One of the things I am planning when I finally get around to the head swap in my car was getting weaker springs. With the way the engine is tuned right now I can't really get the engine to redline anyway the top end is totally weak. I get the best power shifting at 3500 so if I find a set of springs that will float at 3750 I am set
I have a pile of Metro springs sitting around I just have never measured one to see what size they are so I know what to order to replace them. If it ever gets warm here I might get out there and work on something.
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Fortunately, the Suzuki 993cc engine in the Metros are non-interference.
Even so, spring bounce is a bad thing. Pains must be taken to hold revs below that threshold. That probably means an electronic rev limiter of some sort.
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The Ducati Desmodromic system can be spun on the test bench with a snap of the fingers...literally.
Inertia keeps the valves moving quickly enough to seat fully even at idle speeds to eliminate the need for springs which the Mercedes cars used in the late 1950's.
Maintenance isn't a headache BUT you must know what you are doing , it take a lot of time AND it is very easy to get it wrong.
For the consumer this means higher service costs which not all are prepared to pay.
For Ducati it is as much a sales tool as it is an efficiency concern.
Look at the number of bikes not using it and that becomes very clear.
At the moment Ducati are the only builders using that system.
OK Found it after all.
The numbers are lower than 25% and are reported as 19%
A quick copy / paste of the abstract is below:
Engine friction lubricant sensitivities: A comparison of modern diesel and gasoline engines
R. I. Taylor
Shell Research and Technology Centre, Chester, UK
Abstract
Engine friction models have been developed that take account of the variations in lubricants with temperature, shear rate, and pressure. These models have been used to study the lubricant sensitivities of modern diesel and gasoline engines. Total engine friction losses for a Perkins Phaser four-cylinder, 4.0 l, turbocharged, inter-cooled diesel engine, operating at 1300 rpm, with an SAE 15W-40 lubricant, were estimated at approximately 2 kW, with the piston assembly contributing 46%, the bearings 49%, and the valve train 5%. Total engine friction losses for a Mercedes Benz M111 2.0 l gasoline engine (used in CEC sludge and fuel economy engine tests) operating at 2500 rpm, and medium load, for an SAE 15W-40 lubricant, were estimated at 1.5 kW, with the piston assembly contributing 42%, the bearings 39%, and the valve train 19%.
Pete.
Last edited by Peter7307; 02-02-2009 at 05:59 AM..
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