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Permalink Reply by Bob McDonald on June 4, 2012 at 9:17pm

Jabiru 3300 is too much motor (weight & fuel consumption). A Rotax 912 80 hp is lots of motor or a 912S 100 hp is you want to burn 3 litres more / hr than the 8o hp 15 litres / hr consumption. I have and fly a CH601HD with 80 hp Rotax 912... 1200 hrs turn key service.

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Permalink Reply by John Austin on July 27, 2016 at 4:07pm

The installed weight of a Jab 3300 (exhaust system and all engine accessories) is 178 lbs. Yes, it consumes more fuel than a Rotax 912 but you get 2 more cylinders, is super smooth, and has 20 more hp. That 6 cylinder has a great sound, and while I know it is music to some ears,  to be charitable, the Rotax has a "different" sound! ;>)

The older Jabs were difficult to cool and the liquid cooled heads could be resorted to if proper cooling can't be achieved by careful cooling tweaks. However, I've got a later air cooled Jab (#2427) that runs about 260-300F in this summer's heat and humidity and that's in a high drag, low speed STOL 750!  The later model hydraulic lifter engines have a number of improvements that made them much easier to cool.  I would think it would do well in any of the 601/650 series, especially with the higher speeds and less drag - it all helps!

John

N750A

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Permalink Reply by Gene Bowen on July 28, 2016 at 12:20am

I have an older Solid Lifter Jab 3300 in my 601 HDS.  My CHT's run around 330,  and higher

on climb on a 70F day.  I have tried everything to get the CHTs cooler, but with the older style heads,

I think it's near Impossible.  It's nice to know that the newer Jab 3300 cools much better.

I have head bolt movement almost every time I check the Torques.  Makes me cringe.

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Permalink Reply by John Austin on July 28, 2016 at 6:20am

Gene,

Have you tweaked the oil cooling?  Although we have "air cooled" engines, a significant amount of cooling is done by the oil.  The heavily finned oil sump is an effective radiator when ducted tightly with cool air.  Zenith tried this on the 750 STOL by simply cutting an inlet in the lower cowl and ducting air to this area. However, this introduces additional high pressure air into the lower cowl - not good as it upsets the high pressure ram-air duct/low pressure lower cowl differential - one guy said it made his CHT's worse!

I designed an oil sump cooler duct that works well and does not upset the differential. The details are in this thread New Design Oil Sump Cooler Duct.  Basically, it "borrows" ram air from the left ram air duct (which was my coolest side) and ducts it down to the oil sump.  Therefore, there is no net additional high pressure air being introduced into the lower cowl. I saw immediate lowering of oil temps (about 15 degrees F as I recall) and about a 5 degree F lowering of CHT's.

It is simple and inexpensive to install. I originally made a "periscope" scoop of PVC to put in the ram air duct but later made inlet ramps with just a simple hole in the ramp and it worked just as well.

Other tweaks included "butterfly" baffles between the cylinders on the underside to keep the cooling air in contact with the fins longer and end plates between the cylinders to keep cooling air from spilling out laterally between the heads. See the thread Yet Another Jabiru 3300 Cooling Tweak!  The end plates are a little more complex with your external oil lines (which the later engines don't have), but still do-able. I fabricated mine, but CAMit Aero Engines also sells the butterfly baffles and end plates for the 3300.

John

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Permalink Reply by Gene Bowen on July 28, 2016 at 2:24pm

I installed a new 24 row oil cooler,  My oil temps sit at about 170F on the warmest of days. I plan to narrow the air inlet a bit to maybe slow the incoming

air and lower the pressure on the bottom. I have room to spare in the temp range in hot weather.  I do have butterfly baffles between each cylinder, top 

and bottom.  I have recently tried High Temp Foil Tape on my 5 & 6 Cylinders, following the cylinder down part way around with success on lowering

the head temp on those cylinders,  I Will try 1 and 2 the next time i get the chance..  I was reading were the oil drip holes in the heads can be reamed

to a slightly larger diameter,  allowing more oil.  It's possible this might be a way to carry away some of the heat too.  There is a spec for how much

you can go,  I need to look it up.  It was done on some older engines in some cases of under oiling, might help.   I will look at your sump design.  

At the moment, I am working on the Nose Gear.  I put in the Spring Bungee ( oh so nice !!! ) and am making a new lower bearing block.  Next

is new Main Bungees, and Tires.  Then back to the Engine....  I don't like flying at 330F and reaching 350F on Climb.  

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Permalink Reply by John Austin on July 28, 2016 at 3:01pm

Your oil temps sound great but I agree you might want to experiment with reducing your oil cooler opening to the minimum to keep acceptable oil temps but improve your ram air/lower cowl pressure differential and help the CHT's. You could also boost the pressure differential by extending the cowl lip where the cooling air exhausts underneath the cowl.  Seems you really don't need the oil sump cooler since the oil is plenty cool and you can restrict your cowl opening for the oil cooler.  Ian Bent at CAMit says that pressure differential is the most critical parameter!

I was under the impression that that Jabiru, CAMit, and most of the Jab/CAMit forum members all agree that the upper butterfly baffles shouldn't be used as they create turbulence above the fins and restrict the airflow somewhat whereas the lower butterfly baffles keep the airflow in contact longer with the fins as the airflow exits.  Don't think Jabiru uses them at all, but CAMit (essentially an improved 3300) uses them on the underside of the cylinders.  Maybe you've tried, but I'd remove the upper butterflies and see if that helps!  My #5 initially was my hottest cylinder (it usually is on most Jabs!) and I extended the back of the duct around the backside:

This, combined with the cylinder head end plates, really made a difference!

John

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Permalink Reply by Brendon Lindfield on July 6, 2012 at 5:52pm

Hi rob
I own a hds with a jab 3300 goes great heaps of power I am just in the process of fitting liquid cooling and an inflite adjustable prop

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