Date sent: Sun, 11 Apr 1999 09:44:34 -0700 To: 80_series@corp.sgi.com From: dmiller@iea.com (Doug Miller) Subject: [80] '93 80 f/r torque split ratio? Send reply to: 80_series@corp.sgi.com Anyone know what % of torque goes to each axle in high range? I have a US model with factory lockers and ABS. The question came up in the context of towing on the highway while discussing the Cruiser's amazing stability while towing. I have copies of old Audi research detailing their findings on the contribution of the change in tire footprint shape of a driven axle vs undriven (elongates in direction of travel) and suspect this is one reason for it. In casual conversation with a 7.4L S*burb*n owner, he was noting disappointing stability in crosswinds, and wondering if this would help him, etc. I am also wondering if my center diff is a viscous type in high range and mechanical in low range when it auto locks? The manual is as clear as mud on this feature. Thanks in advance. Doug Miller From: "Willem-Jan Markerink" To: 80_series@corp.sgi.com Date sent: Sun, 11 Apr 1999 22:13:24 +0000 Subject: Re: [80] '93 80 f/r torque split ratio? Send reply to: 80_series@corp.sgi.com On 11 Apr 99 at 9:44, Doug Miller wrote: > Anyone know what % of torque goes to each axle in high range? 50/50. > I have a US model with factory lockers and ABS. Doesn't matter, all full-time Cruisers are split 50/50 (including 90 & 100 Series, as well as RAV4 and Lexus RX300/Toyota Harrier....and every other Toyota full-time 4wd system (Previa, Ipsum, Corolla, Hiace). > The question came up in the context of > towing on the highway while discussing the Cruiser's amazing stability > while towing. I have copies of old Audi research detailing their findings > on the contribution of the change in tire footprint shape of a driven axle > vs undriven (elongates in direction of travel) and suspect this is one > reason for it. Very interesting....never heard this particular explanation before, IMO it's the pulling of the front wheels that add most stability....on our part-time 60, when towing very heavy trailers, I often resort to engaging 4wd on the fly to stabilize the combination when it gets prone to swinging on bumpy roads....huge difference. How much pages is this Audi research? Any chance I could get a copy too?....;-)) > In casual conversation with a 7.4L S*burb*n owner, he was > noting disappointing stability in crosswinds, and wondering if this would > help him, etc. Rear 2wd is definately less stable than full-time 4wd. You might suggest that he tries to engage 4wd in such situations, assuming shift on the fly like a (later) 60-series. Warn him that it's not a Cruiser, so he shouldn't keep in 4wd for very long....8-)) > I am also wondering if my center diff is a viscous type in high > range and mechanical in low range when it auto locks? The manual > is as clear as mud on this feature. Correct on both accounts, as long as your realise that the viscous unit is an *additional* LSD, NOT a coupler (like on so many other full-time wannabee vehicles (JGC Quadratrac +96, VW Syncro, Volvo AWD, Honda CRV etc) But with a few tricks/upgrades you can have 4hi-lock and 4low-open (apart fom the viscous LSD) as well. Details are on the 80's site. More stuff about drivetrain differences can be found on my homepage: http://www.a1.nl/phomepag/markerink/main_4x4.htm -- Bye, Willem-Jan Markerink The desire to understand is sometimes far less intelligent than the inability to understand [note: 'a-one' & 'en-el'!] Date sent: Sun, 11 Apr 1999 19:39:52 -0700 To: 80_series@corp.sgi.com From: dmiller@iea.com (Doug Miller) Subject: Re: [80] '93 80 f/r torque split ratio? Send reply to: 80_series@corp.sgi.com >> The question came up in the context of >> towing on the highway while discussing the Cruiser's amazing stability >> while towing. I have copies of old Audi research detailing their findings >> on the contribution of the change in tire footprint shape of a driven axle >> vs undriven (elongates in direction of travel) and suspect this is one >> reason for it. > >Very interesting....never heard this particular explanation before, >IMO it's the pulling of the front wheels that add most >stability....on our part-time 60, when towing very heavy trailers, I >often resort to engaging 4wd on the fly to stabilize the combination >when it gets prone to swinging on bumpy roads....huge difference. >How much pages is this Audi research? > >Any chance I could get a copy too?....;-)) Willem-Jan, After 15 years, 3 jobs and 8 moves, I wouldn't even know how to begin finding that report (begging your pardon). I'll give you the quick version: Audi took Audi 100's and 80's and ran them through several versions of track testing with and without the rear drive shaft connected. Since they had locking diffs then, it was quite easy. The tests included fans to develop