C85 Conversion Complete!

[astjp2]

Okay. Any other downside to running around at redline all the time?

I never said I flew that way all the time, but the airplane is capable, I flew out of Delta Junction a lot for several years and never had any problems. I would fly to chicken; circle, central, tok , Palmer, fai, anc, Merril, all over and if the weather was good, it I would fly 10 hours on a Saturday because I enjoyed it. I did have a weird vibe at 2300 with the old prop so I either had to cruise at 2150 or 2450 because I did not have a spinner to do a dynamic balance at the time. I have yet to fly the new McCauley. I was able to get a new Sensenich if I want to go ack to that one. Tim

[TC747paul]

Kerbs
That is one nice looking T-craft, I did the same conversion but added the starter after a near miss propping on ski's.
i think it makes a great plane even better.
Are those 8.5x6 tires?
Did you happen to note the oil temperature delta to ambient?

[Taylorcrafty]

6.5 gph or so

Okay. Any other downside to running around at redline all the time?

[astjp2]

6.5 gph or so

[Taylorcrafty]

RPM, I am running 2700-2750 and it was a sensenich, I have not tried the McCauley yet. The cruise prop would not turn RPM's, it dropped off at about 2600 with the 7446, the repitch made it a new airplane. The prewar airplanes are quite a bit faster for some reason which I believe is due to the angle of incidence, and mine has covered gear legs and a spinner which helps. Tim

What is your fuel GPH like cruising around at 2750? Is it a stock O-200?

[astjp2]

RPM, I am running 2700-2750 and it was a sensenich, I have not tried the McCauley yet. The cruise prop would not turn RPM's, it dropped off at about 2600 with the 7446, the repitch made it a new airplane. The prewar airplanes are quite a bit faster for some reason which I believe is due to the angle of incidence, and mine has covered gear legs and a spinner which helps. Tim

[Taylorcrafty]

Hey Tim,

How are you cruising at 120mph with that climb prop?

Only asking because I would love to make mine go faster.

My F-19 cruises at about 90mph (gps) at 2450RPM with the cruise prop.


Also, finally installed the fuel valves. Much better. Thanks!

Get the longest and flattest propeller you can get, I ran a 7443 with a o-200, I started with a a 7446, I gained a lot of climb and it can cruise 105 kias with the last prop I had. I am not sure what my current one will do as a swapped from a Sensenich to a McCauley. The marvel carb is also great because of having a mixture.

[PA1195]

To accompany Scott's welcome reference to Stromberg operation in #22 here's a similar brief on Marvel carburetors.

http://www.kellyaerospace.com/articles/Accessory_AMT.pdf

Gary

[PA1195]

As I age my low temp ops have decreased. I also fly less now as I've had almost enough of unexpected adventures. Things can happen quickly in real cold. Previously I'd fly a pre-heated FI engine and cockpit down to -50F but was careful about power applications. Carbed Lycomings would run ok for me to -40F but maintaining oil and cylinder temps were a concern. These small Continentals have me wary below -20F as they never really warm up and maintaining adequate fuel flow can be a challenge. Carb heat in cold can be used if carb icing is monitored. I've had cowl flaps and cooling air baffling on the FI and carbed Lycomings but not yet with the small Continentals.

Another thing is that Marvel carbs with accelerator pumps offer adjustable discharge volumes. The link from the throttle arm to pump piston can be altered by selecting one of three connection holes. The max discharge hole #3 is usually selected, but in warm climates less can be set.

Gary

[N96337]

Mine with the Stromberg was persnickity to start when it was really cold. That being said, I always figured it was a sign that it was too cold for me to be out flying. However, I don't have the long extended extreme cold spells that Gary has to deal with on a regular basis. I'm kinda a fair weather guy. If my circumstances were different, I'd probably go a different route if it gave me trouble.
John

[PA1195]

Not intended to drift Kerb's thread, but here's some disconnected comments to agree or disagree with.

Warm climate/engine and cold climate/engine ops require different air/fuel conditions. And from the automotive world but could logically extend to aviation > https://www.waybuilder.net/sweethave...Num=2&modNum=3

Here's some further info on methods to support the phase change of fuel from liquid to vapor: https://www.hotrod.com/articles/unde...is-hard-to-do/

Most would agree from experience that cold engine components and fuel require a richer fuel mixture (even if only temporary) to start and run properly. Chokes, primers, injectors, and accelerator pumps provide the excess fuel as required. There is also a transitional lag in carburetors between air flow and fuel flow...it takes time for fuel to be discharged into a rapidly increasing air stream if the throttle is quickly opened. As a result throttle movements in flight should be measured unless additional fuel can be quickly available. Alternatively, warm or heated induction air creates a less dense/lighter weight air which alone creates a richer mixture. We add carb heat to both discourage carb icing and maintain that richer mixture when needed.

