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Differentials - Ratios and LSD Clarification


mcoppola
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I'm starting this topic in order to hopefully clear up the rules intent and interpretation on this subject, and to get this discussion out of the National Championship race review going on.

Read through pages 2-4 for background info, but then please direct all comments about this issue here. Thanks!

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These are three of the key posts from the thread Mike mentions.  They should be read last to first - I ordered them backwards.  The essence of the situation SEEMS to be that someone got DQ’d for something that now isn’t causing a DQ.  Everything in life is subject to change, but it seems like a detailed clarification may be needed if the information above is correct.  

Edited by Racer28173
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  • Technical Advisory Committee
1 minute ago, Jab31169 said:

The wording from the rule book seems pretty straight forward:

 

"differential swap: 25pts for any diff. from a vehicle on the VPI list, stock axles/CVs included"

 

Not to me it isn't straight forward. It does not address transaxles at all, nor unique differentials that weren't mass produced and offered LSD.

Say perhaps the transaxle in a certain car ONLY came in that model of vehicle. There is no other "vehicle from the VPI list" that has a diff that can be swapped into said transaxle.

Is the intent of this rule to prevent teams with this make/model of transaxle from being able to install an LSD unit into the transaxle? That's what the current ruling implies - and if that's the case, then once again, the rules are written to favor certain performance oriented vehicles which had an LSD offered from the factory.

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This rule, IMO,  needs cleaned up.  One can change Ratio, Diff type, and Axle Housing (in RWD car) Is it 25 points for each, any, or all?

I have a transaxle that was offered with ~8 different final drives but not all in the same year make model or even platform.

None of them had an LSD available. Does that mean LSD is a hard NO! weld it or nothing) or should aftermarket LSD be on the FPV list?

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This all comes back the BMW e, I, IS, IX, alphabet mix and match soup(like honda motors) and people picking and choosing the best bits of each trim of their respective e30.  We claim our diff swap in our Miata, and as a result were told we can use any ration we want that comes from a vehicle on the VPI list and we are good to go.  Meaning, we have multiple diffs assembled with different ratios that we are exploring swapping in on different tracks.

 

If you want to stop the mix and matching on the BMW e30, then I say you approve specific ratios allowed without taking the 25pt hit.  Have it in the rules that if you are running a 1989 325 you can have this ratio only, otherwise 25 pts. will be applied to your TPI.

 

Or, we just raise the base value of the e30 a bit more and allow it to continue.....It's not like they are the fastest and most reliable race cars out there currently.....🙄

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http://www.e30zone.net/e30zonewiki/index.php/Differential

This links to the place I went to for E30 knowledge when I owned one. I really don’t car which way the ruling falls, it just needs to be consistently applied at every race. If we were to find that all the top tier E30 teams are currently running a 4.10 or switch to one now and that proves to be a distinct advantage over the average E30’s or field as a whole then maybe a VPI adjustment is in order. 

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13 minutes ago, tommytipover said:

This rule, IMO,  needs cleaned up.  One can change Ratio, Diff type, and Axle Housing (in RWD car) Is it 25 points for each, any, or all?

I have a transaxle that was offered with ~8 different final drives but not all in the same year make model or even platform.

None of them had an LSD available. Does that mean LSD is a hard NO! weld it or nothing) or should aftermarket LSD be on the FPV list?

Yes, all the items @tommytipover mentioned need to be clarified. The word differential does not differentiate (like that play on words?) between changing ratios, installing an LSD, or changing the entire rear axle housing. And the glaring omission is that it does not deal with transaxles at all. So, there are 3-4 scenarios that can be done to a "swap a differential" that come into play - ratio, LSD or no, entire rear end housing, and/or entire transaxle. The rule is too vague, and needs to be re-written.

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2 minutes ago, mcoppola said:

Yes, all the items @tommytipover mentioned need to be clarified. The word differential does not differentiate (like that play on words?) between changing ratios, installing an LSD, or changing the entire rear axle housing. And the glaring omission is that it does not deal with transaxles at all. So, there are 3-4 scenarios that can be done to a "swap a differential" that come into play - ratio, LSD or no, entire rear end housing, and/or entire transaxle. The rule is too vague, and needs to be re-written.