side winds of 15-100kph on a variety of surfaces (ice, water, dry, bumps, gravel) and they measured the deviation of the vehicle while cornering and on the straight. They also had sensors on the steering wheel and in car cameras to record driver responses. They also had glass panels and high speed photography equipment to provide contact patch shapes. The testing determined that the Quattros were significantly more stable under all conditions with all wheels driven, with the differences being greater as the coefficient of friction of the surface dropped, the wind speed went up, or the vehicle speed went up. They identified several minor contributors, but by far the greatest was the change in shape of a driven tire's contact patch over a non driven contact patch. The contact patch elongates in the direction of travel, but maintains the same surface area since surface area is a function of tire pressure and simple downforce (plus or minus dynamic loading of course). Even though the comparison vehicle was front wheel drive (driveshaft disconnected), they found quite a difference. As I recall, dynamic handling and yaw behavior at/near the limit was also improved. My family is populated with Quattro nuts, and my wife and I just traded our 97 A6 Quattro wagon for a M*nter*. It shares the garage with our 80 (<-- 80 content). Now, back to my query. If the 80 hi range power transfer is via viscous, does the system need slippage to transfer torque to the other axle, or are they both driven always somehow? For instance, the Subaru system is basically front wheel drive on a dry street. It must have slippage to move the viscous fluid and thereby exert torque on the (usually) undriven rear axle. How does the Cruiser system differ? I should tell you I'm trying to determine if I'm always getting the same torque at all four wheels on the Cruiser. As I'm planning to tow this summer with the new M*nter*, I am trying to get an apples-to-apples comparison on stability under tow. I can run the M*nter* in 4 hi, and 4 hi with the center diff locked and will run down the exact system parameters on this system after establishing exactly what it is about the Cruiser I've been so happy with under tow. Doug Miller From: "Willem-Jan Markerink" To: 80_series@corp.sgi.com Date sent: Mon, 12 Apr 1999 17:47:15 +0000 Subject: Re: [80] '93 80 f/r torque split ratio? Send reply to: 80_series@corp.sgi.com On 11 Apr 99 at 19:39, Doug Miller wrote: > > >> The question came up in the context of > >> towing on the highway while discussing the Cruiser's amazing stability > >> while towing. I have copies of old Audi research detailing their findings > >> on the contribution of the change in tire footprint shape of a driven axle > >> vs undriven (elongates in direction of travel) and suspect this is one > >> reason for it. > > > >Very interesting....never heard this particular explanation before, > >IMO it's the pulling of the front wheels that add most > >stability....on our part-time 60, when towing very heavy trailers, I > >often resort to engaging 4wd on the fly to stabilize the combination > >when it gets prone to swinging on bumpy roads....huge difference. > >How much pages is this Audi research? > > > >Any chance I could get a copy too?....;-)) > > Willem-Jan, > > After 15 years, 3 jobs and 8 moves, I wouldn't even know how to begin > finding that report (begging your pardon). Okay, good thing your brain didn't get reshuffled too....;-)) > I'll give you the quick > version: Thanx, this is definately worth another chapter on my homepage, never saw this particular physical approach before. > Now, back to my query. If the 80 hi range power transfer is via viscous, > does the system need slippage to transfer torque to the other axle, or are > they both driven always somehow? Again, please realise that the Cruiser visco unit is an *additional* LSD, _on top of_ the normal center diff gears (which all full-time Toyota's have, Cruisers included). This means that the normal torque split is 50/50, until slip occurs at either front or rear....it will then lock up, to a maximum of 30% according to Toyota. This 30% is not all that easy to understand, since it refers to percentage of torque transferred....and that torque depends on the gearing between engine and center diff....so my educated guess is that they refer to 30% of maximum torque, which means in 1st gear (remember, it officially doesn't work in 4low, so this means 1st/high)....deducing a bit further, this would mean roughly a 100% torque transfer in 4th or 5th gear (less torque coming from the gearbox, yet visco unit still transfers the same absolute amount of torque, so the relative front/rear bias can be higher; 0/100 or 100/0, vs 80/20 or 20/80 in 1st gear). > For instance, the Subaru system is basically front wheel drive on a dry street. This 90/10 split is only