Best type of LSD for track use

[simpleisbest]

Originally Posted by mhiscott

Thanks for the insight. Very detailed reply.

I do my won wrenching and have a spare pumpkin so I can reconfigure with little downtime. The characteristics of the OS giken sound very favorable. What you stated suggests there would be less sudden push on corner entry with this diff due to the lessened preload. Am I right?

Corner entry push can be due to multiple factors. If you are getting that now with your torsen unit due to you suspension set up or driving line, you would also get that with an OSG or any other diff. The OEM torsen is pretty much open on corner entry.

It can be said though, that the higher the preload the more stiff turn in will be.

That being said though, LSD preload or initial torque (JDM speak) often gets a bad wrap as being the culprit for initial understeer or midcorner push. Some racers try to go overboard and have no preload.

Preload is useful to make a mechanical LSD less reactive. Say if you were driving over wet roads or uneven surfaces. If you had no preload, the diff could begin to lock unpredictably.

For many brands, preload is used assist the diff to get enough lock. Typically this is done when there is not enough surface area to get adequate lock. Too much preload, the diff will not allow for enough left-right "differential action" to allow the car to turn in smoothly, and can make the car feel "stiff". How much preload can the car tolerate typically depends on weight and level of grip. If you have r-comps or slicks, you would want more preload, etc...

[mrk1]

Originally Posted by simpleisbest

It is misinformation to lead people to believe that fiction surface area is totally dependent on the sheer number of disks. You need to look at size and surface type. If you look at the disks face, you will see that the Cusco unit heavy use of oil grooves decrease usable surface area. Similar to tread blocks for tires. Less contact patch.

If you disbelieve, then do the math.

To say they the two are functionally identical is also incorrect. You can tune the two to units to "drive" similar to a point. If your units you are testing are tuned as such, they could be similar for you. The mechanics of how each works and the tuning craft are polar opposites....

It's not marketing speak, it's call an layman explanation of mechanical engineering....

I look at more discs as finer adjustments not just surface area personally. I've got a OSG here on the bench with 12 plates vs the 9 in my Supra LSD. Its appealing to me that I can make smaller changes on the OSG.

Most people think OSG is a great part, however the price isn't for everyone. Thus other brands come into consideration, sure they are down some fancy engineering but get the job done for less.

[CSG Mike]

Originally Posted by simpleisbest

It is misinformation to lead people to believe that fiction surface area is totally dependent on the sheer number of disks. You need to look at size and surface type. If you look at the disks face, you will see that the Cusco unit heavy use of oil grooves decrease usable surface area. Similar to tread blocks for tires. Less contact patch.

If you disbelieve, then do the math.

To say they the two are functionally identical is also incorrect. You can tune the two to units to "drive" similar to a point. If your units you are testing are tuned as such, they could be similar for you. The mechanics of how each works and the tuning craft are polar opposites....

It's not marketing speak, it's call an layman explanation of mechanical engineering....

See, now you're just going in circles, and occasionally contradicting yourself.

Originally Posted by simpleisbest

The OS Giken unit is a negative preload biased unit with an internal design that allows for more plates than other brands (30-50% more).)

Originally Posted by simpleisbest

It is misinformation to lead people to believe that fiction surface area is totally dependent on the sheer number of disks. You need to look at size and surface type. If you look at the disks face, you will see that the Cusco unit heavy use of oil grooves decrease usable surface area.

Which is it? More plates, or more surface area? What if I told you the plates are larger in the Cusco unit? (They are).

Originally Posted by simpleisbest

To say they the two are functionally identical is also incorrect. You can tune the two to units to "drive" similar to a point. If your units you are testing are tuned as such, they could be similar for you. The mechanics of how each works and the tuning craft are polar opposites....

If the net result is the same, aren't they functionally identical, even if they're mechanically different?

An Mac and a Windows computer can both word process right? An iPhone and Android phone can both make calls?


I understand that you most likely have or are considering an OSG unit for yourself, and want to believe you made the best decision. The OSG is a great unit, but calling the Cusco inferior is simply wrong.

