Go Back   Team-BHP > Buckle Up > 4x4 & Off-Roading > 4x4 Technical


Reply
 
Thread Tools Search this Thread
Old 30th August 2011, 01:12   #106
AVR
BHPian
 
AVR's Avatar
 
Join Date: Apr 2008
Location: Ahmedabad
Posts: 930
Thanked: 511 Times
Default Re: Driving all four wheels: how is it done?

Quote:
Originally Posted by nilanjanray View Post
I was researching crawl ratios for 4Wd vehicles, and have a question for the Gurus: what are the factors that go into deciding the transfer case low range ratio?
Why is an interesting question.
1) Perhaps based on how offroad-biased the vehicle in question is? And how much of torque is available from the engine?
2) Perhaps to maintain reasonable crawl speed in idle in 1-L in conjunction with the crown-pinion and gearbox ratios?
3) Perhaps to provide maximum torque in a production vehicle which is within the stress limits of the other components like the axles, differentials and prop shafts?
4) Just because its already being used in the other models in a company's lineup
5) Safari/Scorpio/Thar use the Borg-Warner tc with a 2.48 ratio while it can go as high as 4 for the Wrangler lineup
AVR is offline   Reply With Quote
Old 30th August 2011, 01:34   #107
Senior - BHPian
 
nilanjanray's Avatar
 
Join Date: Oct 2007
Location: Bangalore
Posts: 1,810
Thanked: 2,236 Times
Default Re: Driving all four wheels: how is it done?

Points 1-3: I would think that a more expensive, offroad-cred vehicle (e.g. Pajero) would have a higher number, simply because it aids in slow speed crawling. I would think that offroad use bias, lower crawl speed, max torque tolerance would be better in a Pajero - simply because it is much more expensive, and is positioned/has been conceptualized as an offroader.

I read somewhere on this forum that Safari TC had 2.68 ratio. Could be mistaken.

Last edited by nilanjanray : 30th August 2011 at 01:37.
nilanjanray is online now   Reply With Quote
Old 30th August 2011, 13:46   #108
BHPian
 
Join Date: Aug 2009
Location: Trivandrum
Posts: 913
Thanked: 367 Times
Default Re: Driving all four wheels: how is it done?

Quote:
Originally Posted by SS-Traveller View Post
To the mind of the average car buyer/owner, 4WD gives the car some sort of invincibility in tackling no-road situations - which is not really true in most cases!
It actually improves your odds of getting out (without towing) if your vehicle is stuck. I had two instances in Trivandrum city when I had to take the help of locals to push the (front wheel drive) car:
1. Both front wheels in a deep 'pipeline' gutter across the road, car wouldn't move.
2. One front wheel in a deep gutter that formed during the rains - the car wouldn't move with power only from the other front wheel.
jinojohnt is online now   Reply With Quote
Old 28th September 2011, 14:34   #109
BHPian
 
Endeavour333's Avatar
 
Join Date: Jul 2011
Location: Chennai
Posts: 364
Thanked: 358 Times
Default Re: Driving all four wheels: how is it done?

Great technical thread! I love this stuff.

I have read through this entire thread and everything to do with getting power to all 4 wheels is extremely interesting! I have recently done quite a bit of research on Torsen differentials myself since my Ford Endeavour has one at the rear axle.

Everyone says that the Ford Endeavour is just a 'decent' off roader while the Pajero and Fortuner are better. Comparing their 4x4 drivetrains alone: (correct me if I'm wrong)

Endeavour: Part-time 4x4 with Center Transfer case, Torsen LSD in the rear - Meaning that you would need to lose traction in 3 wheels to come to a halt. Even if one rear wheel is in the air you can use the throttle-brake technique to get some power to the rear wheel that has traction to get out.

Fortuner: Lockable center Torsen differential that will just act like a Transfer case once locked, and also the India version of the Fortuner has No LSD in the rear. Meaning that once the center diff is locked, you would need to lose traction in only 2 wheels to come to a halt.

Pajero: Full time and part time 4x4 with a lockable viscous coupling differential in the middle. No limited slip differential in the rear. The 'Super Select 4x4' allows you to switch between the various modes like with center diff locked/unlocked, etc. No fancy electronics other than that. So once again this means that if you lose traction on one rear and one front wheel you're stuck.

If all the above is true then shouldn't the Endeavour possess the best off road hardware?

I'm also pretty certain that the Torsen Differential is considered to be the best sort of LSD right now. So why then is the Pajero considered to be such a good off roader? (just looking at the 4x4 system)

Next, I understand Suspension makes a difference too, in which the Endeavour comes in last and the Pajero in first. I completely agree, but would this affect off road capability much?