present on automatic versions....manual Subaru's still have the proper 50/50 split. > It must have slippage to move > the viscous fluid and thereby exert torque on the (usually) undriven rear > axle. Yes Sir, correct, and this is where the crappy reactive AWD shows its ugly face....it doesn't help much in fast driven corners, where you want equal torque distribution *before* slip occurs (and before you start sliding out of the corner). In my book, this is reactive part-time 4wd, not full-time 4wd. In the old days, 'full-time' ment 'can be left engaged all the time'....my strict definition is 'sends torque to all 4 wheels all the time' (and more than 5-10%, as that is just barely enough to keep the wheels from being dragged along (with inherent drive-train clunk problems due to slack in the gears/joints)). > How does the Cruiser system differ? I should tell you I'm trying to > determine if I'm always getting the same torque at all four wheels on the > Cruiser. Yes you do, each wheel gets 25% under all conditions, until slip occurs, after that the viscous LSD will start doing its job, ranging from 80/20 or 20/80 (1st gear) up to 100/0 or 100/0 in 4/5th gear. > As I'm planning to tow this summer with the new M*nter*, I am > trying to get an apples-to-apples comparison on stability under tow. I can > run the M*nter* in 4 hi, and 4 hi with the center diff locked and will run > down the exact system parameters on this system after establishing exactly > what it is about the Cruiser I've been so happy with under tow. The full-time Montero's/Pajero's have basically the same drivetrain layout/concept as full-time Cruisers (with the addition of a 2hi option). You might even notice that locking the center diff increases stability when towing, but that's not something you can do for extended periods of time....the more you force each wheel in sync with the others, the more stable it will be....diff locks front and rear would further increase this effect, but be even less recommended for on-road use. -- Bye, Willem-Jan Markerink The desire to understand is sometimes far less intelligent than the inability to understand [note: 'a-one' & 'en-el'!] Date sent: Mon, 12 Apr 1999 12:56:48 -0700 To: 80_series@corp.sgi.com From: dmiller@iea.com (Doug Miller) Subject: Re: [80] '93 80 f/r torque split ratio? Send reply to: 80_series@corp.sgi.com >> As I'm planning to tow this summer with the new M*nter*, I am >> trying to get an apples-to-apples comparison on stability under tow. I can >> run the M*nter* in 4 hi, and 4 hi with the center diff locked and will run >> down the exact system parameters on this system after establishing exactly >> what it is about the Cruiser I've been so happy with under tow. > >The full-time Montero's/Pajero's have basically the same drivetrain >layout/concept as full-time Cruisers (with the addition of a 2hi >option). >You might even notice that locking the center diff increases stability >when towing, but that's not something you can do for extended periods >of time....the more you force each wheel in sync with the others, the >more stable it will be....diff locks front and rear would further >increase this effect, but be even less recommended for on-road use. Yes, I did notice an increase in stability by locking the center diff while on a snowy highway on our first road trip with the M*nter*. I didn't run it that way long as I haven't talked with a Mitsu rep about what it is designed to handle and the owners manual is the usual "buckle up and have fun" type. When you say above that it is basically the same concept as our 80, does this mean my 4hi mode is the same as the Cruiser in hi range? Because it not only differs by adding 2hi, but also 4hi-center diff lock. Still agree with your thought? Since there is a hi range center difflock mod on the 80 list, do you know if this mode can be operated at highway speeds for long periods on the Cruiser? Again, seeking towing stability in an area of high winds, for instance. Also, I tried to send this question to your return email address off the list, but it came back undeliverable - FYI. Doug From: "Willem-Jan Markerink" To: 80_series@corp.sgi.com Date sent: Tue, 13 Apr 1999 00:18:50 +0000 Subject: Re: [80] '93 80 f/r torque split ratio? Send reply to: 80_series@corp.sgi.com On 12 Apr 99 at 12:56, Doug Miller wrote: > >> As I'm planning to tow this summer with the new M*nter*, I am > >> trying to get an apples-to-apples comparison on stability under tow. I can > >> run the M*nter* in 4 hi, and 4 hi with the center diff locked and will run > >> down the exact system parameters on this system after establishing exactly > >> what it is about the Cruiser I've been so happy with under tow. > > > >The full-time Montero's/Pajero's have basically the same drivetrain > >layout/concept as full-time Cruisers (with the addition of a 2hi > >option). > >You might even notice that locking the center diff increases stability > >when towing, but that's not something you can do for extended periods > >of time....the more you force each wheel in sync with the others, the > >more stable it will be....diff locks front and rear would further > >increase this effect, but be even less recommended for on-road use. > > >Willem-Jan Markeri > > > Yes, I did notice an increase in stability by locking the center diff while > on a snowy highway on our first road trip with the M*nter*. I didn't run it > that way long as I haven't talked with a Mitsu rep about what it is > designed to handle and the owners manual is the usual "buckle up and have > fun" type. > > When you say above that it is basically the same concept as our 80, does > this mean my 4hi mode is the same as the Cruiser in hi range? Because it > not only differs by adding 2hi, but also 4hi-center diff lock. Still agree > with your thought? Yes, as 4hi-lock is present on - all 90-98 full-time non-ABS 80's (which means *all* 90-92 full-time models, as ABS/Visco didn't exist back then) - all +98 100-series And you can simply add 4hi-lock on ABS/Visco models by adding the switch....(personally I like it's related feature, 4lo-open, even better). > Since there is a hi range center difflock mod on the 80 list, do you know > if this mode can be operated at highway speeds for long periods on the > Cruiser? Again, seeking towing stability in an area of high winds, for > instance. Wouldn't want to run it for extended periods of time, only as a emergency solution. If you have that strong winds continuously, you better slow down.... You will probably notice that full-time makes enough difference over 2wd that locking the center diff only gives marginal benefits, probably not worth the risk of damage when using continuously. > Also, I tried to send this question to your return email address off the > list, but it came back undeliverable - FYI. Read the very last line of my sig carefully....;-)) -- Bye, Willem-Jan Markerink The desire to understand is sometimes far less intelligent than the inability to understand [note: 'a-one' & 'en-el'!] Date sent: Mon, 12 Apr 1999 13:37:07 -0700 (MST) From: Eric Madsen To: 80_series@corp.sgi.com Subject: Re: [80] '93 80 f/r torque split ratio? Send reply to: 80_series@corp.sgi.com > Since there is a hi range center difflock mod on the 80 list, do you know > if this mode can be operated at highway speeds for long periods on the > Cruiser? Again, seeking towing stability in an area of high winds, for > instance. Not without drivetrain windup or wheelslip. eric o-----------------------------------------------------------------------o * Eric Madsen | 9049 East Karen Drive, Scottsdale, Arizona 85260 USA * * mailto:eric@pnc.com | H:480-657-7576 | W:480-483-6800 | ICQ: 17077201 * * 61 fj25 283v8/sm465/np205 | 86 fj60 | 93 fzj80 | TLCA & AZLCA # 3728 * o-----------------------------------------------------------------------o From: "Willem-Jan Markerink" To: 80_series@corp.sgi.com Date sent: Tue, 13 Apr 1999 00:24:06 +0000 Subject: Re: [80] '93 80 f/r torque split ratio? Send reply to: 80_series@corp.sgi.com On 12 Apr 99 at 13:37, Eric Madsen wrote: > > > Since there is a hi range center difflock mod on the 80 list, do you know > > if this mode can be operated at highway speeds for long periods on the > > Cruiser? Again, seeking towing stability in an area of high winds, for > > instance. > > Not without drivetrain windup or wheelslip. Drivetrain windup can be proven or falsified by looking at the speed at which the center diff lock will disengage....when seriously binded up, it will take a long time to release, and this just doesn't seem to happen at high way speeds on our 80....almost immediate release. Same diagnosis applies to disengaging 4wd on part-time systems btw....same ease of disengaging on our HJ-60. I still don't recommend a locked drive train over longer stretches, but it is not as bad as some people want you to believe....and it is of course a totally different situation when you are not going straight. -- Bye, Willem-Jan Markerink The desire to understand is sometimes far less intelligent than the inability to understand [note: 'a-one' & 'en-el'!] From: 500 UPPL Rúnar Sigurjónsson To: "'80_series@corp.sgi.com'" <80_series@corp.sgi.com> Subject: RE: [80] '93 80 f/r torque split ratio? Date sent: Tue, 13 Apr 1999 10:55:43 -0000 Send reply to: 80_series@corp.sgi.com > Yes, I did notice an increase in stability by locking the center diff > while > on a snowy highway on our first road trip with the M*nter*. I didn't run > it > that way long as I haven't talked with a Mitsu rep about what it is > designed to handle and the owners manual is the usual "buckle up and have > fun" type. I (and most of the drivers) always run our cruisers in 4hi-lock