What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Question about engine pre-heaters

AlpineYoda

Well Known Member
Patron
While first flight is still months away for me, a friend suggested I install an engine preheater like the E-Z heat system while I have easy access to parts of the engine that will later be a bit more crowded.

Preheating the engine with something that is remote triggered makes a ton of sense to me. I've always been a little afraid of those portable propane heat blowers that light one try in five and always seem to be 10 seconds away from an explosion.

So, my question - while wrapping part of the engine to heat it up makes a lot of sense on a cold night, how does that "blanket" let the engine stay cool once warm or on a hot day? Does something big enough to preheat a -540 also prevent air flow for cooling in flight? Do you remove it for May - September? Or do the parts it heats up not require as much cooling airflow?

And what do people do with the plug? Add an access door to the cowl? Route the plug to the air inlets? Route the plug to the oil door?
 
My RV-9A has a Rieff Turbo XP preheater, and it's on a remote switch that uses LTE/IoT...so I can activate it and other electrical devices from an app on my cellphone (Switcheon). It's great service, very cost-effective, and excellent customer service.

The Rieff has a male plug that is secured to the intake...easy to plug or unplug. Heat the the engine up very effectively. It uses cylinder bands and an oil pan heater.


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

https://switcheon.com/
 
There are two types of preheater blankets. One type is a basic blanket that has insulation qualities. The purpose of this type of blanket is to increase the effisiciency of a pad type heater by keeping applied heat from disipatiing into the atmospehere and reduce the effects of any wind. some users put them on top of the cowling, some inside, on top of the cylinders.

The second type has the insulative properties of a blanket plus the addition of electric wires which work like any other electric blanket by supplying heat. It wouldn't make sense to cover your cowling with one of these but there would be some benefit to putting it directly on top of the engine.

Some users report removing the engine's cowling and wrapping it in a blanket but in my opinion, by the time the blanket is removed and the engine is re-cowled, you have lost any advantage the blanket provided.

The pad type engine preheaters are my favorite method of applying engine preheat. they are fast, light weight and easy to use. The McFarlane Safe Heet is my favorite. I believe it preheats your engine quicker than any other unit out there. I mount the plugs where-ever is most convenient; either the oil door, vents, cowl flap openings or the bottom opening of the cowl.
 
Reiff

I have the Reiff system, one pad heater and band heaters on the cylinders...hooked up to a wifi switch. Works great.
 
Tanis says that when preheating we never want oil temps warmer than your cylinders. It has to do with water evaporation during preheat. When the water evaporates from the oil it will condense onto a cooler surface. It will travel up to the cylinders and condense on them unless the cylinders are warmer than that oil temp.

This video linked below is done by Tanis. At about 14:20 though about 17:00 they talk about this and why it's important. So, I guess I favor a Tanis system that places the heat source in the cylinder head over Rieff that does not directly warm the cylinder head.

https://www.youtube.com/watch?v=Qw5OZcSDYwE
 
Thanks for all the responses so far - per the other part of my question - for the cylinder head systems, doesn't something that is capable of warming the cylinder head also block airflow when you need to cool the cylinder head in flight, especially on a hot day? I don't want to solve one problem (cold winter engine) and cause another one (overheating engine in flight).

Thanks!
 
As I note you are in Colorado, you have cold, dry (low humidity) winters. For our engines, such cold storage is advantageous toward reducing internal engine corrosion.

I suggest that if you use any engine heater, you use it only just before flight, never leave it plugged in.

I recommend Rieff engine sump heaters. These do a nice job getting oil temp up to engine start conditions. The secondary effect is the rising heat does do some pre-heat of the rest of the engine.
https://shop.vansaircraft.com/cgi-b...-360-249&browse=engines&product=engine-warmer

As has been mentioned, heating the oil sump can cause moisture to be driven off - that moisture condensing on the upper, cooler areas of the engine (e.g. camshaft). As you only use the heaters just before engine start, this is not a concern. I use a simple WiFi on/off switch to turn on the heaters before I walk down to the hangar.

Carl
 
Thanks for all the responses so far - per the other part of my question - for the cylinder head systems, doesn't something that is capable of warming the cylinder head also block airflow when you need to cool the cylinder head in flight, especially on a hot day? I don't want to solve one problem (cold winter engine) and cause another one (overheating engine in flight).

Thanks!
Review the Rieff website. Their preheater uses heating bands around the base of each cylinder, and a heater pad in the oil sump. Doesn't block anything. That system ought to be just as simple to install on a competed airplane as it would be on one under construction.

I wouldn't leave my Rieff preheater system on all the time and I never use it in the summer. I think that's unnecessary. I warm it up starting 4 -12 hours before a flight if the ambient temp are colder than about 40 degrees.

There are two ways to keep the engine temps in storage at temps that are above the dew point....either keep a heater on it all the time, or don't keep it heated...instead keep the humidity in the crankcase low. I only use the pre-heater for pre-heating. I (try to) abate corrosion by keeping the plane on a dehydrator. Pumping in air 24-7 with a humidity of about 10-12%. The dehydrator I built cost me about $45. It takes about one minute to plug to output hose into the oil dipstick tube.
 
Last edited:
As I note you are in Colorado, you have cold, dry (low humidity) winters. For our engines, such cold storage is advantageous toward reducing internal engine corrosion.

I suggest that if you use any engine heater, you use it only just before flight, never leave it plugged in.

I recommend Rieff engine sump heaters. These do a nice job getting oil temp up to engine start conditions. The secondary effect is the rising heat does do some pre-heat of the rest of the engine.
https://shop.vansaircraft.com/cgi-b...-360-249&browse=engines&product=engine-warmer

As has been mentioned, heating the oil sump can cause moisture to be driven off - that moisture condensing on the upper, cooler areas of the engine (e.g. camshaft). As you only use the heaters just before engine start, this is not a concern. I use a simple WiFi on/off switch to turn on the heaters before I walk down to the hangar.

