Running Too HOT

[Mark C.]

Greg, I will have to "search" for the fix to lower the #3 cylinder with high CHT as you pointed out. That sounds very interesting. I will be flying on Friday 6/2 with cut down air-dams, wheel pants are now on and just to test I metal taped the openings on the top cowl inlets so all incoming air is directed over the cylinders..
Mark C.

[YellowJacket RV9]

http://www.vansairforce.com/communit...ylinder+washer

The washer(s) haven't completely done the trick for me - next I plan to build in some type of channel as described in the above thread. I can now keep #3 a few degrees below 400 in 75% cruise, but the others are around 360, so I know I can do better.

Chris

[BillL]

Originally Posted by Mark C.

Greg, I will have to "search" for the fix to lower the #3 cylinder with high CHT as you pointed out. That sounds very interesting. I will be flying on Friday 6/2 with cut down air-dams, wheel pants are now on and just to test I metal taped the openings on the top cowl inlets so all incoming air is directed over the cylinders..
Mark C.

Mark, send me a PM via email and I will send you the template for this mod. It is pretty easy to make.

[Mark C.]

Bill, send to mjcoplon@te.com

Thanks, Mark C.

[BillL]

Sent to your email.

[Mark C.]

Thanks, Bill.. so far I have cut down the air-dams and added 2 louvers to the bottom of the cowling. Presently even in take-off climb I'm staying below 400F probably not bad with an OAT of 85f. Next time I pull the top cowl I will look at adding a mod as depicted without pulling the baffle.. Thanks again, Mark C. 119RV

[YellowJacket RV9]

Originally Posted by Mark C.

Thanks, Bill.. so far I have cut down the air-dams and added 2 louvers to the bottom of the cowling. Presently even in take-off climb I'm staying below 400F probably not bad with an OAT of 85f. Next time I pull the top cowl I will look at adding a mod as depicted without pulling the baffle.. Thanks again, Mark C. 119RV

I added my channel without pulling the baffle also. It's not as pretty as Bill's but does the trick. Was able to carefully cut out a section with the dremel and fabricated a cover channel that is secured on top with blind rivets and on the bottom and sides with RTV. Has worked fine so far and I can pretty it up next time the baffles are off.

I see you are injected so this won't apply to you, but...

That being said, the more I fly the more I am learning that the throttle setting has the most effect on the mixture and thus temperature of the cylinders. At full power the most fuel seems to get to the rear cylinders and they stay cooler. At 75% and 3000' the front cylinders are richer and cooler. This is verified when leaning by EGTs. I am going to work on finding which position of the throttle leads to the best mixture distribution; I have a feeling it is around 85-90% open, so I will need to be pretty high to make that a reasonable cruise power.

Chris

[DanH]

The bypass can be added without dismantling the entire baffle.

My IO-390:



Old Grumman:



Principle the same for all...bypass the pinch spot.

[Marc Bourget]

Looking at the image, am I correct in assuming the airflow around the cylinder is "witnessed" by the light blue lines? If so, it appears by the bypass that the baffles never come in contact with the fins? Does this hold true for the heads, as well, in the typical RV installation?

Pls help me get up to speed on this point!

Thanks,

mjb

[Mike S]

Originally Posted by Marc Bourget

it appears by the bypass that the baffles never come in contact with the fins?

There are virtually no fins in the area where the bypass duct goes. This is the entire problem, and why the duct is needed.

If there were adequate fins, then the fins/baffling would create the passage that the duct does. As things are, the baffling hits a fin less area of the head, and stops the airflow.

See this post from a prior thread. http://www.vansairforce.com/communit...7&postcount=23