[ExI] Fuel efficient car for anywhere but America

spike spike66 at att.net
Sun Apr 10 19:40:31 UTC 2011



From: extropy-chat-bounces at lists.extropy.org
[mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of Max More
Sent: Sunday, April 10, 2011 10:42 AM
To: ExI chat list
Subject: Re: [ExI] Fuel efficient car for anywhere but America


On the negative side of diesel, not only is it more expensive -- at least in
the USA; I don't recall the difference the last times I was in Europe -- but
it seems that cars and trucks running on diesel are MUCH noiser. Is this a
necessary feature of diesel. (I find that unlikely.) If not, why does it
seem to be typical? I see and hear small pick-up trucks that sound like
enormous commercial trucks ("lorries" for the UK). Can someone point me to a
*brief* but informative answer?  Max



Sure can.  Diesel engines have a higher compression ratio (they need to) in
order to ignite the fuel/air mixture.  At the end of the power stroke, when
the exhaust valve opens, the pressure inside the cylinder is higher in a
Diesel than in an equivalent gasoline engine.  So with identical sound
muffling equipment, the Diesel will be inherently louder, because of the
pressure differential between the exhaust valve and the manifold.  


All is not lost.  If we use a small Diesel and a constant speed and constant
load as in a series hybrid, we can design an exhaust system that will hold
the noise level within reason.  Diesel engines are great if they are used
under ideal speed and load.









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