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Author Topic: No change over (compression) Valves  (Read 8514 times)

TPXX

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No change over (compression) Valves
« on: November 02, 2012, 03:54:10 PM »
I have a Lovson 12/2 which does not have a Compression Changeover Valve on either cylinder. How hard will this be to start in cold weather?





Would my best bet be to just install glow plugs?
« Last Edit: November 02, 2012, 03:56:46 PM by TPXX »

dieselgman

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Re: No change over (compression) Valves
« Reply #1 on: November 02, 2012, 04:02:26 PM »
The COV valves can generally be fitted to any of the Indirect Injection cylinder heads... if your Lovson has indirect injection, then it probably has plugs in the place of the COV valves.
Even the 8/1 and 16/2 IDI has the same setup. Our customers have found the COV valves to be unnecessary on the 8/1s, and Lister did not include them as standard equipment either. We have not handled enough twin cylinder units to know for sure what help they might provide in cold-start situations. The parts are readily available to do some experimenting... a little pre-heat goes a long way in cold-start operations and many folks have added glow-plugs with very good results.

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38ac

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Re: No change over (compression) Valves
« Reply #2 on: November 02, 2012, 04:14:29 PM »
Correct me if wrong but in comparing a plug with a change over valve it would appear that the compression with a changeover valve moved the high side is virtualy the same as a plug? My engines will start down to about 30 F without fail. Never gets any colder than that in the shop so I dont know how cold it has to be for them to not start.
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TPXX

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Re: No change over (compression) Valves
« Reply #3 on: November 02, 2012, 05:21:31 PM »
So if the plug gives an equivalent compression as the cov screwed in, wouldn't it damage the engine as you are supposed to immediately screw the cov out after start?

richardhula

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Re: No change over (compression) Valves
« Reply #4 on: November 02, 2012, 07:52:46 PM »
Don't know if this helps but I understand the original Lister CS diesels had a 19:1 compression ratio for starting with COV screwed in and 15:1 for running under load with COV out.

In the early '60's when the 800 rpm 8/1 and 16/2 were introduced it was found that a compression ratio of 17.5:1 was adequate for starting and running. The COV was dispensed with and the hole blanked off with a plug. To maintain compatibility with earlier models the head remained the same, and a 0.30" shim under the cylinder base achieved the desired compression ratio.

The JP series when replaced by the JK also dispensed with the COV's by using blanking plugs although the heads were different.

ronmar

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Re: No change over (compression) Valves
« Reply #5 on: November 02, 2012, 09:22:29 PM »
How cold are you anticipating having to start it?  Mine is about the same as 38AC, about 30 degrees starts OK., starts first time every time with a little pre-heat applied to the injector. I drip a little alcohol in around the injector and light it.  Below that, compression isn't the problem, cold oil and cranking drag is the problem. It just takes too much effort to get it up to speed.    So if starting colder than that, I would reccomend supplemental heat before I would reccomend a COV.
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bloomers359

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Re: No change over (compression) Valves
« Reply #6 on: November 02, 2012, 11:01:13 PM »
What I find helps with cold starting and is also quicker than heating, I put a few squirts of oil from the oil can down into the inlet...
Raises the compression enough for starting 1st time...

veggie

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Re: No change over (compression) Valves
« Reply #7 on: November 02, 2012, 11:26:59 PM »

My understanding is that the plugs result in a compression ratio that is somewhere in-between the two COV settings.
I removed my COV and installed a plug.
Never any starting issues, but then again I have not tested it near 32 deg. f.

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TPXX

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Re: No change over (compression) Valves
« Reply #8 on: November 03, 2012, 01:55:53 AM »
Thanks for the advice guys. I guess I'll leave the plugs in and see how it goes. I'm in Houston so start up in the 30'a is not out of the question.

Quinnf

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Re: No change over (compression) Valves
« Reply #9 on: November 07, 2012, 02:11:31 AM »
You can drill, tap and install a mid-80s VW Jetta diesel glow plugs in the plug just fine.  Or you can buy a plug with a glow plug already installed from at least one supplier.  Don't know if Gary sells them. 

Installing the COV valve isn't a great idea on a 'roid that came without one.  The British Listers with the COV had a slightly different rod length or wrist pin height that affected the compression ratio such that screwing the COV thingy in would give you about 19:1, and out, about 15:1.  When the Lister 8-1 came out in the 1950s, it didn't have the COV, it just had the same plug arrangement that all the Indian 'roids now have, well, except for the ones that have the COV.  But the compression ratio on most 'roids with the dummy plug is around 17:1, mid way between the British 6/1s two compression ratios.  So the Indian mod is sort of a middle ground.  It should start OK down to 30 degrees or so, but a glow plug will ensure that you don't tear your shoulder cranking it when it's friggin' cold (a technical term) on some frosty morning when it's too cold for male dogs to sit down. 

