flyrotary@lancaironline.net Mailing List Archive

I'd like to both agree and disagree....kinda...with Tracy. :-)

I've related it before, and I will again. I had problems with water temps that were caused by the exit air impacting the firewall and swirling around inside the cowling instead of exiting at the bottom. A "duct" comprised of a single 6"x12" strip of sheet metal on one side of the cowl exit solved the problem. I guess it was more a baffle than a duct, but the issue is that the exit air may not be flowing out smoothly.

If you're cooling well enough to fly now, try tying bits of yarn to various places under the cowl where they want interfere with engine operation, stick a camera under there, and go fly a minute. I discovered my issue when the air blowing past the exhaust melted a plastic intake manifold tube, but now I have one of those inspection cameras that attaches to my phone.

On Sunday, September 30, 2018 2:07 PM, "Tracy Crook rwstracy@gmail.com" <flyrotary@lancaironline.net> wrote:

No elaborate Studies on this, just my observations over the years, so take this with a grain of salt.

I think the advantages of a double pass cooler are highly over rated. I’d use which ever worked out best for hose routing. I also think the stock Mazda cooler is underrated. It works much better than its appearance would suggest.

Inlets and Ducts are harder to get right than I ever suspected. Pressure readings in front and after coolers are invaluable for determining when they are working.

Outlet ducts from the cooler exit would be great but I’ve never found them to be practical. They required too much compromise with other things. BUT, I reasoned that the velocity immediately out of the coolers is not that high and is turbulent, so I concentrated on the cowl outlet where the velocity IS high. Aim to make it as much like a rocket engine nozzle as possible. I found that shaping the exit into a diffuser improved cooling a bit even though adding the pieces that shaped it reduced the throat area of the 'nozzle'. Avoid sharp turns, corners and edges. Cleaning up the exit duct alone got me almost 5 deg F. improvement in cooling on the RV-8.

Tracy Crook

On Sep 30, 2018, at 01:55, Todd Bartrim bartrim@gmail.com <flyrotary@lancaironline.net> wrote:

Hey Rotorheads;
This summer I bought the Fluidyne DB30618 but it is only a single pass. I recently inquired about them with Summit Racing and they say they will provide a 2-pass as a custom order. The stock oil cooler is a 2-pass but much more restrictive. The single pass added a longer hose with a 180 swept fitting to make it work.
I'm seeing higher temps than I'd like to despite my improved duct work. Actually inlet duct was improved, but outlet duct is new as I didn't have one before and I do wonder if the outlet duct is restrictive but I'm limited with space and old nose gear mount being in the way (as much as I'd like to remove the nose wheel mount it is integral to the engine mount, so I'm stuck with it), so I wonder if it would be better to remove the exit duct completely and just leave the oil cooler exit air un-ducted?
But to the main question for tonight, I'm thinking about converting my cooler to a 2-pass. I have been experiencing higher oil temps than expected at around 110C and considering the OAT has dropped considerably, I would like to reduce these somewhat. I suspect that the flow is not going through the entire cooler evenly with a majority of flow channeling through only a few of the tubes as it is not really any different than the temps it used to see with the Mazda cooler. The larger size and more efficient design should produce better cooling if oil was flowing evenly through all tubes and spending a longer time in the cooler.
So I'm thinking it should be simple enough to convert to a 2-pass cooler which should ensure a better distribution of flow through all the tubes. But is it really so simple?? See pic at
https://photos.app.goo.gl/TrU99jXjftz4X8h37
It would seem a simple matter to zip-cut a slot where the red line is, slide in a baffle plate and weld it up, re-sealing the end tank, drill a hole and weld in the new AN10 fitting and at the other end, zip off the old AN12 fitting and weld it up. This would also simplify plumbing, as the oil in line would be shorter and go straight in with no 180 bend.
But the thing is I can only weld on 3 sides of the baffle plate that I would install. I can ensure that it is tightly seated against the tube end plate between the tube but it wouldn't be a sealed junction. Do it right and an insignificant amount of oil may bypass there and not go through the tubes. Do it wrong and it could be a significant amount with a drastic reduction in cooling.
Obviously I've already removed the cooler and brought it home with the intent to do this mod, but now I'm second guessing myself. I've considered that if Summit Racing is modifying these as a custom order then they likely are doing just what I plan to do. Otherwise it would have to be done during manufacture by Fluidyne.
It seems simple, but I lost sleep last night considering all the various issues. Still didn't do it today, so I figured I'd pose the question to the group and go hunting with my kid tomorrow while I wait for the opinions to arrive.

On another topic, during a take-off roll the other day, the diaphragm in my old stock wastegate actuator blew. I didn't catch it with the throttle until I hit 16.5 psi of boost. No damage but I gotta say that's a fun way to get off the ground in a hurry! I usually limit myself to 6 psi of boost as that was the spring pressure. I do have an electronic controller (TurboSmart) which allows me to have higher pressures above the spring pressure, but that is intended for high altitude and mountain flying.
I've ordered a new adjustable piston type of actuator that comes with a selection of 6 springs. I intend to use the 3 psi spring as I usually use the boost very conservatively and the TurboSmart controller can give me more if I need it for short mountain strips.
Anyways, I look forward to your opinions on the oil cooler.

Todd Bartrim ....... 20.6 hours on new RV9 version 2.0..... I had to cash in beer cans for gas money....
C-FSTB
RV9 13Bturbo