In fact, by default the OSG uses 100% of the friction surfaces, while the Cusco only uses 60%, even with the grooves, and yet, achieves similar lockup behavior, so the whole surface area/disk count argument is moot. Because of the negative preload design, the OSG *needs* more area. It's constantly trying to unlock, while the Cusco is trying to constantly lock.

Lets also not forget that the Cusco unit can use MUCH cheaper Motul Gear300LS ($26 retail) or Gear comp ($28 retail), while the OS Giken requires use of the OSG fluid ($50 retail).

There are pros and cons to both differentials, but the fine details are beyond the scope of this thread. Ultimately, both work, and function well.

The bombshell: the Cusco unit is designed by OSG, albeit to a different set of specifications. Hmmm... that only make the decision harder.


Also, on a side note, LSD tuning for track use, and AutoX use, are completely different, as the cornering elements and styles are fundamentally different.

[simpleisbest]

I do not have an OSG in my FR-S due to classing.

I thought my explanations were in plain enough English for most and was to clarify some info regarding diffs, not to pick an internet fight.

My intent was to not discredit the Cusco product, but to emphasis that it and the OSG units are not as similar as some may post.

No one likes the idea that you have to fork out a ton of cash for performance. Many want to just think of aftermarket LSDs as simple commodities and just look at "type", X-way, and costs.

For most street drivers or occasional track users, it may not really matter. For those who are looking to compete and win trophies, cash prizes, and/or make a living racing it does.

If you are looking to actually win something, it is best to understand what you are buying regardless of what brand.

[Thorpedo]

Originally Posted by mhiscott

Thanks for the input Mike.

I likely do more auto slalom than lapping, but I take the track more seriously, and do slalom more for fun.

I have had no issues with the car understeering with the stock differential. It's more that I found I couldn't get on the power exiting turns as early as I figure I should be able to.

Here's a video of the track I run at. You can see at T2 (tight left uphill) I struggle to put much power down without unstabilizing the rear.

The car has all whiteline products available for it, kw v3 coilovers, and ~ -3/-3 fr/rr camber. I currently run zero toe as I do DD the car in the summer, but I am open to mucking with some toe out to stabilize the car a bit on braking.

The car does make over the stock power. Around 280 wheel or so. That could climb to around 300 wheel next year.

From a lot of the reading I've done, many have suggested the 1.5 way for track use. When I brought this up on a local pro solo forum, an experienced driver suggested I would be better off with a 1 way due to the push/understeer I would realize with a 1.5way. I'm not sure what to think as I don't really know of a clear set of pros/cons of both.

I was leaning towards the OS Giken til now, but the Cusco RS seems to get a good rep, and would allow me to try both 1 way and 1.5 way and see what I prefer.

What measurable differences am I likely to see between the 1 and 1.5? Is there a significant benefit to 1.5 way in having a small amount of lockup on decel that I should consider? I see braking stability mentioned alot, but I'd love to hear your take on it, having used both.

Last point - I like to drive like a bit of a hooligan in closed course environments, and enjoy the ability to control oversteer and force slides when I want to. By no means am I constantly drifting around like a mad man, but I wouldn't want to make the car into an understeer machine in order to shave a few tenths at the track. I like having a tail happy car, and enjoy playing with the limits of grip.

Any insight or suggestions would be much appreciated.

Mike

Pay really close attention to the track where you are braking loose there in T2. I'm "Dev" on the ARMS forum and run at AMP as well. You're braking loose right as you transition from concrete to pavement. There are also a couple bumps there to boot. You;re doing T2 the way I used to do it and I always found it really awkward. I've since changed my line and I'm far more smooth.

Edit: Actually if you watch your vid close enough it would appear (to me) that your front end nudges wide just as it passes that point as well. Hard to tell for sure though without the steering wheel in view.

[mhiscott]

Thanks for the heads up Dev. Hope to see you out next season. What's your new line in two? Enter wide?

I'm actually quite enjoying the detail you are all going into on the units. I am definitely going to be wanting one of those two units. Both sound great. The more back and forth discussion that goes on the better for me making an informed decision.

