180hp conversion for the 170A

[MickP170A]

Hi All, Well it has been some time since I have posted here, been to busy flying the 170 Since bringing her back to Aus from Denver CO I ended up tiding the aeroplane up a little and fitting the Horton Stol kit (subject of my last post). I have been extremely happy with the aeroplane and have put 180 hours on the aeroplane in just over 12 months.
Here she is, photo attached, photo taken by good friend Rob Fox.
Back to the reason for my post. I am interested in putting in a Lyc O-360 with Constant Speed. My questions are as follows
1. Is the performance change significantly different ? I am aware it will climb faster, get off shorter, but what about cruise speed ?
2. What changes have to be made to the standard 170A cowl to accommodate the Lyc 0 - 360 ?
3. If I decide to go down the path, what STC's are available for the conversion ?

I am happy to hear of any pro's and con's of converting over. I learnt to fly in a C180 and still love the 180 just cannot justify the Fuel burn etc of a 180, whereas I also love the 170 as it is, but would like to know how others feel about the conversion and if it is worth the effort and expense.

Regards from down under.
Mick Poole

[Jr.CubBuilder]

I've done this on a B model with the A style cowl doors, using the complete DelAir STC kit.

Is it worth the expense? That's an opinion, and the answer depends on your perspective, my stock motor was in need of a rebuild when I converted my plane. In my case I'm glad I did it, but there are some things I would have done differently, the most significant of those is I would have done the work myself. The kit from DelAir is very complete, and has good blueprints. The one piece I wasn't happy with is the air horn coming off the back of the filter housing to provide carb inlet air, the angle had to be modified to work on the 170 cowl, it appears to be designed for the 172 cowl and there must be a difference. It works fine once modified.

If you do this conversion make sure you have access to accurate scales, and have competent people who can do the weight and balance and/or make sure you can do this yourself. Initially I didn't, and this caused me all kinds of unnecessary headache because of some incompetent and ignorant people who initially worked on this. The O360A1A is a bit lighter than the C145, but you are also adding a fifty three pound CS prop on the end of it so although your empty weight doesn't changed, the center mass of the power plant moved forward inside the cowl. Effectively you end up moving the weight of the motor forward from the datum. I moved my battery behind the baggage to compensate, but as things turned out I didn't really need to and I'm thinking about moving it back to the firewall.

With the constant speed prop you get maximum HP out of the motor on take-off, with the O360A1A that's 180hp and the ground roll, climb and high alt. performance improve accordingly. There is another outfit called Stoots aviation in Alaska, they offer an STC with a IO360 and I believe an IO390 if you want more power, but I would look real close at the weight and balance aspect of it, and I know nothing of their kit quality.

I would say if you love the 170, it's simplicity, it's round tail and fuel burn, and just want better STOL and climb performance then go for it. Regarding fuel burn, my experience is it uses the same amount if you don't try to make it go faster.

On the other hand if what you are expecting is a substantial speed increase, more useful load and longer range (essentially a C180) then don't do it, just buy a C180 or some other plane.

[blueldr]

As concerns engine conversions and fuel burn, when I converted my '52 C-270B to the continental IO-360 engine, rated at 210 HP, the take off and climb was inspiring. Starting at an elevation of 1600 ft., the cruise climb time to 9500 ft. went from thirty five (35) minutes to eleven (11) minutes. On a four hour cruise leg flown at 115 MPH , the same speed as with the stock engine, the fuel burn was EXACTLY the same. The reason, I assume, is because the conversion did not make any change in the flat plate area of the airplane, and the specific fuel consumption of both engines was the same. To go faster burns more fuel. I have a friend with the same conversion on an "A" model and he has determined that his best nautical miles per pound of fuel seems to be at about 150MPH TAS at about 8000 Ft. above MSL.

[ghostflyer]

Mick,
I am at YRED in Qld and have a 170a converted to a 180 hp using a Harry Dellicker STC. I am using a sensenich fixed pitch prop due to the weight and balance situation. I am still in the testing mod but so far very happy with the performance. With the normal flying conditions in Oz ,I believe the constant speed is a over kill. My biggest problem is CHT,s at the moment.In cruise it sits at 370 deg . I rebuilt my lower cowl totally . Not a big job but a lot of thought and care needed. The 2 blisters that are required on the top cowl are a piece of cake to fit. Fuel consumption at full throttle is massive. Its about 50 lts a hour. However as you throttle back ,surprising returns in fuel consumption occurs. I cant throttle back yet as I am breaking a new engine in. Contrary to popular belief from our learnered brethern there is a speed increase , it looks like it will TAS around 120 kts.I cleaned up the airframe [eg. all control surfaces as per Mr. Cessna requirements and every thing faired as it should and dumped all the rubbish behind the back seat.]. It climbs like a home sick angle but at the moment I am restricted by CHT,s . My oil temps sit at 190 deg and I would be happy at 170 deg but maybe I want too much. Max oil temp is 240 deg. I have had a lot of fine tuning to do but it is coming together really well.
The fuel tanks are too small for this country but I am thinking of designing a rear cargo tank [with an EO] to help with the c of g situation and longer range..

