frankh

frankh

Well Known Member
Well its that time of year when the first frost up here in Western Oregon has been predicted. I seem to remember from my engine manual that preheating is required below 40F.

I view this as another money saving opportunity. This is typical of engineers, not that we're cheap per se'e, just that every challenge is an opportunity to optimise the feature set and minimise cash outlay all it once.

Anyway, I have my propane shope heater that is the 6 to 8" tube with a propellor fan in the back and a burner.

The obvious solution is to get some ducting and hook the tube directly to the cowl inlets (or outlets) and fire it up...Minimal cash and resuses and existing tool...Cool...Downside is that this is a naked flame.... so not ideal but still difficult to ignite something as the airflow is pushed away from the heater. The other potential problem is that propellor fans do not usually make much pressure, so adding a resistance like duct work and the engine cooling systems which is a high pressure loss (at high speed anyway) may make the heater run ROP..:)..Or not at all. I note that proper preheat machines use a backward curved centrifugal fan...These make much more pressure at low flow.

The other idea is to use a $150 tent heater...This is an indirect heater with flex dryer ducts...You could even carry it with you for Winter camping trips as long as you don't mind propane cylinders on board. This also has a prop fan I believe but the flow rate would be pretty small as its only ay 4" fan...Thus flowrate is low and the pressure drop thru the engine drops off with the square of the flowrate...So it might work.

Anybody tried either of these ideas and lived to tell us about it?

Thanks

Frank
 
We used a 1500W ceramic heater ... with about 10 feet of aluminum flex 4" dryer vent. I taped the dryer vent hose to the front (hot side) and the back (intake side) of the heater with aluminum tape ... one hose goes into the right side cowl and the intake on the left side of the cowl. The heater sits on a latter so it?s off the ground and close to the front of the airplane. On high it @ 32deg F outside air temp ... it only takes a couple of hours to for the CHT and EGT probes to reach 70deg F, oil will reach 50deg F. I stole the idea from Sporty?s catalog preheated ? mine is SO MUCH CHEAPER ? maybe $50.00 total in parts. We use a timer ? just swing by the night before your trip ? plug in the timer and setup the times. It's also easy to take with you on a trip.
 
Nice idea and portable

But a little on the small side. I would really like a solution that will preheat in about the time it takes me to finish my preflight and finish my Starbucks...

1500W is around 5100BTU/H. My blast tube heater is about 85,000 (I think). Of course one cannot recirculate the warmed air like you can with the electric heater as the combustion air will run out of oxygen.

I do like like spirit of cheapness in your solution however...:)

Frank
 
I too have considered using a "torpedo" type heater but I am concerned about the open flame. Two winters ago my neighbor burned his house to the ground using one of these while he worked on a snowmobile in his garage.

Then there is a side of me that asks if preheating is as necessary as we have been led to believe. I belong to a flying club in Michigan. We are a very old club and our engines have always made it to TBO without a problem. We didn't even own a preheater until last year. It was purchased under protest by some of the older members who stated that based on historical data, it wasn't necessary and was a waste of money.

I personally like the idea if preheating, but data is data and the club's data says it's not necessary.
 
Open flame

Yes the open flame thing at first appears to be a concern but it would actually be pretty hard to ignite fuel with one unless fuel vapours gets sucked into the inlet of the heater....Maybe one could mount it 2 feet off the ground on a stand. Thats why most building codes require electrical outlets in garages to be 18" off the ground.

I wonder also if the FBO type preheaters are an open flame type???

Frank
 
frankh said:
But a little on the small side. I would really like a solution that will preheat in about the time it takes me to finish my preflight and finish my Starbucks...

1500W is around 5100BTU/H. My blast tube heater is about 85,000 (I think). Of course one cannot recirculate the warmed air like you can with the electric heater as the combustion air will run out of oxygen.

I do like like spirit of cheapness in your solution however...:)

Frank
Click to expand...

You do want to be careful not to burn the inside of your cowl ... our electric solution does help to control this over temperature problem, with it's thermostat and tip over protection. We learned to set the thermostat to about 80% of max ... this allows it to cycle on and off, without tripping the over heat safety. If the over heat safety kicks in the unit will not turn back on until the switch is turned off, then back on. I think this happens because we are recycling the warmed air back into the unit. But you are right, it?s a two hour process if you want to just go flying ? sometimes last winter, at lunch I would run over and plugged in the heater just to go flying that night.
 
