[Diy_efi] Re: Fairlane

[Michael Richards]

> I'm no expert on the subject but as far as I understand, you "feel"
> torque whereas 400m times are relative to your horsepower and weight. 
> I recently test drove a Golf MkV 2.0 TDi which had 320nm of torque and
> only 103kw of power.  It felt really quick, quite fun to drive, yet it
> takes over 8 seconds to get to 100km/hour.  I guess it's because
> torque is instantaneous power whereas horsepower is torque over time?

This is one of the most misunderstood areas of performance. Something 
you have to realise is that torque is an instantaneous measure of force 
while horsepower is a unit of work - torque applied as the engine turns 
a specific speed.

Think about the concept this way...

You have a dumptruck engine making 400hp. That engine will put out 1500 
ft/lb of torque but only spin to about 3500RPM. Next to that you have a 
turbo honda making 500hp. Only about 350ft/lb of torque and you have to 
spin it to 10,000 RPM. Which engine could move the biggest load of dirt 
up a hill?

With the proper gearing the Honda could. But wait! It doesn't have the 
torque! That's what gears do - they multiply torque. So in actual fact 
the torque figure doesn't mean anything in your go-fast formula. You 
need something with good average horsepower between the operating range 
as you accelerate.

Even though your TDi has lots of torque it's still only making 103kw or 
about 140bhp. Gear it any way you like it's still only able to 
accelerate with the 103kw of energy.

-Michael
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