www.stationaryengineforum.net
Please log in , the forum is open to guests who are now able to view every section, feel free to become a member , you will then be able to post and reply to topics.

Running an engine on half compression?

View previous topic View next topic Go down

Running an engine on half compression?

Post by glowes3 on Fri Jan 09 2015, 22:20

Wondered if anyone had some wisdom to offer on this question:
On my Ruston Hornsby AP 3.5 there is a starting position on the cam for the exhaust valve that holds the valve open a bit during the compression stroke. It makes it easier to start but I've also noticed it runs nice and quiet and smooth if you leave it on that cam position just running it.
The question is whether it could cause any damage to the exhaust valve if you just run the engine at idle?
I wouldn't do it if the engine was placed under load.
Being the model with a low tension maggy it's happy to chug away at low revs.
Regards Graeme

glowes3
A true Stationary engine owner
A true Stationary engine owner

Posts : 101
Join date : 2012-07-12
Location : South Gippsland, Victoria, Australia

Back to top Go down

Re: Running an engine on half compression?

Post by kevjhnsn on Fri Jan 09 2015, 22:43

now that is a very good question to ask,as i would if i was you
in my way of thinking , when running for long spells with the valve not fully closing, i would say the chance of burning the valve or seat with the exploding mixture rushing through the small gap would be acting like a oxy/acetaline torch to the valve,stem and cylinder head valve seat,
so I wouldnt want to be doing it if it was me

thats my idea on the topic ,but i maybe proved wrong by a Ruston Hornsby AP 3.5hp owner or prevous owner of one
kev

_________________
lol! " IF YOU DONT DO ANYTHING " "" YOU'LL NEVER MAKES MISTAKES "" lol!

kevjhnsn
Life Member
Life Member

Posts : 3598
Join date : 2011-02-10
Age : 38
Location : south cheshire

Back to top Go down

Re: Running an engine on half compression?

Post by Villiers on Fri Jan 09 2015, 23:44

[quote="kevjhnsn"]now that is a very good question to ask,as i would if i was you
in my way of thinking  , when running for long spells with the valve not fully closing, i would say  the chance of burning the valve or seat with the exploding mixture rushing through the small gap would be acting like a oxy/acetaline torch to the valve,stem and cylinder head valve seat,
so I wouldnt want to be doing it if it was me

thats my idea on the topic ,but i maybe proved wrong by a  Ruston Hornsby AP 3.5hp owner or prevous owner of one
kev[/quote]

I'd be inclined to agree with what he said.

Villiers
Life Member
Life Member

Posts : 977
Join date : 2010-01-02
Age : 48
Location : Just outside Diss

http://www.rcoleplumbingservices.co.uk/

Back to top Go down

Re: Running an engine on half compression?

Post by glowes3 on Sat Jan 10 2015, 02:49

Thanks for the replies. Burning out a valve has been my concern. However, as the exhaust valve is only open during the compression stroke and closed fully at combustion I'm not sure there would be valve burn.
Am open to be corrected.

glowes3
A true Stationary engine owner
A true Stationary engine owner

Posts : 101
Join date : 2012-07-12
Location : South Gippsland, Victoria, Australia

Back to top Go down

Re: Running an engine on half compression?

Post by Villiers on Sat Jan 10 2015, 12:11

You are to a point, it is valve overlap that changes when running on half compression. To my way of thinking it isn't supposed to run on half compression so why would you? I'd rather run on full compression and be happy I'm not doing any damage rather than run on half and hope for the best.

I know C/S diesels run on "high compression" when running light but this is done via a changeover valve in the head, not by changing the valve operation.

Villiers
Life Member
Life Member

Posts : 977
Join date : 2010-01-02
Age : 48
Location : Just outside Diss

http://www.rcoleplumbingservices.co.uk/

Back to top Go down

Re: Running an engine on half compression?

Post by kevjhnsn on Sat Jan 10 2015, 13:20

villiers I know C/S diesels run on "high compression" when running light but this is done via a changeover valve in the head, not by changing the valve operation.


its a chamber in the side of cylinder with a screw valve closed is just cylinder area compression, and when the screw valve is opened compression is lowered when it goes into the void area inside the screw valve, but as villiers is also saying this on the c/s diesels is designed for ease of starting and adjustment for power needed for job
kev

_________________
lol! " IF YOU DONT DO ANYTHING " "" YOU'LL NEVER MAKES MISTAKES "" lol!

kevjhnsn
Life Member
Life Member

Posts : 3598
Join date : 2011-02-10
Age : 38
Location : south cheshire

Back to top Go down

Re: Running an engine on half compression?

Post by glowes3 on Sat Jan 10 2015, 22:12

Good comments - thanks.

glowes3
A true Stationary engine owner
A true Stationary engine owner

Posts : 101
Join date : 2012-07-12
Location : South Gippsland, Victoria, Australia

Back to top Go down

Re: Running an engine on half compression?

Post by Sponsored content Today at 19:18


Sponsored content


Back to top Go down

View previous topic View next topic Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum