What does Oppo know about this?

"Bryan doesn't drive a 1M" (bryantakespictures) 06/22/2015 at 16:27 • Filed to: None

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A bargain compared to BMW or Dinan, but too good to be true?

Jedidiah > Bryan doesn't drive a 1M 06/22/2015 at 16:36

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They have plastic shim on the inside of them that allows you to alter the harshness of lock-up.

I would avoid it because once you get it in, you want to mess with your rear end as little as possible and not have to take anything apart.

A traditional cone or clutch lsd should be sufficient.

If you don’t care about handling, a mini spool or lunchbox locker are also cheap options.

Arch Duke Maxyenko, Shit Talk Extraordinaire > Bryan doesn't drive a 1M 06/22/2015 at 16:40

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I've been thinking about one for a while, but damn it's expensive to have installed.

HammerheadFistpunch > Bryan doesn't drive a 1M 06/22/2015 at 16:49

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It looks to be a variation on the Torsen principle that works in the same basic way but has additional allowances for lockup at on torque input. Not sure how it really feels but its interesting in concept.

crowmolly > Bryan doesn't drive a 1M 06/22/2015 at 16:49

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I remember when Moser was the only place to get them, and even then it was only for a Ford 9”.

They can take a lot of abuse and are the diff of choice for pro-touring cars.

However they are not 100% bulletproof as failures have been reported.

Personally I would only spend the money if you need a diff this smooth and have the power output to match.

Frenchlicker > Arch Duke Maxyenko, Shit Talk Extraordinaire 06/22/2015 at 16:50

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Why are they expensive to install?

Textured Soy Protein > Jedidiah 06/22/2015 at 16:50

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Are you talking about this?

The Wavetrac diff’s behavior can be altered in the field to suit your needs. It comes standard with carbon-fiber bias plates for the best all around performance and lifetime durability. Changeable plates using materials with different friction coefficients to fine-tune the bias ratio are sold separately.

Unless you replace the carbon fiber bias plates with the optional steel ones, there’s nothing to be adjusted, and no “plastic shims” unless you’re counting carbon fiber as plastic.

Bryan doesn't drive a 1M > Arch Duke Maxyenko, Shit Talk Extraordinaire 06/22/2015 at 16:54

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How much?

crowmolly > Frenchlicker 06/22/2015 at 16:55

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I can’t speak for a BMW, but if you were to install one in, say, a Ford 9” or GM 12 bolt you’d have to reset all the differential tolerances and wear pattern.

It should be roughly the same price as a gear swap.

Textured Soy Protein > Bryan doesn't drive a 1M 06/22/2015 at 16:58

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For Porsches, the Wavetrac and Guard differentials are the most popular cheaper-than-Quaife options for torque biasing differentials.

Guard doesn’t make diffs for BMWs so it’s Wavetrac or Quaife. They seem to be pretty popular.

I’m all too familiar with the one-tire fires in my 135is, so I can see the appeal of a proper diff. Putting it in dynamic traction control mode is decent for the twisties but worthless for putting the power down better.

Arch Duke Maxyenko, Shit Talk Extraordinaire > Frenchlicker 06/22/2015 at 16:59

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The ring gear is welded to the carrier in the later models.

Frenchlicker > crowmolly 06/22/2015 at 17:01

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Hmm, makes me wonder what we charge for our differential rebuilds.

Arch Duke Maxyenko, Shit Talk Extraordinaire > Bryan doesn't drive a 1M 06/22/2015 at 17:01

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About double the price of the diff.

Jedidiah > Textured Soy Protein 06/22/2015 at 17:03

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I got my information from a forum in a quick google search because I know nothing about these things. I’d rather not have to take my diff apart for any reason even to adjust the bias plates. This technology isn’t proven, don’t make yourself a guinea pig unless you have to. You don’t want to have to be replacing, adjusting, or screwing with anything when you could have gotten a more familiar system. Those bias plates are friction surfaces, which will wear out. Unless they are proven to last longer than the cones/clutches, I wouldn’t use it. If they do, go ahead.

Carbon fibre is just a weave of fibres bound in a plastic matrix, so it is a composite by definition. Slightly similar in concept to fibreglass. The official term is carbon reinforced polymer, so I jokingly refer to it as fancy plastic.

Frenchlicker > crowmolly 06/22/2015 at 17:03

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Also anymore for me that stuff is pretty easy. Now taking them off of a car or whatnot is the hard part.

Bryan doesn't drive a 1M > Arch Duke Maxyenko, Shit Talk Extraordinaire 06/22/2015 at 17:04

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_

Frenchlicker > Arch Duke Maxyenko, Shit Talk Extraordinaire 06/22/2015 at 17:06

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I saw that on the link. My view is skewed on how much of a pain this stuff is since I rebuild differentials everyday and have access to good welders and the like.

Frenchlicker > Arch Duke Maxyenko, Shit Talk Extraordinaire 06/22/2015 at 17:07

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I did see that bit. I can't say I'm surprised.

Arch Duke Maxyenko, Shit Talk Extraordinaire > Frenchlicker 06/22/2015 at 17:09

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Do you have access to a lathe and a mill? Because you don’t weld it to install it.

Snuze: Needs another Swede > Bryan doesn't drive a 1M 06/22/2015 at 17:09

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I’m not familiar with WaveTrac so I can’t comment on the quality of their product. But, after looking at the pics and reading the info, I think it’s just a Torsen (torque sensing) type differential with and added pre-load.

