a53f0ddd5ecb09.jpg

 

*Cylinder heads P/No 4779002 and 478000N have more cooling fin area, and a different construction.

 

It would pay to utilise an independent temperature testing method, to ensure that what you're seeing on the gauges, is the true figures.

 

Don't forget, either, that the Jabiru 2200 ignition coils are rated at a maximum operating temperature of 100°C. If the heads are running at over 200°C, then the coils are likely to be overheating as well.

Edited by Guest

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If that is a fair dinkum copy of the Jab info, there is something wrong. It reads 2008C, so I assume the 8 is instead of a degree sign. If they are that sloppy can you trust their writing.

What could be the cause of the EGTs falling after break in? EGT is influenced by mixture and the speed of combustion from initiation.

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Posted (edited)

The "8" figure is supposed to be the degree sign. I think it comes about, due to programming conflicts between Apple Pages to MS Word (and vice-versa) document conversions.

The Jab 2200 installation manual that I found, is an MS Word document converted to PDF, the original has probably been an Apple Pages document.

I trust it's an official Jabiru document, it doesn't list authorship, but it has the Jabiru emblem and corporate address located alongside the drawings.

I just noticed it's also dated 2002, so perhaps there have been more modifications, and changes in specifications since that time, particularly where the Gen 4 engine is concerned.

 

http://web.aeromech.usyd.edu.au/AERO1400/Jabiru_Construction/Manuals/SP-UL/Engine%202200/Installation%20Manual%202200_Issue%203_.PDF

Edited by onetrack

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Here's the 2016 Jabiru Maintenance Manual - which I understand is the current document, and which Jabiru states, applies to all models of Jabiru engines.

 

On page 19, the CHT limits are listed as a maximum of 200°C for climb, and 180°C for continuous (cruise) operation.

I don't know why Jabiru have changed their recommendation for maximum CHT from 150°C for earlier engines, for continuous operation, to 180°C now, for all engines.

This seems like Jabiru are using a dartboard for maximum CHT choices. After all, nothing would have changed in earlier engine/head designs that are in use, yet they suddenly get another 30°C leeway in maximum CHT.

 

https://jabiru.net.au/wp-content/uploads/2018/05/JEM0002-7.pdf

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 There were Changes to compression ratio and  ignition timing. as well as the jetting issues with the Carburetter.. Where you measure it has a bearing on it's VALUE also. High temps are an issue if you don't get it right. On plenty of occasions I've had to increase climb speed  especially on high ambient days, but that's pretty basic isn't it? New motors do tend to run hotter for a few hours at least.. Nev

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Older heads are made from material easier to CNC machine and limits are close to a permanent change point

if new Gen 4 heads are cast?.?? Then they are different material and can maybe handle more heat safely

CAE sed better material too and limits were higher

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Dont think so but would expect that to be a hot location

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29 minutes ago, fly_tornado said:

isn't the exhaust valve the weak link?

The exhaust valve is more related to combustion chamber temp, which is different to Exhaust Gas Temp, and relates more to leanness.

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This may be useless and irrelevant info but lycoming for the 0-320 say 500F or 260C max CHT. To achieve  normal service life less than 435F or 220C in cruise. My aircraft  and many others do not have a CHT gauge fitted. I guess the theory is if the engine is operated per the POH the engine won't be over heating.

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I thought the CHT was an issue because as it rises it stops the valve dissipating heat

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 The valve operates at temps way above the cylinder head. cooled in the usual way Through the valve guide and the valve seat. It's heated by the volume and temp of the exhaust gas . Often the valve is permanently damaged by a single  short term event and small cracks would be evident on the stem in this case. It would also stretch a bit when this happens . That is masked with the self adjusting cam followers but is evident in the earlier motors by reduced tappet clearances. Max temps for heads are usually determined by heat treatment limits approx. 235C and above depending on the alloy and the heat treatment process used.. The jabiru has tended to try to run lower temps than other similar  type engines in the field to prevent/ reduce other engine issues over a long period. .  IF the exhaust valve tends to ride due to cam follower pump up that could raise it's temp and cause detonation  and that will hake temps even hotter. An overheated Head may cause the valve seats to drop out partially and sometimes break into pieces.. Even if the motor is running apparently OK it still should be inspected carefully  if it's been overheated. Nev

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I have a 160C with a 120 hr Gen 4. Dynon probes and a TC3 gauge.  W100 +.

When first added the indicated temps were high round 180C and correct at room temp.

The correct probe type J or K type needs to be programmed.   

I do not go over 150 on takeoff and cruise round 120 at 12C OAT.

With the standard ducts I did have hotter front cylinders but added two deflectors about 70x12 mm about 45 deg to the top underside of the duct.  They are near the rear of the front cylinders and about the same relative distance as the rear of the duct is behind the rear cylinders.

The spread is now fairly tight 

Example Max figures after 1.8 hr flight at 24 C.  709 742 693 721 - 140 136 139 137

cruise CHT 123. 

O F

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 You shouldn't have any trouble with any of that. It's a bit colder than optimum for a conventional  aircooled engine. Certainly OK for the Jab. to be on the safe side. Nev

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Great figures OF. For years, I bragged about how  my max cht didn't exceed  150 but after  upgrading the instrumentation, I found the engine ran hotter than I thought and it can go to 160 on climb. At 160, I throttle back and speed up till it goes closer to 150. And my spread is worse than yours, numbers 2 and 4 are about 20 degrees hotter than 1 and 3.

Any ideas for making the port side ( 2 and 4) cooler will be most welcome.  I can't figure out why there is a difference, the ducts look the same, I have closed the gaps equally on each side, and the internal deflectors are the same on each side.

Strange that no 2 is hotter than 3.

If I saw Paul's figures going to 200 degrees, I would freak out for sure. But, as has been correctly pointed out, Lycomings allow higher figures again. I'm confused, but there is a clue in the materials. The gen 4 Jabiru and the Lycoming  use a cast alloy which appears to be similar and much harder than the old Jabiru heads. Even so, 180 would seem to be an achievable maximum.

Part of the rationale of the gen 4 engine was that the cylinders would expand on heating and reduce the tightening effect of an alloy piston in a steel cylinder, so I would have expected it to run cooler not hotter. 

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When the material used conducts heat better the internal and external figures are closer .You are measuring on the outside.  The difference across the banks is probably due to the nose high position on climb to Rel airflow which works better for one side than the other , because if the rotation of the prop blades. A suitable lip on the cowl may help that but not look much. The absolute figure for many heads is about 235 C but that's based on not causing them to lose the heat treatment  benefits  (harder and stronger) done during manufacture. Nev

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