Rear biased centre differential for MY98UK
 

http://www.rallispec.com/product-diff.htm

CU-1200 Cusco Tarmac Gear (rear biased center differential) -- $1464

or another option, such as the new ScoobySport active centre differential which is supposed to be under development ? Changing car to an E7 onwards could be a cheaper option ;-)

http://www.btrprep.com/e7_qa.htm

btt

I have discussing this with a guy who knows his rallying. And another guy who built the S202 that won Targa Tasmania down here. The former love sit because he can have some serious fun in them but does not mention lap times. He just loves getting sideways in his wrx. The guy who built the S202 says that it will reduce your laptimes, as 50-50 is best split for quick laps.

Depends what you want really. If I had the $ I would get the tarmac rally in a second, but they cost helluva lot here. Over AUD$2,8k.

HTH

Probably the cheapest option would be to fit a DCCD diff, without the ECU to go with it. It would be 35/65 F/R.

You would also need to change your front diff to 3.54 or your rear diff to a 3.9 because your centre diff currently reduces the gearing from front to rear and the DCCD diffs don't. The non-turbo sport rear diff is a 3.9, but it doesn't have an LSD. You can move the crownwheel pinion from the 3.9 diff to your current rear diff (which is a 3.54 as standard).

I thought UK turbos had 3.9 rear diff ?

No they're 3.9 front, 3.54 rear

Hi Guys

I'm stunned at the amount of development required for the scoobysport active diff system.

I notice (for instance) from the details in the second link that it only have brake on/off rather than brake pressure. It *is* possible to do something with on/off but it makes a big difference if you can use the actual brake pressure.

Whilst the level of detail you need to focus on is mind blowing (to do it properly) it is an incredibly good fun thing to develop.

prana

You're contact suggests that 50/50 is the best torque split for lap times. Unfortunately, this just can't be the case.

Firstly you would need to have a fully open centre diff with a 50/50 torque split, so any loss of traction would reduce the power going to the wheels, but also...

any stage of a corner requires different torque splits for ultimate traction, so there is no set split that would be ideal for "lap times". Even from one corner to another, let alone from one circuit to another.

--

I'm looking forward to posting info about the development of the active diff system, as well as the suspension kit which is nearing completion now. :)

All the best

simon

Any ideas when Simon? A non-binding estimate would be fine :)

Thank you all for your responses

Simon,

Regarding "any stage of a corner requires different torque splits for ultimate traction, so there is no set split that would be ideal for "lap times". Even from one corner to another, let alone from one circuit to another." I look forward to the GPS add-on for your active diff system ;-) An update on development progress would be welcome

TopBanana

We are flat out trying to finish the struts currently. Latest prediction on them is around 5 weeks for the final articles for durability testing and final tweaks, so expect about another month after that (Assuming there are no major "discoveries" :D).

I can't see us getting all the final tweaks on the diff side done until after that's finished to be honest :(.. shame as the actual system is almost there.

Regarding development update...

Briefly (and without giving too much away that I'll get shot for)...

We now have a fully sensored car monitoring...

Wheel speed
Steering
Throttle
Brake pressure
handbrake
long G
lat G
Yaw

We have approximately 10 maps, and at any one time anything from 1 to 10 of them may be in force, depending on the "magic formula".

The system is designed to look at what the car is doing, and look at what the driver is asking it to do, and adjust the diff to give you what you want.

This is nowhere near as simple as it sounds.

Currently, we have the hardware installed with a USB / Serial port which allows us to hook the diff controller up to a laptop and run the maps live through the laptop. All the controls are virtual at present. This enables us to tweak things on the fly and quickly make changes necessary for testing.

The final unit will be just stunning...

It will sit just in-front of the DCCD wheel mounted within the centre console...
It will have two push buttons as strategy selectors (to cycle between maps).
A small digital display to show which map is selected.
A pot controller to allow the driver to set grip levels / manually tweak the strategy on the fly.
a USB port, to allow you to connect your laptop and upload new maps which can be downloaded from the scoobysport website. This port will also allow you to log data which you can send to us so our engineers can advise on tweaks to your diff maps to suit your driving.

It's a stunning system. Can't wait to get it on MY car, let alone have it ready for sale! :)

All the best

Simon

LOL re: GPS add-on!