Reiff

Hi again,
We bought a Reiff pre-heater and glued the hot pads to the oil sump with the supplied epoxy. Just plug it in to an extension cord the night before a flight and your oil/pan/carburetor and cylinders will all be toasty in the morning and the oil will be 85 degrees hotter than ambient. A blanket over the cowl as well makes it even better. No chance of fire either.

http://www.reiffpreheat.com/product.htm

You won't regret it Thick, cold oil doesn't sling off the journals very well and the cylinder/piston wear on startup is accelerated. We have our male pigtail near the oil door.
 
I believe a good solution, especially for those who live a long ways from the hangar, is to put a thermostat on the end of an extension cord, and put it inside the cowl through the oil door. Plug the sump and/or cylinder electric heaters into it, and blanket up the cowl. I set the thermostat for 70 degrees F, and leave it on all the time during the winter. The engine never knows it is winter, and very little energy is used to keep the temp at 70. I use about $10 per month of electricity doing this, about what it costs to drive to the airport once to plug it in or turn on a timer.

I don't have data regarding what starting a cold engine does or doesn't do, but if one has a reasonable sense of hearing, you will hear the oil pump growling until the oil is about 60 or 70 degrees. The growl is cavitation, and cavitation is causing some amount of wear.
 
Alex:

I see at Reif's website that their sump heater comes with a thermostat. Is it necessary to include a thermostat like you describe on the extension chord end?

Rief has the thermostat remotely mounted to the sump away from the heating elements.


Regards,
 
Ahh I remember now...

Apparently your not supposed to leave sump heaters pluged in all the time for fear of evaporating moisture from the oil which then condenses on the camshaft etc.

Hmm...Its hard to imagine that you could heat the enitre engine continuosly without burning a lot of heat...Would the engine be heated uniformly with a heater in the cowl, sufficiently so as not to replace cold start issues with more corrosion?

Frank
 
Solve Moisture Problem

frankh said:
Apparently your not supposed to leave sump heaters pluged in all the time for fear of evaporating moisture from the oil which then condenses on the camshaft etc.

Hmm...Its hard to imagine that you could heat the enitre engine continuosly without burning a lot of heat...Would the engine be heated uniformly with a heater in the cowl, sufficiently so as not to replace cold start issues with more corrosion?

Frank
Click to expand...
If the air in your engine is dry, you won't have to worry about condensation. I have no connection with this product except that I own two of them, one for each airplane. I have seen proof they work very well. Write for details.
http://www.flyingsafer.com/2039.htm
 
light bulb?

Frank -
We lived in northern Nevada for 15 years where anytime of year it could get down to freezing, and our hangar was not "wind proof." We saw two methods work without fail. The first was the solution of the ceramic heater, set on a stand and hooked up to large aluminum ducting (think dryer duct) that we insulated. The end next to the heater was an aluminum piece we bought that was round at one end and shaped like a squarish funnel at the other. We simply set that in front of the heater and set the thermostat on the heater to come on at 50 or so. This worked without fail and cost us 30 dollars a month during the coldest months (routinely 20F).
Our hangar neighbor used a 75W light bulb clipped inside the one of the lower cowl ducts. The other lower cowl duct opening was closed with a piece of foam. The light bulb was left on and the engine compartment was kept to a good temperature.

Aviation Consumer did an comparison article on engine heating and preheating a few months ago and concluded that the light bulb method, (probably used since light bulbs and airplanes have coexisted) was about as good as any other method of keeping an airplane engine ready to start.

The commercially manufactured engine heaters are pretty much like gas clothes dryers without the drum. Actually they are exactly like your floor model propane blower, just ducted and on a roller cart. They don't cost a lot to operate, but it always seemed like a pain and depending on how bad the weather was, sometimes I just didn't want to stand around with a lout burner heater. I don't know why, but it seems like it would be better for the engine to keep all the parts at pretty much the same (ready to go) temperature to ease starting, rather than try to heat them immediately. Plus, the light bulb makes it easier to have a look around inside the cowl before you fly...
 
painless said:
Alex:

I see at Reif's website that their sump heater comes with a thermostat. Is it necessary to include a thermostat like you describe on the extension chord end?

Rief has the thermostat remotely mounted to the sump away from the heating elements.


Regards,
Click to expand...
I believe Bob may have gotten the idea from me to put a thermostat in the system (away from the heating elements). I recall discussing the idea with him about 5 years ago. Maybe he already had it in the works, I don't know or care. All that is important is that the thermostat be measuring and controlling the temperature inside of the cowl, so if his system does that, one does not need the additional thermostat.

Regarding the discussion about continuous heating not being good for cams, etc., it would only apply if the cylinders or top of the engine were remaining cold enough for moisture driven out of the oil to condense. This concern is irrelevant when the whole inside volume of the cowl is uniformly heated.
 
