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The Change Over Valve

To understand the Listeroid is to understand the development of the original engine, and why certain things were changed. It also helps to understand the diesel engine, typical compression ratios used in diesels etc.

If you look over a typical CS listeroid, you will find that the change over valve 'COV' has been fitted with a plug. COVs can leak, and as injector spray patterns got better, India found they could get by without this valve, and reduce both cost and problems. I think this was a good decision for their principle market of these engines.

There are Americans who order engines and ask that the COVs be fitted, and they do not understand the implications.

Here's a snippet from an email I got yesterday.

   The engine is a new 12-2 from Annand with COV's installed. When the valves are in, (high compression), the engine smokes less than when they are out. The engine has run consistently with about a 3 to 4 kw load. It now has just over 50 hrs running time, but it still smokes. Also: coolant temps have been right at 195 to 210 degrees F. I'm curious about the continuing smoke.

With this shared, here's what's happened. Some one wanted the COVs and they just added them. since India now 'sets up' the engine for the 'Indian  plug', the piston height, is set to run on the screwed in postion. When the COV is added, the high compression setting is the same as the typical run compression ratio of the CS plug. This means, when you screw the COV out to it's normal work position, you are now, running an all too low compression ratio!

If you want a COV to work right, you will set the engine up for a compression ration of about 17:1 with the valve out, this will require a higher piston height. Now, when you screw in the valve, you will have an even higher compression ratio.

This is a minor problem, and you can fix it, but it is an example of your need to understand it, before you order it, or to work thru people who do understand it. Some might suggest that there's a benefit to running the COV today, well, if that were true, India would be using them, fact is, they are considered more trouble than they are worth.

All the best,

George B.