Its looking like the engine on the ole Cherokee 140 may be getting overhauled this winter and my Dad and I are considering installing a powerflow exhaust while we have everything torn apart.

We are looking at two benefits from the install.

1. A performance increase. I haven't really seen anything in my research to suggest that the numbers powerflow systems quote are way out of line but i'd like to know what unbiased users have experienced. Perhaps the most important thing we are looking for is how much help is it at higher density altitudes.

2. The stock exhaust on the 140 places the muffler right next to the firewall and tends to roast the cockpit especially in warmer weather. I know the new exhaust should help this but i'd like to know how much relief I can expect, a little, or a lot.

I've read a couple of the older threads that dealt with the powerflow but I would like to see what everyone thinks currently.

Drift alert......dunno about the Powerflow, but I know several people who replaced the aft-mounted exhaust on their Supercub or Pacer with a Sutton system. Hangs under the engine like a 172 exhaust. STC'd for the PA18, so maybe an easy approval for PA28?

https://www.propilotsinc.com/exhaust-conversion/

I have a powerflow on my C172 / O-360 / CS prop. The PF was installed long after the engine conversion. IMHO, it's "cheap" extra horsepower. I noticed about 200 fpm increase on climb, and that continued through my normal ops profile up to 11,000'. I also noticed that at the same throttle & MP settings I got better fuel economy for the same cruise IAS in the 60-70% power range.

I know a pilot who put the "classic" PF on his Cerokee 140. He said he got both improved climb and higher cruise after installation.

I noticed a similar increase in climb performance and fuel burn on my 170B when I added the PowerFlow to my O360 with a C/S prop.
Sounds mean too!

On the other side of the coin, my IA and I discussed whether to go the Powerflow route, when my exhaust needed to be replaced. The cost wasn't a whole lot different--about $4650 for the Powerflow (according to their website) and $4200 for the Knisely which was to exactly duplicate what I had. We concluded that the exhaust set-up I already had was probably very close to as efficient as the Powerflow--it's a modified Mooney style with dual pipes, originally taken from the donor Mooney that provided my original engine conversion, not much like any stock Cessna exhaust.

So we had Knisely duplicate the old one, except they made it with pipes which are slightly larger in inside diameter (looks like about 1/8") and noticeably larger in outside diameter (thicker material). It has a different sound than the old exhaust, too--sounds more powerful--but like when we used to put glasspacks on our duals back in high school, any increase in actual performance is likely in my imagination. And it actually cost less than their estimate by a few bucks--surprise!

I have nothing against Powerflow, other than that their "classic" version is ugly, or as their website says, only a mother or an engineer would like it. Their non-ugly short stack version is likely no better than mine is as it is, performance wise.

Incidentally, the apparent workmanship on my Knisely exhaust is outstanding. I wouldn't hesitate to recommend them.

Cary

The PowerFlow systems seem to produce exactly what they say they will - more power, with slightly higher fuel consumption to go along with it (no free lunch). Gains are especially noticeable at altitude.

But if you're overhauling the engine, you can increase your power (+10 HP) and reduce your fuel burn by installing higher compression pistons (along with the appropriate rods, pins, etc). Not sure about your particular airplane, but there are several STCs out there for 150HP to 160HP upgrades via HC pistons. I had this done to a Grumman Traveler I owned, and it transformed the plane. I picked up almost 250 fpm in rate of climb. At lower altitudes, I had to throttle back to avoid over-revving the engine, because I had a brand new "stock" prop, so I didn't buy the "cruise" prop the shop recommended. But I could still turn max RPM at 9500 feet, where it was flying a good 10 knots faster than before the HC upgrade. And the capper is that the fuel burn decreased pretty impressively. I flew the plane for 2 years with the "standard" pistons, and averaged 8.5 GPH (flying at 75% power all the time) over 140 hours of flying. I flew it for almost two more years after the HC pistons were installed, flying it exactly the same way, and averaged 7.6 GPH over 125 hours. That's dividing the total fuel purchased by the total hours flown (block average fuel burn).