on Ice/snow cowered roads. It not only offers slight more stability (they do have plenty off it in the first place tho), but mostly more predictable behavior, specially if you encounter slight snowdrifts or such on the road. Cheers Runar. From: EricRodi@aol.com Date sent: Sun, 11 Apr 1999 23:08:34 EDT Subject: Re: [80] '93 80 f/r torque split ratio? To: 80_series@corp.sgi.com Send reply to: 80_series@corp.sgi.com In a message dated 4/11/1999 7:35:52 PM, dmiller@iea.com writes: >If the 80 hi range power transfer is via viscous, >does the system need slippage to transfer torque to the other axle, or >are >they both driven always somehow? I don't know anything about this stuff. But it seems to me that the viscosity of the fluid means there is always some torque being transfered. I mean, even if all you had in there was water there would be some torque being transfered. But maybe at normal operating temperature the torque is negligible? How much temperature increase is needed in order to get the viscosity to the level it provides the maximum torque transfer? Is it possible to attach a heater (i.e. propane torch?) to the thing in order to obtain good torque transfer without the need for slippage? From: "Willem-Jan Markerink" To: 80_series@corp.sgi.com Date sent: Mon, 12 Apr 1999 13:38:59 +0000 Subject: Re: [80] '93 80 f/r torque split ratio? Send reply to: 80_series@corp.sgi.com On 11 Apr 99 at 23:08, EricRodi@aol.com wrote: > In a message dated 4/11/1999 7:35:52 PM, dmiller@iea.com writes: > > >If the 80 hi range power transfer is via viscous, > >does the system need slippage to transfer torque to the other axle, or > >are > >they both driven always somehow? > > I don't know anything about this stuff. But it seems to me that the viscosity > of the fluid means there is always some torque being transfered. I mean, even > if all you had in there was water there would be some torque being > transfered. But maybe at normal operating temperature the torque is > negligible? How much temperature increase is needed in order to get the > viscosity to the level it provides the maximum torque transfer? Is it > possible to attach a heater (i.e. propane torch?) to the thing in order to > obtain good torque transfer without the need for slippage? Apart from the fact that the Cruiser has a viscous *LSD* (additional to the normal center diff), and not a *coupler*: In contrast to popular belief (including several so called 'automotive journalists'!), visco clutches are not that temperature sensitive....there is a stage where this applies, the 'hump-mode', but normally the coupler/LSD is in 'shear-mode'.... Otherwise anyone in cold climates would not have any traction.... More about this on my homepage, in the FAQ on Traction Aiding Devices: http://www.a1.nl/phomepag/markerink/main_4x4.htm -- Bye, Willem-Jan Markerink The desire to understand is sometimes far less intelligent than the inability to understand [note: 'a-one' & 'en-el'!] From: EricRodi@aol.com Date sent: Mon, 12 Apr 1999 11:22:33 EDT Subject: Re: [80] '93 80 f/r torque split ratio? To: 80_series@corp.sgi.com Send reply to: 80_series@corp.sgi.com In a message dated 4/12/1999 6:21:00 AM, w.j.markerink@a1.nl writes: >but normally the coupler/LSD is in 'shear-mode'.... >Otherwise anyone in cold climates would not have any traction.... Well then how much shear is needed to get the rated torque transfer? How much do the front and rear shafts have to be out phase in order to develop the rated torque transfer? Is it more than 360 degrees or less? Inquiring minds want to know. From: "Willem-Jan Markerink" To: 80_series@corp.sgi.com Date sent: Tue, 13 Apr 1999 00:06:44 +0000 Subject: Re: [80] '93 80 f/r torque split ratio? Send reply to: 80_series@corp.sgi.com On 12 Apr 99 at 11:22, EricRodi@aol.com wrote: > In a message dated 4/12/1999 6:21:00 AM, w.j.markerink@a1.nl writes: > > >but normally the coupler/LSD is in 'shear-mode'.... > >Otherwise anyone in cold climates would not have any traction.... > > Well then how much shear is needed to get the rated torque transfer? How much > do the front and rear shafts have to be out phase in order to develop the > rated torque transfer? Is it more than 360 degrees or less? Inquiring minds > want to know. Way too many variables to make a accurate statement....viscosity of the fluid, distance between the slicing rotors, rotating speed of the unit, diameter of the rotors, the size and density of the holes in the rotors, and probably a dozen more....8-)) General comment: the old style visco units are known to require several revolutions of slip before any meaningful engagement takes place. The VW Syncro is known for this delay, as is the 96-98 JGC Quadra-Trac. -- Bye, Willem-Jan Markerink The desire to understand is sometimes far less intelligent than the inability to understand [note: 'a-one' & 'en-el'!]