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-   -   What happened to low end torque of today's small cars? (https://www.team-bhp.com/forum/indian-car-scene/109589-what-happened-low-end-torque-todays-small-cars-4.html)

I dont know if that is actually the case. The case in point being my back to back test drives of the new Swift a couple of weeks back. T
he petrol was smooth and refined, and power build up was gradual and sweet.

However, when I drove the diesel immediately thereafter (on a Saturday morning with very sparse traffic conditions), the moment I reached the point of 2000 RPM (when the turbo kicked in, if at all) the car lunged forward and lo and behold! I was breathing down the neck of the car in front of me! With the net result that the turbo power was well nigh impossible to use in normal city traffic. On the highways, yes, the diesel would be optimally used, since there is ample open road to free up the turbo and use the torque.

The overwhelming feeling I got was that in normal every day city usage, where revving up to 2000RPM on a consistent basis is difficult for any sustained length of time, the diesel does not feel special at all (in terms of low end driveability). On the other hand, the petrols refined and linear power delivery felt much more suitable to me.

Or maybe its just the petrol head in me who liked the high revving smooth K12:D

Most newer cars have taller gear ratios AND are much heavier than their predecessors.

Taller gear ratios improve highway fuel efficiency and improve cruising speeds considerably.

Depends also on the engine characteristics : DOHC valvetrain design + lighter flywheel = lesser low end torque as compared to an SOHC with a heavier flywheel.

What is happening today is that all cars costing less than 10L are being tuned to ensure optimum fuel efficiency.Say what you want people but petrolheads like us are miniscule in number.The majority of average car buyer are only interested in "average kya hai".

This is economics people.Car manufacturers are responding to what sells in India.A lot of people have praised the Santro and frankly it's a much better car but then a lot of people preferred the Wagon R to it as it offered slighly better FE.The VW 1.4 and 1.2 TSI engines are amazing but they may never come here simply because it would not make economic sense.This is because people compare the FE of a much heavier VW to a Korean or Japanese tinbox.The only thing that most car buyers want is fuel efficiency.They are not bothered about performance,build quality,comfort or safety just "Fuel Efficiency".

The point I am trying to make is manufacturers give customers what they want.We are only after "Average Kya Hai".What we sow,we reap.

And I thought I Didn't know how to drive!

Its been only a couple of years that I have been driving [well, negligible amounts in the first year. I have probably driven about 1500km in total in the past two years]. I had learnt driving in a LPG fitted esteem which was not worthy of being called a car. Since then I have been sharping my skills behind the wheel of my fathers swift VDi. The only petrol car I had driven was a friends esteem [not the above mentioned one] which had an extremely sensitive clutch but was otherwise fine. I used to avoid driving that car as I would often stall it [Although my inexperience did play its part here, it wasn't all me. Most of my friends with significant amounts of experience would stall it too]. Recently he replaced the car with a Vento TDi and an Alto K10. The first time a got behind the wheel of the K10, I was a bit surprised with excessively stiff accelerator paddle. But what really surprised me was the low end response. I am used to shifting at 2000 [+/-] rpms in my fathers car. But in the K10, at those rpms the car almost feels as if fuel supply to the engine has been cut off. Suppose you slow down to about 15km/hr to cross a bad patch of road, if you try to pull away from second, there is absolutely zero response unless you are hammering the accelerator! Downshifting to first too causes problems because the car would knock. It was almost like I was having to learn how to drive all over again!

Not entirely correct, IMO, as we are discussing many petrol engines here, none of which are turbocharged. So the question still remains: If both the Santro and the i10 have a 1.1 litre engine, why does the Santro have more low end torque than the i10?

The Vista65 that i have also has a nice punchy engine. Most times I can do speedbreakers even in 2nd or 3rd gears without breaking a sweat.