Carl

Same here, the oil sump heater does a very nice job heating up the entire engine. I also purchased and installed their oil cooler heater as I don't usually leave it on long enough to truly heat the whole engine compartment.
 
Save yourself a ton of money and installation time/complexity. An EZ heat pad will warm the oil and engine. They are about $150, don't take up any space, and work fantastic. I have had them on 5 airplanes. I have a cellular remote switch (no WiFi in my hanger). I turn it on 3 hours before a flight and the whole engine is warm to the touch when I get to the hanger. If it is really cold out I put it on when I go to bead for an early morning departure.
 
Thanks for all the responses so far - per the other part of my question - for the cylinder head systems, doesn't something that is capable of warming the cylinder head also block airflow when you need to cool the cylinder head in flight, especially on a hot day? I don't want to solve one problem (cold winter engine) and cause another one (overheating engine in flight).

Thanks!

It sounds like you are thinking that the preheat system somehow blocks the cylinder cooling fins and thereby affecting engine cooling. No fixed engine preheat system does that. A blanket is commonly used by many of us to keep the installed crankcase oil pan resistance heaters, and/or cylinder base heat bands generated heat, inside the cowling area, making it a warm environment for the engine. It is a simple blanket, liberated from your house (don’t tell your wife), and thrown over the cowling to keep that heat in. It works great, does a wonderful job, and is stored (hidden) during the warm season. The installed, fixed oil pan, and/or cylinder band heaters have no affect on engine cooling, and of course are only used when the engine temperature is below your threshold. Controlling these heaters remotely is a big plus.
 
Save yourself a ton of money and installation time/complexity. An EZ heat pad will warm the oil and engine. They are about $150, don't take up any space, and work fantastic. I have had them on 5 airplanes. I have a cellular remote switch (no WiFi in my hanger). I turn it on 3 hours before a flight and the whole engine is warm to the touch when I get to the hanger. If it is really cold out I put it on when I go to bead for an early morning departure.

+1

I put two 250 watt stick on heaters on the oil sump of my 540. I usually block the cowl inlets and put a moving blanket over the cowl. In 2-4 hours, oil is 70* and cylinders are a good delta above ambient. I used generic heater pad that cost around $25.

Larry
 
The reason I like the sump heaters, such as Safe Heet is that the point of pre-heating a engine is to ensure oil flow throughout the engine immediately at start-up. Remember that most cylinder walls receive their lubrication from what flies off of other moving engine parts. (called splash lubrication) Even though cold oil is forced into crankshaft and camshaft bearings by the oil pump, it is hard for cold oil to be "splashed" around the inside of the engine for lubrication. The lack of lubrication leading to accelerated wear of your engine.

Most of today's pad type heaters that attach to engine oil sumps are fast and efficiently heat engine oil in a short amount of time. It is not necessary to leave the pad heaters on any longer than necessary, typically 30 minutes should do the job. A blanket can help with this but they are not attached to the airplane and are removed before flight.

To my way of thinking, aircraft engines are designed to be "air cooled", that is they dissipate heat rapidly through their cylinders, especially their heads. It seams to me that putting a heater in the cylinder head is not the most efficient way to heat the engine.
 
And what do people do with the plug? Add an access door to the cowl? Route the plug to the air inlets? Route the plug to the oil door?

I've installed 2 of these in my airplanes and 3 or 4 more for others. I like to run the cord to the oil door using adel clamps. I wrap the excess length around the oil dipstick tube. Easy to reach in and unwind it and pull it out enough to hook up your extension cord.
 
My RV-9A has a Rieff Turbo XP preheater, and it's on a remote switch that uses LTE/IoT...so I can activate it and other electrical devices from an app on my cellphone (Switcheon). It's great service, very cost-effective, and excellent customer service.

The Rieff has a male plug that is secured to the intake...easy to plug or unplug. Heat the the engine up very effectively. It uses cylinder bands and an oil pan heater.


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

https://switcheon.com/

+1 on both of these - we use them on 3 airplanes today and it works great.
 
I don't know how to say, without sounding confrontational, that it seems to me there is some bad information about preheating on this thread.

The use of a remote activated switch and use preheat only when you need it is very good advice. If you have an AL constant speed prop and leave it plugged in all winter, and you have to later replace your Prop due to corrosion, you might have experienced water condensing in the prop mechanism due to that practice. If your cylinders are cooler than your oil, then the same will happen to them.

How does an oil pad heater deal with cold start cylinder wear?

To the OP and others. Do what you want...no problem. And when you go to OSH, swing by the Tanis tent, and talk with them. "I dont know anything about engine preheat. Show me your system and tell me why I should install yours over brand X oil pad heater or a Reiff system." Tanis Preheat will talk to you about the science behind there system design, its simplicity and innovation is not real expensive, and for a couple tanks of fuel you might get a system that was specifically designed for your engine.
 
Heating the oil only is best, IMHO, if it's heated long enough that it can warm the entire engine, including cylinders, by conduction (heated oil) and convection (warm air under the cowl from the heated oil). In this case, since convection is a big part of engine-warming, I would think that cowl plugs and a blanket over the nose would be critically important.

This, as opposed to oil sump AND cylinder bands which are going warm both engine and oil by conduction and therefore be faster and more efficient, and a heating blanket help, but isn't critical if the plane isn't parked outside. If it IS parked on the ramp, then I think an oil-only sump heater would not be a very good idea.

The Reiff website has good information on the effectiveness of the various types of pre-heaters.

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


..
 
Last edited:
Back
Top