I promised on an earlier posting that Power Flow would have more details about a tuned exhaust project for the 4 cylinder Maule. Unfortunately the forum won't let me post the whole announcement here. For the full announcement, performance numbers, and an optional survey on to get Maule owner input, please go to Power Flow's website at:
www.powerflowsystems.com. or straight to the announcement: http://www.powerflowsystems.com/news.php?nid=88

I'll monitor this thread and will be happy to answer questions as best as I can.

Power Flow Systems is pleased to announce that initial research and development work has begun on a Tuned Exhaust System for the Maule MX7 series of aircraft, powered by four cylinder Lycoming engines.

Many Maule owners have asked if a Power Flow Tuned Exhaust System would be available for their aircraft. Owners have cited a desire for better exhaust longevity, reduced noise and improved performance.

Over the past few months and with the invaluable assistance of Maule Air, Inc., Power Flow has worked to design an exhaust system that would fit within the cowling of both the taildragger and nosewheel versions of this iconic aircraft. It is also designed to work with both the Lycoming O-320 and O-360 engines.

Further details, pricing and the terms, conditions and discounts available for initial deposit holders will be announced at the upcoming Maule Factory Fly-in to be held November 1 in Moultrie, GA.

Hello Darren -

What would the improvements be, if any, on an 0-360 with a fixed prop?

Will you be bringing a prototype to Moultrie this weekend?

Thanks...................Rob

MAU MAU wrote:Hello Darren -

What would the improvements be, if any, on an 0-360 with a fixed prop?

Will you be bringing a prototype to Moultrie this weekend?

Thanks...................Rob

The fixed pitch prop Maule will have a noticeable gain in takeoff and climb performance because it will turn the prop faster than you can get now. Our tested gain is for 30-130 RPM gain on other aircraft with exhausts that happen to have original exhausts that are a little better than the original Maule exhaust. I suspect (still to be verified) that the gain is more likely to be a minimum of 50-75 RPM. In terms of improved cruise speed, a fixed-pitch prop can develop more RPM, but unless you choose to use the higher available RPM, you will be going the same airspeed. However, you will discover that it takes less throttle to go the same RPM, resulting in more significant fuel savings. This is exactly the same kind of scenario as the C177-A, Grumman Tiger and C172 with O-360 engines see.

Good news on the Prototype exhaust - we will be bringing the prototype to Moultrie this weekend. Even better, I will be flying it with it installed on the aircraft. Currently planned to arrive Friday morning by 1000. We will be removing the cowling to do show and tell about the prototype and I will be giving a presentation on the "how it works" and why it works.

Are you going to be there?

Thanks for the information and I will be there for all of the action.

The prototype Power Flow as installed on the Maule MX7 we are flying exits the existing cowl flap area where the current 2 original exhausts exit. The Power Flow doesn't stick out quite as far.

A couple of images for you to see a sneak peak. More images will be posted after this weekend.



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Hi Darren
Any chance of a video or photos of the installed exhaust for those of us that can't attend the upcoming fly in at Maule?

bobguhr wrote:Hi Darren
Any chance of a video or photos of the installed exhaust for those of us that can't attend the upcoming fly in at Maule?

Yes- We will have pictures and video posted on our by the end of next week (11/8). Subscribers to our Maule email list will also get information emailed to them.

Does that plane also have a Mogas STC?

Mountain Doctor wrote:Does that plane also have a Mogas STC?

Air scoop was sort of a give-away wasn't it?

What about us 6 cyl guy's, way more 6 cyl Maules than 4 cyl. Exh that is not Mogas

I think I'll do the STC someday but the darned Feds and their alcohol.

While it is my impression that your tuned exhaust is an improvement over the stock Maule exhaust, I have heard (not actually seen myself) that your exhausts still require occasional welding due to cracks.

Could you please comment on this. Thank you............Rob

MAU MAU wrote:While it is my impression that your tuned exhaust is an improvement over the stock Maule exhaust, I have heard (not actually seen myself) that your exhausts still require occasional welding due to cracks.

Could you please comment on this. Thank you............Rob

Almost any exhaust you put on the shaky vibrating Lycoming O360 will probably crack somewhere in it's lifetime due to large mass of pistons, rods, and crank with zero crankshaft dampening. The question is will it require welds on top of welds, on top of welds as the original gets older. Before I put my new sys on, I was doing weld repairs every 25hrs!! I should think the power flow sys with all the slip joints to help with expansion / contraction from heat and ball joints at back end with the shorter collector originally on the power flows, should make for a reliable exhaust sys, certainly much more then original, and should also think you will find performance figures improvements over original as well. Just about any more modern exhaust should give considerable improvements as the original is pure 1940's and 50's technology...

Exhausts are the responsibility of the airframe manufacturer, there were only two considerations on exhaust design, light weight and not getting CO in the cockpit, exhaust scavenging / efficiency etc. were not even a consideration.

Rob/Mau Mau - I think Jim's reply is well stated and I agree with it. The only thing I will add is that the slip joints we designed in to the system work very well - as long as they are maintained. The maintenance is to inspect the slip joint, clean up the old crud and put new high temperature anti-seize in the slip joints during the detailed exhaust inspection that everyone should be getting at annual. We make this inspection and lubrication mandatory as part of the instructions for continued airworthiness. The exhaust inspection is not a big deal to take off and put back - around an hour for the whole deal. We take less time, but we do it a lot (!)

The slip joints are designed to allow the cylinders to expand and contract and they relieve the stress that would naturally occur in that axis of movement. This is why maintaining them is critical to good longevity.

aero101 wrote:

MAU MAU wrote:While it is my impression that your tuned exhaust is an improvement over the stock Maule exhaust, I have heard (not actually seen myself) that your exhausts still require occasional welding due to cracks.

Could you please comment on this. Thank you............Rob

Almost any exhaust you put on the shaky vibrating Lycoming O360 will probably crack somewhere in it's lifetime due to large mass of pistons, rods, and crank with zero crankshaft dampening. The question is will it require welds on top of welds, on top of welds as the original gets older. Before I put my new sys on, I was doing weld repairs every 25hrs!! I should think the power flow sys with all the slip joints to help with expansion / contraction from heat and ball joints at back end with the shorter collector originally on the power flows, should make for a reliable exhaust sys, certainly much more then original, and should also think you will find performance figures improvements over original as well. Just about any more modern exhaust should give considerable improvements as the original is pure 1940's and 50's technology...

When/how can I get one without having to deal with my local FSDO?