Re: Turbo Cars


"Tim S Kemp" <news@xxxxxxxxxxxxxxxxxxx> wrote in message
news:_eCdnbByl7G3KdDeRVnygA@xxxxxxxxxxxxxx
> John wrote:
> > Did anyone see the article in the Sunday Times Driving supplement at
> > the weekend? "Turbos on a global blast?"
> >
> > The article is saying that basically 25% of petrol cars will be
> > turbocharged by 2010, more than double the current number.
> >
> > It says that manufacturers such as Volkswagen, BMW, Peugeot and
> > Citroën are all working on turbo-powered versions of their standard
> > engines as a way of increasing fuel efficiency and cutting emissions
> > to meet EU targets.
>
>
> Indeed - the tree-hugging swedes have been turbocharging their cars for
> ages.
>
> > I'm slightly confused on this because I believe some of the BMW fans
> > in here also mentioned a while back that you can get better fuel
> > efficiency from turbo cars?
> >
> > Or do you just get better efficiency when driving normally? Then when
> > you get up to speed the turbo kicks in and it gets worse? I just don't
> > get it. Not knowing too much about cars I'm really confused on this.
> >
> > I did a quick comparison on two cars (the Mitsubishi Colt) both with
> > 1.5 litre petrol engines, one with turbo one without and these are the
> > fuel consumption figures:
> >
> > 1.5 1.5 turbo
> > Urban 35.3 32.8
> > Comb 45.6 41.5
> > Ex-Urb 55.4 49.6
> >
> > In all areas the 1.5 turbo is worse on fuel efficiency than the
> > non-turbo.
>
> It will be on paper. But a low pressure turbo (say 0.75 bar) 1.5l car will
> use less fuel at steady cruise and idle than an equivalent 2.2l car. High
> pressure turbo cars become inefficient off boost due to the requirement to
> reduce the compression (or more importantly expansion) ratio.

The modern crop of low and medium to highish blow turbo's use a standard NA
type compression ratio now- eg VW's FSI's and the Volvo's 2 and 2.4litre at
around 10 & 9.5:1 respectively to maintain off boost response and
efficiency...

Tim..


.

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