The Grumman Guru who recommended the HC upgrade to me (over the PowerFlow) said that's why he recommends it so highly. Not only does it cost a lot less, but you gain HP, speed, AND range, because the higher compression engine is more fuel efficient. The PowerFlow actually does increase HP and potentially speed, but reduces range at those higher speeds because you'll burn more fuel to get the power.

I have never heard from anyone who did both the HC and PowerFlow upgrades to their 150 HP Lycoming. It would be interesting to hear about those results...

Thanks for the info guys. I happy to hear that folks are experiencing the claimed performance increases.

JP256, can you still burn mogas with the 160 hp mod?

Kansas Flyer wrote:Thanks for the info guys. I happy to hear that folks are experiencing the claimed performance increases.

JP256, can you still burn mogas with the 160 hp mod?

Depends on which STC you use. The Grumman Auto Fuel STC does not cover the HC engines, but others do.

We had the Powerflow exhaust on a couple 172s in a flying club I used to help manage. Definitely a noticeable performance increase. The only bad thing was, as mentioned, the original wasn’t pretty and, more importantly, was a pain because anytime you needed to drop the lower cowl, you had to deal with it. That being said, if the short stack can get the same result, that would be the way to go!

I installed one on my Husky. Small increase in performance, increased CHT, louder, MUCH better cabin heat, better carb heat, better built more robust than stock, about 6 pounds heavier if memory is correct.

Worth it? Hmmmm, hard to say, only reason I changed was my tail pipe was 90 percent separated from the muffler on the stock exhaust system after a 15 minute flight. I lost confidence in the stock system. Cost was about $5,500 or so if I remember correctly. So if it were not for the loss of confidence in the stock system I doubt I would have changed. There are definite improvements but wow, it sure is expensive.

Kurt

I put it on a 1968 172 and it made take offs shorter and about 200 ft per min increase in climb. Fuel consumption was the same at full power ops. When you pulled the power back for cruise , say 2400 rpm, and 3500' the throttle was about an inch and a half farther out than before I put the powerflow on. It seemed to burn less fuel, but I wasn't real technical about my data keeping.

G44 wrote:I installed one on my Husky. Small increase in performance, increased CHT, louder, MUCH better cabin heat, better carb heat, better built more robust than stock, about 6 pounds heavier if memory is correct.

Worth it? Hmmmm, hard to say, only reason I changed was my tail pipe was 90 percent separated from the muffler on the stock exhaust system after a 15 minute flight. I lost confidence in the stock system. Cost was about $5,500 or so if I remember correctly. So if it were not for the loss of confidence in the stock system I doubt I would have changed. There are definite improvements but wow, it sure is expensive.

Kurt

I forgot to mention MUCH better heat as well....

I sat through a PowerFlow presentation at the Maule factory a couple of years ago for the Lycoming O-360 and the data presented looked good, but the rig looked "busy". A "tuned" exhaust should produce better scavenging and larger pipes less back pressure.

End of the day it is heavier and pretty pricey. The Maule STC never went anywhere since PF was asking for a certain number of firm pre-orders which never came.

Not sure if there ever would be a financial return on investment, but if the increased HP is real then the difference between PF and a standard exhaust at time of replacement might be worth it.

TD

I have toyed around the idea of the PF exhaust, too.

Pros seem to be: More power. Better efficiency at same airspeed. Better climb.

Cons: Maintenance can be tricky. Cost (assuming your current exhaust is fine)

High compression pistons plus the PF might be quite the improvement. ( I think you will need to run AVGAS, but I don't know for sure)

The climb rate is definitely nice for mountain flying.

Slight derailment: Are you sure you will stick with your cherokee 140 for a while? Some of the larger Pipers can for gotten fairly cheap. Thats where I am. I am just saving up money, until I know I want to upgrade my 172 or buy/build something better. Just a thought.

