Anyone have any experience with the Poerflow exhaust STC? I spoke to a guy recently who installed one on his 172 and said it made a noticable improvement in performance. I did some online rersearch, but I am not completely convinced. I would like to here what folks have to say about this product.

I think the dyno tests show a pretty good performance increase. Also, every 172 driver I have met that has one says they are great improvement. One said that with cruise prop it climbs like it had a climb prop without the powerflow. Just too bad they cannot keep it under the cowl.

Tim

They make a "Short Stack" tailpiece that costs a little more. I kinda like the look of it with the long one. I have a climb prop alraedy. Someone quoted it as being the closest thing to free hp (it costs $3k). Thats when I suspected it might be "snake oil". This could be a worthwhile improvement to my plane if these figures check out.

The trouble with pireps on mods like this is that most people are not gonna admit that it didn't give them much or any benefit after they just spent three thousand bucks on it. Nobody wants to admit they got snookered. It would have to be a disinterested thrid party pirep to convince me.
As an aside, I hear an awful lot of comments from guys who had some hotrod mods done to their airplane engines abut "it dyno'd out at XXX horsepower". I have yet to see an airplane engine shop with an in-house dyno. And just how do they test it? Is there some provision to bolt the dyno onto the crank flange? I do know of someone who tested a different prop by doing a before-and-after full-power run-up with the tail tied to a strain gauge, to check the pounds of pull (aka thrust) developed. But he's the only one.

Powerflow Systems has performance tables for most aircraft and prop combination's they have an STC on. They have a money back policy if you are not satisfied. You are out the cost of installation and removal. Depending on the aircraft about 4 hours of labor.
Check out powerflowsystems.com.

After returning from our trip through the mountains we decided that the Tundra should have more climb. An upgrade in hp to the O 390 is out of the question so short of an engine change I settled on two things to get the most out of the XP O 360 Plus that I have. One is a tuned exhaust. I spoke with the Power Flow people in Florida and after learning my plane is experimental they referred me to this place which does the same thing for about 1500.
http://www.aircraftexhaust.net/
After visiting with them I found that the results I could expect would vary by how bad an exhaust system was presently in place. Mine was dual mufflers with internal cone baffles. Had the internal baffle been straight and perforated it would have been a little better but looking up the tail pipe I could see the cones. He claims a conservative gain of 8-10 hp over that system with the tuned exhaust. I will do this when I have the plane down at inspection time in Sept. I am also going to a constant speed prop and looking at the MT for that.
I can report more later but since I plan both changes while the plane is out of service I may not be able to separate the effects of each.

I did the Power Flow on a 0360 in a Cessna 175 TW and did extensive before and after testing since they had the return guarantee and it takes only a few minutes to exchange exhaust systems. The "classic long pipe" tuned exhaust does work, although not as well on the 180 Lyc as on the 150 hp engines. The true way to test before and after is to. #1. time climb 2000 ft at the exact same rpm, MP and fuel flow. Leaning makes a big difference. #2. Do the exact same test at least three times at the exact same airspeed, which is usually your POH best rate of climb airspeed. Then change the pipes and do it all again. Remember, some engines run richer then others so leaning is critical to achieve your best rate of climb airspeed. Determine this before testing starts, I probably did 5 climbs before starting the test to determine best rate of climb airspeed.

For example: I have a CS 80 inch "top prop", LASAR electronic ignition, Sportsman cuff, the Lycoming runs rich and burns 19 gph at full rich at 4000 msl, so I test at full power and lean to 12.5 gph, climbing at 70 mph with prop set at 2600 rpm and WOT. You can't read the vertical speed indicator accurately which is the reason to time climb 2000 ft with a stop watch. Doing this three times I averaged 166 fpm increase in rate of climb and 5 mph increase at 6000 msl at WOT, however, the speed increase could not be repeated on a regular basis, since there is a lot involved in cruise speed i.e. smooth air, center of gravity, trimming etc, so take that with a grain of salt. My previous tail dragging Cessna runs a lot faster with 250 lbs of camping gear in the back. At the 2007 Mountain Flying Clinic at Townsend, MT, not a single four place plane could out climb me over a 50 ft obstacle and there were some great 180 hp Cessna 170Bs there, as well as those fabric Piper look-a-likes, that advertise STOL but can't match the Cessna wing. I needed those measurements for my new operating book, since I had so many mods.

feedpro wrote:.... I averaged 166 fpm increase in rate of climb and 5 mph increase at 6000 msl at WOT

So 3 grand bought you 166 fpm and 4kts? Think I would invest that money some other way in my aviation life.

That's like a king yellow tagged HSI or a HID landing / LED taxi light setup with a bit of money left over or new upholstery (if you know where to go) or a new rating on your ticket

Feedpro, was the muffler you replaced an Avcon muffler or a stock Cessna one?

I hear the Avcons had both baffled and unbaffled mufflers. I am replacing one right now at annual and I got it from Aircraft Exhaust. The one they sell is the unbaffled one and should be a little improvement over the one I have because the old one has the baffling and it is warped.

so 3 grand bought you 166 fpm and 4kts? Think I would invest that money some other way in my aviation life.

What is your plane worth? Nearly all of my landings and take offs were into and out of short strips or off airport. I wanted all the power I could get. I had a new 80" Top Prop which cost $10 grand for the same reason. To each his own. I wanted performance.

