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Re: [ST] Diesel vs Petrol bikes



Oops! Matt, you got it backwards. The Otto cycle can run at very low
compression ratios, and relies on an external source for the spark that
starts the burn. Diesel's version of the same basic four stroke cycle
uses high compression ratios and the burn is started spontaneously
without an external heat source. (The "glow plug" is needed only to get
the operating temperature of the combustion chamber up to where the
auto-ignition can take place.) The relatively high compression ratio is
a major contributing factor to Diesel's efficiency advantage over the
Otto cycle. Diesel fuel also burns faster than petrol. (Remember that
the higher a given fuel's octane rating is the slower it burns.)

Mike 
06 ST
Seattle

-----Original Message-----
From: st-bounces@xxxxxxxxxxxxxxxxxxxx
[mailto:st-bounces@xxxxxxxxxxxxxxxxxxxx] On Behalf Of Matthew Heyer
Sent: Thursday, August 24, 2006 3:30 AM
To: ST@xxxxxxxxxxxxxx
Subject: Re: [ST] Diesel vs Petrol bikes

My recollection was that the diesel cycle (as opposed to the Otto) runs
with lower compression.  That in turns allows less refined fuel because
you don't have to worry about auto-ignition/pre-detonation due to the
rise in temperature from the compression of the mixture.  This should
make diesel cheaper (but I haven't really seen that - I guess market
forces...).  I could be wrong, but that is what I recall from studying
the cycles in Thermodynamics.
 
Matt Heyer


----- Original Message ----
From: Marc Van Est <MarcVE@xxxxxxxxxxxxxx>
To: ST@xxxxxxxxxxxxxx
Sent: Thursday, August 24, 2006 5:56:01 AM
Subject: [ST] Diesel vs Petrol bikes


I'm no chemical boffin, but I understand that Diesel has more inherent
energy than petrol, and can run higher compression rations.

This lends itself to turbo charging, plus it has self lube properties.

It makes sense that the long term future of combustion motors lies in
cracking the diesel motor.

My current cage is a Renault Laguna 1.9 Dci. It puts out 110kw and 270nm
of torque. My previous car was the 3.0V6 petrol Laguna, which punted
150kw and 300nm.

The petrol went better, esp. from the lights, but not drastically so,
and it used twice the fuel that the Dci uses. I get 1100kms from a 70l
tank. My car uses less fuel than my bike on the open road at 140km/h.


Cheers


Marc
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