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Oil pressure

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trigo(at)mail.telepac.pt
Guest

Posted: Sat Dec 08, 2007 11:57 am Post subject: Oil pressure

Guys



After making the annual to my 912UL (80hp), in which I put a new oil

pressure indicator (VDO), having obviously changed oil and filter, and also

washed the oil tank, I made a 1,5 hours flight today and in flight, at

4.500/5.000 RPM, it indicated a steady Oil pressure of 3 bar. After landing,

when the engine was in idle, right before switching it off, the OP indicator

was indicating 4 bar (which is the factory indicated nominal pressure)

After shut off, I checked the oil level and it was good.



Is 3 bar a good oil pressure to have continuously in flight?



Carlos Trigo

Portugal

RANS Coyote SuperSix

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Gilles.Thesee(at)ac-greno
Guest

Posted: Sat Dec 08, 2007 1:35 pm Post subject: Oil pressure

Carlos Trigo a écrit :

 	  Quote: 	
		   



  at

 4.500/5.000 RPM, it indicated a steady Oil pressure of 3 bar. After landing,

 when the engine was in idle, right before switching it off, the OP indicator

 was indicating 4 bar (which is the factory indicated nominal pressure)

 After shut off, I checked the oil level and it was good.



 Is 3 bar a good oil pressure to have continuously in flight?

   


	


Carlos,



No problem. Those numbers are quite normal.

The 912 Owner's Manual states normal pressure is 2 bars + or - 0.5 bar 

when above 3500 RPM.

Rotax engines often exhibit seemingly lowish pressures, but remember 

that contrary to other engines, the pressure pickup point is at the end 

of the oil circuit, so many pressure drops have occurred before oil 

reaches the gauge.



Best regards,

-- 

Gilles

http://contrails.free.fr

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Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Sat Dec 08, 2007 2:30 pm Post subject: Re: Oil pressure

Hi Carlos,



3 bar which is 43 psi and 4 bar which is 58 psi are perfectly normal.

Just go out and have some fun.

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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

trigo(at)mail.telepac.pt
Guest

Posted: Sun Dec 09, 2007 2:49 am Post subject: Oil pressure

Merci Gilles

Thanks Roger



I read those numbers in the Manual, but they also state 4 bar as "nominal

pressure", which I'm not sure what exactly means.



So, anything above 1.5 bar and below 5 bar would be safe. 

Why this can be so variable? 

What exactly causes the differences in oil pressure between engines?



Carlos

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Gilles.Thesee(at)ac-greno
Guest

Posted: Sun Dec 09, 2007 3:14 am Post subject: Oil pressure

Carlos Trigo a écrit :

 	  Quote: 	
		   So, anything above 1.5 bar and below 5 bar would be safe. 

 Why this can be so variable? 

 What exactly causes the differences in oil pressure between engines?

   


	


Carlos,



Oil pressure is dependent on

- engine : RPM, relief valve setting, clearances in the engine, etc.

- oil viscosity : oil grade, temperature, pollution.

Some engine measure pressure upstream at the pump outlet, others 

downstream of the the oil galleries.



Best regards,

-- 

Gilles

http://contrails.free.fr

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trigo(at)mail.telepac.pt
Guest

Posted: Sun Dec 09, 2007 5:32 am Post subject: Oil pressure

 	  Quote: 	
		   

 Oil pressure is dependent on

 - engine : RPM, relief valve setting, clearances in the engine, etc.

 - oil viscosity : oil grade, temperature, pollution.

 

 

 Some engine measure pressure upstream at the pump outlet, others

 downstream of the the oil galleries.

 


	


OK, now I got it!

How good is the feeling of learning ...



Merci de nouveau, Gilles



Carlos

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Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Sun Dec 09, 2007 7:02 am Post subject: Re: Oil pressure

Hi Carlos,



Gilles is exactly right.

Most 912's I have seen run between 40-55 psi normally.

On another note I was running an oil pressure when new at around 55 psi and after a while (6-7 months) I was running 41 psi. I prefer my oil pressure higher just to help make sure it does a good lubrication job in the tight tolerance areas and in case things within the engine got too close to operational maximums. I put a Rotax shim under the oil pressure control spring. This didn't help at all. I checked the pressure in the system with a gauge and found with the shim my oil pressure sender was reading 20 psi low. I replaced the oil pressure sender with a new one and now I am at 58-60 psi under normal running rpm.



Moral to the story is if you oil pressure seems too low then you might want to check it with a manual pressure gauge or at least against another known good oil pressure sender. 



Oil pressure senders on the 912's do occasionally go bad due to vibration. If you are in the experimental class then a remote mount of the sender is not a bad idea and very easy. I am in the SLSA class in the USA and can not legally do that without permission from the manufacturer.

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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

rampil

Joined: 04 May 2007
Posts: 870

Posted: Sun Dec 09, 2007 8:14 pm Post subject: Re: Oil pressure

Carlos,



Nominal means perfect. More or less!



Ira

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