Why oh WHY did you have to say that!! A GPS add-on so we can collect data on the type of road or circuit you are at... link it to the met office so we can automatically change your map for the road and weather conditions!!

God help us! :D

And the price is likely to be ??

Simon, remind some of us who can't remember things very well in our old age, is this active differential system only going to be available on; new age cars cars fitted with a DCCD-A, new age car's with the non DCCD-A 6 speed Sti 'box, on classics fitted with a DCCD, on classics either fitted with an ordinary 5 speed or (which is where I'm interested) on classics fitted with a 6 speed?

Price..

it really IS too early to say for sure... (and this is why this is going to be VERY vague - sorry).. but I would expect an absolute minimum of £750, and a maximum of £1500. Sorry that's a massive difference, but we just don't know for sure yet.

Tim

The standard system will be available for anyone with a DCCD or DCCD-A. Once you switch the system on, the DCCD controller, or the DCCD-A ecu will be disengaged and the scoobysport system takes over. Switch it off, and the car reverts back to standard.

So if you want it, you'll need to source a DCCD gearbox I'm afraid :(

We are also investigating replacement diffs, but this is a long way off.

Cheers

Simon

Balls :(

If 'I' were to source a DCCD differential/final drive pack would the diff ecu and controller be required as well, or would your new ECU take it's place?

I would prefer a rear wheel drive bias, but with a little bit of help when things get tricky would be nice ;)

Hi Tim

You wouldn't need the controller, as the "grip level" pot can be used in the same way as the standard unit :)

Regarding what your preference in handling is.. the great thing about this system is that regardless of your preference, you can have it exactly how you want it :)

Hmmm...this is getting better...right all I need now is a really stuffed Jap spec Sti 8/9 where only the centre diff survived ;)

Can it be plugged into a Pectel T6 for some really natty launch control? ;)

:D

It has a launch / drag map which balances off traction on drive train losses, etc. I'll ask Graham about linking it to the T6. :)

This could get very interesting, I'm sure we could find you some very high power/torque cars that the system could be tested on :D (Adam? Are you listening?)

are you fully integrating this into the ABS system on the new age cars? The DCCD-A system has an input to how the ABS system functions. Also the latest spec DCCD-A system has a new yaw sensor based strategy, the old DCCD-A uses a G sensor, the front LSD has been changed too, away from a suretrack to a helical to improve front end behaviour.

There are quite a few variables even on the classic DCCD setup, for example TypeR's have an open front diff, TypeRA's have a plated front LSD. Quite a lot of setup work is going to be needed no doubt, which should be fun. :D

cant wait to see this in action bet it helps with cornering speeds
































Sorry i just couldnt resist :D

LOL @ Tim

Adam is hounding me almost on a daily basis to get the active diff ecu finished!! ;) (sorry Adam, you know I love you for it! :D)

john

wasn't aware that the DCCD-A provides an input to the ABS, will look at that.

We have not (until this point) considered hooking into the ABS at all. We'll investigate, unless you have any specifics about how it interacts?

The DCCD-A strategies are very simple.. even the newer one with the Yaw sensor.

G sensors alone are not a lot of use as it tells you very little about what the car is doing on the limit - although it has to be said, the non-yaw DCCD-A is fun to drive.

One of the great things about this system however is that your comments about the differences in diffs is *almost* irrelevant.. obviously not quite, but not far off..

in that the ecu reacts based on what the car is actually doing, compared to what the driver is asking it to do... regardless of what's making the car do it.

We've tested it with mismatched tyres, pressures, rollbar settings, etc and the behavior is almost identical, which I have to say stunned me.

However.. the real complexities come with different driving styles.. and without question the biggest benefit will be delivered to those who spend time with our engineers in testing in order to map the diff for their specific requirements.

and nobody needs to worry about asking for something stupid.. the very top drivers do that all the time, so the two graham's, and Jim are more than used to it!! ;) :D

gossy.. you really are a true muppet! :D

Cheers

Simon

PS john...

whack an electric or hydraulic diff in the back of your car and we can map the hell out of that for you as well :D ;)

dont tempt me. :D That would be hilareous fun.

the DCCD-A is monitoring the following inputs.

