Jump to content

Engine preheat through the oil filler?


Will.iam

Recommended Posts

Question, I’ve seen preheaters that force hot air through the air inlets and I’ve seen hot air forced up via the cowlflaps. Was wondering if there would be an advantage to just opening the oil filler cap and forcing hot air down the filler and out the breather tube? Wouldn’t that heat up the oil faster via direct contact? Any downsides to this? 
 

just curious as to why i have not seen this done before. 

Link to comment
Share on other sites

One of the reasons why some of us release the oil filler cap after a flight to vent the heat and reduce condensation as much as possible, which helps prevent rust.  I can only imagine that forcing hot air down into a sump to preheat might prove to be the opposite of this...that you're creating unnecessary moisture.

Link to comment
Share on other sites

13 minutes ago, StevenL757 said:

One of the reasons why some of us release the oil filler cap after a flight to vent the heat and reduce condensation as much as possible, which helps prevent rust.  I can only imagine that forcing hot air down into a sump to preheat might prove to be the opposite of this...that you're creating unnecessary moisture.

That hot moist air is from blow by that combustion made that would be very different from an electric heater heating up the ambient air which would have a lower moisture content than the air that was already in the engine i would think? You know how running the heater in the house dries out your sinuses in the winter time. 

Link to comment
Share on other sites

Just use one of these:

https://www.amazon.com/Kats-Dipstick-Style-Heater-15200/dp/B000BO74DG/ref=sr_1_20?dchild=1&keywords=dipstick+heater&qid=1612369013&sr=8-20

Can't imagine it would do any harm.

Apparently, they are illegal in Canada. It seems they occasionally cause engine fires. 

Edited by N201MKTurbo
Link to comment
Share on other sites

Besides the lack of uniform heating, you'd need to work out the logistics of "blowing in" the hot air.  If you take a water bottle and blow in...  how much are you really blowing in vs. just blowing some additional air in the top and increasing the air pressure.

You'd need a tube or a flat guide to create airflow on one side of the filler to get the hot air into the bottom.  Then as you blew in the hot air it would actually displace the cold air out the  top.

Link to comment
Share on other sites

3 hours ago, PeteMc said:

Besides the lack of uniform heating, you'd need to work out the logistics of "blowing in" the hot air.  If you take a water bottle and blow in...  how much are you really blowing in vs. just blowing some additional air in the top and increasing the air pressure.

You'd need a tube or a flat guide to create airflow on one side of the filler to get the hot air into the bottom.  Then as you blew in the hot air it would actually displace the cold air out the  top.

Seems like any pressure would escape via the crankcase vent.  

Link to comment
Share on other sites

11 hours ago, N201MKTurbo said:

Just use one of these:

https://www.amazon.com/Kats-Dipstick-Style-Heater-15200/dp/B000BO74DG/ref=sr_1_20?dchild=1&keywords=dipstick+heater&qid=1612369013&sr=8-20

Can't imagine it would do any harm.

Apparently, they are illegal in Canada. It seems they occasionally cause engine fires. 

Interesting now i have to go measure the length of my dip stick to see if the heater is long enough. Thanks for the link. 

Link to comment
Share on other sites

10 hours ago, PeteMc said:

Besides the lack of uniform heating, you'd need to work out the logistics of "blowing in" the hot air.  If you take a water bottle and blow in...  how much are you really blowing in vs. just blowing some additional air in the top and increasing the air pressure.

You'd need a tube or a flat guide to create airflow on one side of the filler to get the hot air into the bottom.  Then as you blew in the hot air it would actually displace the cold air out the  top.

I already have a dehumidifier that blows dry air into the filler now and you see the moist hot air after shutdown blowing out the breather tube now. That’s why i got the idea why not switch it to a heater say 4 hours before i plan to fly and it should work. Will have to test it out i guess. 

Link to comment
Share on other sites

De humidifiers use this method... 

But, it’s a pretty small amount of air going through the system this way...

It may work...

It may not work...

Do you want to experiment..?

Do you want to use a known solution?

My engine has a lot of surface area...

Driving a small amount of air through the engine, would work up to a point...

You would have to test a bunch of variables...

How cold does your hangar get?

How windy does your hangar get?

How are you paying for electricity?

The known pre-heating equipment takes all the fun out experimentation...

I wouldn’t want to put an unknown heat source into the oil...

  • Too hot, the oil can easily degrade...
  • Really too hot, the oil can light on fire...
  • What controls the temp of the heating element, while it is on?

Expect a home made device to easily heat up past the heat of degradation for the oil... without much effort... past the heat of combustion of oil in an air environment...

PP thoughts only, not a mechanic...

Best regards,

-a-

Link to comment
Share on other sites

Just this week I fashioned an internet enabled CB engine preheater.  I picked up a little 10" (round discharge area) electric heater, some aluminum ductwork adapters, and 4" metallic dryer vent hose from the Aviation aisle at Lowes, as well as 20' of 12ga 3 wire stranded copper cord.  I also picked up a Shelly PM from Amazon Aviation and fashioned an extension cord with the 12ga and the Shelly.  The ductwork adapters cover the 10" discharge area and steps it down to the 4" vent line, which goes into one of the nose inlets (a Mooney nose mod puts the inlet at the perfect size for a snug fit).  The other inlet is clogged with one of those big spongy things used to wipe down/wash grout jobs.  The engine cowl is then covered from prop to halfway up the windscreen with two soft Harbor Freight moving pads, which is then covered with a Harbor Freight painter's drop cloth (doubled up) that completes the "tent", running from floor to floor across the cowling.  The first test was the other night, when I had a below-freezing night with a 7am departure.  I'd left the heater switch on LOW (it has a Low/Off/High rocker switch) and I put the thermostat (rheostat) at the middle.  At this setting, the heater would cycle on and off.  The Shelly allowed me to turn on the heater via my phone when I went to bed, and displayed the amp/current draw that confirmed the heater was kicking on and off as expected.  When I got to the hangar for the 0630 preflight, I turned on the Master switch and snapped this pic of the EDM900 before pulling it out of the hangar (and obviously before cranking).  The EDM900's OAT probe was covered by the "tent", and therefore read about 10 degrees above ambient.  Kinda neat to see the CHT's, EGT's, Oil temp, Carb heat temp, OAT, etc. display the effect of the preheater's work.  After seeing these temps I think it's a little overkill, so it's currently set up with the thermostat set much lower.  Most of the idea was stolen from the V-Tail hangar next to me, but theirs looks like an octopus with a 4" hose going into both sides of the prop, and a 2" metallic vent line (bathroom exhaust vent line) snaking over to the pilot side window to warm up the interior/avionics.

Preheater temps.jpg

Moonet Tent.jpg

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.