trevoratbay

[Guest trevoratbay]

Hi out there in Jabiru land I have a J200 6cyl with the old heads all going ok at the moment, and have been asking around about cyl head temps almost everyone Ive spoken to said their engine runs cool enough but nobody has given me numbers so I have taken a shot of my temp gauge for everyone to see and maybe comment on, [ATTACH]12693.vB[/ATTACH]the gauge is on No6 cyl the hottest, my oil temp is around 75 - 80 C I think this is because of my positek oil cooler

 

 

 

[cherk]

g'day treveratbay,

 

I'd be pretty satisfied with that IF it is the cottest ? What is the range over all heads? What does it get to on full power climb out ?

 

I recon oil could be bit cool to burn out condesates if I recall 90∙°c being more the optimum ! apologies for just questions , need more info.

 

 

[Derby]

Hi trevoratbay, My J400 runs about the same on no6 head. My oil temp is about 85 to 95 depending on oat on the day all good i think

 

 

[Guest trevoratbay]

Thanks for the answers fellas I feel a bit more comfortable now:clap:

 

 

[JabSP6]

Hi Trevoratbay.

 

The cooler you can get your head temps the better mate. I have fitted an MGL gauge with 6 cht sensors and 6 egt sensors. All reports i have read and experienced myself suggests that no 6 cyl is NOT the hottest cyl. In my SP6 no 3 was about 20-25 degrees hotter and No 4 about 15-20 degrees hotter than no 6. Since fitting the sensors i have spent countless hours modifying the airflow in and out of the engine bay and around the barrels to finally achieve fairly consistant temps across all 6 cyl's. Flying out to work this morning the cht's averaged 120 degress give or take 5 degrees on full power climbout and then cruising at 4500ft my temps reduced to an average of 105 degrees. Before i fitted the MGL gauge my standard cht gauge used to read 140 on climb out and 125 at cruise which i thought was all good until i found that no 3 was 20 - 25 degrees hotter.

 

If you get time i would suggest moving your sensor around to check all cylinders especially no 3 & 4. The biggest killer of these Jab engines is high head temps which causes premature valve guide wear and rocker bush wear, also can cause problems with the valves. Keep a close eye on temps and the lower you can get them the more reliable your motor will become.

 

Wags.

 

 

[Guest trevoratbay]

To Wags Mate you make me jealous I too have spent countless hours trying to achieve extra cooling I purchaced a westach system that has 6 cyl sensors and a rotary switch with 1 temp gauge, No4 used to be my hottest cyl I fitted a small air deflector in the air box and gradually reduced it in size until No4 and No6 are running the same temps, I took the little v shaped pieces from between the barrels and put them underneath I also put some alum plates between the tappet covers to keep a bit more air in contact with the cooling fins, I have done nothing to the cowls, Jabiru fitted the larger jets to the carb and Im using 23 ltr/hr on local flights and run 50/50 avgas and caltex vortex 98, It starts and runs better on this mixture than straight avgas if you have anymore secrets to share Im only too happy to listen, Cheers mate

 

 

[JabSP6]

Trevoratbay.

 

I would be only too happy to chat about all the different things i have done to reduce the cyl head temps. I live in Bundy so would be easy enough to catch up maybe at Hervey Bay. Send me a PM with you phone number and email and we can organise something.

 

Wags.

 

 

[jetjr]

Of the things youve tried......what worked?

 

 

[Guest trevoratbay]

Most noticable change in cyl head temps was changing the carby jets and making it run a bit richer, jets changed by jabiru bundy

 

 

[Modest Pilot]

Extending the lower cowl back past the firewalled helped, blocking off the gap on the oil cooler inlet shroud was good for another 10F lower head temp. You'll then need a 30mm air inlet to a shroud on the front and bottom of the engine sump exhausting at the muffler, this gets the oil temp back to where you what it. Final figures heads 245-250F oil temp 85-95C. The 30mm inlet has a butterfly valve to allow pilot ajustment for cold OAT. Interestingly increasing the needle jet from 285 to 290 (needs new needle also) got the EGT's to below the 700C I was looking for but the head temperatures went up a little. My 3300 has the latest heads and the T/O fuel flow went from 33 to 36 litres an hour so it could be the engine just works better. With old heads this might not happen and the heads will just get cooler! Just as I thought it was time for a break my hanger mate launched his new 8 cyclinder 180hp J258!!! and we are now starting the process over again.