Carefull Mike, you're starting to sound like the rule book might need to be a bit longer, that kinda talk isn't too popular with the email club.....😉

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I'd like to know the answer too...   is changing the rear gear considered a differential swap?  Is it free if I use a ratio that was equipped in the generation or year model of my car?  What if i choose a gear ratio on the VPI that came in a differential generation of the car I am running?  What if I just run a different gear ratio, what is the hit, 25 points?  Sometimes I think something is purple and my wife swears it is pink, am I color blind or her?

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In 2015 we were told the 4.10 was 25 points.  We argued that it was an option, so it should be 0pts, but lost the argument.  So we claimed it at the races that we ran it.  In 2016, we discussed again with Phil at Tech and were told it was 0pts now, since it was available as an option for our model.  Nevermind that it was not standard and probably only came from the factory on a handful of vehicles.  It was still available as an option.  Therefore it's not a swap.

 

The next question is why did Chumpcar change their mind between 2015 and 2016?  I'm guessing it's because there were so many E30 teams who believed the 4.10 was not a swap since it is listed in various places on the internet as an option and there's no real way to prove otherwise.  But that's just a guess.

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5 minutes ago, Justin9 said:

is changing the rear gear considered a differential swap?  Depends 

Is it free if I use a ratio that was equipped in the generation or year model of my car?  Not in doll-hairs, but I think it'll net you 0pts.

What if i choose a gear ratio on the VPI that came in a differential generation of the car I am running?  25 pts.

What if I just run a different gear ratio, what is the hit, 25 points?  Yes

Sometimes I think something is purple and my wife swears it is pink, am I color blind or her? C'mon, we both know she's right.

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6 minutes ago, Wittenauer Racing said:

So welded diff free?

yes always has been free.  

 

Rare factory LSD free?

I wound think it's 25 points. 

 

Non-Factory LSD for car that never came with LSD = no?

That would suck as it favors certain sports cars.

 

25pts? free?

The rule is not clear enough to answer this.

 

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I understand Phils response and thought process here.  Except, how does this workout in regards to other parts and options available to certain cars?  What if you car has different trim levels that have different engine hp ratings due to say the "Sport" model having an different intake cam and getting a fancy 25 hp bump as a result?  Does that mean I can run that cam in my car since it was an option and not have to claim the cam swap???

 

I thought the whole idea was to use base models only and any special edition or options were not allowed to be used without adding points?  Thoughts?

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23 minutes ago, FlorahDorah said:

FYI. Phil just posted this in the Championship thread. Don't shoot the messenger. 

 

 

Shoot the messenger? I'd rather give ya a hug. 😋

I was going to copy and paste the response here, but you beat me to it. Thanks for posting, and Thanks to Phil for the clarification.

Some folks seem to have conflicting stories of how this rule was handled previously, but hopefully this provides the clarification we were looking for to move forward.

I still think the wording of the rule could use some work though. Maybe we can eventually do that so that we won't have to "ask Phil" so often.

Edited by mcoppola
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2 hours ago, zack_280 said:

In 2015 we were told the 4.10 was 25 points.  We argued that it was an option, so it should be 0pts, but lost the argument.  So we claimed it at the races that we ran it.  In 2016, we discussed again with Phil at Tech and were told it was 0pts now, since it was available as an option for our model.  Nevermind that it was not standard and probably only came from the factory on a handful of vehicles.  It was still available as an option.  Therefore it's not a swap.

 

The next question is why did Chumpcar change their mind between 2015 and 2016?  I'm guessing it's because there were so many E30 teams who believed the 4.10 was not a swap since it is listed in various places on the internet as an option and there's no real way to prove otherwise.  But that's just a guess.

Where is the info stating it was available as an option? Or is this a friend of a friend told me type of deal?

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9 minutes ago, Ron_e said:

So now we can swap any option available for our year make and model, mix and match as we wish?  Diff ratio, sway bars, springs, shocks, engines, transmissions...???

Not sure if you are green fonting, but it would seem that Phil was only talking about rear ratios. 

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Just now, Racer28173 said:

Not sure if you are green fonting, but it would seem that Phil was only talking about rear ratios. 

 

Springs and sway bars do specifically say OE, which would be an option OE.  It is the exact same wording for engine/trans/diff in the rules.  So if any option diff can be used then it must be so as well for any transmission, engine, spring, sway, shock.  Not sure where I should be green font.

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Sorry to swerve off topic but did anybody get a clarification on the 944, I thought as it's been beat to death in the forum that the car was a 530 pt S2 engine.  I was told that Phil signed off on it .  Not sure if there was any information.  I watched the race online and great stuff, bravo to all who ran it looked brutal out there with the heat.  

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