Re: [alfa] Diesels and dollars

["Gwynne W. Spencer" <gwynnes1@xxxxxxxxxxx>]

You missed my point about throttling - I meant to be talking about fuel 
efficiency (MPG) and it is not only the pumping losses that reduce it, but 
the fact that the cylinders are running at very low pressure effective 
ratios due to the high intake manifold vacuum. If my memory serves me OK, 
the formula for power at WOT includes the compression ratio to the 0.4 
power - at lower throttle settings this does not apply, since the cylinders 
are not filled to capacity at atmospheric pressure, but some much lower 
pressure. This also results in lower fuel efficiency, one of the reasons 
that the gas engine is so much less efficient than the diesel which 
operates WOT all the time.

Just what is the 0 - 60 time for your Saab ?? and what are the gear ratios 
? (another major factor in acceleration performance) the data  I found 
(from Saab) was for the manual transmission car only @ 6.5 seconds (I 
believe the MB data is for an automatic tranny)

But the real story is that we were comparing diesel and gasoline power and 
the MB cars give us the perfect opportunity to compare essentially 
identical cars, one with a gas engine, the other with diesel - how about 
that ??!!

And lastly, I know that throttling losses do not apply at full throttle - 
and that is one of the reasons for diesel superiority in some of the regimens.

Gwynne Spencer

At 06:30 PM 5/25/2004 -0600, you wrote:
>Yeah but, my 1997 SAAB Aero does zero to 60 in the same time as the Benz 
>turbo diesel, makes 256 lb ft of torque from only 2.3 liters, and is way 
>more fun to drive than any Benz in the price range. Of course the Aero 
>weighs only 3200lbs, but the engine is 2/3 the size of the Benz. And it 
>gets 35 mpg on the highway.
>
>BTW, full performance comes at wide open throttle where a gasoline engine 
>suffers no more pumping losses than the diesel.
>
>Cheers
>
>.At 10:04 AM 5/25/2004 -0400, you wrote:
>>Turbo diesels make the engine even more efficient as the EFFECTIVE 
>>compression ratio is higher. This does not translate directly to 
>>throttled gasoline engines as they commonly operate at high intake vacuum 
>>levels resulting in an effective compression ratio way lower than the 
>>full throttle theoretical.  The performance numbers for the E class 
>>gasoline and diesel powered cars comes from  road tests - also 
>>see:  http://www.msnbc.msn.com/id/4863112/
>>
>>Gwynne Spencer
>>
>>At 09:22 PM 5/24/2004 -0600, you wrote:
>>>While I have zero interest in driving any product from Daimler Chrysler, 
>>>with the possible exception of the Mitsubishi Evo and the extremely 
>>>improbable exception of the McLaren Mercedes, I ask whether the 
>>>supposedly superior diesel Mercedes is a turbo. If not, then I accept I 
>>>am mistaken about the superiority of gasoline power for passenger cars. 
>>>If, as I suspect, the Mercedes is supercharged then I maintain my 
>>>position that equivalent gasoline engines are more suitable for 
>>>passenger cars than any diesel. If the engine is the same sized, 
>>>turbo'd, etc then the gasoline powered car should be quicker.
>>>
>>>
>>>Michael Smith
>>>White 1991 164L
>>>Original owner
>>>--
>>>to be removed from alfa, see /bin/digest-subs.cgi
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>
>Michael Smith
>White 1991 164L
>Original owner
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided