[alfa] Re: Diesels and Dollars

[Alcon98340@xxxxxxx]

Greg writes:
"Understood. And these engines are at the limit of the technology. Do you have BSFC data for them when they are turning that fast ?? Compare this to four cycle STREET (motorcycle) spark engines that routinely turn 11K rpm--and engines at the limit of four cycle spark technology that turn 20K rpm !!"

My understanding is that diesels are actually getting more efficient and producing more power as technology is applied to them. Certainly they are producing more power. Much of this is in the way the fuel is injected (higher pressure, more controlled timing events) in my admittedly limited understanding of the subject. I have not had a chance to check your facts quoted in another post, but my understanding is that a higher compression ratio is almost always more efficient, whether it is in a gas or diesel engine. That is actually one of the diesels benefits. Also, how is it that diesels have higher friction than gasoline engines? I don't understand why that would be. There has been a lot of work on 4-stroke engines to reduce friction, but ultimately the faster you spin something the more friction you contend with. This is just as true in the motorcycle engines and F1 engines you seem to be mentioning above. This seems to be mildly off topic if we are referring to automotive equipment (I realize Gwynn did bring boat engines into the picture). Yes, most sportbikes have redlines of at least 11k. The smaller ones are creeping over the 15k mark (Yamaha R6 for one at 15,500). Does this make them more efficient? I have seen fuel economy for motorcycles drop as power increased over the years. And don't tell me that a race car is tuned for economy. There are 600cc sportbikes producing well over 100 horsepower, and 1000cc machines producing close to 150 (only dealing with production machines here). However, as power goes up, fuel economy seems to go down. This need not always be the case, but we have seemingly exhausted most of the improvements that improve power and economy both. Some of the tricks do work for both. Improved engine internals with less drag can produce more power and be more efficient. However, the majority of the auto industry seems to be giving the public what it wants with more and more performance, instead of using the same technologies to improve fuel consumption. Arguably, the trend towards hybrid SUVs (Ford Escape, new Lexus, etc) could be moving towards this. Instead of trying to get maximum power or maximum efficiency (Prius, Civic hybrid, Insight) it appears as though manufacturers are installing smaller gas engines (more effiecent) and supplementing them with additional power from electric motors. The theory being that you'll have fuel economy closer to a V6, with the power close to that of a V8 (or I4 economy and V6 power). Another thought would be to have a purely electric car, but also have a small gas-powered generator to charge the batteries while you drive as needed (no need to plug in, removes short range). Generators can be made to be very efficient, as they are only designed to run at two operating rpms that I am aware of: one for when it is warming up, and one for normal operation. Sorry for the tardy post, but I've been out of town and am just catching up on my digests. I await the digest elucidation.

Regards,
Josh
'71 1750 Berlina
'72 2000 Berlina
'84 GTV6
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