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Discussion Starter #1
Hi:

I searched this board for info on the type of LSD in the 6 MT Coupe. Could not find any thing other than discussion about the 6 MT Sedan. I called the Infiniti dealer who sold me the 6 MT Coupe and they don't know what type of LSD the coupe has. "Some kind of viscus disc thing in there." Was the answer.

Does anyone out there know what type of LSD is in the 6MT Coupe?

BTW, from the internet, I learned that the "Double Mass Flywheel" is primairly used to reduce engine vibration entering the cabin. It was first used on trucks and diesel cars. Porche uses them. I guess Nissan used it to dampen vibrations from the V6 engine. It also provides for less clutch slippage. :)



6MT DP
 

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There was in article in last month's Sport Compact Car magazine in which they upgraded the stock viscous limited slip differential with a higher quality plate-type model. (Actually, the car was a 350Z, but same parts as the Infiniti).

I seem to recall that author was complaining that they had chosen a plate combination that was too aggressive (too little slip) and that performance around corners actually suffered over the stock setup.

If it's really important to you, I can dig up the magazine and give you some more specifics.


*** 2003 G35 Coupe, 6-Speed manual ***
 

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Discussion Starter #3
Hi:

Vittopaparazzi;

Thank you very much for the info and offer! Since I made the initial post, I have been searching the web for info on LSD's. I wanted to learn about the quality/effectiveness of the viscous LSD, after reading the posts in the sedan forum on this topic.

This is what I gleened from the various searches on the topic of LSD's. Please don't take it as gospel.

"What then is a limited slip differential (LSD)? As the name implies, it is designed to limit slip... it does this by using a secondary mechanism to transfer power back to the slower wheel when a large difference in speed exists between the wheels. There are several ways to accomplish this transfer, and the most common types are the clutch-type and viscous-type LSD."

Viscous-type limited slip differentials:

A viscous-type LSD uses a thick fluid sandwiched between plates, one plate being connected to (drives) each wheel. When a rotation difference occurs between wheels, the faster plate spins the fluid which in turn spins the slower plate, hence transferring power from the faster wheel to the slower wheel. Viscous units have two spinning disks that face each other. Each has a vaned surface and there's a viscous (oddly enough) fluid between them. The fluid has the property that shear forces thicken it. As long as the two disks spin at relatively similar speeds the fluid is "thin". When there is a differential between the two, because one wheel is slipping or you're going around a corner, the fluid is sheared and thickens. The thicker fluid loosely couples the two vaned disks thus limiting slip. <u>Viscous LSDs generally provide something like 20-25% coupling efficiency</u>.

A viscous-type LSD has the advantage of requiring little to no maintenance, since the fluid never wears out. However, from a performance standpoint, a viscous-type LSD is not ideal. On a viscous LSD, it takes a split-second for the LSD to react to slip as the fluid must speed up before it starts turning the slower plate. On higher horsepower cars, any lag in response resulting in uneven traction is especially undesirable.

In Miata’s, Viscous LSD's are notable for failures at your 145K milage with moderate to hard usage.

Clutch-type limited slip differentials:

A clutch-type LSD uses a set of clutch discs, that are connected to each wheel, and the discs are clamped together at a certain pressure when in operation. When one wheel tries to rotate faster than the other wheel, the clutch discs start to slip, the faster disc transfers power to the slower disc through friction, hence transferring power from the faster wheel to the slower wheel.

A clutch-type LSD responds immediately to any slippage, unlike the viscous-type LSD, and is so better from a performance standpoint. A clutch-type LSD is also much more easily upgradeable to handle high horsepower, as the number of clutch discs can be easily increased or the clutch disc sizes can be enlarged. Most aftermarket clutch-type LSDs have larger/more clutch discs. The downside with a clutch-type LSD is that with the slipping of the clutch discs, they eventually wear down and will require maintenance. Also clutch discs will chatter when they are engaged, so a clutch-type LSD is not as quiet as other LSDs.

Clutch type LSDs are often offered as 1way, 1.5 way or 2-way. A 1-way LSD only engages the clutch discs only on acceleration. The 1.5-Way L.S.D. means that when the car is braking, there is little L.S.D. effect. A 1.5-way LSD is a compromise between a 1-way and 2-way, as it engages the clutch discs with less pressure on deceleration, which allows for more slip on deceleration and hence less oversteer. A 2-way LSD engages the clutch discs on both acceleration and deceleration; the 2-way L.S.D. is always active. If the clutch discs work to limit slip on deceleration, they can optimize traction under braking, but at the same time as they transfer power from the faster wheel to the slower wheel, this increases oversteer in turns. Therefore a 2-way LSD is generally considered more difficult to handle, but superior for handling, while a 1-way LSD is more forgiving.

Note: a viscous LSD is always 1.5 or 2-way by design.
Note: Mechanical LSD’s require proper break in. A mechanical clutch LSD is noisy and better suited to full competition use.

Gear-type limited slip differentials:

Another type of LSD works through gears to limit slip. These LSDs can offer very immediate response like a clutch-type LSD, with little maintenance and quiet operation. However, there are not as easily upgraded for high horsepower as with the clutch-type LSD, they are limited by the strength of their gears. Gear-type LSDs are also generally a lot more costly than the clutch-type or viscous-type LSDs.

Helical LSD:

Manual versions of the Nissan 2005X are fitted with a helical limited-slip rear differential, as fitted to the V Spec Skyline GT-R coupe. Under acceleration, the helical LSD provides faster traction control than a conventional clutch-type LSD or viscous LSD and without relying on the performance of the Viscous Coupling oil as used in a Viscous LSD. Basically, the Helical LSD generates torque to both left and right rear wheels by frictional force between the gear teeth and the differential case.

If one wheel loses traction and tries to spin, that axle's side gear rotates slightly faster, so transmitting the lost torque through the helical gears and back to the differential case. The engine torque is also applied to the same part of the case through the final gear so it in turn drives the road wheel through its side gear.

Honda equipped the Integra Type-R with a helical LSD, which is a superior type of LSD that does not incur power loss compared to the normal viscous coupling LSD

The helical LSD tranny of the Nissan SE-R Spec-V allows the front wheels to rotate at different rates while still applying torque equally, reducing understeer in the corners and allowing you to grab gears on the twisties and apply the throttle in turns sooner with more control.



Torsen LSD (Torsion sensing LSD):

Torsen, which stands for torsion-sensing, LSD's use gears and typically provide more like 75% coupling. The MRT Torsen style front LSD locks under load so provides more grip when exiting a corner, but acts like an open diff under trailing throttle so it does not induce understeer coming into the corner. This is the major difference with a mechanical LSD. Most rally and full race cars use clutch pack diffs as a Torsen LSD is unable to transfer torque if there is none, ie if the wheel is off the ground it will not work, a clutch diff will. A Modena Torsen LSD is a non-adjustable unit that in theory transfers torque from a spinning wheel to the other wheel before it spins.

Point to consider - a torsen LSD, has silent operation and is ideal for street use.



Some Aftermarket LSD Manufactures

http://www.quaife.co.uk/
http://www.kaazusa.com





6MT DP
 

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WOW!! Great research Ripley... i learned a lot from that little blurb on LSD =P thanks again!

-no sig this time
 
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