As what the titles have said, can someone please clarify the difference; what are the advantages of the two sides in 1) daily driving 2) Track performance

Thanks,
G Mans

 

The open-diff is ok for driving daily but it would be terrible at the track. The vlsd would be fine for both, though it wouldnt be the best thing at the track. The open differential is bad for the track because all it does is make both your rear tires spin at the same rate. If youre going around a turn and applying the gas, your tires would definitely break traction with an open differential, since the open differential would try to keep the two tires rotating at the same speed.

The vlsd is a bit better on the track, because it allows i think around 30% torque transfer to the tire that still has grip, meaning you can still power through a turn, though it usually takes the slipping of one tire before the vlsd will actually kick in. Thats because the vlsd uses viscous fluid and plates and only when theres a decent disparity in the rotation of the plates will the vlsd work.


hope that wasnt too confusing O_O

 

ditto



the vlsd is better than nothing, but it isn't going to help you much at the track. If you have some racing tires, really good brakes, and are a GREAT driver, you can actually burn up the stock vlsd pretty good in a single 20 min session...

 

that's some very good information; coz I am looking for a pumpkin swap from 3.3 to 3.53 FD (for my 5AT); however, the pumpkins that i found with the VLSD are usually quite a bit more than that of Open-diff..

thus, I am just wondering if i can justify the extra money spent on swapping on an VLSD versus an open-diff pumpkin.. where I will track over this summer (but not that frequent anyways... like once a month max)

FYI: my 04 5AT is equipped with open-diff; and i see the problem that you described when I tried to put power down when I exit a curve lol..

so i guess I should be leaning towards open-diff? since I wouldn't be willing to get a true clutch-type LSD anyways.

 

I love my clutch diff. the cornering and straight line grip are too great to not want one IMO

all you need to smooth it out are some BIG tires in the rear and good synthetic oil and some redline friction modifier and it smooths out a lot - I know what people mean though when they say a clutch diff is a pain on the street - I had one when I had stock tires and normal gear oil...

it still might make some minor noises in parking lots during slow turns though

 

There's a couple things that need to be cleared up... Both wheels do not spin at the same speed with an open diff through the turn. That would be the case if you had you rear-end welded into a solid axle. If your wheels spun the same speed you would drag your outside wheel, or overspin your inside wheel hopelessly through every turn.

They key to the open diff is that its best suited for low speed turning because the diff housing rotational speed is the average of the two axles. Whats wrong with the design is an open diff tries to balance the torque to both wheels equal to that of the wheel with the least resistance. So if one wheel starts to lose grip with an open diff, (easy to happen at high speeds as the outside wheel is spinning faster) the torque required to push the wheel losing traction is applied to the wheel with resistance. Meaning if it only takes 25 ft-lbs of torque to make your left wheel spin because of slick conditions, only 25 ft-lbs of torque is applied to the right wheel that might have traction. This is why RWD cars with open diffs do very simple one wheeled burnouts and are very easy to upset the rear in slick conditions.

The VLSD is a mild improvement on the open diff. There is a viscous coupling in the middle with near touching fins that spin the same speed as each axle. So drivability is the same as the open diff. But when a wheel loses traction like an open diff and starts to spin faster, this causes the fin on the one side to speed up. Because of the nature of the viscous fluid, it will cause the other fin to gradually speed up as well, poweing the wheel with traction. So with VLSD, it doesn't really engage until after you've started to lose traction or get a larger disparity between wheel speeds. Not very confidence inspiring unless you know how to really handle it. VLSD is better than open because that viscous coupling is always engaged, but you are limited to 20-40% power transfer depending on the situation.

If you want a truly streetable diff, that makes a huge difference in your traction, get the Quaife. Its a drop-in for the open diff pumpkins, and its a fully mechanical torque-biasing setup. If you have any desire to track the car though, you'd be crazy to not consider it for an open diff.

 

First of all, thanks for the info

However, isn't it expensive (labour wise) to open the pumpkin? that's the main reason why I am just doing a 3.3 -> 3.5 pumpkin swap instead of a FD gear upgrade..

Secondly, off the bat, if say the difference between an 3.53FD open-diff pumpkin and a 3.53FD VLSD pumpkin is around $300.. which one would you take?

Thanks again

 

I would take the VLSD, its still better than an open diff.

 

I'd keep the $300 and save up for a real LSD

 

I guess for now, I will probably just take the open-diff 3.53FD pumpkin, swap it in; and see how does it do on the track, if it is too bad, then I would consider upgrading to a real LSD !

however, I do have to take the pumpkin apart to upgrade my differential from open-diff to LSD, right?

 

No, pumpkin swaps do not require to open the actual pumpkins. But you'll save money in labor if you throw in a Quaife or one of the clutch type LSD's now since you'll have the pumpkin down.

If you wait to do an aftermarket LSD, you'll be paying for labor again to drop the pumpkin a second time.

 

Okie, say I can get a open-diff 3.53FD pumpkin, and I buy an aftermarket LSD say Qualife or Nismo, do I have to pay alot of labour to have them open up the pumpkin to drop in the LSD into the open-diff pumpkin that I am getting?

If so, then I guess I might just wait till I buy the LSD, then I put the new pumpkin on my stupid 5AT !

Thanks for clarifying !

 

Nice.

VLSD helps u exit faster out of the corner as a result.

 

The typical length of doing a LSD install is about 5 hours. So if you were jsut doing a straight pumpkin swap I'd say it would take around 2-2.5 hours. Not a whole lot more to get a Quaife or a Nismo in. Plus why would you want to run on an open diff if you have any aspirations for performance?!?

 

Yes, but if you track at all you will find the stock VLSD quite lacking to say the least.