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Hi

 

Can someone explain what the the section in bold means:

"

Differential swap: 25pts for any diff. not originally available 
for your year, make, and model or chassis generation 
(excluding specialty high-performance models not listed on 
the VPI table)
"

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Which defeats the main purpose of the tech desk  

Ok, so got a response from tech:   "You can swap to a diff outside your platform if that diff is used in a car that is on the VPI list for 25 points.A diff not found on the VPI list (OS Gike

You are correct you don't stop ,as I read through this I find not a scrap of truth. I do not know where you dream this stuff up.

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3 hours ago, turbogrill said:

Hi

 

Can someone explain what the the section in bold means:

"

Differential swap: 25pts for any diff. not originally available 
for your year, make, and model or chassis generation 
(excluding specialty high-performance models not listed on 
the VPI table)
"

I’m fairly sure was a bit of a typo. I brought this up when the rulebook was revised to no avail.
 

The rule used to be ‘swap any diff from any car on the VPI table -25 pts.’ And I think that is still the intent with the caveat that you can swap in diffs that were used in your chassis generation for free (RVA BMW 4.10 rule change).... but they may be restricting “chassis generation” to standard models in the generation.

 

TBH, this really needs a rewrite. I’ll reach out to Jay.

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11 hours ago, turbogrill said:

Hi

 

Can someone explain what the the section in bold means:

"

Differential swap: 25pts for any diff. not originally available 
for your year, make, and model or chassis generation 
(excluding specialty high-performance models not listed on 
the VPI table)
"

Some cars came with LSD and some did not. For example you couldn't get a LSD in my E39 540i sport but you could in an M5, You could get a 4.10 Dana in a 440-6 4 speed Road runner but not in a 383 4 speed roadrunner, only an 8.75 Sure Grip. So I'm guessing if your car didn't have a LSD or offer a specific gear ratio you'd have to claim 25 points for the swap. 

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11 minutes ago, turbogrill said:

Got it. So is aftermarket LSD more points?

 

My car came with an LSD but internet says it breaks during racing. Seems like I don't have to claim points for my LSD.

 

But still very interested in the aftermarket point value

I would expect an aftermarket LSD or spool to be 25 points. A factory LSD option would be zero. 

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42 minutes ago, turbogrill said:

 

So this is the confusion. It seems like the rules states that the LSD has to come from a car on the list.

I understand your position now. To my knowledge, it hasn't been defined to the detail that you're asking.

 

Here's a statement that wasn't questioned:

 

"People have welded diffs in this FWD car and others with good results. Another option would be an aftermarket LSD, quaife or OBX (usually needs shim work done to get OBX right), paying the same points as any other limited slip diff swap into a car with no factory LSD option (25)." 

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I submitted a tech desk on this.

 

We are putting a wavetrac diff in our 190E.  190E came with a stock clutch type LSD as an option. We wanted an aftermarket performance diff, the response was a wavetrac is 25points. If we used the stock LSD that was an option on the 190E it was 0 points.

 

Anything other than that OE option = 25points.

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This model option thing is confusing. Multiple times it's been base model is all you get for the VPI. Yet I've seen multiple people, from competitors to the TAC, state you can mix and match parts for free if it was an option on the model listed on the VPI table. From brakes, suspension parts, and now diffs. The diff ratio I've seen the tech ruling on, but all this other stuff has been confusing as hell.

 

So is the winter option lsd for BMW back to zero points. And that would put a chili package for the r56 at zero points with the lsd too? Somehow I think not. As few base cars have a LSD diff.

 

 

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19 minutes ago, chbright said:

This model option thing is confusing. Multiple times it's been base model is all you get for the VPI. Yet I've seen multiple people, from competitors to the TAC, state you can mix and match parts for free if it was an option on the model listed on the VPI table. From brakes, suspension parts, and now diffs. The diff ratio I've seen the tech ruling on, but all this other stuff has been confusing as hell.