ShadowAviator wrote:I have toyed around the idea of the PF exhaust, too.

Pros seem to be: More power. Better efficiency at same airspeed. Better climb.

Cons: Maintenance can be tricky. Cost (assuming your current exhaust is fine)

High compression pistons plus the PF might be quite the improvement. ( I think you will need to run AVGAS, but I don't know for sure)

The climb rate is definitely nice for mountain flying.

Slight derailment: Are you sure you will stick with your cherokee 140 for a while? Some of the larger Pipers can for gotten fairly cheap. Thats where I am. I am just saving up money, until I know I want to upgrade my 172 or buy/build something better. Just a thought.

We are trying to decide whether or not to keep the Cherokee. We would like to have something where you could put an adult in the back and have them be reasonably comfortable. The Cherokee has almost no leg room for the back seat especially since both my Dad and I are tall and fly with the seat all the way back. It won't get the powerflow if we decide to sell. The problem is getting it sold for a reasonable amount with an engine that is 2100+ SMOH. If we decide to keep it and overhaul the engine I think we'll put the powerflow on and keep it for at least a few years.

Kansas Flyer wrote:We are trying to decide whether or not to keep the Cherokee. We would like to have something where you could put an adult in the back and have them be reasonably comfortable. The Cherokee has almost no leg room for the back seat especially since both my Dad and I are tall and fly with the seat all the way back. It won't get the powerflow if we decide to sell. The problem is getting it sold for a reasonable amount with an engine that is 2100+ SMOH. If we decide to keep it and overhaul the engine I think we'll put the powerflow on and keep it for at least a few years.

A GOOD overhaul could cost you $22,000 to $25,000. I would be wary of anyone quoting less than that.

Even if you have to sell it at a lower price, it may still be worth doing so. Here's what I do. Take the current value of your bird. Add $23,000 to that. Then look around at what planes are available for that total.

EXAMPLE: Lets say you had a plane worth $28,000. That plus $23,000 is $50,000. My oh my, what can I buy for $50,000? Well, on trade-a-plane there is a 1960 Piper Comanche 250 for sale. Mid time motor, looks good, and the owner claims you can cruise 157kts on 13 gph. He is asking $45,000 for it. Or there is another Cherokee 140 with a 180hp motor. Owner is asking $48,000. I bet he could be talked down.

Anyway, you get the point, thats just the method I use for deciding how much money to spend on my plane. It has made me change my mind on several things I have looked at doing to my Cessna 172.

Also I was wondering, why do think you may need to overhaul your engine?

ShadowAviator wrote:

Kansas Flyer wrote:We are trying to decide whether or not to keep the Cherokee. We would like to have something where you could put an adult in the back and have them be reasonably comfortable. The Cherokee has almost no leg room for the back seat especially since both my Dad and I are tall and fly with the seat all the way back. It won't get the powerflow if we decide to sell. The problem is getting it sold for a reasonable amount with an engine that is 2100+ SMOH. If we decide to keep it and overhaul the engine I think we'll put the powerflow on and keep it for at least a few years.

A GOOD overhaul could cost you $22,000 to $25,000. I would be wary of anyone quoting less than that.

Even if you have to sell it at a lower price, it may still be worth doing so. Here's what I do. Take the current value of your bird. Add $23,000 to that. Then look around at what planes are available for that total.

EXAMPLE: Lets say you had a plane worth $28,000. That plus $23,000 is $50,000. My oh my, what can I buy for $50,000? Well, on trade-a-plane there is a 1960 Piper Comanche 250 for sale. Mid time motor, looks good, and the owner claims you can cruise 157kts on 13 gph. He is asking $45,000 for it. Or there is another Cherokee 140 with a 180hp motor. Owner is asking $48,000. I bet he could be talked down.

Anyway, you get the point, thats just the method I use for deciding how much money to spend on my plane. It has made me change my mind on several things I have looked at doing to my Cessna 172.

