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Old 05-05-2003, 01:08 PM   #16
GR8 Ride
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Re: Hmmm..!



Quote:
Originally posted by Garrett
Hmmmm...!!

Have to talk apples to apples... the Truck weighes 6 times that of the integra.... now place the Integra's motor into the Deisel Truck then race them and see who wins.....!!!
It takes Torque to overcome weight to creat acceleration and HP to maintain Volecity. The are a function of each othe in in some respects. More torque is better than equally amount of more HP.
Not entirely true. Let's try the inverse of that, and take the diesel motor and drop it into the Integra. All other things will be equal however (same transaxle, same gear ratios etc).

Assuming both have 250 HP, but one has 460 lb-ft of torque, and the other one has 210 lb-ft of torque. The diesel, however, has a 3100 RPM redline, while the Integra has a 7,000 RPM redline.

Remember, each time you shift gears, you're exchanging available torque for speed. Therefore, you'll NEVER accelerate as hard as you do at your HORSEPOWER peak (and not the torque peak, as some people might believe...).

The torque peak is the point at which the engine is capable of exerting the most FORCE, but the HP peak is the point at which the engine is capable of doing the most WORK. This can be demonstrated on a dyno, assuming the dyno can be setup for a particular speed.

Let's take 100 MPH, which might occur at 6500 RPM in 3rd, and let's say this is the HP peak for that car / motor. Let's say the engine is putting out 250 HP at that point.

Now, shift to 4th gear, and at 100 MPH, take the dyno reading (which might be down to 4500 RPM for example). Say the torque peak is 210 lb-ft at this point, which equates 180 HP or so. While the engine is capable of exerting the most FORCE, the amount of WORK it can do is quite a bit less, due to the lower RPMs.

It's hard to get your head wrapped around this sometimes, because usually power drops off significantly after the HP peak, and it doesn't *feel* like the car is accelerating that hard any longer. But at any given speed, your car will accelerate hardest at the HP peak.


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Old 05-05-2003, 06:07 PM   #17
Garrett
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Hmmm

GR8, If we took the inverse of what i suggested, then you could slap some EXTREMELY tall gears into the car with the diesel, where the baby engine would stall with this effort. The 450 ft/lbs would launch up to 60 MPH in first gear then to 100+ in second.

Just like I can start my Z06 out in 3rd gear at the stop light. If you can lay down more work over a shorter distance... or more work over less time... then you can gear it for faster acceleration.

Your arguement isnt about Torque.. it's about gearing.

In any gear WOT.. your maximum acceleration will be at the engines highest peak torque point.....PERIOD.

Now, I dont suggest when racing to shift at this point... cause you would drop out of the powerband. If you go past the peak Torque point your still accelerating hard and gettings higher volocities but your achieveing them at a slightly slower rate.

Hope this helps:

http://www.geocities.com/MotorCity/S...2/m3shift.html

work=force/time
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Last edited by Garrett; 05-05-2003 at 06:19 PM.
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