Power flow exhaust on 170B-360 Lycombing

[Francis Cahoon]

Bruce, I think I just sent you a picture of my plane that one guy requested. please put it where ever that guy requested. Thank you. A guy from Alaska called me with some very good info. He does the same type of flying I like, and had some great ideas, spoke from experience he has had while living in Alaska. Thank you, and this form for helping me along. F.Cahoon

[N419A]

Some other thing to look into:
Wing eccentrics set to maximize angle of incident.
Slightly drooped flaps as mentioned earlier.
Larger tire diameter, increases angle of attack on take off and less rolling resistance on rough surfaces.
Prop and RPM you mentioned a Hartzell is it the 80" dampened prop, they seam to work really good on the Lyc 360 and are you achieving peak rpm 2700, though out take off and climb out.
I think it ultimately comes down to power to weight ratio. A good efficient system to produce and deliver the power and an current and accurate weight and balance, I've seen planes that wouldn't perform like the should and it was because the had a 30 year old weight and balance that was off by a hundred lbs. plus. So, they thought they were flying a 1260 lbs airplane that was really a 1430 lbs plane.

Good luck let us know if you find something that gives you a significant increase in take off.

Paul

[Francis Cahoon]

Thanks for your info Paul, I think I am starting to get some ideas that should help me achieve the shortest take off distance with my plane. After talking to Ron from Alaska, the V-Gs on the wings looks very encouraging. Plus stripping more stuff, like the radar stuff, that I do not know how to run, nor care to learn. Sounds like the most weight I can get out of the plane is a good start. Also Bruce, were you able to get the picture I e-mailed you to Frank ? Thanks F Cahoon

[blueldr]

If the power flow exhaust provided the ridiculous boost they claim, you can bet your sweet ass that the STC holders of the O-360 conversions would be damn well requiring it.
The only guy I ever knew that had one did not have a significant static run-up RPM increase, but he ignorantly insisted that that did not make any difference.
He claimed that the CS prop made the difference even though the static RPM never came up into the governing range.

[Bruce Fenstermacher]

Francis, I did not get a picture. Did you send it to my gmail address? Use the link in my signature to do that.

[DaveF]

Why are you guys so dismissive of the PowerFlow claims? Ok, so it's crazily expensive, unattractive, and there's probably some advertising exaggeration, but you're not disputing that the design of the exhaust system makes a difference, are you? Haven't car guys done tuned and other improved exhausts for decades? It seems to me that an airplane engine, running at constant RPM, is an ideal candidate for tuned exhaust. I find it hard to believe that what I'm using - four pipes dumping into an oversized coffee can - is somehow optimal. What am I missing?

[Francis Cahoon]

Bruce, I tried again, so let me know if you get the picture, thanks for being so patient with this old Indian. I really am enjoying the different views, hope some people with the power flow will respond good or bad. In my opinion, it is quite a bit of money for this old logger, but if it helps me achieve my end goal of short takeoffs, then I would consider it worth the money. thanks. F. Cahoon

[GAHorn]

Why are you guys so dismissive of the PowerFlow claims? Ok, so it's crazily expensive, unattractive, and there's probably some advertising exaggeration, but you're not disputing that the design of the exhaust system makes a difference, are you? Haven't car guys done tuned and other improved exhausts for decades? It seems to me that an airplane engine, running at constant RPM, is an ideal candidate for tuned exhaust. I find it hard to believe that what I'm using - four pipes dumping into an oversized coffee can - is somehow optimal. What am I missing?

DaveF, Have you listened to their sales pitch in their video?

When describing factory exhausts, they claim that "all" the original exhaust does is direct the engine exhaust out of the engine and away from the cockpit." (Sounds OK to me so far, but it's not true. It also provides carb and cabin heat.)

While comparing the physics of OEM versus their own system, they claim the OEM system dumps each cylinder's exhaust into a "coffee can" where "some of it goes out the exhaust....."But {QUOTE} MOST of it goes up the other three (cylinders) tubes ...(to block exhaust from those cylinders...reducing efficiency...)"

