Goughary

Our front diff is open. The torque transfer to the front halons from the trans.
If we had no diff locks we would have open diffs in the rear and front. Which isn't ideal.

On the track the awd is fantastic- when the car is set up right. But under certain circumstances the awd system indices understeer- and that is what needs to be addressed. Less differential locking may be the key there...

kos11-12

Do you then think its more a rear lock, side to side problem rather than transfering power to the front ?
It's mechanical right ? not electronic ? would something like and ECU could manage ?

r-mm

In principal its the F/R locking that would induce the most noticable understeer as the rear locking is in principal similar to the viscous limited slip in a C2. Similar obviously not identical. I have no idea what the Solonoid and brain are doing when it locks the rear and how it compares to a purely viscous unit which is what I believe all aircooled rear LSDs are?

Seems inside the realm of the possible to disable the F/R lock solenoid to drive with a permanent 69% Rear 31% Front power distribution and PDAS only providing rear diff locking.

kos11-12

kos11-12

http://www.rsr911.eu/en/2016/12/15/h...-modification/

Et voila

Goughary

Now where did that come from!?!!?!?

I like it! But is it as plug and play as it looks?

kos11-12

Doing a Research I came across an Italienne man that races quite successfully a 911 in safaris. I will post later the picture of the safari race car, it is very impressively prepared .
I then found the engineer, Mr Robert Sikkens from 911 RSR, based In the North of Italy .

In the mean time I emailed mr Sikkens to hear the details of the conversion, he also supplies electric heating and AC .
Maybe we could do a group buy .

Peteinjp

Off topic but the A/C compressor is interesting. Its a much simpler setup than the classic retrofit in that it does not require an ECU and or connecting to a computer. The down side being that there is only on/off with no speed scrolling.

Back on topic- I've been waiting for a c4 to pop up for winter use. Would be a blast and there is ice racing in Hokkaido.....

Pete

kos11-12

I be happy to remove the CCU if his AC works, simplifying things, maybe his electric fan will compensat.
Anyways Off topic as you said,
l am waiting to hear what are the parts involve and the setting for the manual AWD system.

Goughary

Yes - my thoughts are to do the manual diff lock control- and his four pole abs! Change both systems- that would be awesome. Did you happen to notice that abs controller?

Would make an enormous performance improvement

Mikke_Possu

More off topic but I remember that Sikkens from 911 RSR offers also 6 speed gearbox conversion to G64. Interesting stuff from that company.

kos11-12

Hi yes I have seen it, I need to talk to him to understand what parts are involved, I guess the quote on his web is including the work.
Personally not so sure of the hydro brake .
but the ABS may well be in the package .

-nick

Let’s pause for a moment.

Does it seem like a good idea for the rear diff and longitudinal clutch packs to be under constant preload? Mechanically, that’s a lot of heat and sounds like a good way to roast the clutch packs and gear oil. What was the g64 rebuild schedule for the C4 lightweight? New/inspected clutch packs after every race I’m betting.

Now the dynamics-
Having the rear diff under constant preload means the rear wheels want to always turn at the same speed. The result is more understeer all of the time. Twist the pdas **** on dry pavement for an example.
There’s more involved when it comes to the front/rear bias. Having the longitudinal clutch under constant preload means that the 69/31% rear/front weight distribution, is now much more front biased. The rear bias is part of the 911’s advantage in having more available thrust out of a turn when weight is transferred heavily to the rear wheels. With a preloaded longitudinal clutch, the torque bias may now be more like 50/50. So when you power out, half your thrust is sent to the front open diff. The front wheels are already unloaded and being asked to steer. You’re now asking them to do additional work pulling the car forward. The result is even more understeer and a loss of forward thrust because you’ll have an inside/unloaded front wheel spinning and providing no steering or propulsion.

The default 31/69% longitudinal torque split mimics the weight distribution and gives optimal accel traction, *when there is no weight transfer*. The system was tuned for street driving. In a steady corner, if the rear starts to lose traction, power is sent to the front. This pulls the car straight, and also induces some understeer. Both being good for street drivers.

When the pavement is wet, or off-road, weight transfer is greatly reduced. That’s when having more awd traction is beneficial for forward thrust.

The above is greatly simplified, but you really do not want to preload the clutch packs.

I know that Streather wrote that brake input releases active pdas intervention, which is also stated in some of the factory docs. But I’m not convinced that’s the full story. The 928 PSD system uses the rear diff lock to induce understeer under heavy braking (minimizing the “Ferraria effect”). Seems likely that the 964 is designed in the same way. If so, the logic of tapping the brakes to unlock the diffs when they activate during acceleration remains true, but pdas will still intervene to induce understeer under heavy trail braking.

We really need someone to disassemble the pdas/abs code.

Now on to the CCU... you know that it also controls the oil cooler fan, and all of the hvac flaps? The unit weighs about 1lb. Why get rid of it?

kos11-12

Dear Nick,

Thanks for your inpout.
I woun't pretende I undestand perfectly how our C4 system works, I was going to ask Mr Sikkens to explain me if the mod is realiable for a road occasionaly track cars.
Do you think the gearbox of Mr Agostini 964 rally car is dismantle every races during Paris-Dakar or Lybia rally ? Those are long races during the day and everyday for a few days, Maybe.
I guess I need to go back to basics and review everything on how our AWD systems is working.

Yes the CCU is opperating the flaps and at the same best is to remove them and go with the electric fan and heating, and I am surprise it controls the oil cooler fan, could you please explain how and why .