Projects

Exhaust07

Exhaust

The problem isn’t the exhaust itself, matter of fact it has been (one of the few things) trouble free. The issue I have is the huge amount of space it takes in the cowling, primarily the crossover pipes below the intake. These 2 pipes, cylinders 1 and 3, have to cross over to the collector on the pilots side of the airplane. This ruins any chance for a good looking cowling and a less than ideal aerodynamic shape. Now don’t forget, this is an angle valve engine in a cowl designed for a parallel valve engine that is more narrow and not as tall. So this big header just makes it worse. Old system pics:

Old 4 into 1 SystemOld 4 into 1 System

I know I know, from a horsepower standpoint, 4 into 1 is the best. So that makes this decision that much harder. The next best system for power is 4 individual pipes. That also works well for my space restrictions. Each side with have two pipes exiting, so I decided to make what I call “ramps” or “exhaust tunnels” down the bottom of the cowl. This makes room for the pipes and makes the curve as gentle as possible. More on the cowling in a different update.

PVC System DesignPVC System Design

I called around looking for an off the shelf system, and couldn’t find one. Imagine that. Having a custom system made also had a wide variety in cost and build process. In the end, I went with Sonic Headers. I got their “PVC Kit” and got to work. For a deposit, they send flanges that bold to your exhaust ports that are sized for 1 1/2″ Schedule 40 PVC pipe. A quick stop to Home Depot netted a bag full of elbows and some pipe.

I lost count of how many times I just took it off and started over.  You think your headed in the right direction, only to expose a new issue.  Don’t screw or glue anything till your done with all 4 pipes.  Once I had them where I thought it was all going to work, I screwed each section together and shipped them to the welder.

It took a bit longer than I had wanted, but what I got back was great!  I had them ceramic coated as well, so not only do they look great they should perform better as well.
Completed Exhaust SystemCompleted Exhaust SystemCompleted Exhaust SystemCompleted Exhaust System

Exhaust Hanger Exhaust Hanger TemplateHangers, damn hangers.  There are a lot of opinions about hangers.  I am of the opinion that a moving engine, and a fixed hanger (firewall) is a bad mix.  In theory, if your hanger was on the engine, and moved with it, you would be in good shape.  So once I had the exhaust, I used wood dowel rod to simulate 4130 steel tube.  I trimmed them to shape and then matched the wood with steel.  Carefully I tack welded the brackets in place, on the engine.  Then removed them for final welding and paint.

UPDATE

Reno taught me a lot about exhaust brackets, as I broke mine all to hell.  The general consensus from those that know what they’re doing (the Steadfast Unlimited Team) is that I was on the right track, but made them too stiff.  What I didn’t account for was the system growing in length.  Also that I am not a welder, and shouldn’t pretend to be one.  A later version will have a long curve, and welded by a professional.

Everyone on the ground says they sound pretty awesome, so that is a bonus!