The muff that I took off was not stock and I sold it to a friend. Other then that I know nothing about it.

NineThreeKilo wrote:

feedpro wrote:.... I averaged 166 fpm increase in rate of climb and 5 mph increase at 6000 msl at WOT

So 3 grand bought you 166 fpm and 4kts? Think I would invest that money some other way in my aviation life.

That's like a king yellow tagged HSI or a HID landing / LED taxi light setup with a bit of money left over or new upholstery (if you know where to go) or a new rating on your ticket

Thanks feedpro for sharing the testing that you did on your plane. Sounds like you did a good job and you got what you wanted out of the mod. I will choose not to crap on your post.

Tim

I've been in alot of situations where I definately would have chosen adding 166fpm over a yellow tagged HSI or upholstery.

In fact there could be instances where not having increased climb performance could put a "wicked brown streak" on the bottom cushion of your new upholstery

Feedpro,

Did you get a decrease in fuel flow at comparable power settings? In some instances it can be as high as 2 gallons per hour, but usually in the 1- 1.5gal/hr range. This can amount to an hour extra of range on a 50 gal tank. Nice to have in the backcountry, plus the savings of $600/100 hours of flight time.

dawgdriver,
I did not note a decrease in fuel flow. I got a good 10% decrease in fuel flow with the addition of the LASAR electronic ignition, but also an increase in CHT in climb. Solved that by putting the LASAR on a switch so I could shut it off when doing a long climb after take off, also I glassed in the lip on the top of the cowl to smooth the air flow coming in over the top of the cyl.

No one has ever mentioned to me a decrease in fuel flow with the Power Flow. However, cut back on the throttle to the original HP and you save fuel. In my (cheap) old age, I started running at 65% for 8gph (7gph above 10k). Used to burn 10gph with the balls to the wall (backing off the prop to 2450), but got 2700 hours out of my new engines, doing that in 10 years.

For the Husky. which they are in the process of obtaining an STC, they guarantee a 1gal/hr decrease at comparable power (actual testing 1.2gal )

qmdv wrote:... I will choose not to crap on your post.

Not my intention to crap on someones post.

This thread is about what does everyone think about PF exhaust systems, not give me a BJ about what I just put on my plane.

My opinion was that the price to performance was a little lopsided.

I understand the idea behind getting all you can out of your equipment however there is a line and 3k is allot of money for a minimal amount of performance.

All I suggested was perhaps spending that money and doing something like getting a glider rating or float rating will wield experience that will allow you to outperform someone who doesn't have that knowledge but a overpriced tail pipe. IMHO that is

Exhaust mods are tricky. Aircraft exhaust systems have to work every time with out blocking the flow, with out a fire. Most aircraft engines have low back pressure already, so the gains you will see with something like this are from shock wave tuning extraction effects (at an RPM of choice made by the engineer), and the reduction of pumping losses. If an exhaust system like these works, I would expect higher CHT's because you are filling the cylinders with more fuel and air, because of the lower pressure in the cylinder when is is filling.
In short you are dealing with a stone age engine with 1950 tec and fixed timing in most cases. That is to say the ignition curves have to match the mods if you can expect these things to work, and I don't think people in the industry do testing together at all. So if you change one thing, and then something else, you might get cross profiles in performance. Look out, it might cost you power and money.
I think you could get more power on a case by case mod, if you set it all up right....but remember these engines turn so slow, that it's not going to be anything like the power gains you would get with a motorcycle or a car. In fact airplane engines turn so slow that the engines are at the low end of the internal combustion engines range, as RPM X Torque = HP.
Spin it fast for more HP....but the prop hates that and goes sonic at the tips...or push the air in (not thank you, I hate cylinders dropping on my boots when opening the cowl.)
I wish there was a clear way out of this, but so far, it seems our fathers simple engines have not yet been bested for all around weight, power and simple construction. Even cylinder filling is the best way to tune these engines, as that is the area where the most gain can be had. That is to say it makes it easy to run lean of peak, and save fuel. Bla bla blabla ect.

If you have the money to burn, go for it, just watch it for safety and cracking till you trust it.

I

Id like to ask about powerflo exhaust as well. Why is it that they can have a system made for an O-320 in a Cessna 172, but not one for the O-320 in my Citabria. Same engine... Is it just the different cowling? Can anyone explain this to me?

A1Skinner wrote:Id like to ask about powerflo exhaust as well. Why is it that they can have a system made for an O-320 in a Cessna 172, but not one for the O-320 in my Citabria. Same engine... Is it just the different cowling? Can anyone explain this to me?

They are working on the citabria. They have had it installed for some time, but approval takes time.
I have installed 2 on citabrias, but they were both experimental, they work great.
After installing and testing the powerflow on 6 aircraft, I am confident in their claims.
The engines are whisper quiet, and turbine smooth, and there are noticable gains in thrust. I do pull tests with every plane that I work on, so I have a fair amount of data that backs it up.
It is not uncommon to repitch the prop 2 inches, after putting the powerflow on.

Low back pressure on the engine?
Zommies on my Boat, 562 BBC sounds great, absolutely no BP, 750 HP
Set of tuned 4 into 1, long collector, almost 75 more HP!
Different cat but same idea
Tuned back pressure makes a helluva lot of difference!!
Just my $.02
Anyone wants to go from 0 to real fast in a 200' let me know.
We won't talk about fuel consumption tho!!!!
GT