Knowing things like OS Giken doing setup and rebuilds as well as gear oil being much cheaper for the Cusco are both great examples of those tidbits I'd have never known otherwise.

[mhiscott]

Originally Posted by simpleisbest

Corner entry push can be due to multiple factors. If you are getting that now with your torsen unit due to you suspension set up or driving line, you would also get that with an OSG or any other diff. The OEM torsen is pretty much open on corner entry.

It can be said though, that the higher the preload the more stiff turn in will be.

That being said though, LSD preload or initial torque (JDM speak) often gets a bad wrap as being the culprit for initial understeer or midcorner push. Some racers try to go overboard and have no preload.

Preload is useful to make a mechanical LSD less reactive. Say if you were driving over wet roads or uneven surfaces. If you had no preload, the diff could begin to lock unpredictably.

For many brands, preload is used assist the diff to get enough lock. Typically this is done when there is not enough surface area to get adequate lock. Too much preload, the diff will not allow for enough left-right "differential action" to allow the car to turn in smoothly, and can make the car feel "stiff". How much preload can the car tolerate typically depends on weight and level of grip. If you have r-comps or slicks, you would want more preload, etc...

I'm not getting any push or understeer currently. It's just I've heard I am likely to pick some up in changing to a 1.5way clutched diff. It's currently not a problem at all.

[CSG Mike]

Originally Posted by mhiscott

Thanks for the heads up Dev. Hope to see you out next season. What's your new line in two? Enter wide?

I'm actually quite enjoying the detail you are all going into on the units. I am definitely going to be wanting one of those two units. Both sound great. The more back and forth discussion that goes on the better for me making an informed decision.

Knowing things like OS Giken doing setup and rebuilds as well as gear oil being much cheaper for the Cusco are both great examples of those tidbits I'd have never known otherwise.

Theoretically speaking, the OSG will never require a rebuild, but I don't know anyone personally who's used a OSG long enough to say that for certain.

I've seen *one* cusco unit wear enough to need a rebuild, but that was more a result of overheating the differential, rather than the differential itself actually wearing out. Note that this was on a different platform that has a *TINY* differential, and the overheating was a result of multiple drivers flogging the car, back to back, with no time for the car to rest.

[mrk1]

Kaaz has there new line of Super Q LSD's that come with WPC treated internals, pretty cool.

Sure you can have any parts WPC treated but coming in the box already done is nice.

"The new Super-Q units are designed to perform at lower operating sounds and overall superior total performance. Some features are as fallows: Dramatically reduced chattering noise, Excellent Heat Dissipation, Smoother Engagement, longer life-wear, and no break-in period required! These new features along with KAAZ’s standard characteristics of lightning fast reaction time, adjustable engagement settings, and virtually hassle free operation make the new Super-Q LSD a must for all vehicles. Whether your vehicle is a daily driver, weekend warrior or full on race car, the new Super-Q LSD is fitted for all styles of performance operation! SUPER Q UNITS ARE AVAILABLE FOR ALL KAAZ L.S.D MODELS AND APPLICATIONS! CALL NOW!"

[D K]

The Super Q sucks for track duty.

We had that before we got a custom cam which works much better.

[mrk1]

Originally Posted by D K

The Super Q sucks for track duty.

We had that before we got a custom cam which works much better.

How so?

[Captain Snooze]

Originally Posted by CSG Mike

Lets also not forget that the Cusco unit can use MUCH cheaper Motul Gear300LS ($26 retail) or Gear comp ($28 retail), while the OS Giken requires use of the OSG fluid ($50 retail).

What is/are the consequence/s of using non-OSG oil in a OSG diff?

[CSG Mike]

Originally Posted by Captain Snooze

What is/are the consequence/s of using non-OSG oil in a OSG diff?

It may work fine or you may have a badly behaving diff with erratic behavior and potential damage. Everyone I know isn't willing to risk their $1600+ diff to save a few bucks per fluid change.

No different from using oil that deviates from the factory fill from the engine. Most diff oils are not 250 weight. You wouldn't use a 5 weight in your engine, would you?

[D K]

Originally Posted by mrk1

How so?

Much More positive lockup