2002 NSX-R Differential

[nsx1]

One of our NSX Prime members owns a 2002 NSX. He installed an NSX-R 4.235 Ring and Pinion believing at first, as did others, that it would fit. Low and behold, it didn't. He was finally able to get it installed using a 1994 NSX differential.

I also have a 2002 NSX and have wanted to get this R&P for my car, but at this point, I'm not quiet ready to do it yet seeing I would need an aftermarket differential.

Moments ago, I read in the NSX FAQ that the 1995 NSX-R used "a stiffer limited slip differential". So I thought, maybe the 2002 NSX-R has a different OEM differential.

Does anyone have this technical info? Or, know how to get it?

 

[ScienceofSpeed]

There are two differences between the NSX-R differential and the common 6-speeds. The first is the pre-load on the differential discs and secondly the planetary gear cut style used in the torque control differential (91-94 & NSX-R models) vs. the later differential torque reactive style. All of our NSX-R final drive kits include the parts to set the pre-load and break-away torque to NSX-R spec. The differential can then be used from an early car. The diagrams published by Honda for the 2002's showed a torque control differential, which is why we presumed that the ring gear would be a drop in for the 2002. However, as John discovered with a 6-spd out of his 2002, the differential was indeed a later torque reactive diff. If it is indeed true that all 2002-up NSXes are supplied with a torque reactive diff, the upgrade to the NSX-R 4.23 final drive would consist of:

1. 4.23 NSX-R gear set with 6-spd NSX-R pinion shaft
2. torque control differential
3. signal modifier for EPS sensor on ring gear

Of course, the signal modifier would not be required on a non-EPS car with 6-speed conversion like our 92. We have the parts available if this is the upgrade path you do want to take.

Cheers,
-- Chris

 

[nsx1]

Chris,

Thanks for the information. The more I learn about modern differentials, the more I understand what you just said. I've worked as a driveway mechanic all my life (I'm 53) and I thought I knew quiet a bit, but the more I read about differentials, the more I realize I have allot more to learn... at least where differentials are concerned.

Up until today, I thought that 1991-1994 NSXes did not have LSD style differentials (I'm not sure where I got that idea). But now I realize that in 1995, the manual transmission NSXes received the torque-reactive type differentials while the automatics continued receiving the torque-control differentials.

Given all that, I have a bunch of questions... here are some.

1) Was the exact same differential used for both auto and manual 1991-1994 NSXes? (excluding the R&P difference.)

2) Do the current automatic NSXes still use the torque-control differentials?

3) Would a late-model OEM torque-control differential fit into a 2002 6-speed NSX? (with either auto or manual R&P set.)

4) Do you think the 2002 NSX-R R&P set would fit into a 2002 6-speed NSX if the late-model OEM torque-control differential were used?

5) Are the late-model OEM torque-control differentials available?

6) Could the pre-95 torque-control differential be different from the 95+ differentials, hence, the cause of the EPS issue? (i.e. since pre-95 was not a power steering car?)

According to Honda, the torque-reactive differential generates ~10% more lateral acceleration force than the torque-control differential (0.255 g vs. 0.230 g on a 15-meter skid pad).

7) Does anyone make a torque-reactive differential that would do the job?

 

[NSX/MR2]

How much faster does the R&P does for acceleration in a 2002?

 

[nsxtasy]

There are two differences between the NSX-R differential and the common 6-speeds. The first is the pre-load on the differential discs and secondly the planetary gear cut style used in the torque control differential (91-94 & NSX-R models) vs. the later differential torque reactive style. All of our NSX-R final drive kits include the parts to set the pre-load and break-away torque to NSX-R spec.

My understanding is that these can be set on the stock five-speed drivetrain, too.

How much faster does the R&P does for acceleration in a 2002?