Now regarding approach, departure, and ramp angles, the Endeavour actually has greater angles than the Fortuner in Ramp and approach and equal in departure (according to each manufaturer's brochure). So the long wheelbase of the Endeavour is not that bad afterall? Not sure of the Pajero's angles.

So considering all this, the Endeavour should be considered the best off roader in theory right?

I've always wondered about this and would be glad to have my argument critiqued
There may be a chance that I have got some facts wrong so please correct me if you are sure that I have indeed gotten some wrong information.

- Vishnu

Last edited by Endeavour333 : 28th September 2011 at 14:39.
Endeavour333 is offline   (1) Thanks Reply With Quote
Old 28th September 2011, 15:42   #110
Team-BHP Support
 
Samurai's Avatar
 
Join Date: Jan 2005
Location: B'lore-Manipal
Posts: 22,233
Thanked: 13,978 Times
Default Re: Driving all four wheels: how is it done?

Endeavour's main Achilles Heal is the approach/departure angle. Don't worry so much about LSDs, most Jeeps/Gypsies on Indian offroad scene have open differentials in the front and rear.

And if Endeavour gets stuck, there is no tow hook to pull it back.
Samurai is offline   Reply With Quote
Old 28th September 2011, 16:07   #111
BHPian
 
Endeavour333's Avatar
 
Join Date: Jul 2011
Location: Chennai
Posts: 364
Thanked: 358 Times
Default Re: Driving all four wheels: how is it done?

Yup I understand that approach/departure angle is a concern. I am not even comparing off road capabilities of the Endeavour to the Jeeps. Just comparing to the Fortuner itself, the approach/departure angles for the Endeavour are the same if not greater than the Fortuner (according to the brochures).

Also, I'm getting a rear tow hook attachment done soon. As soon as I figure out the best way to do it that is - Another thread already exists for that purpose.

Last edited by Endeavour333 : 28th September 2011 at 16:08.
Endeavour333 is offline   Reply With Quote
Old 7th February 2012, 18:11   #112
BHPian
 
redrage's Avatar
 
Join Date: Mar 2005
Location: Bengalooru
Posts: 544
Thanked: 58 Times
Default Re: Driving all four wheels: how is it done?

Could someone explain the following queries,

1) As per the below indicated systems what category does the Fortuner belong to? Full Time 4WD or Permanent 4WD?

Name:  ft4wdp4wd.jpg
Views: 2269
Size:  73.6 KB

If it is full time 4WD as per the badge on its rear, in the open center differential condition, 2WD driving is also possible? If so, then in what conditions?

2) Does the Indian version of the Fortuner have Torsen LSD? Or the model sold here dosent have LSD system at all?

Sorry for the basic queries but looking for some inputs from the experienced folks.
redrage is offline   Reply With Quote
Old 7th February 2012, 18:21   #113
BHPian
 
Endeavour333's Avatar
 
Join Date: Jul 2011
Location: Chennai
Posts: 364
Thanked: 358 Times
Default

Quote:
Originally Posted by redrage
Could someone explain the following queries,

1) As per the below indicated systems what category does the Fortuner belong to? Full Time 4WD or Permanent 4WD?

If it is full time 4WD as per the badge on its rear, in the open center differential condition, 2WD driving is also possible? If so, then in what conditions?

2) Does the Indian version of the Fortuner have Torsen LSD? Or the model sold here dosent have LSD system at all?

Sorry for the basic queries but looking for some inputs from the experienced folks.
1) The fortuner by the categories in the picture is a "permanent 4 wheel drive". The fortuner has only one torsen and it is in the middle. It is always in 4 wheel drive and can lock the center diff alone. 2wd not possible. When center diff is not locked the torsen splits power between the front and rear axles. Power is split 50/50 until there is wheelspin at any 4 of the wheels. The front and rear axles are always open diffs regardless of what mode you put the fortuner in.

2) Indian version has open diffs front and rear. No torsen.

Hope this answered all your questions
Endeavour333 is offline   (1) Thanks Reply With Quote
Old 7th February 2012, 18:41   #114
Distinguished - BHPian
 
SS-Traveller's Avatar
 
Join Date: Jan 2009
Location: New Delhi
Posts: 6,594
Thanked: 10,643 Times
Default Re: Driving all four wheels: how is it done?

^^^@redrage: ...and to continue on Endeavour333's answer, the Mitsubishi Pajero by the classification you have given, is a Full-Time four-wheel drive - wherein it can also be used in 2wd mode.
SS-Traveller is offline   Reply With Quote
Old 7th February 2012, 20:13   #115
BHPian
 
redrage's Avatar
 
Join Date: Mar 2005
Location: Bengalooru
Posts: 544
Thanked: 58 Times
Default Re: Driving all four wheels: how is it done?

