Center Clutch Gtr R33. How Strong ? How To Do The Torque Splitting ?

[doo doo]

GTR diffs are pretty strong, the front is open and the rear is a mechanical LSD, a tighter centre on the rear is probably better for track, you can get LSD centres for the front. The centre clutch system is the only thing activated by attessa hydraulic system and is completely separate to the diffs.

[jogge]

so now i thought about something depending on the wet cluch system in the case.

i understand how it works, because this is pretty simple like every automatic gearbox will work.

but for example with the chrysler corvette with automatic gearbox when you are going for quatermile races, you upgrade your wet clutch system, to get all the power through it without breaking.

so i think if you want to run the active torque splitting system of an gtr box in a high powered car you also have to upgrade the center clutch !!!

because the system is calculated and built for approx 400HP/500NM ?! i think of these numbers, because the V-Spec version of the gtr is around this.

but in asia or i guess also in australia the people run much more than 500NM. and they use the cars on track and strip.

so how do they do that with the center clutch ?

Edited August 18, 2010 by jogge

[jogge]

thx for explaining.

so it isn´t necessary to use the gtr diffs. because they are NOT active.

ok less work for me.......

[doo doo]

The centre clutch is going to wear clutches before it breaks, Mine has 700hp at the fly and you can see the wear in my previous case, it was running RWD before I bought it though, plus that's 15 years of wear. Remember the attessa only transfers power in certain running conditions, not all the time so it's not going to wear like an auto box. Plus the GTR was designed for group A homologation racing and the strength of the stock driveline reflects this. Just remember the diff ratio scenario when running your stock diffs.

[jogge]

the gtr was homoligatet for group a. perfect !!!

it´s the same like with the cossi´s.

all the Escort Coworth have installed a lot of real good parts because of the homoligation.

the diffs of my car are 3.62 in front and rear.

if we change diff ratio, we only change it rear. and the balancing we do in the transfer case at the ratios of the splitting.

the system of the Ford MT75 4x4 gearbox is similar to the gtr box. only without the possibility of active torque splitting. and of course not so strong.....

[doo doo]

You'll have to run the same ratio diffs front and rear with the GTR transfer case, having not seen the ford AWD box transfer system I would also check the front diff is going to be turning the correct way too.

[T04GTR]

with regards to the 30/70 or 50/50.

it is not done that way. gtr sends a pre determined amount of torque to the front. ie the transfer case is set up to deliver up to 50kg/m torque. it pumps up the system with pressure and a very sensitive pressure valve. as the torque is transferd, it heats up. the system then dumps off pressure to the same it had in the begining.

you could do it manualy with some sort of pressure regulater to stop the pressure building up.

you could set up your ecu to turn on the pump in a form of traction control if it senses slip. or you could have it set up to throttle...

the hardest bit would be to modulate the pump fast enough to vary the torque output.

the standard gtr pump assembly has a pump,accumulator,dump valve and a pressure sensor.

the rest is tps input, rpm, speed(from speedo) fore and aft g sensor and steering angle with 4 wheel speed sensors.

it would be easier to adapt all the hardware from a gtr into yor car.

[saliya]

and also the semi-hellical gears are more stronger than straight cut gears, because the area of contact is bigger.

the only beneffits of straight-cut gears ist that they don´t loose so much power than the helical sets.and they are lighter.

... and there's no axial load component with straight cut; there is with helical (unless you get double-helical; which is unlikely).

Cheers,

Saliya

[doo doo]

... and there's no axial load component with straight cut; there is with helical (unless you get double-helical; which is unlikely).

Cheers,

Saliya

So I also thought that helical gears only had one point of contact that is transfered across the gear surface as it rotates, whereas the straight cut has full contact across the gear surface, this being part of the strength-in-design difference- the load on the straight cut is distributed across the whole gear face (better load distribution)whereas the helicals have a concentration of stress on the gear face at the point of loading. Correct me if i'm wrong. I've read that PPG have dealt with issues of gear design, strength and noise and as far as I'm aware it's the dog engagement that needs servicing rather than the straight cut gears. Yet to deal with this issue personally so simply info I've read but not yet experienced.

[jogge]

... and there's no axial load component with straight cut; there is with helical (unless you get double-helical; which is unlikely).

Cheers,

Saliya

correct...and also the gearbox case has not to take any significant torque.only the gears take it all.

in track day and race operation it´s often a problem that the gearbox case become warm. and because of that it loses stability because it´s alloy. so that´s a big problem for all gearboxes but more a problem for helical-gears. caused by the style of construction of the torque handling in the gears and the box itself.

