Side Exhaust?

GR8 8 · #1 10-20-2012, 11:47 PM

Tried searching for this but not finding anything under "side exhaust". I am considering routing the exhaust out the side of the cowl like a P51. I've seen photos of fake systems, but wondering if anyone has actually done it. I'm trying to balance the weight vs power issues and would like to hear from you if you stepped out of the box.

Thanks!

Bob Axsom · #2 10-21-2012, 01:05 AM

When Mark Frederick first developed the Continental 550 installation on his F1 Evo Rocket he ran the exhaust out the side of the cowl but at Reno this year he had a bottom exhaust. I believe the new installation was a centerline all into one exhaust but I didn't study it closely. He was so much faster than all of the other Sport Class racers in the Bronze heat that they moved him up to the Silver heat where he was the only fixed gear racer. As a distant unscientific observer I think his switch to the bottom was an improvement. His is the only one that I have seen with the exhaust coming out the side and it was shrouded, not coming straight out with a little angle like a P-51.

I have recently completed a fairly long experimental modification of the outlet of the cooling air and exhaust on the bottom of our RV-6A that lead me to believe the exhaust exiting at an angle from the centerline into the air the airplane is passing through reduces speed.

This is just feedback on your request and it is not intended to discourage you creative interest. If you do proceed I request that you provide detail progress and test results here.

Bob Axsom

DanH · #3 10-21-2012, 04:42 AM

What do you hope to accomplish?

Walt · #4 10-21-2012, 07:00 AM

Hey it would look cool

Kyle Boatright · #5 10-21-2012, 07:12 AM

Quote:

Originally Posted by Bob Axsom

I have recently completed a fairly long experimental modification of the outlet of the cooling air and exhaust on the bottom of our RV-6A that lead me to believe the exhaust exiting at an angle from the centerline into the air the airplane is passing through reduces speed.

Bob Axsom

Bob, this is absolutely correct. The issue is that if you point the exhausts parallel to the airstream, you get heat and vibration on the cockpit floor. The turned down tips eliminate this problem at the expense of drag.

bret · #6 10-21-2012, 08:22 AM

Don't forget you lose out on opposing cylinder common exhaust savaging when you have single exhaust pipes. I believe four into two into one is the best best set up. But that's just me

GR8 8 · #7 10-21-2012, 08:48 AM

Thanks guys.
Bob & Kyle, not surprised that speed may be affected.

I am told that up to 10% of thrust on some turboprops comes from exhaust when in the cruise mode. I'll certainly consider the angle that the exhaust exits at in my overall plan.
Dan H, I hope to save weight, get heat out of the cowl faster, simplify and declutter the installation, make the plane easier to work on, save room, and not degrade power or speed...

Also hoping to make it look like the cowl is all aluminum with an aluminum or SS section added between the top and bottom cowl for the stacks to come through. It might make you look twice!
There are other problems to solve though too. Cabin heat has to come from BTUs in the oil... Anyone have any experience with that?

N427EF · #8 10-21-2012, 08:58 AM

I am sure you have already thought of this but you'll need to relocate your NACA vents and make sure your canopy is really tight.
A carbon monoxide detector would probably help to make sure you are not routing your exhaust gases into the cabin.
That arrangement would look cool though, maybe you can add a couple of extra pipes to give the impression of a V8 or something.

GEM930 · #9 10-21-2012, 10:09 AM

Quote:

Originally Posted by GR8 8

Thanks guys.
Bob & Kyle, not surprised that speed may be affected.

I am told that up to 10% of thrust on some turboprops comes from exhaust when in the cruise mode. I'll certainly consider the angle that the exhaust exits at in my overall plan.
Dan H, I hope to save weight, get heat out of the cowl faster, simplify and declutter the installation, make the plane easier to work on, save room, and not degrade power or speed...

Also hoping to make it look like the cowl is all aluminum with an aluminum or SS section added between the top and bottom cowl for the stacks to come through. It might make you look twice!
There are other problems to solve though too. Cabin heat has to come from BTUs in the oil... Anyone have any experience with that?

I get my heat from the oil cooler and it seems to work great for the weather I fly in, but I've been told by several people (Larry Vetterman bring one of them) that in really cool areas the oil cooler route would not work so well. I've flown at -2F at 10,000 over Reno and you could definately tell then the vernatherm (sp?) was opening and closing when I was decending at low power settings. Not uncomfortably cold, but noticeable.

F1Boss · #10 10-21-2012, 10:26 AM

There is a LOT of heat in the exh stream. If you manage to keep most of the laminar flow along the side of the fuse, you will be slowly cooked. Don't take my word for it - ask any P51 driver. I would recommend staying with a more traditional system, and its under-the-fuse outlets - sorry to say.
That being said, I told folks that I was paying for all that noise, and I wanted to hear it. The side exh worked in that respect, but OH! the heat..which, BTW, eliminated the requirement for any cabin heat. No problems with CO, as I always had the cockpit vents full open.

Now, consider all that cabin heat, in the summer, in Texas. Ugh.

Carry on!
Mark