[GAHorn]

CHT redline for a Lyc 0-360 is 500 Fahrenheit isn't it? So what's the problem?

[Jr.CubBuilder]

My biggest problem is CHT,s at the moment.In cruise it sits at 370 deg . I rebuilt my lower cowl totally .

Fuel consumption at full throttle is massive. Its about 50 lts a hour. Contrary to popular belief from our learnered brethern there is a speed increase

It climbs like a home sick angle but at the moment I am restricted by CHT,s . My oil temps sit at 190 deg and I would be happy at 170 deg but maybe I want too much. Max oil temp is 240 deg.
The fuel tanks are too small for this country but I am thinking of designing a rear cargo tank [with an EO] to help with the c of g situation and longer range..

The plane will go faster if you feed it enough gas, but I suspect that you will discover you get the same fuel burn at the same speed you previously cruised with the stock motor. For the flying I do more speed is not desired, nor is the increase in fuel consumption. In an interesting correlation I've found that I can get lower fuel burns than with the stock motor when flying around at 80mph with low RPM, and I think this is where the Hartzel CS prop is a bit more efficient than the 76/51 I had on the C145.

That's interesting about your CHTs, I have a hard time keeping mine warm. My temps vary with the season, but usually run in the 230-260F range. My oil temp is also on the low side, and during the winter I keep the cooler tape'd over with duct tape. Over the year the ambient temps most of the time are running 15-85F where I fly. How hot is it where you are flying?

[ghostflyer]

Our temperature around here at the moment is 85 deg to 95 deg with 90% plus humidty. To triple check my gauges [ Brand...electronics Instruments] My oil temp ,Cht, Egt all read the outside air temp before start up. What you say about fuel consumption sounds basically what I am getting but havent done any set performance figures until the engine is run in. When cylinders reach a temperature of 500 degs they have lost 50% of their integral strength in the alloy part of the head. 400 deg is the max I will let a cylinder head go to for reliability reasons. I have discussed this with Lycoming reps in the past and they have suggested a good temp is around 340 degs. The Continental and Lycoming and the Superior engines all have different thermokinetics and the original cowls were designed for the Continental. Thus modifing a airframe is creating all different problems.
I know of another 170b that has a very similar mod to mine and his CHT,s were higher than mine [ 390 to 430] degs. He had to modify his intakes where foam was placed internally to form a smooth air flow to the cylinders directly. Sometimes the theory doesnt work.
However next week I will set up the temperory instruments to check under cowl pressures and temps and will adjust the outflow rate of the lower cowl. The biggest problem at the moment is rain. we are having a rainfall rate of 1 in an hour as I type this. we have had bad flooding this time last year and this could develop into the same again. Many people lost their homes or were damaged beyond repair. I am reasonably safe due to living on the coast as it drains away very quickly.

[Jr.CubBuilder]

However next week I will set up the temperory instruments to check under cowl pressures and temps and will adjust the outflow rate of the lower cowl.

Sorry about the flooding, we have a bit of that here from time to time but not catastrophic.

How are you adjusting the outflow?

[ghostflyer]

Basically what goes in the intake cooling is slowed down in velocity[pressure increase] and heated [pressure increase ] and then is extracted out the bottom. There is a formulae [rough] thats gives you some direction where you start . The intakes are the hardest to change and a certain heat transfer has to take place also. However the heated air leaving the cowl can be extracted by the shape of the lower cowl. At the moment I have a 90 deg dam at the lower lip of the cowl. The distance between lip amd the fuselarge is 2.5 ins. and 21 ins wide. however after testing this ,I feel it might be causing the exhausted air to choke in this area. So a 40deg lip will be fitted. Continental engines have a higher mass flow of air through their engines also thats why the bottom cowl on the 170 has that great hole. I have a superior engine so thus a smaller exhaust hole. The greater the size of the outflow air duct creates greater the drag. Have a look at the lastest model 172 and see how the air is exhausted overboard. I have just been told that there is a heap of information on the RV web site on this subject. I can do this work through a STC and a Engineering Order.

[Green Bean]

CHT redline for a Lyc 0-360 is 500 Fahrenheit isn't it? So what's the problem?

According to the AVCO Lycoming 76 Series Operator's Manual for the O-360, given by AVCON from Lycoming prior to the William's purchased in the late 70's. The manual states the following:

Never exceed the maximum red line cylinder head temperature of 500°F (260°C). For maximum service life, cyllinder head temperatures should be maintained below 435°F (224°C), during high performance cruise operations and below 400°F (205°C) for economy cruise powers.