These are the figures that Bob Butler has calculated for each of the three R&P options on a '97-01 NSX Coupe:

Speed Stock 4.23R&P 4.55R&P
0-30 | 2.03 | 1.94 | 1.80
0-40 | 2.67 | 2.56 | 2.38
0-50 | 3.77 | 3.68 | 3.54
0-60 | 4.79 | 4.67 | 4.47
0-70 | 5.89 | 5.76 | 5.92
0-80 | 7.61 | 7.49 | 7.28
0-90 | 9.20 | 9.05 | 9.12
0-100 | 11.04 | 11.26 | 11.06
0-110 | 13.71 | 13.55 | 13.27
0-120 | 16.44 | 16.26 | 16.41
0-130 | 20.30 | 20.22 | 19.90

1/4mile 13.24 | 13.17 | 13.06

A 2002+ NSX-T would take slightly longer, due to the weight difference between the Coupe and the NSX-T, but the differences among the three R&P options should stay the same.

 

[nsx1]

How much faster does the R&P does for acceleration in a 2002?

There has been much discussion/argument about what the 4.235 R&P will do for the NSX.

Here are some handy links...
Got the 4.235 installed in my 2002 NSX T
2002 NSX times (1/4 mile) with 4.235 gears
Exedy+4.235R&P+Short Gears First Impression
4.23 final drive ratio and your 6-spd

In the mean time, any of our resident experts (I won't name names ) have answers to my questions in the 3rd post?

Or maybe I should just consider the 4.44 or 4.55 R&P?

 

[Eddy]

I have researched this quite a bit and you can see what fits what from this page I have made.

The automatic diff is a "torque control diff" in ALL years identical to 5 speed diffs except a part called "planetary carrier set" is different.

According to Honda/Acura's parts catalog, the "torque reactive diff" is used in ALL (including 2002's) 6 speed transmissions with the exception of Type-R's..

The 2002 Type-R "torque control diff" is also identical to the diffs used in the older 5 speed transmissions.

So basically, 5-speed diff=auto diff=type-r 5-speed diff=type-r 6-speed diff all being "torque control" diff (with minor differences between them)
and the rest of the 6-speed diff are all the same being "torque reactive"

This page with parts number cross reference should answer most if not all your questions. Each particular "style" of transmission is assigned a color and you can tell what part is shared from the color of the cells.

http://home.earthlink.net/~eddyanm/nsxparts.html

Hope this helps..

Eddy

 

[ScienceofSpeed]

Don't forget that the 1995-96 US model 5-speeds use the torque reactive differential as well (which is why the NSX-R ring gear is not compatible in these years with out changing the diff).

Cheers,
-- Chris

I have researched this quite a bit and you can see what fits what from this page I have made.

The automatic diff is a "torque control diff" in ALL years identical to 5 speed diffs except a part called "planetary carrier set" is different.

According to Honda/Acura's parts catalog, the "torque reactive diff" is used in ALL (including 2002's) 6 speed transmissions with the exception of Type-R's..

The 2002 Type-R "torque control diff" is also identical to the diffs used in the older 5 speed transmissions.

So basically, 5-speed diff=auto diff=type-r 5-speed diff=type-r 6-speed diff all being "torque control" diff (with minor differences between them)
and the rest of the 6-speed diff are all the same being "torque reactive"

This page with parts number cross reference should answer most if not all your questions. Each particular "style" of transmission is assigned a color and you can tell what part is shared from the color of the cells.

http://home.earthlink.net/~eddyanm/nsxparts.html

Hope this helps..

Eddy

 

[1BADNSX]

I am trying to learn. Please explain the difference between these LSD’s based on method, rather than terminology. I am pretty sure the original 5-speed LSD is a clutch pack type unit, is this what you refer to as “torque control”? How are the “torque reactive” LSD’s different? Are they helical gear units similar to Quaife or Torsen?

My favorite quote from Carroll Smith is “Limited Slip Differentials are limited, and yes they do slip”!

Bob

 

[ScienceofSpeed]

The clutch packs seem to be the same. The only difference I can see is that the early car's planetary gears have straight cut teeth where the later models are tapered. I can not find the definition of "torque control" vs. "torque reactive".

Cheers,
-- Chris

 

[PorknBeanz]

The FAQ explanation sounds to me as if the earlier Torque Control Differential is superior to the later Torque Reactive Differential. Specifically, the earlier system compensates for crosswinds. Does the Reactive Differential not deal effectively with crosswinds?

From a technical standpoint, is there any reason why the manual NSX would benefit from the Reactive Differential and an automatic car would benefit more from the Torque Control Differential?

