What's an L.S.D. Volkswagwen like to drive (high horsepower)?

[Jim Ratto]

Curious how they behave in corners with power applied.

Thanks

[Zach Gomulka]

Good question for Bruce Tweddle...

I imagine it just flat goes... instead of the inside rear wheel lifting and spinning, more power is applied to the outside wheel??

Anyway, I plan to find out in the GTV, somewhere in the not too distant future

[Jim Ratto]

there's a canyon road I take home, with many uphill, decreasing-radius corners, perfect for power-on-oversteer. I can wait to get into corner late, then apply a little throttle to point car in the right direction, with a little wheelspin. It actually makes the car handle "better" to me. I wonder how it would react with it locked up.

[Bruce]

Just like the Dukes of Hazzard! 

If you get hard on the throttle in the corner, the tail goes out.  In some ways, an open diff is very forgiving.  You can do whatever you want in the corner and not get too much into trouble.  When the inside wheel lifts, no power is being applied to the ground.

If you gradually apply power, you don't get wheel spin.  The LSD will prevent that, allowing you to put more power to the ground.  The lockup % of a VW diff is quite low compared to many others, so it takes a lot more hp to get into trouble with a VW diff than others.

What's the name of the canyon road?

[richie]

Fun

cheers richie,uk

[Jim Ratto]

Just like the Dukes of Hazzard! 

If you get hard on the throttle in the corner, the tail goes out.  In some ways, an open diff is very forgiving.  You can do whatever you want in the corner and not get too much into trouble.  When the inside wheel lifts, no power is being applied to the ground.

If you gradually apply power, you don't get wheel spin.  The LSD will prevent that, allowing you to put more power to the ground.  The lockup % of a VW diff is quite low compared to many others, so it takes a lot more hp to get into trouble with a VW diff than others.

What's the name of the canyon road?

Box Canyon
runs from Canoga Park area to Simi Valley.

Fun 3 miles or so 

[Lee.C]

Fun

cheers richie,uk

it sure looks it dude 

[Tony Wilkie]

Just like the Dukes of Hazzard! 

If you get hard on the throttle in the corner, the tail goes out.  In some ways, an open diff is very forgiving.  You can do whatever you want in the corner and not get too much into trouble.  When the inside wheel lifts, no power is being applied to the ground.

If you gradually apply power, you don't get wheel spin.  The LSD will prevent that, allowing you to put more power to the ground.  The lockup % of a VW diff is quite low compared to many others, so it takes a lot more hp to get into trouble with a VW diff than others.

What's the name of the canyon road?

Box Canyon
runs from Canoga Park area to Simi Valley.

Fun 3 miles or so 

Miss that canyon back road! When I lived there. I would race my gti through the hills and let it all hang out.

Hey Jim, is arao engineering still in chattsworth?

tw

[gingabloke]

Fun

cheers richie,uk

Seconded! 

Although roundabouts (turning circles for our colonial cousins ) can be fun/tricky in the wet. Put the power too early and you do a quick 180º! 

[Bruce]

What's the name of the canyon road?

Box Canyon
runs from Canoga Park area to Simi Valley.

Fun 3 miles or so 

Mapped and noted! 
Gonna check it out next time I'm in the valley.

[Jim Ratto]

Just like the Dukes of Hazzard! 

If you get hard on the throttle in the corner, the tail goes out.  In some ways, an open diff is very forgiving.  You can do whatever you want in the corner and not get too much into trouble.  When the inside wheel lifts, no power is being applied to the ground.

If you gradually apply power, you don't get wheel spin.  The LSD will prevent that, allowing you to put more power to the ground.  The lockup % of a VW diff is quite low compared to many others, so it takes a lot more hp to get into trouble with a VW diff than others.

What's the name of the canyon road?

Box Canyon
runs from Canoga Park area to Simi Valley.

Fun 3 miles or so 

Miss that canyon back road! When I lived there. I would race my gti through the hills and let it all hang out.

Hey Jim, is arao engineering still in chattsworth?

tw

Hey Tony, yeah Russ (?) is still there, more V8 stuff than VW I think

[mg]

Jim, Mark Herbert use to say “cars without a limited slip do funny things”.
I believe on Mark's wild donut video he was testing the Quafe TBD.
With an open diff you can't throttle steer.
Mark's video was a great display of his throttle steer talents.
Throttle steer is how you corner in racing, at the limit you steer it with both the gas pedal and the steering wheel.

