Found it. Here's the article....
As I said, it's forthcoming emissions legislation that will eventually force manuf's to start reducing the size of petrol engines. That's when the smaller capacity hi torque lightweight diesels will start to take the advantage. They are talking about the short, but torquey rev range of the small diesel engine being coupled to 8 or 9 speed touch shift gearboxes, and outperforming current setups by a long margin.
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The diesel bike question is more relevant than most people think. Here goes.....
There is a lot of R & D going on into smaller capacity, higher output diesel engines among the car engine manufacturers. This is because emission laws will get tougher, and diesel engines have the potential to run cleaner than petrol engines because of the way the fuel is burnt in the combustion chamber. As it stands already, much more of the petrol injected into an engine goes unburnt compared to that of a diesel, and that makes the petrol engine more of an emissions issue than the diesel.
Diesel engine technology is moving forward much quicker than the petrols, and it's all about torque. The BMW 330d engine produces more torque than the Ferrari 360 Modena. And Lotus are well involved in the development of a 1.2 litre diesel Elise that can already out accelerate a Porche 911 on 0-60. The bike manufacturers are watching closely for the car engine manufacturers to develop the small capacity diesel engine technology.
Why?
Because there's a shock in store for the bike makers in 2006 - "Euro 3". The Euro 3 emissions test will be far more stringent than at present and is going to bring problems for the big sportsbikes. For the first time bikes will have to compete on equal terms with cars re emissions.
Paul Etheridge is manager of the motorcycle group at Ricardo, one of the worlds foremost automotive technology providers and a company hugely instrumental in the development of the latest generation direct injection high speed diesel engines. Say's he "bikes have had it easy up 'til now. The emissions tests were carried out at no more than 50 kph, on fully warmed up engines. Euro 3 demands far higher speeds and loads - up to 120 kph - from a cold start. It gets worse. The engines will have to pass the same tests when it's 30,000 kms old, before the bike will get type approval. Getting petrol engines to return the kind of efficiency to pass those tests is going to be a Herculean task. To put it into perspective, were talking about R1's going from 150 bhp back down to 100 bhp". With ultra-high top-end power engines under threat, super-torquey, super-efficient diesel engines look more attractive.
The venture Roxxo mentioned is partly British, Hayes Diversified Technologies (HDT) are the brains from the Royal Military College of Science. They supply the modded Kawasaki KLR engine to the American Military (dubbed the JP8), a bike-specific diesel engine which is only 1 ft-lb of torque behind the original petrol motor.
David Blundell of Lotus Engineering says "The easier ride afforded by the big bang engines and large capacity four strokes is well established in MotoGP. The relatively flat torque curve of a diesel would offer the same advantages. And as the technological demands of smaller and smaller car diesel engines coincide more and more with the needs of potential bike engines, so things become much more exciting"
Ricardo predicts that in the next few years, automotive engines will get as good as they can get as far as emissions testing goes. That means the attention of the legislators will turn from the traditional emissions measures of testing for Carbon Monoxide, Hydro-Carbons and Nitric oxides, and instead will turn towards Carbon Dioxide - and that means reducing overall fuel consumption. Diesels are already most of the way there, but the rest must come from downsizing... making smaller engines more powerful.
That's why behind closed doors manufacturers the world over are working like mad to come up with the trickest sub 1.5 ltr turbo diesel engines they can - the sort of thing that would fit nicely into a bike frame. With variable vane turbo technology about to overcome the blight of turbo lag, it all becomes more obvious the way things are likely to go.
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