Question Using an engine pre-heater on a piston engine

[Cubonaut875]

Tsquared observation on the metal prop sucking heat from the engine is spot on also. The Trailblazer is composite so it is not as good a heat conductor as the Borer metal prop. I covered my prop on my previous plane while I preheated.

 

[Cubonaut875]

The Reiff will just keep heating unlike the Tannis that will go to I think 50 or 60 degrees over ambient. I, like you, wait to do run up at 125 oil temp. It usually dosen't take that long. If you take the moving blanket and use a couple rachet straps to fully wrap it around the cowl, I'm sure it will be as good as the pricy cover.

 

[Neal]

A quick google search:

According to information available, a Reiff engine heater typically aims to raise the engine oil temperature around 80°F above ambient temperature, with a thermostat limiting the maximum oil temperature to around 150°F, effectively capping the engine's maximum heated temperature at that level.

 

[Neal]

From Aircraft Spruce but not sure if it's the same Reiff product:

OPERATING INSTRUCTIONS​

To use the heater, just plug it in! The recommended procedure is to place a blanket over the engine cowling and prop blades, and foam rubber plugs in the front air inlets to minimize heat loss, and plug the heater in several hours before engine start, overnight for maximum heating. Without covering, just the oil will be heated and very little heat will transfer to the rest of the engine, just like if you try to bake something with the oven door open. The thermostat will limit the engine oil temperature to 150o F. The heater is built for continuous use, but leaving it on continuously may create condensation inside the engine which may cause internal corrosion. You may use a timer, thermostat, or remote telephone or beeper activated switch to turn it on in your absence. These items are available from Reiff Preheat Systems or others. In remote areas without electricity a DC/AC inverter can power the heater from a car or truck, or a portable generator can be used. Some generators are small and light enough to be carried in most aircraft. Always use a grounded outlet for safety. For the best protection against shock, use a ground fault type outlet or extension cord. During each annual or 100 hr. inspection the heater system should be checked to make sure it is secure, undamaged, and functioning. With the engine compartment sealed, typical maximum under cowl temperatures will be about 35o - 45o above ambient (no wind), depending on the heater’s wattage. For faster and warmer preheats, the Reiff HotBand Cylinder Heater System may be added to your engine at any time. When this system is used along with the oil heater, under cowl temperatures will be about 70o to 90o above ambient, and the preheat time will be significantly reduced. It also heats the engine more uniformly, reducing the risk of condensation.

 

[Neal]

Last one for Reiff:

Aircraft preheat FAQ's

 

[Neal]

1. Does your system have a thermostat?

There are two reasons to use a thermostat. One is to turn on the preheat system if the ambient temperature falls below a certain level. Our system does not include such a thermostat but they are available from various sources.

The other reason is to prevent overheating while the engine heater is operating. Our cylinder heaters do not have a thermostat control, but some of the oil heaters do. While the engine is running the cylinder normally runs about 300-350oF. Our cylinder heater heats it about 70-90o over ambient, so there is no danger of overheating anything and, therefore, no need for a thermostat.
Our oil heaters are sized to raise the temperature of the oil up to 100o above ambient, and a thermostat on some systems further limits the oil to about 190o actual. This means in normal winter use the thermostat never cycles - it just stays closed (on). This design approach gives you the benefit of a thermostat controlled maximum oil temperature, without the disadvantage of limited thermostat life due to constantly cycling on and off.
One brand does not use a thermostat and criticizes them because they have a finite life expectancy (100,000 cycles for ours) and when they fail they can fail closed (although this is rare - they almost always fail open) and allow the heater to run continuously and overheat the oil. This is a valid concern with some other brands of oil heaters. It is not a concern with ours because our thermostat does not cycle, and because our oil heaters are sized so that they will not overheat the oil even if the thermostat fails closed and the heater runs continuously. In fact, we had to demonstrate this to the FAA to get PMA approval.
The other brand's approach with their multi-point system is to use a low wattage oil heater with no thermostat, which heats the oil 30-50o above ambient. We feel this is not enough heat in cold weather. More heat thins the oil for better circulation and lubrication on start-up and reduces your engine warm up time. A higher wattage oil heater will also give much faster preheating. We believe more heat is better, as long as the oil temp remains at a safe level.
Another thing to be aware of with the other brand's approach to oil heating is that on many engines they use a submersible probe heater in an oil drain hole. We considered using this type but decided against it. Even though it's only 50 watts, the watt density (watts per square inch) is very high due to the small surface area of the heating element. We are concerned about the possibility of the surface temperature exceeding 300o, which would overheat and damage the oil. Our 4" x 1.5" element has more wattage but much lower watt density, so gives more gentle heating of the oil without risk of scorching.

 

[Cubonaut875]

You are a wizard and my best resource! Usually when I turn on the IBBS when I start it at 2:00 am with 20F OAT the oil temp is up to 80, which I think is good since when it's summer and I don't preheat, it usually starts at 70 to 80F. I just want the engine to think it's summer.

 

[Cubonaut875]

That is an interesting read from Reiff. It reminds me of reading a study paid for by a drug company on their drug. I think I'll read it a little more carefully

 

[Cubonaut875]

I think I'm going to Infrared the temp in the engine compartment next time I preheat, check how warm it actually is.