Please do not make the Torsen standard.

Sam Mitani drove the RX-8 and said that the car took off with a chirp from both rear tires. That would indicate that there is a torque sensitive differential.

Also he said that the turn in was on the soft[weak] side. Take out the torque sensitive and then see what the turn in would be like.

 

That would also imply that he didn't launch it properly. All sports cars if not properly launched will chirp off the line. Hell, even my crappy Maxima does it and there's no LSD at all.

 

Yeah, I can 'launch' my mom's Intrepid with a chirp of 1 tire.

He lauched it by either a semi-abrupt clutch engagement or by slipping it from above 4000 rpm. The traction was exceeded for just a little while, then the car had more traction (Torque sensistive) than power.

If the car had a speed sensitive differential, he would have had 1 wheel spin rather quickly (abrupt engagement) then the differential would bias torque (helping traction) and the faster wheel slow down rather quickly.

 

I don't know how this car will catch. I realized something though, that Car and Driver gets the best launch times because they hold the brake down, get the rear tires spinning (and smoking) then let go of the brake to get their 0-60 times. What a cheap way to do it

I think the ideal launch of this car would be around 3,000 RPMs without doing the previously mentioned Granted it could be lower but who knows until we start driving it!

 

Where did you see that method of obtaining 0-60 times? There is no way that will be the quickest lauch. I almost didn't even post in this thread because I thought it was stupid but It would be a disservice to society to let someone think that is how you make a car launch quickly. And depending on what you are driving a quick chirp could give you an ideal launch (probably a V-8 with some god low end torque) but smaller low torque motors need some revs to make power so wheel spin for the first 10 ft is about perfect. For example my '99 Z-28 would get the best sixty foot times with just holding revs @2000, drop the clutch then roll into the throttle, my 328 now needs 3900 rpm and some slipping to keep it from bogging and keep it mashed, an S2000 has to be on the big boy cams before it can get a good jump somewhere around 7500rpm and just dump it and let tires work. I'm thinking the renesis will like a 4500rpm dump and let the flat torque curve take over from there. What do you guys think?

 

Motor Trend television... they roared up this car and kept the brakes on while the rear tires spun and got 0-60 times....

 

You can hold the brakes and spin the rear tires on the stock car? Interesting.


I would think the best launch (depending on tire/surface/temp) is going to be around 4500rpms. Enough to not bog and take off with a little wheel spin, which is a good thing. With grippy tires, I would not be surprised to see a 5500-6000rpm launch.

 

Trick is first with grippy tires, that they have to also come to temperature.

So a few laps on the tires, then a stand-still launch would be ideal.

 

So that means that that is how Car and Driver launches cars too, huh? And that means that that's how Motor Trend launches cars for the best times, instead of just making a scene for a TV shot, or warming up the tires, huh? Shyeah, right...

---jps

 

*shrug*

 

I think it's already been stated by Mazda that a Torsen will be standard.

I'm not sure if I would attribute the soft turn-in as an effect of the Torsen. I think it's more to do with suspension tuning.

I'm pretty happy they're putting a Torsen on the RX-8. Doesn't wear out like a clutch LSD and it doesn't have the lag of a viscous LSD.

 

Does anyone know what the new Z uses?

It says "Viscous limited-slip differential"
Sure limited-slip is completely meaningless, but the last Z used a Viscous coupling clutch pack.


A Torsen differential, or any kind of torque sensitive differential [Rear Axle Drive], will cause power-on understeer, and off throttle oversteer (less of an effect than the power-on understeer)


I want my GeroDisc
http://www.audifans.com/archives/1998/09/msg00454.html
http://www.rubicon-trail.com/gerodisc/

 

Mike,

Can you explain a little more to me where you are coming from...I'm a little confused by your aversion to the torsen.

As far as throttle induced handling characteristics go, ANY car will exhibit power on understeer and off throttle oversteer due to the weight transfer under such conditions...simple physics...it really has nothing to do with what type of differential the car is using.

And generally speaking, as far as the torsen goes, it was always my understanding that torsens are very good as far as handling is concerned...in fact I've read an article where an automotive journalist attributes a great deal of the FD RX-7's handling ability to it's torsen differential. And Audi's famed Quattro is supposedly such a great handling AWD system because it uses torsen differentials as opposed to a viscous coupling.

Could you explain what it is about the torsen that you don't like?

 

Perhaps Mazda engineers already compensated for this understeer? I hope so, understeer is not fun!

Turn in, no bite... gotta keep turning!

 

The biggest asset of a torsen is the fact it alway works. Lets say we have a TorSen with a 3:1 TBR (torque bias ratio) 25% of the torque goes to the L (or front) 25% to the R (-ight or -ear) the other 50% is frictional torque (it can go anywhere) to as long as either side can take 1/2 of a nominal 50% your good.

This explains Audi Quattro's EXCELLENT 'jump' capabilities 60/40 F:R static unladen weight distribution (1.5:1) is within their TorSen's 2:1 TBR, and as they accelerate, it becomes even more inside the TBR 55/45 1.22, 50/50 1:1 (S4)

Side to Side weight distribution changes way more than the Fore/Aft. A Porsche 911 40/60 F/R goes to 60/40 under 1g braking, if it could pull a lateral g, the side to side would be about 80/20. Even if you only pull 2/3 g, you'd get 70/30. Since nearly every car uses a bevel gear differential 50:50 1/2 of let's say 200 hp=100hp to the unloaded wheel with very little traction. This get's even worse with a torque sensisitive differential because they distribute more torque to the inner wheel in turns.

Bottom line is that wheel spin would happen in something far less powerful than an RX-8, so it would be prudent to allow the driver to easily control it. The M3 uses the VKN ViscoDrive newest for it's M variable differential lock, and since the RX is like a junior M3, a speed sensitive differential is a must.
http://www.a1.nl/phomepag/markerink/viscolok.htm

 

Thanks for the info Mike!

 

Ditto. Thanks Mike

 

Hey all my bitchin' could be moot if the TBR is 1.5:1 or lower.

http://www.torsen.com/products/T-2.htm

 

OK, can one of you explain how that thing works... I looked at the diagrams for ages... but I don't think I am gonna get it without an explanation unless I can hold one in my hands... LOL

 

See if you don't reply somebody will always ask the question you wanted :D

 

Hey Guys,

I haven't posted much, but here goes. My 3rd gen 7 is the first car I've had with a Torsen rear end and I must say it works very, very well. I responds exactly how I want it to. So I was very happy to see that it would be standard equipment on the 8. just my 2 cents.

Mike

 

The FD is one badass handling car even when stock..up to par with about any exotic costing 100K+
The RB Miata post highest G's and fastest through the slalom as tested by 2 magazines
Both have Torsens
Heck even an MP3 can deliver faster slaloms times than a Maranelo. Now it has a turbo to boot
During the SevenStock 5 banquet, Mazda execs showed us an in-car video of a car sticking a Spirit R on some windy canyon road, the RX-7 pulled away on the straights but was caught under braking and turning, granted it has some 30 more HP and weighs about 200 lbs more ...they told us that we didnt see an RX-8 though ..heheh
Can we say that Mazda knows how to make affordable cars that have great handling?..YES!

:p