There are two basic differentials used in racing, Torque bias differentials and limited slip differentials.
Torque bias diffs only work under acceleration, so on decel you basically have an open diff.
This is the choice for a lower speed auto cross with tight turns where drivers may want to pinch the car on entry to tight corners at lower speeds.
 The TBD acts as an open diff off throttle allowing the car to rotate easily, the rear is loose and the car will experience less push compared to an LSD.
(I use to AX a 911 with an LSD, the car was a bit tight. Perhaps offset by Torsion bar choices, sway bar settings and driver technique).
A Limited Slip Diff works on both acceleration and deceleration.
An LSD is the choice for road racing. At high speed you want the added stability the LSD provides off throttle.
Basically in a 90 mph sweeper in 4th gear you want the rear end to be as predictable as possible as you throttle steer.
Contolling the wieght transfer with the throttle transfer the wieght/traction to the rear allowing the car to push, during neutral or lift transfers the wieght to the front putting more wieght on the front tires so that the car goes into slight over steer.

An open diff will not give you that control or feedback either on or off throttle.

I just had my 911 LSD rebuilt in Lake Havasu by the brother of long time VW racer/engine builder.
Those guys are the best 915 rebuilders in SO Cal.
What was his name? Raced in PRA with his 10 second street car, think it was green?

Here's an early 911 throttle steering.
Patrick Long is a factory Porsche driver just playing/racing for the day in a buddy's ametuer level early 911 race car.
Patrick is sawing at the wheel making corrections but his right/trottle foot is controlling the wieght transfer.
Listen to the throttle...
http://www.plavanracing.com/media/Patrick%20long_0001.wmv

 

[mg]

there's a canyon road I take home, with many uphill, decreasing-radius corners, perfect for power-on-oversteer. I can wait to get into corner late, then apply a little throttle to point car in the right direction, with a little wheelspin. It actually makes the car handle "better" to me. I wonder how it would react with it locked up.

To some power oversteer looks impressive but as you know it's not the quickest way around a corner.
It may handle a little better but what you might find most impressive is that with the LSD you can now throttle steer it.
Next you might consider ways to improve your suspension to better control power oversteer.
Many Hot VWs are set up for drag racing and 60 foot times, not the optimal set up for canyon carving.

[Bruce]

Mike, can you comment on what the lockup % means?  I believe a VW diff is either 25 or 40%.  What would this mean?

[mg]

Mike, can you comment on what the lockup % means?  I believe a VW diff is either 25 or 40%.  What would this mean?

Hi Bruce,
My track/street 911 LSD is set at 80/60.
The first number indicates the percentage of lock up on power and the second the percentage of lock up on decel.
Imagine the first number were 100%, on power it would act more like a spool, no diff at all.
I can't say what is right percentages for all cars but this works well in my 911 at the track.
Google LSDs for expert advice.

My experiences with spools, LSD and open diffs.

An LSD is like a rack and pinion for the rear of the car.
It’s how you steer the back of the car.
Now that Jim has an LSD/TBD? the rear of his car has power over steer.
In racing you would disconnect the sway bars and do a spring scan.
Find the correct spring rates, select spring rates so that car is more neutral on and off the throttle.
Reconnect the sway bars  and re-valve the shocks to match the new spring rates.

(with respect to Jim’s spool comment)
With a spool in medium to tight turns you really have to be aggressive to get the car to rotate.
Lift throttle,  turn the wheel, pitch the back of the car, at the proper time stop the rear rotating with the throttle and if you’ve waited a bit too long counter steer.
Many 935s ran spools, I don’t know why?
Were their wide tires and big power too much for 70s diff technology?
I had a spool in my drag bug, combined with slicks in the back and tiny front tires on acceleration you were not going to steer the car much. But it also tracked very straight on decal.
Dave Folts would say if you want to turn with the spool you will have to lift (or go neutral on the throttle).
This just transfers weight to the front and takes it off the rear, the end with the most weight on it gets the most traction.

(No TBD/LSD known as an open diff)
My other 911 has an open diff and it is fine daily on the street.
Although at the local AX when it was pinched in tighter corners it would get light on the inside rear wheel and spin it.
How frustrating not to be able to get the power down and then have to change my line through the turn to keep more weight/traction on the inside rear wheel.
When the free spinning inside wheel does grab it can do funny things to axles and CVs at the same time disrupting car balance.

Driving cars fast is all about weight transfer.
Left foot braking is another effective technique to gently control weight transfer.
FYI developing brake sensitivity in your left foot takes time.
Remember to put your left over the clutch when it's time to upshift.