Welcome back from our convict colony!

I think you got the most elegant solution there Bob, little high on the running cost but the power in my rental hangar comes as part of the deal....:)

No I would offer more money of course, darned ethical standards are spendy..:)

Frank
7a ....30.3 hours out of 40
 
Question for Sam

Sam Buchanan said:
My RV-6 has enjoyed warm winters in the hangar due to continuous wintertime sump heater operation since 2000. Here are my notes and observations:

http://thervjournal.com/cold.html
Click to expand...


What power is your old style silicone sump heater rated at?

I have 2*50W hater pads on order ($80 for the pair from Wolverine) and I'm wondering if I have enough heat?

Cheers

Frank
 
What power is your old style silicone sump heater rated at?
Click to expand...

I don't recall and it appears Reiff has pulled all technical info about the HotPadd from his website. Apparently the HotStrip which replaced the silicone pad heater is rated at 200W. The wattage needed will depend on climate, expected ambient temps and how efficiently the heaters transfer heat to the engine.
 
Last edited:
Hot Padds

I've got the Hot Padds and have only used them once so far. It got down into the low 30sF overnight but my CHT was at 65F when I got to the hangar in the morning. No blankets or anything.

It's just very easy to plug it in and not hassle with heaters/blowers etc. I'll try it sometime in the morning and see how long it takes to warm a cold engine. The Dragon types might be much faster if you're in a hurry.

John
 
Pre-heat?

I know this won't be too helpful for Lycoming owners but with the Subie, EFI and 5W50 oil, we don need no stinkin' preheat. Even up here in the Great White North. :p

Nine blades and she fires like clockwork. Every time, every temperature. The magic of newer technology...
 
In cool (not cold) weather, I usually get to the hangar, plug in the hotstrip, do my preflight, clean the windshield, unplug the hotstrip and start the airplane.

No, the oil probably isn't up to temp, and the cylinders, crank, etc. are definitely still at ambient temperature, but the oil pumps more easily than if it was at ambient. Best of all, the carb is warmer and the fuel vaporizes much more easily, making starting very easy.

If it is <35F, I usually set a timer to turn the hotstrip on 2 to 4 hours before I plan on being at the airport. I have a packing blanket I use to cover the cowl, and I use old towels in the air intakes. The engine is nice and warm after a few hours. Often, I see 100F oil temperatures on start-up.
 
Update on wolverine preheat

frankh said:
What power is your old style silicone sump heater rated at?

I have 2*50W hater pads on order ($80 for the pair from Wolverine) and I'm wondering if I have enough heat?

Cheers

Frank
Click to expand...


About a week back I installed my 2*50Watt silicone pad heaters from Wolverine on my FF sump.

After running a couple of days with a simple foam plug in each inlet my oil temp and CHT's were 25F above ambient temperature...In other words the engine is heated pretty evenly to 75F when the hangar temp is 50F.

Pulling out my handy psychrometric chart I can confirm for this part of the world that condensation within the engine is very unlikely.

Here are a couple of examples.

Mid Winter 30F OAT... means the engine block will be 55F.
Now to condensate inside the engine (55F at 100% RH) means the daytime temp would have to be 76F at 50% RH.

Here at least there is no way that you will get 76F in the daytime but 30F overnight.

Lets take a Fla Summertime example....I.e daytime at say 90F at 80%RH. In this case the nighttime temp would have to drop to 60F with the same heaters installed in order to get condensation inside the engine.

Of course I don't live in FLa so the actual conditions may not be appropriate but it gives you an idea of the size of heater required for your conditions.

Note i also have a fiberglass plenum so this may keep the cylinders a little better insulated than standard.

Enjoy

Frank
 
I forgot to mention

According to the engine manual you don't want to start below 40F....Quite simply, 100W of heat gets you 25F or temp rise in my installation so its good down to 40-25= 15F.

But at 15F I'm staying by the fire...:)

Frank
 
Coooooold start

I took my RV4 up to Ft Collins, CO this week (FNL) and had a bear of a time getting it started Thursday morning with the outside temp @ 35 degrees. $80 for a hanger was too pricey for just one night!

Next time I'll go to the nearby Hooters for an early lunch and wait for it to warm up.

I made it back to San Antonio in only 5 hrs and one fuel stop!

dsc07946et2.jpg

On the Ft. Collins ramp.

Bob
N96111C
O-320-E2A
150 hp, Catto prop
 
Last edited:
Recommendations from Lycoming

In not arguing that you should not pre heat, I?m sure it is fine and will do no harm, but is it necessary? Below is what Lycoming recommends for pre heating in there cold weather operation article found on there sight. I use 15-50 and go flying in the thirties in the winter with no problems and no pre heat and according to Lycoming I am operating well in limits.