And lest anyone think that there is any real power  gain between 15:1 and 17:1 compression ratio, Dr. Diesel himself learned to his chagrin that the optimal compression for a compression ignition engine is only so high that it lights off the fuel charge reliably.  Chasing higher compression in the quest for more power resulted in more wear issues with little more power produced.  That finding undercut the basis for his initial 1892 patent that made him a rock star in his day.

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38ac

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Re: No change over (compression) Valves
« Reply #10 on: November 07, 2012, 04:38:41 PM »
OK this subject has been one of curiousity for me for some time and the postings here caused me to get off my duff and due some actual checking.
As measured with a gauge the compression readings of my KOEL 8/1 is virtualy identical with the plug  or after I installed a COV turned in. So the answer the oringinal question, there will be no differance in starting with an Indian plug or COV. Does this apply to Dursley parts? I cant say?

  India specs call for about an .020 increase in bump clearance for the 8/1. Why? I always suspected that it is to lower the compression to a happy medium for starting and running?  Some might be due to growth in the 8/1 alum piston but hard to believe that one would grow .020?  The increase in valve timing on the 8/1 also llowers compression pressures to some extent but I am not sure how much.  A person with a whole lot more ambition and curiousity than me could make science out of all of this.  Just the thought of all that hand cranking made my arm sore, ;D
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Tom

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Re: No change over (compression) Valves
« Reply #11 on: November 07, 2012, 05:25:47 PM »
Perhaps the aluminum piston in the 8/1 grows that much more than castiron when hot.
Tom
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Quinnf

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Re: No change over (compression) Valves
« Reply #12 on: November 08, 2012, 02:33:12 AM »
From David Edgington's most excellent and eminently useful book, The Lister CS Story, page 11:

David is quoting some notes Arthur Freeman Sanders wrote in 1931, about a year into production of the CS line of engines.
Arthur Freeman Sanders was the chief development engineer behind the CS line of engines at Dursley (and was for sure a cool frood who really knew where his towel was at.)

Quoth:

"The auxiliary combustion chamber has a cubic capacity which, as previously stated (page 10),
gives a difference between compression ratio of 19:1 and 15:1.  The higher ratio
being sufficient for immediate starting while the lower, being the best running ratio
for a fairly large range of fuels.  That combustion takes place in this chamber is evident
by the swirl marks, yet superimposing indicator diagrams taken from both chambers at
the same time; show no evidence of a time lag, the diagrams being identical."


Looking at the drawings in the book, it's evident that the plug which replaces the COV reduces the combustion chamber to the same volume as one with the COV screwed fully in.  
I think it was George Breckenridge that answered my question about that in about 2005 to the effect that the connecting rod was shorter or piston pin height was higher in Indian engines to compensate.  
And I seem to recall Dave (XYZER) did some measurements and confirmed the 17:1 compression ratio for the plugged Indian 'roid engine.  I myself cced a 6/1 head and found its volume, but I don't recall what that number was.
However, when taking that volume and adding the volume over the crown of the piston, I also came up with 17:1.  So with everyone in violent agreement, the issue was considered to be settled.

[Edit:   Page 35 of David's book talks about the 8-1.  It says,
"The salient feature of the 8-1 must surely be the cylinder head which does away with the Freeman-Sanders change-over valve in favour of just a single combustion chamber.  A plug is used to seal off the starting chamber (see illustration) from the combustion chamber proper, this plug being enclosed in position by screw-in plug 008-03179.  [The] revised combustion chamber size reduces the compression ratio from 19:1 to 17.5:1 for both start and run conditions.  Starting is effected in the normal manner but without any means of adjusting the compression ratio."  

So there you have it.  17.5:1 compression ratio, at least with the 8-1.  And I know we confirmed the compression ratio of the Rajkot 6/1 engines to be the same when set up properly. ]

Quinn







« Last Edit: November 08, 2012, 04:56:10 AM by Quinnf »
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TPXX

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Re: No change over (compression) Valves
« Reply #13 on: November 08, 2012, 01:10:18 PM »
Great info. No Change over needed! I may worry about glow plugs later but for now I'll leave the plugs alone.

xyzer

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Re: No change over (compression) Valves
« Reply #14 on: November 08, 2012, 02:49:45 PM »
I never went as far as finding the volume but did find not all COV plugs are the same. I had to modify the ones I purchased from CMD.

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