[jogge]

So I also thought that helical gears only had one point of contact that is transfered across the gear surface as it rotates, whereas the straight cut has full contact across the gear surface, this being part of the strength-in-design difference- the load on the straight cut is distributed across the whole gear face (better load distribution)whereas the helicals have a concentration of stress on the gear face at the point of loading. Correct me if i'm wrong. I've read that PPG have dealt with issues of gear design, strength and noise and as far as I'm aware it's the dog engagement that needs servicing rather than the straight cut gears. Yet to deal with this issue personally so simply info I've read but not yet experienced.

in my case it´s not a problem of the dog-engagement.

all the dogrings and selector forks are always in really good condition.also after 15000km. no problem.

but always having problems on the surface of the gears. the guys from quaife calle it "bitings".

and this is caused by the long term use of the box. the gears are not built for use for 15000km.

it´s only built up for using at trackdays and races. so normally in one saison less than 5000km.

[jogge]

with regards to the 30/70 or 50/50.

it is not done that way. gtr sends a pre determined amount of torque to the front. ie the transfer case is set up to deliver up to 50kg/m torque. it pumps up the system with pressure and a very sensitive pressure valve. as the torque is transferd, it heats up. the system then dumps off pressure to the same it had in the begining.

you could do it manualy with some sort of pressure regulater to stop the pressure building up.

you could set up your ecu to turn on the pump in a form of traction control if it senses slip. or you could have it set up to throttle...

the hardest bit would be to modulate the pump fast enough to vary the torque output.

the standard gtr pump assembly has a pump,accumulator,dump valve and a pressure sensor.

the rest is tps input, rpm, speed(from speedo) fore and aft g sensor and steering angle with 4 wheel speed sensors.

it would be easier to adapt all the hardware from a gtr into yor car.

do you think it is possible to set the pressure in the center case manually to a fixed amount of pressure to have always the same torque splitting ?

what kind of pressure means what kind of torque splitting ?

the Escort Cosworth is fitted also with a G-Sensor and wheelspeed sensors at all four wheels.

so i think it should be possibel to get this all in function with the pectel motormanagement.

because the ECU is also running Lunchcontroll,Tractioncontroll.....

[GTRNUR]

the Escort Cosworth is fitted also with a G-Sensor and wheelspeed sensors at all four wheels.

Kudo's for having such a great project!

My recommendation would be to source an R32 gtr chassis loom from a wrecked car, along with the standard G sensors and Attessa ecu that are located under the center console. Then get a wiring diagram and a good automotive electrician.

Since you have speed sensors on all the wheels already, you would need to work out how to adapt those sensors into the GTR loom. The ecu then uses feedback from the throttle position, RPM tacho signal from the ecu, and steering angle.

If you can get an attessa system to work in standard form your 1/2 way there. Then you can get a torque split controller to allow you to fiddle with the torque split depending on the type of driving your doing at the time.

[jogge]

Kudo's for having such a great project!

My recommendation would be to source an R32 gtr chassis loom from a wrecked car, along with the standard G sensors and Attessa ecu that are located under the center console. Then get a wiring diagram and a good automotive electrician.

Since you have speed sensors on all the wheels already, you would need to work out how to adapt those sensors into the GTR loom. The ecu then uses feedback from the throttle position, RPM tacho signal from the ecu, and steering angle. WOW !!!

If you can get an attessa system to work in standard form your 1/2 way there. Then you can get a torque split controller to allow you to fiddle with the torque split depending on the type of driving your doing at the time.

it should be also not a big problem to install the wheel speed sensors of the GTR in my car.

but i have already wheel speed sensors at all 4 wheels caused by the use of the traction controll.

so i think i have to look in the workshop-manuals of a GTR how the sensors work.

i mean at which voltage it operate.perhaps it is compatible with my sensors-output.

i always wondering again, what kind of special features the GTR has already installed. WOW !!!!

Edited August 28, 2010 by jogge

[GTRNUR]

The speed sensors are a typical reluctor type sensor. Your standard cosworth sensors will be of the same type and should produce a compatible signal. Its best to keep your wheel sensors and in particular the wheel speed sensor trigger wheel standard so as to not interfere with the operation of your ABS system.

The GTR awd system is designed to be rear wheel drive most of the time.

The most basic operation of the transfer case occurs when the Attessa ecu detects a speed difference between the front and rear axels. Depending on how much speed difference there is, and the position of the throttle and engine speed the ecu deliveres an appropriate amount of front torque.

During cornering the G sensors come into play, as well as the steering angle sensor. Assuming a traction loss is detected while cornering, the amount of front torque delivered will be less than it would be in a straight line so that the AWD system does not cause the car to understeer(as much).