?In cold weather, preheat is another factor that must be considered prior to starting the engine. There are specific guidelines in Textron Lycoming service instructions which establish when preheat should be used, but how much, or the method of preheat is generally left to the good judgment of the pilot or maintenance person doing the preheating. Use of the heated dip stick is not recommended by Textron Lycoming, although most other methods are considered to be satisfactory. For most Lycoming models, preheat should be applied anytime temperatures are at 10oF or lower. The exception to this rule is the 76 series models that include the O-320-H, and the O/LO-360-E. These engines should be preheated when temperatures are below 20o F. It is recommended that these guidelines be followed even when multi-viscosity oil is being used. In addition to hard starting, failure to preheat the entire engine and oil supply system as recommended may result in minor amounts of abnormal wear to internal engine parts, and eventually to reduced engine performance and shortened TBO time.?
 
I have a couple times started my engine (O360) when the entire engine was in the 30F range, where no preheat was available. It fires off just as quickly, but the sounds made are a bit different than what I hear when the engine is at 70F. I don't think the "new" sounds are an indication that the engine is happy, but I don't know that damage (albeit small) is occurring either. But, the sounds of a cold engine trying to pump 20-50 semisynthetic oil just isn't good, and I prefer to not do it. The sounds it makes resemble those made upon the first startup after an oil change, before the oil has filled the filter. For $10 or whatever worth of electricity per month it takes to keep the engine at 70F, I get some peace of mind.
 
Last edited:
Peace of mind

Yup thats probably is what we are buying. The other thought is that urban legened has it that 80% of an engine's wear occurs at start up...Cold thick oil has got to be worse than warm and thinner.

The other thing for me is if I don't manage to get to the hangar engine's weekly workout, keeping on the heat will stave off any corrosion.

As to oil circulating thru a new oil filter, I don't know about you guys but when I put a new filter on I drop out the bottom plugs and crank it without compression until I see oil pressure.

Once again does it do any good?...Who knows, but I sure feel better...:)

Frank
 
painless said:
Alex:

I see at Reif's website that their sump heater comes with a thermostat. Is it necessary to include a thermostat like you describe on the extension chord end?

Rief has the thermostat remotely mounted to the sump away from the heating elements.


Regards,
Click to expand...

Alex was referring to a T-stat under the cowling that monitors the air temp and keeps the engine compartment at 70F. The T-stat that you are referring to is bonded to the oil sump to limit the oil temp to about 150F.
 
AlexPeterson said:
I believe Bob may have gotten the idea from me to put a thermostat in the system (away from the heating elements). I recall discussing the idea with him about 5 years ago. Maybe he already had it in the works, I don't know or care. All that is important is that the thermostat be measuring and controlling the temperature inside of the cowl, so if his system does that, one does not need the additional thermostat.

Regarding the discussion about continuous heating not being good for cams, etc., it would only apply if the cylinders or top of the engine were remaining cold enough for moisture driven out of the oil to condense. This concern is irrelevant when the whole inside volume of the cowl is uniformly heated.
Click to expand...

Our system does not have such a thermostat to control the under cowl temperature. That can be easily and cheaply done by using this http://www.reiffpreheat.com/Thermostat.htm
 
Russ McCutcheon said:
In not arguing that you should not pre heat, I?m sure it is fine and will do no harm, but is it necessary? Below is what Lycoming recommends for pre heating in there cold weather operation article found on there sight...
Click to expand...

Keep in mind the Lyc preheating recommendation is the minimum. Just like I change my oil a lot more often than they say I have to, I also like to preheat more than they say. That advice applies no matter what type of heater you choose to use.
 
If one listens carefully to the engine when started cold, 30 to 40F, for example, on some engines one can hear the oil pump cavitating until the oil is around 50F or so. I have talked to others who have also noticed this - it is a background growl similar to that of a car's power steering system low on fluid. Cavitating means some wear is occurring on the pump gears, and I prefer to not hear it.

Bob, thanks for clarifying what your offer in terms of thermostats.
 
If one listens carefully to the engine when started cold, 30 to 40F, for example, on some engines one can hear the oil pump cavitating until the oil is around 50F or so. I have talked to others who have also noticed this - it is a background growl similar to that of a car's power steering system low on fluid. Cavitating means some wear is occurring on the pump gears, and I prefer to not hear it.
Click to expand...

Yep, I've heard it on the very few times I've started my cold engine unpreheated, and I don't like it...
 
You must log in or register to reply here.