 

So is the winter option lsd for BMW back to zero points. And that would put a chili package for the r56 at zero points with the lsd too? Somehow I think not. As few base cars have a LSD diff.

 

 

 

As far as I know only the S ever came with a factory LSD, and it's a Torsen type I thought. 

 

FYI- putting an S diff in a base is a huge pain. We're still working on making it work.... Different spline counts, different ring gear bolt pattern, different axle lenthgs, etc.... If we were to do it again we'd take the whole S trans and hope it all bolts up better....

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11 minutes ago, Wittenauer Racing said:

 

As far as I know only the S ever came with a factory LSD, and it's a Torsen type I thought. 

 

FYI- putting an S diff in a base is a huge pain. We're still working on making it work.... Different spline counts, different ring gear bolt pattern, different axle lenthgs, etc.... If we were to do it again we'd take the whole S trans and hope it all bolts up better....

 

I wish my 07 had the chili package but it did not, and was an open diff. They all have an electronic "lsd". Only a few r56 do not have an open diff, turbo "s" or the justa r56. The jcw I'm not sure about, it may have been in all of those but I havent looked into them.

 

Really though this isn't just about the r56, there are others, BMWs,  Nissans, and others that offered an lsd as an "option".

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1 hour ago, Gkuhn41 said:

I submitted a tech desk on this.

 

We are putting a wavetrac diff in our 190E.  190E came with a stock clutch type LSD as an option. We wanted an aftermarket performance diff, the response was a wavetrac is 25points. If we used the stock LSD that was an option on the 190E it was 0 points.

 

Anything other than that OE option = 25points.

 

Ok, got it.

 

So the rule is pretty simple? If your car came with LSD as an option then that OE diff is allowed.

Any other LSD is 25 points.

 

Not sure why they mentioned the VPI list in that rule...

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  • 3 weeks later...

Ok, so got a response from tech:

 

"You can swap to a diff outside your platform if that diff is used in a car that is on the VPI list for 25 points.

A diff not found on the VPI list (OS Giken and Cusco) is not allowed in any class other than EC.
"

 

So you can't have any aftermarket diffs....

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6 hours ago, turbogrill said:

Ok, so got a response from tech:

 

"You can swap to a diff outside your platform if that diff is used in a car that is on the VPI list for 25 points.

A diff not found on the VPI list (OS Giken and Cusco) is not allowed in any class other than EC.
"

 

So you can't have any aftermarket diffs....

Thanks for sharing. I reached out to Jay a week ago about diffs (as I said I would) this must be the answer he came to. This is the way I have always read the rule despite word changes over the years and I’m glad tech has maintained that. Now we just need clear wording in the rulebook. 

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9 hours ago, enginerd said:

Thanks for sharing. I reached out to Jay a week ago about diffs (as I said I would) this must be the answer he came to. This is the way I have always read the rule despite word changes over the years and I’m glad tech has maintained that. Now we just need clear wording in the rulebook. 

Next question:

If the vehicle has a diff swap from a particular VPI list car that doesn't come from the factory with an LSD but a factory LSD from another VPI car will fit, would combining the two be 25 points or 50 points?

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5 minutes ago, mender said:

Next question:

If the vehicle has a diff swap from a particular VPI list car that doesn't come from the factory with an LSD but a factory LSD from another VPI car will fit, would combining the two be 25 points or 50 points?

 

 

 

So, like putting the LSD from a solid axle Xterra into a 240SX open diff housing, then swapping that R200 carrier into a Subaru?

 

If you're paying 25 points does it really matter where the LSD came from besides being on the VPI list?  I doubt there is a magic factory LSD out there that will benefit a car enough to make the 25 point hit from being substantially too low.

 

Sometimes I think you enjoy being deliberately difficult.

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8 minutes ago, SonsOfIrony said:

 

 

 

So, like putting the LSD from a solid axle Xterra into a 240SX open diff housing, then swapping that R200 carrier into a Subaru?

