balancing.

[drew at scirocco.cs.uoguelph.ca (Drew MacPherson)]

Dan's on the money- diesels get better mileage because there's more 
energy in diesel fuel AND the diesel engine is more efficient.  On top of 
that, VW diesel flywheels are pretty much the same as their gas 
counterparts, except that they have a O degree TDC timing mark.

Big diesels have big flywheels because they're big-ass engines with long 
strokes and low idles, and as Dan said the inertia in the rotating 
flywheel keeps the engine idling.  Large, low revving gasoline motors 
(such as one might find in an antique tractor, for example) also had large 
flywheels for the same reason.

Drew


On Fri, 31 Oct 2003, Dan Bubb wrote:

> >   Do you know how heavy a Diesel flywheel is in comparison to a gas 
> >flywheel?  Part of the reason is that they have a higher mpg is because of the 
> >higher inertia they have once up to speed... 
> 
> I disagree. Diesels get better mileage due to the higher energy content
> of diesel fuel and the more efficient diesel cycle. The heavier flywheel
> is required because of the significantly higher CR of a diesel engine.
> More energy/inertia is required to get the engine through the
> compression stroke and maintain decent idle quality doing so.
> 
> >  The reasons you cited for having weight on the flywheel are good
> > reasons as
> >well, but they are not the only ones...
> 
> Sorry, your original statement that a heavy flywheel would increase
> highway fuel mileage implied that was the Primary reason for a heavy
> flywheel which is incorrect.
> 
> >David
> 
> >PS  And while I read the Vortex quite a bit, I weigh that against hands-on 
> >experience, as well as reading good technical sources (read that 
> >as 'accredited'), as well as long conversations with a good friend of 13 years 
> >who has been a mechanic for almost 40 years...  The one thing I will promise 
> >each and every one of you is if you can prove me wrong, I will admit it, 
> >period...  I don't know it all, nor do I pretend to (hopefully) :-)  I can 
> >only ask that if you do not agree/understand, please ask questions...  I have 
> >not insulted anyone here, nor will I throw jabs at someone, even if I 
> >disagree, but especially if I do not understand...  I am here to learn, and to 
> >share.  I thought that was that this list was for...  Did I misundestand? 
> 
> Ya know, I'm an engineer and I've spent way too much time thinking about and working on cars. Maybe, I'm overly concerned about trying to help make the Scirocco list technically correct and, hopefully, a huge step up on some of the laughable statements made on Vortex.
> 
> But, whatever. 
> 
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