The R33 and R34 transfer cases have preload on the clutch packs and different attessa programming in the ecu which causes faster reacting front torque, which can lead to making the car understeer more. This also means you can not completely disengage the front drive, as there will always be a tiny amount of front torque. So you can not do burnouts without burning your attessa clutch packs.

Starting with an R32 transfer case would eliminate this issue, as the clutch packs completely disengage in 2wd mode. Its my belief that this, and the different attessa programming is a key factor in why the R32 gtr is such an awesome "drivers" car compared to the later models that are designed with more understeer in mind for safety reasons.

Good luck with the project.

[jogge]

Thx for explaining !!!

I will become a more and more clearer picture of the torque splitting system and the gearbox itself !

but do you think it is possible to set the torque splitting fix to 50:50 or 30:70 ?

or does i always have to use it in 2WD mode with an controller to do the torque splitting for AWD mode if needed ?

how can i identify a R32 or a R33 GTR box ?

i mean whats the difference if i look at the boxes ?

do i understand right, that it would be best if i order a complete new built up box from PPG, it´s best to order a R32 GTR box.

because that means also i will get the "better" torque splitting system !?

i want my car always more oversteer, because that suits most my driving style.

[Transpass]

As far as i remember, there's not much of a difference. R33 GTR box has 2 vents at the top (small and black) and a pull type clutch actuation - means the holes for the hydraulic clutch cylinder are behind the opening for the fork/arm. The R32 GTR box is a push type system. You can change the R33 GTR box from pull to push if needed (drill 2 holes in front of the opening for the fork/arm and get them threated M8 or M10 [not sure about that]).

Setting the torque split to less than 100% permanently would cause a lot of wear - just like a normal clutch sliding the whole time. Especially under hard racing conditions with such an amount of torque. Another issue: heating up (?)

As GTRNUR said: The system wasn't designed for long time AWD. Maybe there's a way to change the clutch packs to a longer lasting material or to put a complete new diff into the existing housing.

[T04GTR]

as for your gears waring out, have you got a pump and cooler set up? hollinger use an internal pump with a paper filter to stop all the bits waring out the gears...

[Transpass]

The "bits" you're talking about are metal particles coming FROM the gears - it's like a circle of death. The well known "whining" of a straight cut gearbox is caused by the teeth of the gears knocking and "grinding". Cheaper straight cut gears are made with less precise machinery and so they're prone to wear. Helical cut gears, on the other hand, are very pricy, have more contact area and are often more precise, therefore they can last longer (and some of them can handle more torque than straight cut gears, too).

Whining and wear can be reduced by filling more oil into the gearbox (-> lost performance) or buying very precise gears. Semi-helical gears (between helical and straight cut - very small tooth angles) are a compromise between wear/noise and performance, if you don't want to spent a looooot of money!

Better oil can also help, something like Motul 300LS (full synthetic) or Motul Gear Competition. And no i'm not a german Motul dealer, though german is correct.

[doo doo]

The preload in the 33's and 34's is hydraulic, and not in the mechanical setup of the system. Mechanically, the transfer case for the 32 and 33 is pretty much identical. Later 32's (april 93 on i think) have a pull type clutch so identical system to 33's.

The 33's run about 10% preload in the hydraulic system so running a set preload shouldn't be problematic- the wear in the clutches will come from different wheel speeds front and back and when there's load on the clutches through the hydraulic system. Heat in the system is in the electric pump itself- if it runs for more than 10 seconds in bleed mode it will shut itself off to protect from overheating, but pressure pumped into the system seems to be stored so it doesn't have to keep pumping to maintain pressure. You see this when bleeding the system, when you pull the white fuse and turn the key you hear the pump and watch the pressure gauge, then the pump stops but the pressure remains. When you crack the bleed valve the pressure starts to drop and the pump goes again- if you open the valve enough the pump goes continually, but will shut itself off after 10 seconds to stop itself from overheating as mentioned.

Ok, so this to me means you should be able to run a preset hydraulic pressure to the hydraulic actuator to have a continual percentage split. this can be variable- I don't think you'll be able to really accurately determine a percentage, just vary the pressure setting till you get the split that you need. If you get rear wheel spin and you have preload then you will start wearing the clutches more quickly- electronically controlled system would up the pressure in this scenario and there would be less rear wheel spin.

Transferring all the electronics to control it would make the most of the system, this is how it was designed after all.

A 32 attessa computer won't have preload and is slower in computing torque split (but this enables more oversteer characteristics and is more 'engaging for the driver' IMO) and I assume a 33 attessa computer will be responsible for the preload (and computes info quicker).