Quote:
Originally Posted by Endeavour333 View Post
. The fortuner has only one torsen and it is in the middle. It is always in 4 wheel drive and can lock the center diff alone.
Indian version has open diffs front and rear. No torsen.
Ok, then:

Quote:
Originally Posted by 4x4addict View Post
To add my 2 cents:

the Fortuner uses a more expensive and robust Torsen Limited Slip system to attain the required objective of providing power to the front differential. If either off these systems are not used, then a center differential pretty much makes a vehicle 2WD (either front or rear only) unless it is manually locked.
Did he mean for the international version the fortuner uses Limited slip?
redrage is offline   Reply With Quote
Old 7th February 2012, 20:22   #116
BHPian
 
Endeavour333's Avatar
 
Join Date: Jul 2011
Location: Chennai
Posts: 364
Thanked: 358 Times
Default

Quote:
Originally Posted by redrage

Ok, then:

Did he mean for the international version the fortuner uses Limited slip?
The international version has a lockable rear differential in addition to the torsen in the middle.
Endeavour333 is offline   Reply With Quote
Old 8th February 2012, 15:30   #117
BHPian
 
redrage's Avatar
 
Join Date: Mar 2005
Location: Bengalooru
Posts: 544
Thanked: 58 Times
Default Re: Driving all four wheels: how is it done?

Ok. So i presume the Indian T-fort comes with such a configuration? (Only Torsen LSD for Center Differential)

Name:  TORSEN Centre Diffrential.jpg
Views: 2052
Size:  78.6 KB
redrage is offline   Reply With Quote
Old 8th February 2012, 20:51   #118
BHPian
 
Endeavour333's Avatar
 
Join Date: Jul 2011
Location: Chennai
Posts: 364
Thanked: 358 Times
Default

Quote:
Originally Posted by redrage
Ok. So i presume the Indian T-fort comes with such a configuration? (Only Torsen LSD for Center Differential)
You are correct. The Ford Endeavour and believe it or not, even the Tata safari 4x4 both have torsen LSDs at the rear. The Endeavour's Torsen works extremely well when both wheels are in contact with the ground. I've tested it quite a few times.

With a torsen LSD, when one wheel is in the air, 0 torque goes to the wheel that has traction. The trick to getting power to the other wheel on the ground is to apply the hand brake to provide some resistance to the wheel in the air. The torsen LSD multiplies whatever resistance the handbrake puts on the wheel in the air 3 to 5 times (depending on some ratio of the torsen) and transfers that torque to the wheel that has grip. Works very very well on the road. Lots of sports cars use torsen LSDs including the Lexus LFA. But when Offroad, their use is sort of limited. The only places where a torsen will help you Offroad is when you are in slush or sand (both wheels are making contact).

Hope this has helped your understanding.
Endeavour333 is offline   (1) Thanks Reply With Quote
Old 9th February 2012, 21:46   #119
Distinguished - BHPian
 
Join Date: Jul 2009
Location: Kolkata
Posts: 3,477
Thanked: 2,013 Times
Default Re: Driving all four wheels: how is it done?

Quote:
Originally Posted by Endeavour333 View Post
You are correct. The Ford Endeavour and believe it or not, even the Tata safari 4x4 both have torsen LSDs at the rear.
Hi,
Thought the Safari LSD was clutch based.
No idea about the Endeavours LSD, but a Torsen is expensive.

Regards
Sutripta

Last edited by Sutripta : 9th February 2012 at 21:47.
Sutripta is offline   Reply With Quote
Old 9th February 2012, 22:28   #120
Distinguished - BHPian
 
SS-Traveller's Avatar
 
Join Date: Jan 2009
Location: New Delhi
Posts: 6,594
Thanked: 10,643 Times
Default Re: Driving all four wheels: how is it done?

Quote:
Originally Posted by Sutripta View Post
Thought the Safari LSD was clutch based.
The Safari indeed has a clutch pack based LSD - as is the Xenon's.
SS-Traveller is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
All Hail Crusoe! Fiat Linea T-Jet+ : Four years and 47,000 kms done Biraj Long-Term Ownership Reviews 258 8th June 2017 16:18
Does ABS require disk brakes on all the four wheels? abhilashvk Technical Stuff 26 23rd February 2010 00:36
News: Car loses all four wheels on highway DriverR Street Experiences 10 10th July 2009 13:52
Two sets of four wheels uy663z SUVs, MUVs & 4x4s 37 3rd December 2007 09:39
Four Wheels under 3 Lakhs gemithomas Hatchbacks 33 16th April 2007 13:21


All times are GMT +5.5. The time now is 11:06.

Copyright 2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks