Re:torque to weight ratio?

Please don't tar all journalists with the same brush; some of us know what we're talking about. :whistle:

I always make a bee-line for the engineers if they've been made available at a launch. Having to listen to the sanitised crap that oozes out of the mouths of most PR people makes me want to gouge my eyes out with a spoon.

On the subject of power/torque ratios, they're meaningless, in my opinion. Is it true to say the Jimny doesn't have much power? Yes, it is. Does it cause it a problem? Certainly not off-road, and I'd argue it's hardly a handicap on-road, either. It does have a problem with its emissions, though, but that's another topic.

Lambert wrote: Sorry peeps but I'm not sure if I recognise the description of the driving dynamics of Jimny being bandied about here. Zebedee is a completely stock Jimny vvt auto 1.3. He isn't quite as quick off the mark as Ermintrude but how could he be. What he is though is every bit as capable of making decent cross country progress as any other vehicle in general British driving conditions ie traffic. He is never at the front of a queue of cars unless he has just overtaken the slow one and is pulling away. He can easily hold a line on corners at the speed limit etc etc. Yes on a deserted A road there's enough cars that can go faster but in all honesty when was the last time that ever happened? And then there's Ermintrude. A few Gucci parts and... "See ya!" It's rare that a well driven Jimny is out of it's depth on any surface. Most drivers on the other hand.....?

Sorry not saying it can't do it, just by comparison to the majority of road cars manufactured today. Not intended as a Jimny bashing, after all I own one as my daily drive and love it. But the same can be said of my 2CV, it is every bit as capable of making decent cross country progress as any other vehicle in general British driving conditions ie traffic, but I am not going to say it's as easy to achieve this as it would be in my Jimny if you see what I mean.

I wasn't meaning you. I was more meaning some sections of the motoring press.

Lambert wrote: You could have a thousand torque per tonne but if you are also gearing for a hundred mph in first you're not going to accelerate too quickly.

I beg to differ. Many motorcycles have less torque/ton but do 100mph in first and are anything but slow.


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And are motorcycles with entirely different dynamics to cars.

Preaching to the quire here but.........

When i first got the idea of understanding torque, i would think of my Makita drill. On notch 1 - It is slower but unstoppable. On its highest notch 8 - Its zippy fast .....but i can stop it with just 2 fingers.

You got me wondering about that motorbike example now - Scratch noggin!

I'm no engineer - Clearly

With a bike. The high speed available in first gear is not so much a factor of torque as it is the ability of the engine to rev extremely high and given that torque drops off as power increases over the rev range it's power that is giving you the ability to maintain the high revs. Also with bikes there is so little weight to move that acceleration is always going to be quite vigorous. There's also the implications of aerodynamics bikes having such a small frontal area. Different dynamics to cars. To get the same levels of performance you're going to have to have gert big lumps of power and torque to heave the cars weight and to bludgeon its way through the air.

Lambert wrote: With a bike. The high speed available in first gear is not so much a factor of torque as it is the ability of the engine to rev extremely high and given that torque drops off as power increases over the rev range it's power that is giving you the ability to maintain the high revs. Also with bikes there is so little weight to move that acceleration is always going to be quite vigorous. There's also the implications of aerodynamics bikes having such a small frontal area. Different dynamics to cars. To get the same levels of performance you're going to have to have gert big lumps of power and torque to heave the cars weight and to bludgeon its way through the air.

Makes perfect sense to me.

So surely as with the bike, torque to weight in the jimny is a big factor and is pretty important? Example being, the car bogs down x1 rear wheel and x1 front wheel in mud. The torque is directed to the non spinning wheels and it is able to pull the jimny out with just 2 wheels, and in some cases extra weight bearing down on said wheel/s. SaxJ had an interesting video where nearly all the weight was on one front wheel, the second wheel was kinda moving in slippy mud, but the other 3 were spinning there nuts off. You could see the weight bearing down on the front wheel, but the torque got the car moving. It was incredible.

Dont know where im going with this....... But me thinking toque is awesome.

Its always power that is moving things. That's why your car doesn't accelerate through the garage wall when you torque up the wheel nuts.
If the motorbike had 4x the torque, weight and power (aka an F1 car) the results would be much the same. I don't know the ratios, but I'm sure an F1 car could happily pull a 100mph first gear too and do it very quickly!
Now imagine a big diesel engine, that makes 1000/ton torque but at low revs so has a low power/weight ratio? That wouldn't work so well. Because its the power that is doing the work.

Jimny's have low power and low torque and low weight, so they compare reasonably well against bigger cars. But you do need to rev them to make good progress.

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In that situation it was entirely the traction control that is saving the day. If only one wheel is getting traction then the action of the differentials is to send all the torque and power down the paths of least resistance. Given there's no central diff that means that power and torque are evenly distributed to each axle. If the rear tyres have no traction they will spin pretty much evenly. Then if the front has one wheel with traction the differential will send the available power and torque to the spinning wheel. To remedy the situation the traction control will individually brake each spinning wheel and force the drive to the wheel with traction until such time as all the wheels are rotating at the same rate either because the vehicle is moving again or all four wheels are spinning uselessly and you're in need of the winch.

Busta wrote: Its always power that is moving things. That's why your car doesn't accelerate through the garage wall when you torque up the wheel nuts.
If the motorbike had 4x the torque, weight and power (aka an F1 car) the results would be much the same. I don't know the ratios, but I'm sure an F1 car could happily pull a 100mph first gear too and do it very quickly!
Now imagine a big diesel engine, that makes 1000/ton torque but at low revs so has a low power/weight ratio? That wouldn't work so well. Because its the power that is doing the work.

Jimny's have low power and low torque and low weight, so they compare reasonably well against bigger cars. But you do need to rev them to make good progress.

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Bingo!

"If only one wheel is getting traction then the action of the differentials is to send all the torque and power down the paths of least resistance"

You can shoot me if im wrong, but shouldn't it be "send the torque and power down the path of . most, resistance.?