[Rahul Rao]

Dynamic's of diesel are such that larger engines at lower speed give you better economy and cleaner engine. Longer stroke gives you better torque at lower speed, more efficiency, and a cooler exhaust.
The best speed for an engine is fractionally above where the peak torque is achieved, or just above the beginning of the turbo band.
First gen Innova had flat peak torque from 1400 rpm and above, this means it was electronically controlled, so as long as you down shifted in time to keep your engine spinning above 1400 rpm you remained in engine comfort range.


Many commercial vehicles where down sizing is not govt mandated have gon in for larger engines and lower speeds. Volvo reduced redline from 2400 to 1900 rpm and increased engine size from 7 Lit to 9.4 Lit during BS3 to BS4 change over, if you observe the few buses with AT engine remains in 1300 to 1600 rpm range.
In Scania buses that have only AT, lower gears take you above 2000 rpm, but stable cruising means engine is upshifting, and remains at or below 1500 rpm.



Rahul

[spr1ngleo]

Originally Posted by --gKrish--

PS : I'm way too young to be a 'Sir'

Never heard of Sir Ravindra Jadeja ?

[a4anurag]

Originally Posted by spr1ngleo

Sorry, raking up an old thread.
I have a 1.5 TDCi EcoSport 2019 model. Do I need to drive the vehicle in turbo zone (1500-2000 RPMs) continuously to squeeze out the best fuel economy? I doubt it because a lot of forums talk about the fact the more revs climb, the less fuel economy will you get. Does that mean driving in 1000-1200 RPMs range, and upshift ASAP?

The engine is happy when it is around the peak torque range which is generally 1,600-1,900 RPM in current generation cars.

If the engine is driven longer between the 1,000-1,200 range, it'll struggle to accelerate due to the engine is in the turbo-lag range. Once the turbo spools up, everything becomes better automatically (read combustion + driveability + FE).

I upshift around 1,800-2,000 range and can hardly notice turbo lag thanks to the good torque spread on the 1.6L CRDi.

[spr1ngleo]

Thank you all for those wonderful insightful responses, much appreciated. I am wondering what happens when the revs drop too low, and the engine races to keep itself alive, and speeds the car up automatically. This generally happens at crawl speeds. Such a behaviour bad for the engine's health?

[tharian]

Originally Posted by spr1ngleo

Sorry, raking up an old thread.
I have a 1.5 TDCi EcoSport 2019 model. Do I need to drive the vehicle in turbo zone (1500-2000 rpms) continuously to squeeze out the best fuel economy? I doubt it because lot of forums talk about the fact the more revs climb, the less fuel economy will you get. Does that mean driving in 1000-1200 rpms range, and upshift ASAP ? I doubt it again, as this will leave unburnt fuel stuck to the exhaust and may cause long term engine wear and tear. Really confused, please enlighten me (coming from NA petrol engine).

I was in the same boat when I started driving a diesel Aspire coming from a Figo petrol, few years ago.
The first year, I was driving it just like my petrol car, but since it was before I remapped the engine, I used to get 15kmpl with AC regardless of my driving habit. It took me a while to get used to the diesel character and drive accordingly, especially on highways. What I realized was, there is no point revving the engine through the gears, apart from the fifth gear when you are on a highway and need more speed. In city, don't look at the revs all the time to make your shifts, instead you will get used to the characteristic and automatically start shifting at the right revs and still have enough torque to take you through.
The other point is, in any rev, the more deep you press the accelerator, the more fuel it drinks. On a diesel, being gentle on the pedal is enough for you to move.

[theGeekyLad]

This is an awesome thread and I think the right place to drop my query in!

I drive the 2019 Innova, the 2.4L engine of which churns out its peak torque at 1400 revs. I understand that it's rather prudent to circumscribe the engine within the power band at all times (correct me if I'm wrong?).

Ever since I started driving this car, I've consistently mapped the RPMs to fallback RPMs across all gears and conventional speeds to ensure my shifts are smooth and also accompanied by rev matches done perfectly (yes, I'm a martinet) so much so that I realize, for the most part, after a gear shift (up with rev match or down with heel toe) I just slip my leg off the clutch abruptly every other time without even the slightest jerk in movement. That's a little background to my driving but here comes the real question ...

Given the power band (starting at 1400 revs) for this car, when I shift up 2-3 at around 1800-1900 revs, the fall back (on gear-3) is ~1200-1300 revs which is a notch / way below the the power band. Is this the right thing to do? I usually don't punch the revs beyond 2000 revs (maybe it's just on the ghats) especially because the ECO light flips off making me queasy (psst. I can change myself).

tl;dr
Long story short ... Innova's 2.4L engine has it's peak torque at 1400 revs ... gear 2-3 shift made under 2000 revs leads to a fallback RPM of ~1250 revs which is below the power band ... should I make the 2-3 shift at 2000+ revs such that the fallback is WITHIN the power band (1400+ revs) or have I been doing it right all the way?