Can't speak to the leading edge exhaust on a 520, but I installed it at the same time I installed a 550 on my 185 last year. Cutting another exhaust hole in your cowling will be required. Takes a bit of time to get the fit right as its tight. Be sure to install heat shield on the inside section of the cowling where the fit is tight as the pipe joints will slip a bit after the first flight (make it 20-30 min, then land and check the fit). Looks good, sounds good. Dane, the prior owner, claimed up to a 10% increase in hp. Hard to say, but my engine sure seems to breathe easy and engine runs cool even at high power settings. Belly skin is a pita to clean now . . . but I'd do it again.

skywagoncub wrote:Dane, the prior owner, claimed up to a 10% increase in hp.

I don't understand these HP claims. On an O470, you have a 230 hp engine. I get how a poorly designed Cessna exhaust system "robs" the engine of power and a well designed system can restore some/most of that power. But, you still have a 230 hp engine, which the manufacturer has demonstrated/certified under ideal conditions (test cell, etc.). So, are you saying that with the Powerflow system bolted on you now have a 230+ hp engine?

As I mentioned, I installed the exhaust when I installed my 550, so I don't have any empirical data to validate improved performance. If I did, I would be happy to post those numbers. You are welcome to climb aboard with me for a spin and form your own opinion. I only referenced Dane's "claim" and if he hadn't passed last year, I would refer you to him for further explanation. His website had links to topics on performance gains.

I can't speak to a 470, but I know the leading edge exhaust is an option. But as to whether or not it's possible to increase hp above the rated hp on a 550, I can offer TCM spec'd the 300hp io-550 at +5/-0 %. To ensure the minimum is met, any particular engine rolling off the production line is 310 hp vs. 300 hp. I also understand that there are variants of the 550, including turbo charging and normalizing that produce 315 hp. Vitatoe Aviation converts an 550F to a 550F-CF for a claimed 325 hp by adding a top tuned induction manifold. Regards.

skywagoncub wrote:But as to whether or not it's possible to increase hp above the rated hp on a 550, I can offer TCM spec'd the 300hp io-550 at +5/-0 %. To ensure the minimum is met, any particular engine rolling off the production line is 310 hp vs. 300 hp.

Right, that's my point - TCM spec'ed and certified the engine in a test cell under ideal conditions and achieved 300 hp. So, bolting on a Powerflow system is not going to give you more than that. My understanding - and someone please correct me if I am wrong - is that the Cessna system robs the engine of power (5%? 7%?) because it is a lousy design (designed for production cost?) and the PF system is restoring some (maybe most) of that "robbed" power.

I have a Leading Edge Exhaust on order from Power Flow. I believe my number in line waiting for their production to start is 4. The old Leading Edge web site stated 27 horsepower improvement from stock. That’s nearly a 10% increase on a nominal 300 hp motor. I don’t know what exhaust system Continental uses to set their horsepower statements, but it doesn’t matter to me. An extra 27 hp from stock to Leading Edge is what I’m really interested in.

I’m not sure what engine the testing was accomplished on. I have an IO-550. If it was an IO-520 in testing, it doesn’t really matter. The IO-550 will experience a similar, if not identical gain. They pump near identical displacement when factored for RPM. In my younger years I was a stock car racer. I don’t need convincing that a good header pays returns.

My engine was also ported by Lycon, so my results may be skewed better or worse by that. Still don’t care. Going to get an improvement, more even flow through the cylinders which should improve smoothness, and it should even sound nicer!

So, are you going from a 300 hp engine to a 327 hp engine? Or, are you going from a 273 hp engine to a 300 hp engine? Have you seen the dyno sheets? You are spending like $6K+ and I would want something more than exuberant hope, optimism and wishful thinking. But hey, I would never tell another guy how to spend his money. One more thing - "butt dyno" doesn't count.

I tell you - I am on other hobby forums and the motorcycle guys make one small cam change and they have dyno sheets out the yin-yang and car forums where they will argue almost to the death over things like reputed cold air intake hp gains and guys start whipping out cfm measurements and all kinds of stuff.

There is a thread on this on the Skywagon FB page. Like one of the guys posted, I too am happy with my Knisely system. They keep them in stock and for a reasonable price. Regarding flow and sound, I have no doubt the powerflow (nee' LEE) will provide that (so does the Knisely).

Good luck.

If we were down to the small incremental gains, I’d agree that a dyno run to prove each improvement would be necessary. The Leading Edge Header by Powerflow is such low hanging fruit with a large benefit that it’s a no brainer to me. Even if I only gain half the benefit claimed, I’ll be satisfied, and I believe I’ll do better than that. It’s not like I’m choosing from a wide variety of options. It’s either a collection manifold, or a tuned exit for the exhaust. I’m choosing the tuned exit.

The Leading Edge Exhaust was demonstrated to produce significant improvement on a dyno during its development. Good enough for me. It’s just not practical to test my specific engine on a dyno.