Also I was wondering, why do think you may need to overhaul your engine?

Our overhaul won't cost quite that much if we decide to go that route. My brother is an AP/IA so he, my dad, and I will do as much of the work as we can ourselves. We will have to send off some parts to be done by specialists but should be able to save a bunch in labor costs. We are thinking we should be able to get the overhaul done for less than $10k. It sure saves money on maintenance to have relatives that will trade work for rides.

As too why we might need to overhaul. The engine is now at about 2100 SMOH and while I know many O-320s go way past that this particular engine has spent the last 10 or so years sitting outside in Maine averaging less that 10 hours per year during that time. We borescoped the cylinders which looked decent and we may pull a cylinder at the next oil change so we can get a look at the crank and cam. We have also started an oil analysis program and the samples have been good so far but we don't have enough for a trend just yet. We may be worried about nothing, but we know that we will need an overhaul sooner or later so we are considering our options.

Kansas Flyer wrote:Our overhaul won't cost quite that much if we decide to go that route. My brother is an AP/IA so he, my dad, and I will do as much of the work as we can ourselves. We will have to send off some parts to be done by specialists but should be able to save a bunch in labor costs. We are thinking we should be able to get the overhaul done for less than $10k. It sure saves money on maintenance to have relatives that will trade work for rides.

As too why we might need to overhaul. The engine is now at about 2100 SMOH and while I know many O-320s go way past that this particular engine has spent the last 10 or so years sitting outside in Maine averaging less that 10 hours per year during that time. We borescoped the cylinders which looked decent and we may pull a cylinder at the next oil change so we can get a look at the crank and cam. We have also started an oil analysis program and the samples have been good so far but we don't have enough for a trend just yet. We may be worried about nothing, but we know that we will need an overhaul sooner or later so we are considering our options.

Ah, I figured you had someone who could help get the overhaul done. Everyone seems to have a relative who is an A&P, but me.

Sounds like you are taking the right precautions on the engine.

I usually ignore TBO except for a few cases. My bird has 2300 hrs total. TOTAL. Airframe and engine. I believe its the original motor from 1969. Mechanic said the engine checks out fine. I put on an engine monitor to keep a close eye on it.

At Oshkosh, I talked to someone with a VERY similar 172. They were over 3000 SMOH on their O-320.

Now all that said our motors may fail in a year or not for another 10 years. We can't really know. You guys seem to be keeping a good eye on yours, though.

One more point. I found an article where they took small aircraft NTSB data from 2001 to 2005 on accidents attributed to engine failure and put them on a graph. What it showed was:

Engine Hours-- Number of Accidents
0-500hrs -- 70 accidents
501-1000hrs -- 45 accidents
1001-1500hrs -- 25 accidents
1501-2000hrs -- 23 accidents

From 2000 to 3000hrs there were less than 10 accidents, but since many people overhaul at TBO, that number is kinda skewed.

The point of the article was that newly overhauled engines are not necessarily safer than high time engines.

The new parts aren't always the best either. The latest Lycoming AD showed that.

Like you said, though, it will happen at some point. The ol' saying, "Hope for the best, prepare for the worst", comes to mind.

Edit: I guess I will post a link to the article: https://www.savvyaviation.com/wp-conten ... a-myth.pdf

Grassstrippilot wrote:..., if the short stack can get the same result, that would be the way to go!

According to Darin Tillman who was chief engineer about 8 years ago (don't know if he still is) the short stack produces about 15% less of a boost in power than the "Classic" (which I call the "Rat Tail) exhaust. I've got the short stack and like it. I get about 200 fpm more climb going through 7000' msl than I did with the stock exhaust on my O-360-A1A CS STC'd C172. I have a couple of friends (one with a FP IO360, the other with an O-320) with the "rat tail" both like 'em and said they got noticeable boosts.

Interesting. Good to know!


Sent from my iPad using Tapatalk