Cruising during break in should be done at 65% to 75% power until a total of 50 hours or oil consumption has stabilized. The engine should be operated on straight mineral oil for a minimum of 50 hours or until the oil consumption has stabilized. Then switch to an approved additive oil Spec MIL-L-6082 or Ashless Dispersant MIL-L-22851, if so desired.

[MickP170A]

interesting info. thanks.. '
Ghostflyer, I will be up in BN several times over the next few months. Would be keen to talk further and have a look at your machine at some time if you don't mind. If you haven't already worked it out, Im in Melb, the aeroplane is kept at Tyabb.


Can someone provide contact details for DelAir ?

appreciate the info.

Regards,

Mick

[GAHorn]

Our temperature around here at the moment is 85 deg to 95 deg with 90% plus humidty. ...I have discussed this with Lycoming reps in the past and they have suggested a good temp is around 340 degs. The Continental and Lycoming and the Superior engines all have different thermokinetics and the original cowls were designed for the Continental. Thus modifing a airframe is creating all different problems.....

While I agree that modifying airplanes can produce unexpected results, I suspect you are spending inordinately large amounts of time and expense regarding the CHT "problem". Undoubtedly the Lyc Rep was speaking anecdotally ...and with regard to a STANDARD DAY...(59F/29.92") ...not the density altitudes you've indicated in which your engine is running 10-deg. warmer than his off-the-cuff remark.

I'm not intending to ridicule your efforts to modify your airplane and tinker with it at your pleasure. I'm only hoping to encourage you to stand back a moment and consider that while Lyc/TCM make slightly different engines....they are subject to the same thermodynamic problems. Doubtless, you have an abundance of incoming air. While one must slow the cooling air down sufficiently to allow it to absorb heat before exiting the cowling, that is best done with internal baffling (where an air-dam is appropriate to force the high-press. air thru cyl cooling fins)...not with exit obstructions, unless one uses variable flaps (cowl-flaps). If I understand your description correctly, It sounds as if you've placed undue restrictions at the exit. If your cruise indications are around 370F, that is not excessively high, depending upon OAT/PA. (But I digress...)

Even OEM/original aircraft can experience higher-than-normal CHTs occasionally and the usual and recommended "fix" is to increase forward speeds and enrichen mixtures to raise internal cowling pressures while reducing EGTs/CCTs/TITs....and to open variable cowl flaps to increase exit air-flow. (Not to raise internal pressures with exit-dams.)

In any case, the loss of strength of Cyl head alloy is not linear and one cannot imagine that 400F is at 80% of ultimate strength. Even if one should experience a 500F indication, a theoretical 50% reduction in strength is transient and already under consideration by design, with large safety margins. It's an operational red-line, not a point where catastrophic failure is predicted....or even likely.

Just hoping to reassure you. Not intending to discourage your creativity or pleasure in modifying your bird.

[ak2711c]

Ghostflyer- I would encourage you to consider installing the seaplane lip on your cowling that is part of the factory float kit. This lips purpose is to provide better cooling. It is common with other aircraft that have been converted to larger engines to require that lip to be extended as part of the conversion in order to get adequate cooling. The 170's that I have installed that lip on had a large decrease in engine temps. The best part is that it was a factory option anyways. Good luck.
Shawn

[hilltop170]

ghostflyer-
Some of us have done quite a bit of work on getting our engines to cool better and more evenly. If you could post some pictures showing your baffle seal arrangements, intake openings and outlet openings, and cowling, it would be much more evident whether you have a good system that is doing all it can under the circumstances or one that could be improved on.

[jamyat]

I have a 170A with the Cont IO360. My mechanic/installer had a different idea regarding the cooling air exhaust. He wanted to decrease the cooling drag so he removed the lip from the lower cowl. The twin exhaust pipes extend through the cooling exhaust hole very close to the firewall. He attached sheet metal to the cowl that extended the cowl almost to the exhaust pipes. The result is that the cooling exhaust hole is greatly reduced in size, probably by over half. The line of the cowl flows smoothly back to just ahead of the exhaust pipes. When he told me he was going to do this I was a bit skeptical, but he has so much experience I didn't argue. I am at home so I can't provide any measurements right now, but if anyone is interested I will measure clearances and the width of the cowl extension.

I don't have a way of estimating how much the cooling drag has been reduced, but I can say that the engine cools just fine during cruise. During hot 100+ days the oil temp runs about 190 at cruise speed. During normal days, 85 - 95 degrees, the oil temp will be 170 - 180 at cruise. Now with the temps running in the 40's and 50's it runs about 140 - 150.

It heats pretty fast during the climb even though I climb at 100 mph indicated. During hot days, I climb rapidly about 3000 feet then I level it and set it up for cruise. Then if I want to go higher, I put enough up trim in to make it climb 300 - 500 feet per minute. This technique keeps the temperature at about 180 - 200 during hot days. Then when I reach my cruise altitude it will cool to the temp corresponding to the outside temp as I explained above.