Good decision Pinecone. There is 0-320 dyno info on powermaster’s website if one really needs it for justification. Something like 23 hp more than the standard exhaust. There are also links therein regarding tuned exhaust. Beechtalk.com is a great resource for researching reviews on the powermaster exhaust. Dane had info on his website about an IO-550 tested by Lycon. I recall it was a souped up 550, but with his exhaust it dyno’d over 350 hp. He wouldn’t have claimed up to 10% improvement if he couldn’t back it up. Regardless, I haven’t met anyone, including myself, who regrets installing the leading edge exhaust. As I mentioned earlier, the engine breathes easier as a result of less back pressure. That in and of itself will pay dividends towards engine longevity. I took off on floats with a full load last summer at 85 degrees and climbed ROP at 500 to 750 fpm to 8,000 and one cylinder approached 400, the rest were 370’s. No way I could have done that with my 520 with the acorn exhaust, which is also great btw. Sometimes I miss the pre-internet hangar parties where one could query an old timer about a particular mod. Some of those guys had remarkably accurate “butt” dyno’s!

I've been running a Leading Edge on the IO-520F in the 206 for about 10 years. I bought it because I got tired of having the stock exhaust welded every other year and didn't want to worry as much about CO leaks and continued repairs. It was a good deal even then ($2k as part of a group buy), and I've been very happy with it. I'm told that the headers give the engine a unique sound (and that it's not quieter than the stock setup). I have a suite of tools I use for working on some of the lower plugs. Access can be troublesome, but nothing that can't be worked out. I didn't do any before/after flight testing to see if there was a change in performance. I made the change for reliability, and haven't been disappointed.

CAVU

I didn’t anticipate any spark plug access issues. My mechanic will not be pleased. Any photos of the tools you accumulated to ease the inconvenience?

Pinecone wrote:I didn’t anticipate any spark plug access issues. My mechanic will not be pleased. Any photos of the tools you accumulated to ease the inconvenience?

The LEES came with a special spark plug socket, so as long as you hold on to it for him he should stay happy. Is really not that bad, especially on the 185 where you can take the lower cowl off. 206 is a bit more of a PIA, but still not terrible if you keep track of that socket.

Pinecone wrote:I didn’t anticipate any spark plug access issues. My mechanic will not be pleased. Any photos of the tools you accumulated to ease the inconvenience?

I'll try taking some pics and posting next trip to the hangar.

My exhaust came from leading edge with a special short plug socket to use on the lower plugs. This socket lives in the onboard tool kit. There is one cylinder bottom plug that can only be r&r'd with this socket. It comes in handy on others, though. A 6" wobble extension (3/8 drive) does too. I also cut a 7/8" end wrench in half and ground down the head for plug wire nuts. Regular wrenches don't fit on some spots. I've also used the goofy-looking split plug wire tool that a friend of mine picked up at OSH, (https://www.google.com/search?q=aircraft+spark+pug+lead+wire+wrench&oq=aircraft+spark+pug+lead+wire+wrench&aqs=chrome..69i57.16590j0j7&sourceid=chrome-mobile&ie=UTF-8#imgdii=4qS1Ei0hdnwN6M:&imgrc=03OUpARBnwDdlM:) but it's hard to tighten enough with that, IMO.

If you have a 6 place engine monitor, a 3/8 short split socket helps installing CHT probes. Otherwise, it's 1/16th of a turn at a time, flipping a mini 3/8 end wrench in one hand while compressing the probe spring with the thumb and index finger of your other hand. Perhaps no big deal for someone with better/smaller hands than mine.

I have expanded my vocabulary working around these headers, but still endorse the product.

Good info. I’ll inquire about inclusion of the special socket with PowerFlow when I pay my next instalment.

Isn’t the LEES for the 206 significantly different than the LEES for the 180/185? As I recall the 206 has 2 separate collectors with no crossover as the lower mount structure’s in the way?

Photo of the 185 system looks much easier to deal with sparkplug service.

Halestorm wrote:Isn’t the LEES for the 206 significantly different than the LEES for the 180/185? As I recall the 206 has 2 separate collectors with no crossover as the lower mount structure’s in the way?

Photo of the 185 system looks much easier to deal with sparkplug service.

Yes. The headers for the U206 are totally different due to the engine mount. The 185 (pictured above) looks pretty straight forward. Not so with the 206. The pipes are tuned, but it looks more like spaghetti, and there's no crossover. I'll post a picture along with the tools this weekend.

CAVU

My “butt dyno” says the lees on my 550 powered amphib c185f did more for me than the sportsman and the wing x combined...although I didn’t get to try my 550 powered c185f without sportsman and wing x and with the lees. Make sense?. I did deal with Dane and am sorry such a talented man has passed. And I’ll concede many of you will have a far better ass than mine for the “butt dyno” test....I’ve only been flying for 30 years in the heavily loaded world of ag and floats. I did however need a full new exhaust system at the time so I was into spending a fair bit anyways and took the chance on Dane and so far have been extremely happy.
Bkn

Pinecone wrote:I didn’t anticipate any spark plug access issues. My mechanic will not be pleased. Any photos of the tools you accumulated to ease the inconvenience?

Here are some pictures of the Leading Edge Exhaust on the U206F and the tools I carry to work on plugs and engine monitor probes.











The cheater bar was a salvaged 170 control column. The end wrench is 7/8" The plug wrench came from Leading Edge and is to be used for #3 and #4 lower plugs. You can see that it can be challenging to get to the plugs, intake hoses, heat shields for the intake hoses, and CHT probes.

CAVU

Are there any improved exhaust option for the duminitive little Conti 0-300

I’ve not seen an improved exhaust system for an O-300. Seems most opt for a Lycoming O-360 to replace them. Some replace with a Continental O-360. Performance exhaust for them is scares also. Depends on airframe and engine. You can search the FAA database for STCs for your airplane.

Thanks for the photos CAVU. I’m relieved that the 185 has fewer access issues than the 206.