Hangar Flying

Hangar Flying => Hangar Flying => Topic started by: Lowlevldevl on April 05, 2007, 04:14:29 PM

Title: Downdraught Cooling with Exhaust Augmentation
Post by: Lowlevldevl on April 05, 2007, 04:14:29 PM
Hey everyone,
I've decided after reading a number of articles (Bill James's EZ Chronicles in particular. Inspiring!) that I'd like to convert my 0-320 Long to downdraught cooling with exhaust augmentation. Unfortunately my construction talents are nothing like Bills' so I'm looking for a conversion that is way simpler than that. I'm thinking pressurized top cowl (like Drews) with simple alloy tubes surrounding shortened exhaust stacks for augmentation. I'm sure some others on here must have either done it, thought about it more than me or tried and failed :cry: I would love to here from any of them.
Happy Easter!
Title: Downdraught Cooling with Exhaust Augmentation
Post by: Drew on April 05, 2007, 07:35:33 PM
I was plenty cool without the exhaust aug.  But I also had separate air going to the oil cooler and the carb---completely cut off from cooling the engine.

My baffling was similar to a berkut (except for the downdraft part)---see the berkut13.com for details.  I also spent a lot of time looking under a lot of cowls in production aircraft as well as other experimentals.  I spent a lot of time seeing how everybody sealed off engines----attach points, etc.  Also looked at aircraft with lopresti inlets to see how everything sealed up.

The other thing that made things easy was that I used the standard intercylinder baffles that covered the huge gap between the cylinders---then made the remaining intercylinder baffles.

Also, there are good articles that tell you how much entrance and exit area you want for the intercylinder baffles.

And don't forget to get all the hoses and other crap out of the way----you want the air to actually make it through the cylinders---not get blocked by all of your "stuff".
Title: Engine cooling
Post by: GlennBob on April 05, 2007, 10:32:51 PM

Where can we find the articles you mentioned on engine cooling ?

Title: Downdraught Cooling with Exhaust Augmentation
Post by: Drew on April 06, 2007, 07:43:43 PM
I'm in the process of moving---so don't have access to my binders to confirm the articles.  However here is a list worth looking at (all Central States articles):
issue         page         subject      title
58   20   engine   downdraft cooling
63   14   engine   downdraft cooling
63   23   engine   downdraft cooling
63   32   engine   super augmented eze cooling
65   20   engine   design for optimum cooling efficiency
67   7   engine   naca diffuser
74   17   engine   Downdraft Cooling Experience
76   10   engine   Engine Cooling Design
76   12   engine   Engine Cooling

My guess is that it is issue 65.  The one that I am thinking of talks about how much to close off the top and bottom intercylinder baffles.  If I remember right it was based off of a CSA member researching some NASA (or maybe NACA) files talking about cooling air-cooled engines.
Title: Cooling
Post by: GlennBob on April 07, 2007, 02:01:07 PM

Thanks for the info.  I'll be tackling that issue soon.

Title: Downdraught Cooling with Exhaust Augmentation
Post by: Bill James on April 07, 2007, 05:50:36 PM
Howdy Guys-
Don, I will be following your DD progress with interest.
Since stumbling onto a successful oil cooling combo last summer, am finally out of the test stuff and back into a comfortable routine of sunset rides and occasional weekend lunch flights, with a couple of efficient family business runs thrown in.

With all the oil cooling work, it is hard to admit that it is now almost identical to what I previously finally did on the 0-235. A considerable amount of effort and epoxy was spent trying not to stick that scoop back out the lower cowl, but common sense finally demanded giving up and just getting it cooling and enjoying flying again.
Unfortunately, cruising back from RR against a 35 kt headwind allowed enough time for a new cooler location idea to creep in. It is independent of other systems. If it works, you all will be the first to know. But right now the current setup is good I am still enjoying the more relaxed just-flying mode.

Terry Schubert's excellent CSA article on oil cooling this month explains everything we need to know. I guess it's just a matter of what drag price we are willing to pay.

As you move to DD cooling, I can mention a significant element that probably wonít be an issue for you, but caused big differences with my new engine installation - the aft cowl shape.
With the 0-290, the new top cowl was closed down too much and air circles back into the aft cowl opening. This is at odds with the oil cooler air flow, among other things. I chose to make small changes and watch the progress. A small mustang inlet was installed. Air came out of it backwards, forward - out of a forward facing inlet! That is how bad that air wanted to come in the aft opening. With the engine not broken in yet, oil vapor from the case vent tube provided obvious evidence of the aft air flow coming back in.  Again, one of my prouder days. The large helo i flew had similar surprising airflow. You could immediately tell if anyone in the aft cabin puked.
The easy cure of course, would have been to have snuck out at midnight at RR and secretly made a mold of Hertzlerís top aft cowl shape. This cowl shape redo was on the to-do list I got from him at RR this year. I felt good because Bill Allen evidently got as many demerits as I did. Back at home I did slit and raise the aft top cowl edge two inches. This helped, with the fog of oil vapor not coming into the aft opening as far. I expect it will take several steps in the right direction before 'arriving'.
Rob Martinson mentioned benefiting from trimming the aft cowl edge and increasing the space to the prop, which I will be playing with. Since your plane was already flying, the cowl shape and prop distance is obviously already perfect and it won't be an issue for you  :D

I have posted EZ Chronicles 40 and 41 at an upcoming site http://www.ezchronicles.com/blogger.html  including a note on one of the recent hamburger runs. These should also be up here on ez.org soon. Congrats to Avery and Crew for getting the site protected and going again. Thanks.

Don I wish you success with your DD conversion. Even though we all start with basically the same cylinders to cool, everyone ends up a little different. Or a lot different. Hope yours is the best!
Bill James, Fort Worth VariEze
Title: Downdraught Cooling with Exhaust Augmentation
Post by: Lowlevldevl on April 07, 2007, 09:10:46 PM
Hey Bill,
Thanks for the reply. I find your chronicles particularly interesting and I'm getting some great information off this and other forums as well. As a matter of interest, since my last post I changed the position of both my armpit scoops rearward about 4 inches each side because my new engine monitor was telling me that cylinders #1 and 2 needed more airflow. #1 in particular!
The result is that #1 being further aft is running cooler and in line with #3 (they're on the same side of course so, perfect!) #2 is running much cooler than #4 so obviously I need to move the scoop forward again on that side so that its in the same position relative to cylinders 2 & 4 as the scoop on the opposite side is to 1 & 3. It won't look symmetrical from the outside but it should work better. I'll let you know!
Your article on the longer intake tube from your carb got me thinking. My internet research tends to suggest that I'm not going to be able to run LOP smoothly until I do something similar, or go injected$$$$. Anybody else have any suggestions for repositioning an MA-4 on an 0-320 to achieve better fuel air mixing?
I haven't subscribed to the CSA newsletter yet. Guess I should get onto that! Is it possible to get back issues from them?
Cheers again,