Quote:
Originally Posted by Surprise Tsk, how do u rate the given below figures
CAR-1 : 91bhp@5500rpm , torque - 130.5Nm@3000rpm , Wt - 985 kgs (1600 cc)
CAR-2 : 106bhp@6800rpm , torque - 135@4700rpm , Wt - 985 kgs (1500 cc)
CAR-3 : 87bho@6000rpm , torque - 113@4500rpm , Wt - 1000kgs (1300 cc)
If you can throw some light and characteristics of the cars with the specs above (an rough idea how the car would behave). This is purely to understand the terms and method of evaluation. |
To understand the characteristics of the cars we do some calculations:
We find out the torque at max bhp and divide the first two cars torques by .985 to get it per ton.
We assume that 1000 rpm is around the idle rpm.
Adjustment for 1000 kg is done by dividing by 985/1000.
% range example CAR-1 (5500-3000)/(5500-1000)
torque dip = (130.5-116.2)/(2.500) and (14.3/55.5)
CAR-1: Torque
130.5Nm @ 3000rpm and 116.2Nm @ 5500rpm - Wt 985 kgs
132.5Nm @ 3000rpm and 118.0Nm @ 5500rom - for 1000 kgs
between 3000 and 5500 (2500 rpm range = 55.5% of max range) torque dip = 5.72Nm/1000rpm (.26/%)
CAR-2: Torque
135.0Nm @ 4700rpm and 109.5Nm @ 6800rpm - Wt 985 kgs
137.0Nm @ 4700rpm and 111.2Nm @ 6800rom - for 1000 kgs
between 4700 and 6800 (2100 rpm range = 36.2% of max range) torque dip = 12.1Nm/1000rpm (.70/%)
CAR-3: Torque
113.0Nm @ 4500rpm and 101.8Nm @ 6800rpm - Wt 1000 kgs
between 4500 and 6800 (2300 rpm range = 39.6% of max range) torque dip = 4.87Nm/1000rpm (.28/%)
Acceleration:
If you test driven Ikon and fiesta or NHC Vtec or OHC Vtec, you must have come to know that although new cars have good accelaration figures but you don't feel the acceleration. Now if you see the above figures you find that CAR-1 and CAR-3 has got almost same figures of torque dip (in percent) but CAR-2 has highest torque dip (around 0.7), so CAR-2 is going to give the accelaration tug (the sudden surge) if you are "floor the pedal" type of driver. If you are light footed driver and prefer to keep a car in narrow rpm margin and like to use gear then CAR-3 will give you smoothest accelaration (4.87Nm/1000rpm). But the best (smoothest) driveability is offered by CAR-1 (the sudden surge won't be there like CAR-2). You can see that CAR-1 has got a max torque at the lowest rpm. Therefore (assuming the gear ratios to be almost same), when you have reduced the speed of CAR-1 to quite low speed (around 3000 or say 2700 rpm - which is the normal driving conditions), this one will have maximum torque margin to accelerate and won't require gear changing compared to others.
Top speed:
The CAR-2 has got the max torque closer to max rpm and also max power is highest, it will be probably be having the highest top speed. The CAR-3 again has got the max torque closer to max rpm, but again you can see that CAR-1 has still 118.0Nm at 5500 rpm which higher than 113.0Nm and hence the CAR-3 will be having the lowest top speed.
To analyse the 0-100 or 0-60, you have to have gearing and resistance charaterstics of the car, but going be the thumb rule, CAR-2 has got highest bhp and highest redline rpm, so it will last longer in lowest gear and hence give best acceleration figures. CAR-1 and CAR-3 amy be quite close to each other although CAR-1 seems to have an edge.
You can visit Under the hood > Technical > Physics behind car movement
or
http://www.team-bhp.com/forum/techni...-movement.html