scott wrote:
> Yeh, I doubt any car makers falsely advertise the displacement.  But
> calling your car a "1.6 TDI" or whatever and it actually having a
> displacement of 2000cc is probably ok (even though 90% of people would
> assume the displacement was 1.6 litres).

The only manufacturer I actually know done this is Saab. After all, BMW
doesn't call eg. 116d a 1.6l - they just refer to 116d (I think the
first BMW with misleading model name was 318i somewhere at 90's running
with 2.0 engine). Saab's 1.8t is actually a 2-liter engine (pretty much
the same as 2.0t) - they say that 1.8t is just the model name, not the
engine. And all the manufacturers actually have theier engine specs
available, so they aren't actually hiding the truth.

> I doubt many people are actually interested in the maximum power their
> engine can develop at one particular engine speed.  What's more useful
> is how quickly the car can accelerate, eg 40-70mph or 70-100mph times. 
> This depends on how much power the engine can develop across a wider
> range of RPMs, and also the mass of the car.

Yep, the curve telling this is called torque curve, the higher and wider
it is, more practical the car and more easy the engine usually is.
Turbocharged engines manage to get high torque even at low rpm's, so
they tend to be easy and nice to drive, even while providing high
hp/liter -ratio and reasonable economy.

>> MPG if you want to know how efficient it is... I never did understand
>> the fascination with displacement. (Other than that I guess you can
>> unambiguously measure it.)

The displacement tells you roughly how much torque you'll get from the
engine. The basic feature for a naturally aspirated engine is somewhere
around 100Nm/l nowadays - charged ones get even to 200 and over it (eg.
Saab 9-3 1.9 TTiD - 1.9 liter engine and 400Nm of torque). That also
tells you the nature of the engine - do you need to rev it to make the
car accelerate, do you need to change the gear often etc.

> 2400cc for F1 currently).  The HP/litre figure is also a good guide as
> to how well engineered and advanced the engine is.  And of course higher
> displacement usually means a heavier engine, which is something you
> usually try to avoid.

Yes, and it also tells you if the engine is nasty to drive as a
daily-driver. Sure, you can get 200hp from naturally aspirated 2-liter
engine (Honda Civic Type-R), but you'll also *need* the 4+krpm revs to
make the car actually accelerate and to find that power. Hit in a
turbocharger or even couple of them, and you'll get the power even from
1500rpm's.

-Aero

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