Team-BHP - What is better for driveability : 0-100kmph OR 20-80kmph?

Quote:

Originally Posted by ashish22 (Post 1112251)

i think cars having better 20-80 kph timings would suggest that the engine has strong midrange??
holds true for linea...
one more thing would'nt doing 20-80 kph in 3rd gear actually reduce FE?
anyone has 20-80 kph figures for vRS?

i dont think it will reduce FE , if you watch the rpm and and not watch the stopwatch.

Quote:

Originally Posted by Shan2nu (Post 1112218)

Ok let me make it clear how all 3 are related.

Consider 1 car with 100bhp@6000rpm. It has a 3rd gear ratio of 1.5:1 and a final drive ratio of 3.8:1. Wheel size is 195/60 R14.

Now at 20kmph in 3rd, this cars engine will be revving at 1039rpm.

Lets say it does 20-80 in 15 secs.

Now take the same car change the 3rd gear ratio to 2.2:1 while keeping everything else identical.

But even though its the exact same car tested before, the shorter 3rd gear will now let this car's engine revv at 1507rpm at 20kmph.

We know that an engine will produce more torque and power as the rpm increases. So this 468rpm increase in engine revvs will oviously make this car gain an advantage compared to its earlier run where it had to start accelerating from 1039rpm.

This is how gearing is related to engine rpm and vehicle speed.

When Hyundai chose the gear ratios for the Verna, they prob wanted the car to perform better from 40-100 in 3rd. This is just a design choice which a manufacturer makes.

If 20-80 in 3rd is more important to you than 40-100 or anything other roll on speed, then you buy a car which has been designed for it.

Shan2nu

thats a comprehensive presentation mate.
but the verna has a VGT right?
so the turbo should come in earlier than 2000rpm?
what say?

Quote:

i think cars having better 20-80 kph timings would suggest that the engine has strong midrange??

Not really, it is mostly bcos the gearing lets these engines revv at a higher rpm at those speeds as compared to the ones that are more powerful but slower.

It would be interesting to see which car is doing what rpm in 3rd at 20kmph.

Shan2nu

Quote:

Originally Posted by aseem (Post 1112204)

I drive a petrol car and i have never in my life shifted to 3rd in 20 kmph. If I do that in Swift the car will start knocking. I mostly shift to 3rd at around 40kmph. I remain at 3rd till about 70 or 80 depending on how fast I want to accelerate. The only time I would be doing a 20-80 in third/second if I am stuck in traffic and am too lazy to change gears. But than in that scenario I wouldnt be to worried about the 20-80 timing, would I?

I always thought that diesel cars have better in gear acceleration due to higher torque, and petrol cars have have higher outright accerlation due to lower torque but higher power.... Isnt this funda applicable?

aseem i think that the lower down power and torque determines whether the car will knock or not
my petra can ride at speeds od 20-30kmph at 1000rpm all day and not knock even once.but that happens only if i carry decent speed from the 2nd gear.

Though a little off topic, just a related question:

If two vehicles have the same gear ratio for a particular gear, will the top speeds of both the vehicles in that gear be the same, irrespective of the kerb weight? I understand that the acceleration differs though.

[quote=rrs1951;1112161]I agree with amitoj. It all depends on where you do most of your driving. I, for instance, seldom get a chance to accelerate form 0 to 60 kmph straight away, because I stay in a crowded area, and do a lot of driving through fairly slow moving traffic. What matters for me, is the ability to quickly overtake slow moving vehicles. In other words, it's the pickup in third/fourth gear that matters to me.

i too agree with you.its the quick acceleration in 3rd and 4th that matters in day to day running be it city or highways buttt if you drive a lot on 4 lane highways,expressways then i feel that 0-100 is better.

Quote:

thats a comprehensive presentation mate.
but the verna has a VGT right?
so the turbo should come in earlier than 2000rpm?
what say?

Atleast when i test drove the car, i could see the car picking up revvs around 2000rpm. I think the Verna produces its torque at 1900rpm.

Ok got it.

Verna gear ratios :
3rd - 1.18:1
final drive - 3.705:1

tyre size : 185/65 R14

According to this data, the car should be doing around 800-850 rpm at 20kmph in 3rd.

This is why it struggles to perform in this test.

Shan2nu

Quote:

If two vehicles have the same gear ratio for a particular gear, will the top speeds of both the vehicles in that gear be the same, irrespective of the kerb weight? I understand that the acceleration differs though.

Not always.

Mechanically/Electronically limited top speed in a gear is also affect by variables like max engine revvs, final drive ratio and wheel circumference.

Shan2nu

a 20-80 timing in 3rd serves no purpose whatsoever.

If you're a speed maniac you wouldn't ever use 3rd in this range. In my car (Swift petrol) I would hold 1st till about 45 and shift to 2nd and hold that till about 90.

If you're very excited about fuel efficiency, again its impractical. In my car I would shift from 2nd to 3rd at 30 and upshift to 4th at about 45.

However, 0-100 is a good indication of a car's ultimate performance.

Quote:

Originally Posted by deepakhon (Post 1112290)

There are a lot of parameters. The answer is NO.

Quote:

Originally Posted by nanopano (Post 1112326)

I think a car that accelerates 0-100 km/h have better drivability.

NO. Swift petrol is good in 0-100, but Getz petrol 1.3 beats it in 20-80kmph. 0-100 demonstrates the raw acceleration capacity of car. An engine that has all its power concentrated at top end, for eg. Swift, is good for acceleration, like 0-100 where the engine is revved to redline. But in case of 20-80, at 20 kmph in thrid the revs are low and there from there on the car has to accelerate. Here the bottom end torque matters more than high end power.

The reason why Swift and Linea are faster than Optra magnum in 20-80. Both, high end power and bottom end torque are important for me, but in general if we are considering the driveability, then we must look at 20-80 kmph figures in third ( mainly for city driving ) and also at 40 -100 kmph in fourth.