I know it says it’s better than a Torsen, and it is, but it’s still basically a Torsen, if that makes any sense. They just add a preload so that you can always have some resistance in the axle, even if you lift or otherwise completely unload a wheel, so you can transfer at least *some* torque to the grippy wheel. The problem is you become torque limited to the total amount of preload. So if you have 200 ft-lbs of torque available this instant and its a 4:1 TBR (torque bias ratio), and one wheel starts to slip relative to the other, the diff will begin transfering torque to the grippy wheel. If the slip situation continues it will continue until it maxes out by putting 160 ft-lbs to the grippiest wheel. 40 ft-lbs will continue to go to the slipping wheel, assuming it has enough traction available to handle this torque

Let’s say the problem persists and you have even less traction, the available grip in the slipping wheel decreases to your preload point - let’s say it’s 10 ft-lbs of torque. Well you had 200 ft-lbs available, but because the diff has a fixed max TBR and fixed prelaod, it can only send 40ft-lbs to the grippiest wheel (4x10). It sucks but at least it’s better than doing a one-wheel-peel.

Torsen automatic torque biasing is great for race cars with sticky tires on prepped surfaces. Many racers use the characteristics to their advantage by using anti-rollbars to control the amount of grip and therefore torque transfer, helping to dial in/out understeer/oversteer. But people found them lacking in the real world, especially in conditions like ice where it is possible to completely unload a tire. At this point you lose all available traction as discussed above. What WaveTrac (and several other varieties of Torsen) do is add a preload spring inside the diff unit that presses against both axle stubs. It’s usually made up of bellevile washers and you can tune the diffs behavior by adding or removing washers. More washers means better zero traction performance because there is more available preload, but it means less overall torque transfer because there’s more friction in the differential.

Source: I was the keeper of the diff on my FSAE car and we ran a Taylor Racing ATB diff with preload.

Frenchlicker > Arch Duke Maxyenko, Shit Talk Extraordinaire 06/22/2015 at 17:16

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Wow. But to be honest yeah, I have access to both of those. We are one of the leaders in differential rebuilding. The only downside is the milling would have to be done by another division of our company meaning I would have to pay for it, albeit at a discounted price.

Snuze: Needs another Swede > HammerheadFistpunch 06/22/2015 at 17:24

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We had one in the FSAE car, a Taylor Racing ATB unit. Ours used a pack of belleville washers inside to provide preload. It actually worked incredibly smoothly all the time. Unless WaveTrac is doing something new I don’t understand, it never fully locks. We ran a single cylinder engine when I was on the team and had huge aero so it always had massive grip, never enough to cut loose. On our 600cc car, you could light em up and then both wheels would slip because the engine could overpower all available grip. But other than that, it worked like a charm.

What they do is use the washer pack like a spring that rides between the axle stubs. As a wheel slips it the ATB shuttles torque to the opposite wheel, up to the torque bias ratio. So if it’s 4:1 and you have 100ft-lbs on tap at the moment, it can send up to 80ft-lbs to the grippy wheel, the rest gets wasted on the slippy wheel. If grip continues to decrease on the slippy wheel, you just piss away torque, but it will still shuffle torque over to grippy wheel. So lets say you only have 10ft-lbs worth of grip, it will send 40ft-lbs to the grippy wheel, the rest is spun away. The big difference is, on a standard Torsen, if you reach full slip, it becomes an open diff, all power goes to the slipping wheel and none to the gripping wheel because 4x0=0. In the Taylor ATB we used, and presumably the WaveTrac, that washer pack between the axle stubs adds resistance, so you can never really reach zero, so you’ll always be able to send at least a little bit of torque to the wheel with grip.

Will with a W8 races an E30 > Snuze: Needs another Swede 06/22/2015 at 17:24

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Looks like it goes a little farther than that - it also has a cam system to load the clutch with high torques. Can’t be much with just a single plate, but probably unloads a bit more smoothly than a clutch LSD. Still not sure what the advantage is though, because you get all the negatives of torsen and clutch LSD as well (chatter, funny wear, heat....)

HammerheadFistpunch > Snuze: Needs another Swede 06/22/2015 at 17:27

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yes, to all. The graphic indicated that it could fully lock, but I was skeptical of that so thanks for the clarification.

Textured Soy Protein > Jedidiah 06/22/2015 at 17:28

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Yeah yeah, CF is technically plastic.

I don’t have any first hand experience with Wavetrac diffs either, but I think you’re confusing an optionally-replaceable part with the need to do a bunch of maintenance and adjustment.

Just going from Wavetrac’s description on their site, that reads to me like if you use it out of the box with the standard carbon fiber bias plate, there’s nothing to adjust. The only “adjustment” per se is if you went with the different bias plates. Which as far as I know is very uncommon to do.

The Wavetrac diff has more in common with a gear-based torque biasing diff like the Torsen or Quaife than it does with a clutch-type LSD. It should last a lot longer than a clutch-type diff.

As for “not proven,” Wavetrac diffs have been around for about 6 years and there are plenty of user reviews on forums out there, especially Porsche & BMW.

Jedidiah > Textured Soy Protein 06/22/2015 at 17:43

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Well if it’s a competitive price and performs similarly, then perhaps he should go for it. They wouldn’t have stayed in business for 6 years unless they at least did something right.

I was worried that system like that would be an annoyance given my limited knowledge/experience with the subject matter and should be avoided. If it’s optionally replaceable, then that’s okay.

I’d still research durability before I purchased one.

The pro-touring crowd really likes Torsens, but those are not without flaws and failures have been reported before. However, these guys often make a ton of power and pretty much don’t leave anything stock.

If the OP thinks it’s appropriate for his car, then perhaps he should consider it

Snuze: Needs another Swede > HammerheadFistpunch 06/23/2015 at 09:14

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Another commenter (Will) replied to my long post saying that it also has a cam system that can provide additional internal load, essentially making it fully locking, or almost so. I’ll have to go back and look at it again when I have more time. That could be an interesting addition to the Torsen, but I wonder how good it is.