[Vwdiesel] something worth trading the A4 in for
r.c.brown at ieee.org
Sun Jul 6 08:14:08 PDT 2008
Tony and Lillie wrote:
> What's funny about this whole conversation is nowhere does anyone mention
> that HP is simply a calculation from torque. The formula for HP is torque
> times RPM divided by 5252. So, they are directly related to each other.
> A more accurate description of what this discussion is about is power curve
> related to where the peak is in RPM's.
> Tony Hoffman
Carroll Shelby is the person that quote is attributed to:
"Horsepower sells cars, torque wins races"
And yes, you can have 1,000,000 ft-lb. of torque @ 0 RPM and have no HP, likewise
1,000,000 RPM @ 0 torque and still have 0 HP.
Since Shelby was mainly a sports car/road racer type, I think the gist of his quote was
that the vehicle with more torque, at a given RPM, is the one that wins races. If you
look at two cars coming out of a tight corner on a track, given that they are otherwise
pretty similar (weight, gearing, etc.) the one that can make more torque down at lower
RPMs will accelerate faster out of that corner. Sure, horsepower is what gives you top
speed down the straightaway, but you need to get the engine RPMs up to the range that give
you that peak HP, and to do that you need the torque down lower to get those RPMs up.
And in every day driving, with gas and diesel engines, you'll probably be able to use the
torque of a diesel since it comes at the RPM ranges you typically see. With the 4-cyl VW
diesels peak torque is down in the 2400-2500 RPM range and peak HP is in the 4K RPM range.
Since I rarely rev mine that high, I am more in the peak torque range. And take a small
4-cyl high revving gas engine that high peak HP at 6-7K RPM, I doubt the average driver
would ever hit that. So while that small high-revving gas engine may make 170HP, if you
never get to use it, what is the point of having it (other than that that big HP number
helps to sell the car).
I used to go out with the local VW clubs on some of their "spirited" drives with my '82
pickup. I could pretty much hang on the bumper of most any of the hopped up GTIs and
Sciroccos in the turns. I usually had to back off a little coming out of the turns as the
diesel torque down low would out pull the gas engine in the vehicle in front of me. Only
place I could not keep up was on the long uphill straights. Between the lower top end on
the diesel and the big jumps between gears in the FN transaxle, I just could not keep up
there. Was always fun when we would get to the first rest stop on those drives, all the
gas guys would come over and ask me what the heck I had under the hood. Seeing as I was
the only pickup, a high topper on the back, skinny 13" tires and a diesel engine to boot,
they always stuck me in the back of the group figuring they might never see me catch back
up to them.
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