For liquid fuel to provide combustion it experiences two transitional stages-initial raw fuel to fine particle atomization and then vaporization and mixing with the intake air (the optimum gaseous air/fuel mixture of around 12.5:1 +-). Raw fuel burns poorly when cold as it's the vapors from the fuel that quickly oxidize/ignite. As ambient temps lower, cold unheated intake air gets heavier while fuel flow and weight remains relatively constant. That's controlled by the number of the carb's air mixing and diameter of the fuel jet orifices. Then there's fuel vaporization rate controlled through seasonal blending...more for auto fuels than aviation which is stable.

As air temps decline the engine progressively runs leaner as evidenced by increasing EGT and eventual loss of power as the A/F ratio exceeds optimum and goes lean. As temperatures chill, carbureted engines typically require larger orifice jetting to maintain the desired air/fuel ratio and performance, or preheated air is added. Temperature sensing fuel injection can be designed to compensate.

So how does all this relate to engine hesitation or potential stoppage in cold climates? Any time the induction system is excessively cooled during a power-reduced descent there's a potential for a lean air fuel ratio condition. Continental engines without the oil sump heat provided to the induction system by Lycomings are more susceptible. Ensuring the idle mixture is set rich for expected air temps (results in the approximate +50 rpm rise at idle cutoff we set) and having an accelerator pump available to quickly add fuel can minimize a power response problem in my opinion and experience.

Gary

[astjp2]

In the process of the gas being discharged out of the nozzle, it cools the intake air and when it gets too cool, the fuel droplets fall out of suspension, carb heat helps reduce this phenomena. Lycomings have their induction air go through the oil pan, it make for a consistent air charge and therefor less issues when flying in cold weather compared to a small continental. Tim

[Scott]

Another issue in colder weather is fuel condensation in the induction system.

I and others have had that happen primarily on initial startup and on descents to landing. Carb heat can help keep the fuel from condensing to a point, but low power produces less heat which eventually dissipates and the help diminishes. There are lagging /covering kits that are intended to prevent overcooling of the induction tubes and oil sump but typically the induction spider and cylinder intake elbows remain exposed to cold air.

No carb is perfect and in reasonable climates I'm sure a properly maintained Stromberg works as well as intended.

Gary

Interesting. I have not heard about this before. Is this a mogas thing or 100LL as well? The latter of course being designed to include operation at altitudes where temperature is always in the low double digits. Our engines also have the induction system in the the relatively warm zone of the cowling i.e. downstream of the cylinders and their dissipating heat. The lower pressure in the induction system would also tend to lessen the likelihood of condensation of fuel.

Also I was under the impression that gasoline does not really vapourize in an induction system but "atomizes" i.e. the state of the fuel-air mixture is tiny droplets of liquid suspended in air. So is this actually condensation of gasoline in the induction system, or some form of coalescance?

I can understand water condensing out of the air (and fuel if it has ethanol or other contamination) in the induction system, this is the essence of carb icing, but can't really get my head around condensation of gasoline (which has a flash point of -43C) and is mostly in the liquid state already. Would like to understand more if you can elaborate or point me to and article about this.
Thanks
S

[Kerbs]

I wasn't looking to debate the merits of which carburetor. Just simply stating in my case, I am enjoying the marvel carb more than the stromberg I had previously. That said, I would not have replaced the stromberg on my A65. The only reason I replaced it on the C85 was because I needed a carb and elected to go with an overhauled Marvel vs tracking down and overhauling a stromberg. Obviously strombergs work, these planes have been flying a long time on them, a lot with little maintenance to the carb over the years.

[PA1195]

Another issue in colder weather is fuel condensation in the induction system. Depending on air and engine temps, in-cowl airflow, and baffling fully or partially atomized fuel in the cylinder intake air can condense and attach to nearby cold metal. When that happens the air fuel mixture goes leaner than desired and proper running can become a problem.

I and others have had that happen primarily on initial startup and on descents to landing. Carb heat can help keep the fuel from condensing to a point, but low power produces less heat which eventually dissipates and the help diminishes. There are lagging /covering kits that are intended to prevent overcooling of the induction tubes and oil sump but typically the induction spider and cylinder intake elbows remain exposed to cold air.

No carb is perfect and in reasonable climates I'm sure a properly maintained Stromberg works as well as intended.

Gary