Really! Well... I never....

Those poor other cylinders can't even push their own exhaust out their exhaust pipes because of ONE SINGLE CYLINDER shoving it back up their ...err...umm... exhausts.
If anyone believes that, they should send their checkbook to Powerflow. Immediately.

They claim increased service ceilings of 2-3000 feet. 300 RPM increase. 2.2 gph less fuel burn. (OOps...I"m sorry...they don't guarantee that...they only claim you MAY experience UP TO those increases. Hmmn.. that's different than actually claiming any improvement at all.)

I also didn't see any approval basis for increasing the certificated ceiling of airplanes. another oops.

Well, anyway, did you see their ICAWs??? (Instructions for cont'd airworthiness)
You must maintain your engine so that all the cylinders maintain 70 over 80 compressions. oops. That kinda changes your engine maintenance schedule a bit, heh?
You must maintain your magnetos to EXCEED the mfr's recommendations. (I don't know how you do that. oops)
You must rebalance the prop to less the .2 ips each 500 hrs. (hint: they're worried about their system welds cracking)
ad nauseum.

Looking at their system, their primary change is that instead of dumping all cyls exhausts into a "coffee can" (your collector/muffler) then piping it overboard.... THEIR system waits to dump them into a smaller container all at once after a longer journey ....into their smaller and longer and heavier tailpipe.

But, that's OK. I guess it proves the point that after you spend that kind of money you absolutely MUST be happy with what you've done. Everyone who does it says so.

[blueldr]

George,
You sure can manage to connect a lot of classy words together to explain how a lot of absolute BS is put together.
When the ignorant suckers spend that much for an exhaust system, you can bet your sweet ass they're going to be convinced it's the greatest thing aince sliced bread.

[DaveF]

Never mind, I'm sorry I asked.

[Francis Cahoon]

Bruce, did you received the picture I sent you?

[c170b53]

Dave I don't think your missing anything...but the improvement in performance is likely minimal when compared to the standard equipment and not worth the money. Then again what's cheaper their new system or a new old system?. Fortunately I haven't had to sort that out.
As for the best performance improvement, I'm always trying to remain fit and trying to keep my weight in check. And just because that makes total sense doesn't mean I'm alone in the struggle to thwart the usual seasonal increased displacement syndrome.

[Francis Cahoon]

Dave, please do not hesitate to voice your opinion on this form or any other form, I asked for any ones views. I may not like the views and opinions, that I have received, but you can bet I will use them to help me gain knowledge on the subject that I have zero experience with. I also would like to thank all the people that have responded thus far, and hope that more will respond, with out feeling bad about voicing their opinion. I assume that this form is for everyone that has or would like to have a Cessna 170, and is interested in all aspects of these great plane. I have talked to two really great guys on the phone that have a vast knowledge of the type of flying I would like to do, and have shared this knowledge with me. So please continue to have a positive input to my questions, good or bad. Thank you .F.Cahoon

[Bruce Fenstermacher]

I'd say that behind MOGAS and MMO and maybe VGs, the Power Flow exhaust has brought out the most strongest and colorful opinion on each side of the debate.

As for the Power Flow, many of us familiar with hot rodding our cars know restrictive exhaust hurts performance. And therefor a "tuned" exhaust has to be better. At least that is the conventional wisdom and that is why it is so hard to hear someone say it is a load of pooh.

I know a tuned exhaust can improve the horsepower of a given engine. In most cases when discussing this sort of thing we are not limiting the engine to a certain RPM which is the case with aircraft. Seems to me you want to increase torque not RPM in an aircraft engine so the engine can swing a courser prop at the same RPM it did a finer pitch prop. A "tuned" exhaust might be able to improve torque but it is a pretty complicated and I believe more than tuning an exhaust would have to be done.

