While we wait for the BS6.2 Gurkha, here’s a breakdown of what actually makes these two similar beasts so different.
BHPian vigneshkumar31 recently shared this with other enthusiasts.
Force Gurkha Vs Mahindra Thar – Engine & Drive Train – Technical Analysis
The Thar and the Gurkha have their own strengths and weaknesses. While the Thar has enjoyed runaway success, the Gurkha sales figures can be celebrated only in comparison to its own previous generations.
While I have often lectured that these are two different beasts for different kind of folks, the loudest nay against the Gurkha, where it has been battered to shreds by netizens has been for its paltry 91bhp power output. This is the popular opinion of many test drivers and unanimous complaint of even more keyboard warriors. But you ask the GURKHA owners – while they nod vigorously that they would love more power, they silently agree that the Gurkha does pull clean at the low end, out of anything. And while its not meant for triple digit speeds on highways, it slowly climbs up to 90-100 and it can hold it all day like a freight train. The Thar on the other hand zooms past and rides triple digits on highways comfortably (for jeep standards). The Thar is more eager and the Gurkha laid back and ponderous.
So while wait for the BS6.2 Gurkha, here’s a breakdown of what actually makes these two similar beasts so different. As I wrote in my initial review, what makes one the Swiss Army Knife and the other a Sledge Hammer?
While this tech breakdown may be basic knowledge to many forum members, I hope few would find it educating.
Let’s start with the gurkha’s FM 2.6 common rail – this is a mercedes-derived engine the good old om-616, it’s been called a dinosaur of engines and has been around for decades. Force has it across the board as its staple even right up to its latest premium urbania. This is mated to the mercedes-derived old Workhorse g28 5-speed gearbox this combo is old but it works- it’s simple and gets the job done. But in my personal opinion this combination is unfair to the bs6 gurka.It deserves the 2.2 liter engine and the g32 gearbox combination which we saw in the extreme, that would have been a fitting kit for this purpose-built off-roader sadly we have to deal with what’s on offer so the 2.6 and g28 it is.
We will pit it against the thar’s 2.2 M-hawk for equivalence, we will not involve the petrol M stallion.The mhawk is mated to the 6r320m six-speed manual gearbox. I just love the mhawk and how versatile Mahindra has tuned it in its different products. it’s a superb engine!
But how are these two powertrains different? You will not find that answer anywhere on the internet so here is the exclusive engine performance curves, I have generated, of both these motors.
The mhawk makes its peak power at 3750 RPM putting out 130 horses while the Gurkha’s 2.6 puts a lower peak of 91BHP but a little earlier at 3200 RPM. It is sad that they didn’t even bother to give us the Tempo Traveler tune of 115 BHP on this gurkha
The mhawk and 2.6 both have torquey motors with flat top curves but the gurkha hits its peak talk earlier at 1400 RPM itself while the mhawk takes its time till 1600 RPM to put out a decent 300 newton meters of torque and holds its flat over a wider RPM bandwidth.
Hitting Peak at 1400 RPM, so early is a very impressive thing for the Gurkha which makes it a very strong low end puller. Within their respective flat top bands you will see that the power delivery is nice and linear and makes both these engines strong torquey Motors. But, on the right side of the graph the Gurkha has virtually no top end and that’s the region where the thar clearly shines stronger it gets better run at speeds on highways and the wider torque band also means that the thar will have better in gear acceleration and overtakes better on the highways while at these speeds, the Gurkha will run out of breath.
In summary, make no mistake the mhawk is clearly the more powerful engine because simply at every RPM it makes more power and torque than the 2.6 but the engine is just one part of the puzzle!
The next bit is the gearbox. Let’s break open both these gearboxes -The gurkha’s g28 has five gears whose diameters are in the ratio shown in the image, which we call the gearing ratio and the thar has six gears.
Lets calculate the “gear ratio spread” which is simply the largest gear divided by the smallest gear – this gives us an idea of the bandwidth within which the gears are distributed.
The Gurkha has a wide 5.83 bandwidth while the thar crams its six gears in a narrower 5.53 bandwidth. What this means that the gurkha’s ratios are wider and relaxed spread than the thar’s.
The lower gears are of a larger diameter and help in torque multiplication and pulling while the higher gears are ideal for speed and easy cruising. We can immediately see how wide the lower gears including the reverse gear, are in the Gurkha compared to the thar. The Thar has a smaller fifth and sixth gear for highway speeds additionally.
What are these gearing ratios and diameters and physically what do they mean?
Well if the first gear has a 3.96 is to one ratio in thar – it means that whatever torque the engine supplies the gearbox will multiply it 3.963 times when the vehicle is in first gear, so the gurkha’s wider first and second gears are going to help it with the torque and pull better while the thar’s narrow fifth and sixth are going to help it with speeds and Highway cruising.
The next part of the puzzle is the differential on the axle, which introduces another set of Gears which multiply the torque again by the number which we call- “axle ratio” which is 4.3 for the thar and 4.363 for the Gurkha.
The combined effect of all these gears is what is called the “final drive ratio” which means the torque which is supplied by the engine of the Gurkha gets multiplied about 20 times by the time it reaches the wheel, the Thar does it 17 times!
This is the reason for the tractor-like pull in first gear of the gurkha- strong low end torque!
This also means that if the engine’s crankshaft is spinning at 2000 RPM then the wheel axle will only spin at 100 RPM (or 20 times rotation speed reduction)
In Top Gear you want the opposite you, want a smaller torque multiplication and more speed instead so the overdrive gears (which have ratios less than one in decimals) they are slotted into in respective top gears the thar has the
final drive ratio of 3.08 which is better because we want a lower number and more speed while Gurkha does 3.52, so Thar is going to hit higher speeds on highways easier and cruise with lesser strain on the engine and return a better mileage because of these smaller overdrive gears. The Gurkha climbs up on the speedo slow and steady and settles down comfortably at around 90 to 100 kmph its large displacement 2.6 liter engine, can hold the speed and cruise all day like a freight train effortlessly.
But the story is not finished even now because these are four wheel drive trucks and they have transfer cases, which again have a set of Gears inside one for high range and one for low range. If we slot into 4H, the transfer case ratio is (one:one) so we get no torque multiplication additionally but we merely clutch in the front differential and the transfer case splits torque to front diffs where it is identically multiplied by the front differential ratio which is same as the rear differential.
In four wheel drive low 4L, is when you get the beast mode The transfer case multiplies the torque, by another 2.018 times before the split so the final drive ratio in this case when you’re using all extreme gears – like first gear on the manual box and four wheel drive low in the transfer case will result in the maximum possible final drive ratio which is called the “crawl ratio” which is a whopping 41 times stock multiplication
So the 100 Newton meter your engine put out comes out as a massive four thousand hundred Newton meter at the wheel and that will pull through anything on your path in four wheel drive low. Remember your axle now spins only one time for every 40 RPM of the engine so you’re going to get that much control while applying this torque through yourslow moving wheels and hence this is called a crawl ratio. The Thar similarly has a slightly better crawl ratio of 42.26 which makes both these trucks beasts – when four low is engaged.
Hope this clears the air out -Sledgehammer vs Swiss Knife! I’ve explained this in more detail in this video.
Keyword: 2020 Mahindra Thar vs 2021 Force Gurkha: A technical comparo