Calculating maxium incline ablity.

[ericmark]

Thank you you are confirming my calculations I selected 2007 Kia Sorento 2.5 CRDi XS (man. 5) it shows a speed at 1000 rpm in first of 5.3 MPH double that as 2000 rpm then divide by 2.48 gives 4.27 MPH which is close enough to the 4.4 MPH you quote.

I would not select a steep hill just for the fun of it, too many things can go wrong, however I think if in error I came across one, it would likely pull up it from what we have worked out.

I remember getting stuck with a land-rover on a concrete dispersal on an air field, one wheel had gone into a hole, I had jacked up the land-rover and in true Kelper style was going to drive off the jack, however the inter axle diff lock would not engage, so all it did was spin one wheel, at that time there was no link with ABS to auto brake a spinning wheel.

However even with the ABS this is not transferring power, it is simply turning some into heat it was the same with limited slip early diff they had cone brakes which braked the spinning axle. OK the Ford Sierra was one of the first cars I saw with a fluid link across the inter axle diff, so there are units now which I am sure are rather clever, but I think the Sorento simply uses the ABS.

I see nothing there to transfer power and stop the wheel spinning it seems all is done by the ABS, I only have a Auto/Low switch, in high range the car decides when to engage 4 wheel drive, not the best of systems as uneven tyre wear and cause it to keep auto engaging and disengaging so when time to change tyres has to be all together or at least an axle at a time.

So I have to expect some power to be lost, so the figures could be half that calculated, so I will not intentionally try to climb steep hills.

 

[Avocet]

You're welcome! I'm surprised that there's only a switch to swap from high to low ratios though - that would involve moving fairly "heavy metal" inside the transfer box!

If that image is of the Sorento centre diff, it's probably a bit cleverer than you think. It looks like it senses front wheel speed relative to rear wheel speed. There's also a multi-plate clutch in there. I'm guessing that it will have a computer which will be programmed to allow small differences in wheel speed between the front and the rear wheels (as you say, to account for tyre wear or a soft tyre or snow chains), but if the speed difference exceeds a threshold, it will engage that multi-plate clutch to force the torque towards the axle that is turning slower. How much it will allow that, I don't know, but it will provide SOME useful drive to the axle that doesn't have the spinning wheel on it. Most of them seem to be quite progressive (My wife has a Nissan X-Trail which does something similar but with a viscous coupling). I think the ABS will only be used to brake a wheel that is spinning on one particular axle - so in other words, if the left hand front wheel starts spinning, it will gently apply the brake to it, in order to try and make the right hand front wheel do some work - but that process happens independently of the "centre diff" that I think you're showing above. Whether the multi-plate clutch can lock up completely or whether it only allows (say a 50% difference in speed between the two axles, I don't know.

The other important point, is that almost every traction control system I can think of, doesn't JUST apply the brakes if a wheel starts spinning. It also controls the throttle (and in some turbo cars, the boost). The first strategy, on detection of wheel slip, is to reduce the power. Only then do they try applying one or more brakes. What this means, is that if it does break traction, it will just go really gutless - which is exactly what you DON'T want half way up a steep hill! For that reason, I might be inclined to turn off the traction control (and Electronic Stability Control!) before starting the ascent (although many cars turn it back on as soon as you exceed (say) 30 MPH).

 

[ericmark]

There is no option to turn traction control or anything else in high range, it is all automatic. I do miss the Yellow push leaver of the Land Rover. Can't remember the Gypsy, seem to remember unlike land rover you could select front or rear or both in high range, but low range always 4 wheel drive.