But to be honest I haven't put much thought into it because unless it significantly improves performance to say 5 times what they claim, I'm just never going to hang that exhaust pipe from my classic airplane. I think that is the number one problem most people have with the Power Flow. It looks stupid and there are so many other things can do to improve performance with the number one being learn to fly your plane better.

[GAHorn]

Never mind, I'm sorry I asked.

DaveF, you and I are friends, and we both know that. My previous response was not an effort to denigrate you or your curiosity.
I only quoted their sales pitches. It's their words. The fact they make money off of people by making their strong claims just goes to prove that marketing works.... similar to motor oil arguments. Just because the FAA approved something to be installed on an airplane is absolutely NO proof any benefit is derived. It only proves FAA doesn't think there's any serious harm in it.

In years past, there used to be travelling salesmen who used a mule-drawn wagon to hawk their "patent medicines".
The guvmint outlawed those things and regulated them by creating the FDC. They can no longer sell Grenadine syrup and claim it cures ingown toenails, but every day on TV there's someone selling "REAL MALE" testosterone pills and making a lot of money off it. (Orin Hatch, senator from UT defends the homeopathic/generic-vitamin crowd because they toss a lot of money in his PAC. It's why FDC makes 'em place notes on the pkg that mention no proof of treatment of any disease is claimed.)

I have a carnuba wax I'll send you that will not only reduce drag, save fuel, extend range, raise serviced ceiling, and attract the attention of young females.... it'll actually improve the appearance of your airplane while reducing the chance of surface corrosion, and it costs far less than the PF exhaust while providing more benefits and has a much simpler ICAW ... simply re-apply it occasionally. It carries a 30-30 warranty and, while it will not prevent male baldness, it will make your pate look nice and shiney. Guaranteed.

It's one more thing I'll never do to my own, but It will provide very real and measureable improvements to your airplane. I promise.

Race cars dispense with factory exhausts and use tuned exhausts. Why? Because factory exhausts are designed to get the exhaust out behind the car and do it as quietly as possible using lots of soundproofing/baffling. It creates a little bit of back-pressure, yes.
But race cars don't run on public streets, and they frequently use multiple carbs (which must be balanced, which in order to balance them it's helpful if each cylinder has identical back-pressure...hence the tuned exhaust idea.) It's also helpful for injected engines if you're going to use ONE standard injector which delivers the same fuel charge to each cylinder (along with tuned intake runners as well, of course). All of that is just fine for an off-street roadster or sling-shot dragster.
Unfortunately those will no longer meet EPA or municipal laws regarding automobiles on public streets, so they don't work well in autos that run at 30% power in stop and go traffic and idling at the supermarket.
Your personal airplane is not a Reno racer. It's a supermarket 4-placer. A tuned exhaust will not help it to the tune of the dollars you must spend on a majic exhaust system, which places undue burdens upon you to keep your airplane engine and it's accessories constantly in "better than new manufactured" condition. (ANY airplane will perform better if you could actually do that, heh?)

Airplanes performance is documented and certificated and weight and efficiency is already in the minds of developers because of the constant penalties under which airplanes operate. (It's why some engine "upgrades" like Lycomings in 170's don't provide actual performance numbers...they only state the airplane "meets or exceeds" original performance. If they made real claims they'd have to go to the expense of recertification and endurance flights. That eats into profit so they take the cheap/easy way out.)

Aftermarket products will hop onto that commonly accepted answer and make claims of "up to 2.2 gph fuel reduction" "Up to 2-3000 ft increased service ceiling", etc etc in the full knowlege they cannot, and will not and will never have to document that...they cannot guarantee that because they have not proven that even to themselves. But they know it's just too tempting for the average guy to dismiss because of the incredible number of variables to prove anything different and Mr. Average is already convinced that race car exhaust system design simply MUST be applicable to airplanes. Right?

A simple wax-job can quite legitimately and safely make the exact same wild claims.

My can of Simonize is yours for the asking.