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Smooth / Improve #1 Baffle Ramp (Vans Cowl)?

blaplante

Well Known Member
Looking at the airflow path *into* the stock cowl, it looks like the flow is much easier on the left (#2 & #4) side, as the #2 cylinder is stepped back, vs. the #1 side. On the #1 side the baffle ramp promptly hits the #1 cylinder and deflector plate, and the clearance is quite tight between the #1 cylinder and the cowl.

Has anyone played with making a modified ramp so that the air doesn't come in and then hit the wall of the #1 cylinder deflector nearly head-on? Seems like that would improve flow.

Here's a link to a pic of the area I'm talking about (although you don't realize how restrictive it is without the top cowl) https://images.app.goo.gl/gbGJEw43qbKMvh3h6

Maybe a cone shape in front of the #1 deflector?
 
Often builders find that they need to remove one or both of the dams in front of #1 and #2 to improve cooling on those cylinders ... I needed to remove the #1 dam to improve cooling on that cylinder.

I wouldn't try to fuss too much with perceived airflow issues until you get the plane flying and engine on the way to break-in. There are lots of factors that affect cooling performance and you'll need to tweak quite a bit to make things work for your engine. Good baffle seals and gap plugging will be your friend. Getting a good seal on between the ramps on the top cowl and the baffle seal is also a typical challenge.

VAF has lots of great threads on engine cooling; I've read them all and have lots of good insight on practical aspects of dialing things in.
 
Been Flying the 6A for 4 years...

Yes, It is flying and broken in.

I'm looking at ways to optimize the cooling flow (living in SoCal where it seems to get hotter every year - today it is currently 106 F). Cooling flow can help CHT (not normally a problem, but a climb in 106 after refueling - hence already hot engine, can be). Also I'd expect that smoother cooling air flow could reduce cooling drag.

Dan, that's a cool link you posted. I never knew that! And as a result, mine is built un-trimmed.
 
Dremel

Took both off. Left enough to pull rivet back on if needed. No need, one has to try real hard to get #1and #2 past 400 on climb out. Always thought it was too much.
 
Can't see in the picture but the ramps have a fairly sharp bend at the top to the vertical and go down to the baffle proper, resting against the cylinder fins. I played with this a bit before getting to a height that balances the temps front / rear. Left side only, on the other side I just have a low (3/4") dam that's the traditional angle piece, but with a cutout for the bypass modification.
 

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