I have seen the torque/bhp map of this engine and it peaks at about 2400 rpm. But is available around 1200. In the city I can easily keep up with cars with better PTW ratio and still get a good FE (13-14 kmpl with AC). Where I really feel the pinch is above 80 kmph on highways where I have to really work the engine to get speed up. But in the city, I believe this is one of the rare engines of today which have a good low end torque.

Very true.
The Fire 1.2 engine that powers the Vista and Punto has adequate amount of low end torque.
The Chevy Beat has good low end torque.
Once into 3rd gear it pulls neatly from 15kph to 60kph without any strain. In moderate traffic i don't need to change the gear at all, unless i encounter a red signal and i drive it almost like an automatic:).
In comparision the Santro's 3rd gear too pulls neatly from 15kph but needs to be upshifted once you cross 45kph or else the engine sounds coarse. The only sore point with the Chevy is the 2nd gear which is too short but is very useful in tackling speed humps.
Thats from my usage of first gen and eRLX versions of Santro for 10 years and Beat for past 10 months.

I guess the problem of poor low end torque is more prevalent among the 3 cylinder engines.

OK a slight modification.
"For the same state of tune a higher displacement engine will have more low end torque compared to a smaller displacement engine."

In your example, both Santro and the i10 have the same engine, except that the i10 engine is tuned for slightly higher power 69 vs 63 and better torque 10.1/4500 vs 9.8/3000.
http://www.hyundai.com/in/en/Showroo...825215032.html
http://www.hyundai.com/in/en/Showroo...313114502.html

When you tune for better performance the torque curve peaks, that is the lower powered tuning gives a flatter torque, higher power engine gives a peaked torque curve, reducing torque at lower end.

From the figures you can see that for i10 the peak torque is at a much higher RPM, hence there will be less torque at say 2000 RPM compared to the Santro.

Forget small cars, i was overhearing a funny conversation between two TN government bus drivers. They were loathing the turbo charged buses because these buses dont climb the steep speedbreaker (found in Coimbatore bus stand, which only L/HCVs can pass without scraping) from standstill.

The NA buses seems to do it easily.

Umm.. not sure about the weight part, as cars are getting lighter and lighter. Eg: Front bumper.

Also, a heavy flywheel means, you can sustain the low momentum, like the older Bullets. In fact, its bad for starting from standstill.

Actually heavy flywheel was there to smoothen out jerks in low speed fewer (than 6) cylinder engines. In modern engines it reduces the effect of engine braking and hampers acceleration, hence the trend to lighter fly wheel.

Another reason was to facilitate starting, as older cars rarely (unless tuned perfectly) started in what we call 1/2 self, so that the momentum built up by the starter motor could start the engine easier.

I had planned for a Figo Petrol in April this year. Test drive was very unsatisfactory & i had to extend my budget to Figo Diesel.

The low end response & driveaability of Petrol Figo was not as good as M800 (2005 YM, which i was using at that time)

Great thread. The Palio 1.2 also suffered from poor low end torque, but that just provided an excuse to rev it! It can get frustrating in tight traffic where you need to get through a gap though. The Polo 1.6 is also awfully sedate before 2-2.5k rpms.

Interesting to read about the engine design/regulatory factors that have led to this. What actually determines how much power and torque an engine produces, and at what point in the rev range it is produced?

I do not own one but have driven my bro's ride and man NANO is fun to drive. Cannot compare it with Santro's experience but NANO is definately a city car and works in the b2b traffic with its zippy nature.

Any owner comments here on the NANO ?

Actually your point is in agreement with what thermalpast said. Heavier flywheel means you can maintain low momentum. Remember torque is Force X radius to put it simply and Force is a product of mass & acceleration.

By standstill means if you are saying that the engine is not running, then what you say is correct. But if the engine is running, then vehicle having heavier flywheel will be able to move the mass of the vehicle better, since smaller or lighter flywheel have to spin (or accelarate) to a higher rpm to produce the same torque. Here we should be comparing vehicles of same weight, though