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RX7 KLR:

I think the difference is a real LSD will always put power down through one of the wheels, if it is a good one it gives power to the wheel with grip.

 

A "virtual LSD" only slows down the spinning wheel, it does nothing to apply more power to the wheel with grip. So while the V-LSD might help to stop the endless one-leggin, it will not help you accelerate by transferring power to the other tire, it is still an open diff.

 

I think the 135 might have a shot in HS.

Actually, the virtual LSD, if implemented correctly on the software side, would be able to transfer up to 100% of the power to the wheel with grip (inside wheel in the air situation). Remember, it's an open diff. Torque into the system must equal torque out of the system, minus what is burned up in friction. A conventional LSD uses friction in the clutch packs, a torsen uses friction in the gear teeth, the virtual LSD uses friction in the brakes. The problem with conventional LSD's is that they aren't vehicle speed sensitive, rather they are sensitive to differences in axle speeds. With an aggressive enough lockup, you run into a situation where the balance of the car is different in a high speed sweeper then it is in a low speed pin turn. The vLSD doesn't have this drawback. Does it perform as well in real life as it does in theory? Apparently not, but I think that is a limitation of the software more then anything else.

solo-x:

Actually, the virtual LSD, if implemented correctly on the software side, would be able to transfer up to 100% of the power to the wheel with grip (inside wheel in the air situation). Remember, it's an open diff. Torque into the system must equal torque out of the system, minus what is burned up in friction. A conventional LSD uses friction in the clutch packs, a torsen uses friction in the gear teeth, the virtual LSD uses friction in the brakes. The problem with conventional LSD's is that they aren't vehicle speed sensitive, rather they are sensitive to differences in axle speeds. With an aggressive enough lockup, you run into a situation where the balance of the car is different in a high speed sweeper then it is in a low speed pin turn. The vLSD doesn't have this drawback. Does it perform as well in real life as it does in theory? Apparently not, but I think that is a limitation of the software more then anything else.

I think you are giving the system way to much credit... I would put it right up there with OE traction control. I don't know of to many stock class cars that are running faster with TC on. btw I have driven a 335i on R tires with an alignment, it will one-leg on in both directions, the vLSD does not get it done.  

RX7 KLR:

I think the 135 might have a shot in HS.

Now you have my interest. But Cashmo and the SCAC/SEB is going to rain on that parade. Oh, woe is me. Everyone is against my car (said JK).

RX7 KLR:

I think you are giving the system way to much credit... I would put it right up there with OE traction control. I don't know of to many stock class cars that are running faster with TC on. btw I have driven a 335i on R tires with an alignment, it will one-leg on in both directions, the vLSD does not get it done.  

To be clear, I'm giving the theory credit, not the system.

Out of curiosity, did the owner of that 335i try running a more aggressive rear pad? Going back to the programming of the software, if Joe The Engineer programmed the ECU for a binary application of the vLSD then adding sticky tires and not changing to a more aggressive pad would yeild the exact results you complain of. ECU sees wheelspin and applies a predefined percentage of brake force. It's just not enough for this higher performance environment. Throw a pad with more bite into the equation, what happens then?

And before anyone starts jumping down my throat, I'm not trying to say BMW's system works. I'll readily admit I don't know how the logic was programmed, or even if it gets turned off completely when you turn off the TC. I'm just not going to dismiss a technology because the first few iterations of it sucked.

Nate

solo-x:

To be clear, I'm giving the theory credit, not the system.

Out of curiosity, did the owner of that 335i try running a more aggressive rear pad? Going back to the programming of the software, if Joe The Engineer programmed the ECU for a binary application of the vLSD then adding sticky tires and not changing to a more aggressive pad would yeild the exact results you complain of. ECU sees wheelspin and applies a predefined percentage of brake force. It's just not enough for this higher performance environment. Throw a pad with more bite into the equation, what happens then?

And before anyone starts jumping down my throat, I'm not trying to say BMW's system works. I'll readily admit I don't know how the logic was programmed, or even if it gets turned off completely when you turn off the TC. I'm just not going to dismiss a technology because the first few iterations of it sucked.

Nate

So you think the system is smart enough to work like an LSD, but not smart enough to compensate for the added grip or race tires. Guess you better never drive the new BMWs in the rain, the vLSD wont know what to do with the lack of grip.  

RX7 KLR:

So you think the system is smart enough to work like an LSD, but not smart enough to compensate for the added grip or race tires. Guess you better never drive the new BMWs in the rain, the vLSD wont know what to do with the lack of grip.  

