Very Cold Start

[rwtucker]

Anybody had any experience with that type of unit and how long it really takes to warm the engine?

Toward the beginning of this thread, I briefly mentioned a Plan B that I also lashed up for a small back country situation. It was a Coleman backpacking stove (Micro Max or similar; several models are available) with a chimney made out of a short piece of collapsing aluminum clothes dryer hose and safety wire for positioning. This system delivers a hot stream straight up the cowling with BTUs close to that of the 1,500 W electric space heater and dryer hose lash ups that many of us have had setting in our hangars for years. I was worried about carrying propane so I decided to carry used tanks with about 75% capacity remaining. I probably could have carried full tanks but this way I knew I was reducing the pressure a bit and, more importantly, testing the valve.

A very important factor in either the gel cell/inverter/Tannis or the Coleman/dryer hose configuration is a good cowling blanket and foam nose plugs. In very cold Wx, you will get nowhere without both of those. I carry a Costco padded quilt and use a bungee cord to keep it positioned where I want it. I have never had a situation where I could not get to starting temps (especially the barrels) in 30 minutes or so, often less. Oil is a tad slower to come up but I'll settle for 35 degrees oil whereas I want 45 degrees on the barrels.

[Gary]

Why not get a small gasoline generator? With the excess capacity you could also use a forced air electric heater hooked up to a duct to blow warm air up the cowling.

Yep. I've done that too on my Dakota with 1,350 lb useful and a roomy storage area. The forced air heater really speeds up the warming. On the other hand, I never felt like stowing a gas engine and fuel in the DA40's tiny cargo space. Too close and all that weight in the rear.

Together, the 7 AH gel cell, 400 W inverter, plugs & cable weigh less than 10 lbs and do not present any special safety hazard. A flea-weight 700 W 2-cycle portable generator weighs about 40 lb with fuel . . . and they don't start very well, sometimes not at all, in below zero Wx.

I would not fly with the generator. I would store it in the back of my truck. It's hard to get enough heat from a battery powered device.

[rwtucker]

. . . It's hard to get enough heat from a battery powered device.

Gary, as you suggest, it is impractical to try to run a forced air space heater via batteries; 1,500 watts at 12 volts is 125 amps, assuming the near 100% efficiency of tungsten coil heating and subtracting 35 watts for the fan. You would need a 1,500 W inverter and a couple of deep cycle Pb batteries to do the job with decent design specs. A portable generator might be lighter and perhaps easier to work with.

If you only want to pre-heat at your home base, a gas powered portable generator is a great idea. I have a small Honda that I have used in such situations. Even though it costs twice as much as the average generator. I like the Honda because of its metallurgy. You can store it for long periods of time without fear of corrosion. Since it uses an inverter, it also puts out a fairly clean pseudo sine wave, which makes is more suitable for powering delicate electronic equipment.

However, the scenario you are interested in solving is a bit different from what I was discussing. My Gel Cell/Inverter option applies only to those of us who have barrel and oil pan heaters (Tannis, etc.). Since these heaters transfer heat directly to the barrels and oil pan, they are much more efficient than the forced air fan model many of us have used for years. Other things being equal, the 250 W Tannis will heat your engine more efficiently (i.e, same or less time using 16% of the power) and better (i.e., applying heat exactly where it will prevent engine damage) than a 1,500 watt space heater. The bonus is that you can toss it in your baggage compartment to pre-heat on the return trip if you need to. The other bonus is a $50 total cost.

[cbrinton]

I just ordered one of these: http://smile.amazon.com/Earthquake-1161 ... ql_qh_dp_t

It seems to be the best combo I was able to find of price/power/positive ratings/weight ($285/700W/4.5 stars/21lbs). I think it will fit the bill. I'll carry it in my car/garage where it will be warmer and then carry it out to the plane when its needed.

I was intrigued by the Gel battery/inverter discussion and started looking at putting together the pieces, but unless Im mistaken in order to drive a 300w engine heater for 2 hours (which based on the Reiff website is what it would take to go from 22 to 46 degrees) it would require a 12V battery with 50AH. That seems like a lot of lead to be lugging around.

[rwtucker]

That is a great generator Chris. About half the weight of my old Honda 2000i which supplies mostly wasted wattage.

I have built a few variations of the Gel Cell packs we were discussing (different batteries, etc.). I built one with a deep cycle 24 AH AGM that weighs about 21 pounds (http://www.atbatt.com/csb-battery-12v-2 ... attery.asp).

As temps decline, I'm concerned first about barrel clearances (below 40), then oil viscosity (below 20), then bearing clearances (below zero). All of these are conservative. Studies suggest that you don't reach zero bearing clearance until around -20.

I have found that the oil can take awhile to catch up, especially for those who pack a full 8 quarts and keep pasting 3-1/2 of them on their belly. On the other hand, if you have good insulation (nose plugs and padded blanket sealed all the way around the bottom) you can get the barrels expanded enough in 30 minutes to take the stress off of the engine. The Tannis is only 240 W. That helps a little. If I were limited on AH capacity and starting in 20-30 degree Wx, I would consider powering only the barrel heaters.

[rwtucker]

Just saw this on sale today. Less than 5 pounds, 8AH, $18, free shipping. http://www.rakuten.com/prod/upg-ub1280- ... 13954.html

[BkFlyer]

Just saw this on sale today. Less than 5 pounds, 8AH, $18, free shipping. http://www.rakuten.com/prod/upg-ub1280- ... 13954.html

I would be a little wary of using that battery, or any non deep-cycle variety. I generally see that model used as a short-term low voltage backup supply in alarms and UPSs. Infrequently discharged, slowly and rarely completely. The quality is probably crap and I doubt you'd get many uses out of it with deep-cycles. Careful not to overload.

[BkFlyer]

That is a great generator Chris. About half the weight of my old Honda 2000i which supplies mostly wasted wattage.

This winter was pretty bad in the northeast. The fuel vaporization trick worked well for me, but starts were still very tricky. Power is not easily available at my field (and they really don't care).

My experience has been starting successfully and then waiting in the tie-down for 10 minutes until the oil temps were up past 95 for run-up. Given that I now know how long it takes to warm up the "bad" way, how long do you typically need to wait for the temps to come up with a generator & Tannis??

[rwtucker]

. . . how long do you typically need to wait for the temps to come up with a generator & Tannis??

It depends on OAT and insulation Adam. I carry two padded covers (Costco), foam nose plugs, and bungee cords to seal the entire nose. With this good insulation and 20 F OAT, I can get to a place where I'm OK starting (see other discussions on this) in 30 minutes. I haven't done much winter overnight parking on guest ramps this year. The one time I needed it, I packed an inverter and a garden tractor battery I had in the hangar. You are right that you may not get too many cycles if you discharge too far. On the other hand, these batteries and gel batteries are cheap. The battery experts tell me that the length of time a conventional lead acid battery sits in a discharged state is a big factor in suplhating. I try to recharge ASAP.