I know the theory is sound but does anyone have any real data to show that plenums really make you go faster or cool better on an RV?
Practically every customer of mine that has a plenum struggles with higher CHTs than my stock cowl.
If using a Van’s cowl you will have some cowl glass work to do.
I know the theory is sound but does anyone have any real data to show that plenums really make you go faster or cool better on an RV?
Practically every customer of mine that has a plenum struggles with higher CHTs than my stock cowl.
I know the theory is sound but does anyone have any real data to show that plenums really make you go faster or cool better on an RV?
Practically every customer of mine that has a plenum struggles with higher CHTs than my stock cowl.
A plenum lid is just one aspect of making all inlet air go through cooling fins. A builder can construct the most exquisite, air tight plenum lid known to man, then throw it all away with a poor seal to the case, leaky inter cylinder baffles or countless other leak paths. Details matter, and a plenum lid is just an easy way to solve the big air leak potential at the top of the engine. RV's have far more inlet area than they need, so "poor cooling" is almost certainly a result of poor building, poor attention to detail, or poor engine tuning (like too much timing).
Consider this: I have a plenum on my Rocket and I'm cooling very well with 38 total inches of area (less total inlet area than on my RV-8). This engine made 330+ HP on the dyno, I have backed that up by soundly beating the "fast" Rocket in our group in head to head sustained climb tests, and I live in an environment that is the equivalent of the surface of the sun.
Nothing fancy here - just a simple flat wrap of 0.016 aluminum with piano hinges around the edge for a lid. It's the details that make the difference: fanatical attention to eliminating every leak path, substantially retarded timing at high MP, bypass ducts on #2 and #5 cylinders, and attention to smooth cowl outflow.
Nothing fancy here - just a simple flat wrap of 0.016 aluminum with piano hinges around the edge for a lid. It's the details that make the difference: fanatical attention to eliminating every leak path, substantially retarded timing at high MP, bypass ducts on #2 and #5 cylinders, and attention to smooth cowl outflow.
Michael, how are you sealing the dip-stick tube? It looks like it is entirely under the plenum lid, but I don't believe you have to pull the top cowl and the plenum to check the oil.
-Marc
A plenum lid is just one aspect of making all inlet air go through cooling fins. A builder can construct the most exquisite, air tight plenum lid known to man, then throw it all away with a poor seal to the case, leaky inter cylinder baffles or countless other leak paths. Details matter, and a plenum lid is just an easy way to solve the big air leak potential at the top of the engine. RV's have far more inlet area than they need, so "poor cooling" is almost certainly a result of poor building, poor attention to detail, or poor engine tuning (like too much timing).
Consider this: I have a plenum on my Rocket and I'm cooling very well with 38 total inches of area (less total inlet area than on my RV-8). This engine made 330+ HP on the dyno, I have backed that up by soundly beating the "fast" Rocket in our group in head to head sustained climb tests, and I live in an environment that is the equivalent of the surface of the sun.
Nothing fancy here - just a simple flat wrap of 0.016 aluminum with piano hinges around the edge for a lid. It's the details that make the difference: fanatical attention to eliminating every leak path, substantially retarded timing at high MP, bypass ducts on #2 and #5 cylinders, and attention to smooth cowl outflow.
Consider this: I have a plenum on my Rocket and I'm cooling very well with 38 total inches of area (less total inlet area than on my RV-8).
5" diameter (well, ok, 4.9") isn't real small. Not that it really matters. The inlets can be large, or small, or very small, depending on design approach, i.e. internal or external diffusion. Mass flow is controlled the exit area, not the inlet. The inlet is responsible for delivering the mass without wasting any of the available total pressure.
Love the Boomerang inlets! Get some before and after upper plenum pressure measurements if you decide to switch to fixed rings and condoms.
The Cat is the last remaining evidence of a lifetime of Pontiac ownership. GTO's, Trans Am's, Formula 400's... I've owned dozens. Can't let this one go. There's a pumped 455 and a Muncie 4 speed waiting to go in. No time... Airplanes now