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James aircraft Cowl

fieldbaren

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I have a RV6 with a Lycoming O360,A1A with a Sam James Cowl.The cylinders get hot on climb out.I even added Anti Splat Aero electric cowl flaps to no avail.
Anyone that may be familiar with this cowl please let me know what you think.
The number 3 cylinder got up to 427 degrees F on full power climb out even after installing the cowl flaps! OAT 75 F. full throttle 2500 rpm.(Hartzell) IAS 120mph, even the front cylinders get hot!
any ideas will be appreciated.
fieldbaren
 
I assume you are using the matching James plenum. Is so, put the nose down after passing ~1000' following take off and climb at a higher IAS. 120- 125 knots (below 5000' or so) should solve your problem

You got the James Cowl to go faster and have a more efficient aircraft in cruise - right? Remember there is no free lunch. You gained speed and efficiency by reducing engine cooling drag, but still getting the most cooling from the air you are taking in.

If you want a plane to do "Time to Climb" competition, the James Cowl is not for you.

Carl
RV-10 with the James Cowl and enjoyed a very fast and efficient plane. Working with the new owners of James Aircraft to get another cowl for the new RV-10 project.
 
I was able to bring climb temps on hot summer day to 405 degrees or less,
added an air bypass to go around the short fins on the front of #2 cylinder, and the aft of #3 cylinder. Also, on #2, I fabricated a bit of a "wing" to force some air to go under the front of the cylinder for better cooling. Also, my engine being a bit "pumped up". I use a cooler spark plug, and also added cooling louvers to the aft bottom cowl.

Regards,

DAR Gary
 
I have a RV6 with a Lycoming O360,A1A with a Sam James Cowl.The cylinders get hot on climb out.I even added Anti Splat Aero electric cowl flaps to no avail.
Anyone that may be familiar with this cowl please let me know what you think.
The number 3 cylinder got up to 427 degrees F on full power climb out even after installing the cowl flaps! OAT 75 F. full throttle 2500 rpm.(Hartzell) IAS 120mph, even the front cylinders get hot!
any ideas will be appreciated.
fieldbaren

What carb do you have? Maybe you are too lean???
Do you have a fuel flow gauge?
The James cowl flows just as much air as the Vans cowl, maybe more. The plenum just seals the top and slows the vibration transfer. So any heating issues are most likely leaking air or fuel related.
 
The James cowl flows just as much air as the Vans cowl, maybe more.

How do you know? Got some pressure data? I do, and that James cowl wasn't very good.

Not sayin' a fellow can't live with a James cowl, but that sexy look is a lot like high heels and tight skirts...it comes with practical compromise.

So any heating issues are most likely leaking air or fuel related.

Assuming you can actually get a Cp of 0.8 or better with a James cowl, add ignition timing to the list.
 
more on my James Cowl

First of all, I am not the builder. It came with the "James" cowl.It does have the plenum. Now that I have plenty of exit air with the cowl flaps, I am going to look at the air intakes which appear to be small.Not much I can do about that without major alteration of the cowl which I am trying to avoid. The neoprene
that connects the cowl to the plenum has "puckers", wrinkles I suspect could cause a disturbance of the air flow.I'm going to see if I can find another way of making that connection that would make the air intake smooth.
I replaced the carburetor with the recommended,Marvel Schebler 4164. Electro Air ignition for bottom plugs. Slick mag for the top. Timing has been checked.
25 degrees BTDC.
 
Climb at lower VS...

I have the Sam James cowl on the 7A I did not build. I climb at 130TAS to help with cooling...
 
Check the lower baffles to be sure they are tight around the bottom of the cylinders. If air is escaping through the sides instead of flowing through the fins it has a large effect on cooling. If there is a gap, tighten the baffles and seal up with a little RTV. The James cowl & plenum are on plenty of aircraft with no cooling issues.
 
First of all, I am not the builder. It came with the "James" cowl.It does have the plenum. Now that I have plenty of exit air with the cowl flaps, I am going to look at the air intakes which appear to be small.Not much I can do about that without major alteration of the cowl which I am trying to avoid. The neoprene
that connects the cowl to the plenum has "puckers", wrinkles I suspect could cause a disturbance of the air flow.I'm going to see if I can find another way of making that connection that would make the air intake smooth.
I replaced the carburetor with the recommended,Marvel Schebler 4164. Electro Air ignition for bottom plugs. Slick mag for the top. Timing has been checked.
25 degrees BTDC.

The standard ID of the inlet rings for the 0-360 is 4.75.
The neopreme is easy to remake.
 
Marc, the standard James inlet rings do not tolerate inefficiencies and internal loss of air across the engine fins. This is a system - - oil cooler, loss management, and pressure recovery from inlet to plenum volume. Part of the air management are the original recommendations by Sam James for the exit gaps of the baffles under the barrels and heads. They are quite small, requiring low bypass leakage around the fins and good pressure recovery to the plenum volume. The James plenum cover also was made to fit the RV3/4 which had a low height over the baffle mounted oil cooler resulting is high oil temps. A larger oil cooler simply lowered the plenum pressure and reduced engine fin flow further aggravating the poor balance.

I made my own plenum to address the diffuser and plenum issue of the old James plenums. I also applied some DanH style sealing around the engine to ensure ALL air went past the fins. My 180hp engine cools just fine.

We could be more helpful with better knowledge of your specific installation. Electronic timing advance? (looks like you answered that) Pictures of the plenum, oil cooler installation and possibly under the plenum or of the bottom of the cylinders where the air exits the baffles.

Meanwhile, speed increases plenum pressure and cooling air.

Edit 2.0: BTW the "O" cowl has more exit area than a Vans cowl, ~+ 15 in^2, so it is no surprise that the cowl flaps did not help.
 
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Ignition timing

Check ignition timing first. I’ve used 3 Sam James cowlings and ran Perfect. My RV8 ran very cool even with high compression.
 
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