 

If you're paying 25 points does it really matter where the LSD came from besides being on the VPI list?  I doubt there is a magic factory LSD out there that will benefit a car enough to make the 25 point hit from being substantially too low.

 

Sometimes I think you enjoy being deliberately difficult.

No, I just don't like surprises, and I've seen more than enough interpretations that could go either way.

 

It doesn't matter whether the performance value is there for a particular car or not; what matters is that the points are consistent for everyone.

 

 

Edited by mender
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14 minutes ago, mender said:

No, I just don't like surprises, and I've seen more than enough interpretations that could go either way.

 

It doesn't matter whether the performance value is there for a particular car or not; what matters is that the points are consistent for everyone.

 

 

What I'm asking is, is there a theoretical combination that would boost any given platforms performance to a degree that 25 points is not enough?

 

I honestly don't believe that there is a situation where you can take the LSD carrier from tunaslapper A, bolt on a ring and pinion from tunaslapper B, install in the housing from tunaslapper C, and install the whole assembly in tunaslapper D then turn around and magically win races because a 25 point hit isn't enough.

 

Besides.  Both your cars use a transverse transmission, so unless you're also taking the points for a transmission swap, this rule doesn't really effect you.  So no surprises.

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18 minutes ago, SonsOfIrony said:

 

What I'm asking is, is there a theoretical combination that would boost any given platforms performance to a degree that 25 points is not enough?

 

I honestly don't believe that there is a situation where you can take the LSD carrier from tunaslapper A, bolt on a ring and pinion from tunaslapper B, install in the housing from tunaslapper C, and install the whole assembly in tunaslapper D then turn around and magically win races because a 25 point hit isn't enough.

 

Besides.  Both your cars use a transverse transmission, so unless you're also taking the points for a transmission swap, this rule doesn't really effect affect you.  So no surprises.

It's not about me, or you, or performance, it's about rule consistency. 

Edited by mender
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I have run a welded dif and a limited dif in the VW/ Audi platform . We are at a handicap on the dif because there is no limited dif on the vip list of our cars,  and a lot of the fast cars on the list come with them stock. They should be no points for a limit dif. if you where to take the LSD out of the fast front group and run a open dif where do you think they would finish??

It is very costly to take a LSD for some other car build and make it fit some thing else and hope it would last.  

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45 minutes ago, DRVOLKS said:

 

It is very costly to take a LSD for some other car build and make it fit some thing else and hope it would last.  

 

Agree, this seems nuts. How would you do that? 

 

How much do you think the average OEM diff affects lap times? Reading on the Miata forum it seems like going from OEM diff -> aftermarket diff helps but the oem diff sucks.

 

 

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12 minutes ago, turbogrill said:

 

Agree, this seems nuts. How would you do that? 

 

How much do you think the average OEM diff affects lap times? Reading on the Miata forum it seems like going from OEM diff -> aftermarket diff helps but the oem diff sucks.

Depends on the car and combo.

 

In the Fiero it would basically be extra weight, but in a high-powered FWD it would probably be a difference of 1.5- 2 seconds per lap.

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1 hour ago, mender said:

Depends on the car and combo.

 

In the Fiero it would basically be extra weight, but in a high-powered FWD it would probably be a difference of 1.5- 2 seconds per lap.

You are very right on the TT with a open front dif if I add the boost it will light the inside wheel up big time. Welded, its off the corner like a rocket but with a welded dif you got to safety wire every bolt and nuts axle nuts it try to ripe ever thing apart.

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8 hours ago, DRVOLKS said:

You are very right on the TT with a open front dif if I add the boost it will light the inside wheel up big time. Welded, its off the corner like a rocket but with a welded dif you got to safety wire every bolt and nuts axle nuts it try to ripe ever thing apart.

 

Ran a welded diff for years.  Never had any issue with things wanting to come apart more than a normal race car.  Race cars just vibrate a lot.

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