VVRC 40cc Twin

[witchfingers]

The heads on mine basically are out in the open.

 

[Lojik]

I haven't tested mine for heat but i have some decent holes in the bottom/back of the cowl and the shape of the front directs the airflow directly onto the cylinders, might get an checker to be sure though next flight.

 

[witchfingers]

I am running the stihl ultra in mine as per vv recommendations. I doubt the oil is causing a problem.

 

[Flyingjon]

Mine is baffled-on an EF78 Extra 300. It really didn't run consistently and was a booger to jet until I did baffle it. Cylinders also run evenly after baffling. Just directed flow from the inlets of the cowl over the fins. Have a deflector in front of the opening on the bottom of the cowl.

Do you have pics? I'd like to get a better idea on how you did it.

 

[Lojik]

I am running the stihl ultra in mine as per vv recommendations. I doubt the oil is causing a problem.

I'm no expert but id say the angle of attack of your cowl is actually deflecting air away from that cylinder head and not into it, the holes you have might not be helping as much as intended, being so close to the prop hub it may not be getting much air if any at all through there as the closer the hub you are the flatter and more solid the prop is effectively making a barrier where air cannot pass and is forced along the prop to its tip, that combined with the angle of the cowl towards the cylinder head might be creating a "vacuum" of sorts inside the cowl effectively blocking air penetration

are there other holes to allow air to exit the cowl, further back than the cylinder head?

 

[Alky6]

Do you have pics? I'd like to get a better idea on how you did it.

I will take some photos and post them here. You want baffles and exits? I did a bunch of different trials on exits using telemetry to find the most effective setup.

 

[Alky6]

I am running the stihl ultra in mine as per vv recommendations. I doubt the oil is causing a problem.

What does your air exit look like? I also found that the scale carb hole below the output shaft made a huge difference in cooling. Blocking that off made about a 20 degree difference. Not that all cases would perfom that way, but it allowed too much air not doing any cooling to use up the exit hole area in my particluar case (no change in jetting). FWIW.

 

[Alky6]

I damaged the cowl - long story - so I used it as an opportunity to play before finalizing on a new one. Duct tape was used to open holes and close them. The pipe tunnel was open originally and had louvers there. Tried moving the aluminum dam all over but found it works best in this first pic. Also, the side wings of tape on the dam made a huge difference in its effectiveness. My final is this current first pic setup along with louvers over the opening in the tunnel just in front of the LG. It is also on a cannister now versus stock muffs.

 

[Ohio AV8TOR]

Remember you need 2-1/2 to 3 times the area of exit air as inlet air.

 

[bigblueswope]

Thanks for the pics Alky.