RV-9A / Jabiru 8 cyl combo - cooling.

Has any member had real practical experience with achieving satisfactory cooling of the Jab 8 cylinder engine in all flight regimes?
I'm looking for advice on how to balance out uneven CHT's. and how to avoid high CHT's at higher power settings. My middle cylinder heads run noticeably hotter than the front or rear heads. The hotter cyls easily exceed 150 deg centigrade in a 100 kt climb at 2600 rpm. I have not let the CHT's approach the max specified 175 deg C. Ram air pressure in each duct is within Jab spec.
What benefits have owners achieved from fitting the newer fine finned heads?
Has any redesign of the ramair ducts proved effective?
What practical experience exists re ROTEC's liquid cooled heads on the 8 cyl engine?
If owners believe that experience with cooling the 4 & 6 cyl models can be read over to the 8 cyl version I'd be interested in some constructive comments!

Hi Bob,

I used to correspond with a gentleman who lived in Australia and who had built an RV9a with the 8 cyl Jabiru. His first name was Ivan and he is a friend of an Oregon builder named Jake Thiessan (sp?). Look up Jake in the member list and see if he can get you in touch with Ivan. He built the plane several years ago and should have some practical experience on this combo.

Hope this helps.

Cheers,

db

I have a friend with a 6 cyl. Jab in a Zodiak 601XL who has a problem with high cyl head temps. The High CHT seem to follow the high EGTs on one bank of cyls. He's been told by some of the Jab experts to twist the carb (It's just held in place by hose clamps) to balance the EGTs. If when he gets the EGTs balanced out and they are still too hot he may have to change the fuel metering.

How's your EGTs?

It is a problem

But this seems to be a solution....

http://www.rotecaerosport.com/product-info/lch/

Installing liquid cooled heads seems to defeat the purpose of installing a jabiru power plant in the first place...

I noticed there is someone selling a FWF package for a jabiru 5100 / RV9A in Freo in the latest Aviation Trader. $15,000AUD. Seems cheap enough for a 180HP kit, but IMO worried enough about the cooling aspects of it to not enquire if it is still available.

Did you try more exit air area?

Jabiru 8 cyl cooling

Thanks for all the comments - yes I have increased exit area via a louvred opening in the cowling floor. Also i built a lip around the exit opening to assist with air extraction. Next step is to improve sealing of ram air ducts and to add some baffling under the gaps between the heads.
Before I spend big $ on LCH by Rotec I need to have tried all possible air cooled options.
Bob H

Cool way of cooling

Paul Lipps is currently building an RV-9 and has written some articles on moving air from the spinner thru the engine and if you contact CONTACT magazine and ask for the Paul Lipps Issue I believe you may use some of his info to help your cooling issues, Background he has designed propellers that are radical compared to the standard look but in function he has some reno speed records 259mph in a highly modified bipe. also look at the cooling photos on his lancair

Give us a call!

We build J230s and Arion Lightning S-LSAs in the states, and have been building Jabiru powered experimental aircraft for close to 15 years. We do our air baffles a little bit differently than the Jabiru manuals call for, and find it's really simple & easy to fine tune each CHT on our 3300-powered airplanes.

If you haven't talked to Pete Krotje already, give us a call or send me a PM and I'll forward your information to him. I'm sure he'd be happy to talk with you. We do have some RV and other builders over here who've used the 5100, so hopefully Pete can help you out.

Katie Bosman
Jabiru USA Sport Aircraft, LLC
931-680-2800
www.usjabiru.com