Throttle position
Lateral G (and now yaw)
Hand brake switch
ABS active state (either on or off)
the four wheel speed sensors
stop light switch (brakes on or off)
rear diff oil temperature (either OK or too hot)
manual/auto switch
manual adjust pot

When the ABS becomes active, the centre diff controller lock rate is lowered to bring it to a more open centre diff, it looks like the ABS system is designed to work with an open centre diff (or at least a less locked static state diff setting), so if you are still controlling the wheel torque actively when ABS activates, the ABS system may have "issues". Worth looking into further anyway, this may be why the manual DCCD system could never be used with ABS, because it wasnt inteligent enough to unlock when ABS became active.

The rear diff temp also affects the DCCD-A setup, when the rear diff gets too hot the controller opens the centre diff, probably there to stop you killing the diffs when off road forcing you to get stuck in the mud till it cools down. :D

This thing sounds awesome ! I would love to hear of its progress... keep us updated Simon....

Simon, this sounds good as mentioned.. only minor concern is why USB??? some of us prefer to use serial, as used on most other 'ecu's'

A T6 specific input isnt much use to most, but a method of triggering the launch control via a seperate input would be nice.. then would add options for anyone with spare outputs.. unsure on what adam is thinking though.

When could we possibly have a look at the prototype or the finished system?

David

Thanks for the info John.

That's a relief as, if I understand you correctly, the DCCD-A does not affect the ABS, but rather the ABS affects the DCCD-A. This is already being considered.

The reason (and probably the reason why the DCCD-A does it also) is two fold...

In a non ABS car, the most powerful centre diff strategy for straight line braking is a fully locked diff. The reasons are that a) with a locked diff, the torque is split to the same split as the resistance (which is usually traction) and b) you are less likely to lock a wheel as you'll need to overcome the combined (now increased) traction of the two ends in order to lock an axle...

You can however still lock a single wheel as the rear and front diffs are still free to do what they like.

The problem is that it is more difficult to unlock a wheel than it is to lock one. In other words, it takes a lot more reduction in braking force to unlock a wheel than it does to keep one from locking. ABS is great at this, so from a safety point of view, the abs would be better equiped to do its job without the complication of the centre diff being locked.

---

So, we had already planned to recognise that the ABS was on, and (currently) half the diff lock - this 50% is obviously mappable, and we're still testing.

The ecu gives the most benefit to a non-abs car however, so some may actually want to switch it off.

There are four main master strategies selectors..
1) On Throttle (TPS > a certain percentage)
2) Off Throttle (TPS < a certain percentage, and brakes < a certain percentage)
3) On Brakes (brakes > a %)
4) Left foot braking (TPS & Brake > a %)

The problem with ABS is that it gets in the way of the LFB map, and can of course interrupt the On Brakes map.

It is incredible what you can do with all of this..

A nice story that one of our engineers tells (won't say which just in-case he'd rather I didn't say) is when he was working with a certain top wrc team.. the drivers were testing the new fly-by-wire throttle and mapping everything (including the diffs and engine, etc) based on this.

He told them all that he had programmed it so that if they went for the old "confidence lift" going into a high speed corner, the software will recognise this and just keep the throttle flat! :D

prana

Agreed, it's one of the most exciting things I've worked on. :)

All the best

Simon

Hi David

USB is purely because of space and simplicity. Every laptop has a USB port, but not all laptops have serial. A USB port takes up a few mm, but a serial port takes up a lot of room.

It also means the drivers install themselves so it was the closest to plug and play we could get.

If you want serial, you can hook up a USB > serial adapter :)

Regarding triggering the launch control...

As things stand.. one way you could do it, is simply to set the strategy to launch, then switch it on to your desired map once away from the line.

This isn't ideal, so I think we'll provide a port to allow an external device to switch maps.

Cheers

Simon

Simon, most new laptops might have usb, but not all old ones, Im thinking more in terms of I would have to upgrade from windows 95 to at least w98 for my laptop that gets used in the car so I could use my usb port :rolleyes:

Im well aware that you can get the convertors as we use them in the other direction to talk to serial ports on ecu's.

However some are using parallel now :o

Drivers can install themselves???? what the whole unit?

Hi David

Pure business sense tells us to focus less on people running operating systems that are nearly 10 years out of date!! ;) :D

With a USB device you can program the device to tell windows what kind of protocol it is going to use to communicate with it. Windows then loads the "friendly driver".

You still need to install the software to use the advanced features, but it's just a lot simpler.

Cheers

Simon