To work like an LSD, the system doesn't need to be smart. To work like a GOOD LSD, the system needs to be smart. 

Your rain situation is a no-brainer anyhow. Less lateral load transfer means it would need less of a vLSD effect to control wheelspin on THAT tire. Of course, if you've turned off the TC, you'll just spin em both but that's neither here nor there.

FWIW, SOP was to shut down the various electronic control devices (applied to both the BMW and the plain Jane 996). So I would make the electro systems dumber (matched the driver). But I know that with a very unintelligent true limited slip would deliver better performance than the current offerings.

About the only exception could be a true rain downpour. This year's (2007) Tuesday morning's drying conditions would not favor the electro slip. It would detent the car too much.

In 2005, I drove the 330i at a lot at NHIS. Very similar surface to HPT. Raining cats & dogs for my heat. It was the only time that the electronics "felt" better. At the Tour later that year, Day One, I was cursing the conditions. I opted for dry tires. I am not sure if even being on Wets would I have been competitive with the Integra Type-Rs. Of course, then the ITR handed my lunch to me the next day and later at Nats.

 Of course, IMO.

Interesting data point, in the new issue of Roundel they say that the electronic limited slip isn't actually turned on *until* you turn off DSC... So this could certainly be something different...

Lynn:

cashmo:

Are twin turbo's allowed in STU? 

Jeff 

No. 

they were when STU was first created in a fastrack, but then there was a mysterious takeback with no member comment so now STU inherits the single turbo provision from STX...  write your letters. 
 

mitchman:

I would think that with a stiff enough front sway bar (think BIG) you could keep the inside rear on the ground for exiting corners.  But then you'll have to drive around the additional understeer created by the larger front bar.  Maybe you could add some DA rear shocks with lots of rear compression so that car would at least be drivable in the transitional elements.  But you'll still have to slow down for middle of the sweepers.  Should be okay for transitions, corner entry and corner exit though.

Mazda MRS, eh? 

BMWs usually like a big front bar anyway.  It helps preserve what little camber they have and doesn't generally make them too pushy. 

Even with the big bar, I suspect it'll still set fire to the inside tire, based on my experience with the power delivery of that motor.  I wouldn't want to try one of these for stock class.

Lynn:

cashmo:

Are twin turbo's allowed in STU? 

Jeff 

No. 

Dont know where it will go, but I submitted a letter regarding this.

NA displacement is lifted to "unlimited" for STU, so I suggested lifting the single turbo limitation.

I did get a log number, but havent heard anything else about it.

Scott

Whiplash_Motorsports:

I did get a log number, but havent heard anything else about it.

Can you tell us what the "safety word" is for getting a log number?? 

murph1379:

Whiplash_Motorsports:

I did get a log number, but havent heard anything else about it.

 

Can you tell us what the "safety word" is for getting a log number?? 

I didnt say anything too spectacular.........below is my original message and the response I received.

----- Forwarded Message ----
From: Doug Gill <DGill@scca.com>
To: Scott Strickland <stricklandjs@yahoo.com>
Sent: Monday, November 19, 2007 10:56:58 AM
Subject: 07-442 RE: Twin Turbos in ST

Hi, Scott,

Your request has been logged 07-442 and sent to the SEB.

Thanks for your input!

- Doug

Doug Gill
SCCA Solo Competition Manager
1-800-770-2055
SCCA National Solo Rules
Fastrack News
-----Original Message-----
From: Scott Strickland [mailto:stricklandjs@yahoo.com]
Sent: Saturday, November 17, 2007 4:35 PM
To: Doug Gill
Subject: Twin Turbos in ST

Im interested in presuing the idea of opening up the
allowance for turbo'd vehicles in STU.
In STX, the rules specifically limit turbos or
superchargers to a "single" unit.
However, in STU, the na displacement is lifted and
noted as "unlimited".
Would it not be within the same logic to lift the
"single" limitation regarding turbos and superchagers
for STU?

Thanks,

Scott Strickland

texlbs:

I notice the original email was sent to Doug directly as opposed to seb@scca.com.  Maybe that is the trick?

Actually...when I went back and looked at my original message in yahoo it doesnt say Doug Gill, but this:

Its just the reply that says Doug and I have no idea why.........

Scott

Now that wasnt so hard, was it.... :)

(From the March Fastrack) 

Remove the word “single” from 14.12.3 in class STX. Note: this will allow any forced-induction configuration