Marty d's CH-701 build log

[rgmwa]

I’ve checked it both hot and cold. Seems to work fine either way. I would check it cold if I thought it needed topping up which it rarely does. Warm the engine before doing an oil change. 

[facthunter]

If you want to e fussy about the best time to drain  the OIL, It's just after a long trip, but you don't feel like doing it then. Nev.

[skippydiesel]

15 hours ago, Marty_d said:

IUnfortunately all the user groups - Rotax-owners, Vans air force etc - have opposing points of view on the issue.

Just work through the logic -

 

If the engine has been recently run, it will take quite some time for all the free oil (not trapped in galleries/filter /etc) to drain to the lowest point.

To assess the oil level  - to decide, do I need to add oil or not - your system of measurement must be consistent AND relevant (is the assessment actually representative of the oil quantity).

A hot engine/oil is unlikly to give you the ability to assess the amount of oil in your engine, simply because insufficient time has elapsed to allow as much oil as possible to drain into the lowest point.

As stated earlier - I have never seen  informed/authoritative  advice, to check oil level in a hot engine - its always cold.

 

You suggest that Rotax Owners Forum may be giving a hot engine oil check advice - please quote or give web connection😈

[skippydiesel]

14 hours ago, rgmwa said:

I’ve checked it both hot and cold. Seems to work fine either way. I would check it cold if I thought it needed topping up which it rarely does. Warm the engine before doing an oil change. 

"I’ve checked it both hot and cold"

Almost every system of assessment requires consistency (eg temperature/hrs of service/etc) - what is the point of a hot engine/oil assessment UNLESS you are concerned there has been a resent loss of oil???

 

"Seems to work fine either way"

Defies logic - no offence intended

 

"Warm the engine before doing an oil change."

Bit vague - resent discussion in Rotax Owner Forum - Owner /Maintainer concerned about high fuel content report in Oil Analysis.

The likly reason -

• He was briefly warming the engine, on the ground, before draining the oil.
• To start a Rotax 9, the fuel enrichment circuit is engaged (engine runs rich)
• In the rich condition some of the fuel remains unburnt - passes the compression rings & enters the oil

If you want to heat the oil before draining, get the engine up to FULL running temperature, for at least 30 minutes (an hour would be better). Make a point of getting the oil to 100C, in extended Climb. By doing this you drive off the volatile contaminants (fuel/ water / etc) AND your oil will flow nice and quickly when you drain it.

 

Personally I cant see the point in warming the oil - On the last flight before I will be doing an oil change - I do my usual hand rotation to "burp". When I return to do the service (day or so after) I burp the engine again (usually burps within one complete rotation)- I have now returned all the oil (that will return) to the oil tank. Drain tank and refill.😈

[facthunter]

Some people try to purge the Oil from the entire system on a Rotax.. The risks involved don't justify this when you have a good filter in the system.  85 degrees is the advised oil temp. Lots of engine Parts will be above that temp. Oil dilution is unlikely in a Rotax. Rich Mixture will Produce amorphous Carbon (soot) Hydrogen is Preferentialy Burnt then SOME of the Carbon. WATER is a by product of burning hydrocarbons. Use the equation and apply the Atomic weights. Nev

[rgmwa]

1 hour ago, skippydiesel said:

Personally I cant see the point in warming the oil - On the last flight before I will be doing an oil change - I do my usual hand rotation to "burp". When I return to do the service (day or so after) I burp the engine again (usually burps within one complete rotation)- I have now returned all the oil (that will return) to the oil tank. Drain tank and refill.😈

So you have warmed the oil and returned it to the tank before doing the oil change, despite not seeing the point of warming the oil. Defies logic - no offence intended.

 

[skippydiesel]

1 hour ago, rgmwa said:

So you have warmed the oil and returned it to the tank before doing the oil change, despite not seeing the point of warming the oil. Defies logic - no offence intended.

 

I apologise if my oil change methodology description, left something to be deduced;

 

I did say -"When I return to do the service (day or so after)........"

 

My point is simple- warming the oil (as apposed to getting the engine up to heat soak temperature), in a Rotax 9, specifically to drain it, has few if any benefit(s) and may have unforeseen repercussions (eg oil analysis).

 

I always burp my engine after the last flight of the day - Aside from an easy burp, when oil hot, it also means that there is only a small amount of oil, that has collected in the crankcase, that I can transfer when cold, with less than one complete rotation of the prop, to the oil tank, for a good (cold) oil drain.

 

I also check the oil level before draining, as the tank will take a little more than 3L to refill - I note the "little more" quantity as part of  my documentation/monitoring of oil used.

 

Have I provide sufficient "logic" for you?

 

😈

Edited Tuesday at 05:33 AM by skippydiesel

[rgmwa]

No need to apologise, Skippy. I understood the methodology and your logic is as sound as usual.

 

[skippydiesel]

13 minutes ago, rgmwa said:

No need to apologise, Skippy. I understood the methodology and your logic is as sound as usual.

 

Flattery will get you a long way - What do you want?

😈

[facthunter]

Don't get too excited.  He only said your logic is as sound as Usual..  Nev

[BrendAn]

7 hours ago, skippydiesel said:

Just work through the logic -

 

If the engine has been recently run, it will take quite some time for all the free oil (not trapped in galleries/filter /etc) to drain to the lowest point.

To assess the oil level  - to decide, do I need to add oil or not - your system of measurement must be consistent AND relevant (is the assessment actually representative of the oil quantity).

A hot engine/oil is unlikly to give you the ability to assess the amount of oil in your engine, simply because insufficient time has elapsed to allow as much oil as possible to drain into the lowest point.

As stated earlier - I have never seen  informed/authoritative  advice, to check oil level in a hot engine - its always cold.

 

You suggest that Rotax Owners Forum may be giving a hot engine oil check advice - please quote or give web connection😈

If you ever operated or worked on caterpillar equipment you would have seen the marks on the dipstick for checking the oil  while the engine is running.  And hot at the same time

[onetrack]

Caterpillar engines have two marks on the dipstick, one mark for when oil is cold and engine is stopped, one mark for when engine is at operating temperature, and idling.

[skippydiesel]

45 minutes ago, BrendAn said:

If you ever operated or worked on caterpillar equipment you would have seen the marks on the dipstick for checking the oil  while the engine is running.  And hot at the same time

No - never have worked on equipment like that.

If look back at what I wrote, I acknowledged there were exceptions to the cold oil dipstick check.

Hot oil checks are the exception - When did you last see a recommendation for a hot oil check on an engines powering a car/motorcycle/mower/etc (what might be thought of as common equipment) ?

I suspect that hot oil checks are largely confined to engines that run continuously or almost so.

😈

 

 

[Blueadventures]

1 hour ago, BrendAn said:

If you ever operated or worked on caterpillar equipment you would have seen the marks on the dipstick for checking the oil  while the engine is running.  And hot at the same time

And sample oil while running.

[facthunter]

The Main occasion where you have to wait a while is When you change the  Oil  in an upright Motor where you pour the Oil via the Rocker cover, and always recheck it to allow the Filter Qty to be catered for.. If the filter can be filled before fitting, all the better..  Nev