 

[Eddy]

If you look at the design of a LSD you will see how and why they are called what they are. Btw, torque is angular force which is equivalent to force in a linear direction. Best way to understand torque is that it's the force used to turn a shaft. Engines turn/spin, and so do wheels so that's why we describe it as torque and not force.

"Torque Reactive Diff" is similar in principle to Quaiff LSD (if you are familiar with them). The helical gears causes a thrust against the friction discs and thus creating different level of lock/slip threshold based on the torque differences between the ring gear and the driveshafts. Quaiff LSD have no friction disc and the gears actually lock against the LSD casing instead of plates. This design is clearly "torque reactive" as the LSD's response is based on the torque applied to the LSD body by the ring gear from the engine and the driveshafts in addition to controling the torque to the wheels.

"Torque Control Diff" on the other hand has straight gears and doesn't cause any thrust against the friction plates and therefore doesn't change the amount of lock/slip. The lock/slip torque threshold is preset by springs and washers (which explains why Type-R's have different springs/washer, to increase the slip threshold). And in this case, the LSD controls the torque to the wheels based on the torque difference between the driveshafts but it doesn't "react" differently based on the torque difference.

The primary function of a LSD is to prevent the "slip of a wheel". In a typical open differential, if you have one wheel on the ground and one wheel in the air, the engine's torque will be transferred to the wheel in the air, not the one on the ground. This makes the power from the engine useless in moving the car forward. You can easily verify this using a RC car. Pick one up, run the car forward and stop one wheel with your hand and you will see the other wheel will spin while the wheel you are holding has very little toque against your hand.

On the other extreme, if the driveshafts are locked (i.e. in drag race cars), both wheels will exert the same amount of torque regardless of their condition but this makes turning difficult as the wheels cannot turn at different speeds; which is why this is ideal for drag race cars.

A LSD is a compromise (therefore "limited slip") between fully open (unlocked) and locked. However, the locking torque limit that's useful depends very much on the condition of the wheels/road surface so there are many designs to achieve different goals. That's why a lot of 4WD cars/trucks have LSD that are driver controllable as are some race cars (when allowed by rules). It's to better customize the LSD to different conditions.

I guess each have their own ups and downs depending on the driving condition. You will have to be the judge of it.. Or.. Let the car maker be the judge of it for you when you buy a car.

Eddy

 

[1BADNSX]

"Torque Reactive Diff" is similar in principle to Quaiff LSD (if you are familiar with them). The helical gears causes a thrust against the friction discs and thus creating different level of lock/slip threshold based on the torque differences between the ring gear and the driveshafts. Quaiff LSD have no friction disc and the gears actually lock against the LSD casing instead of plates. This design is clearly "torque reactive" as the LSD's response is based on the torque applied to the LSD body by the ring gear from the engine and the driveshafts in addition to controling the torque to the wheels.

"Torque Control Diff" on the other hand has straight gears and doesn't cause any thrust against the friction plates and therefore doesn't change the amount of lock/slip. The lock/slip torque threshold is preset by springs and washers (which explains why Type-R's have different springs/washer, to increase the slip threshold). And in this case, the LSD controls the torque to the wheels based on the torque difference between the driveshafts but it doesn't "react" differently based on the torque difference.

Eddy

Thank you Eddy and this is why I asked the original question, but it doesn't sound like the NSX "Torque Control" is different enough (based on Chris's description) to be a Quaife or Torsen type diff. If it were, I would argue based on my racing experience that this would be the better of the two differentials to have. Chris, does the NSX "torque control" diff have clutch packs? If they do, I don't believe they are Quaife or Torsen type differentials that Eddy explained above.

Thanks, Bob

 

[Eddy]

Both type of LSDs have clutch disc packs. And just to clarify, the "torque reactive diff" is similar in working priniciple to Quaiff but the "torque control diff" is NOT.

Eddy

 

[1BADNSX]

Both type of LSDs have clutch disc packs. And just to clarify, the "torque reactive diff" is similar in working priniciple to Quaiff but the "torque control diff" is NOT.

Eddy

Quaife differentials do not have clutch packs. "The Quaife is extremely strong and durable and since the Quaife is gear operated, it has no plates or clutches that can wear out and need costly replacement."

http://www.quaifeamerica.com/

This is why I think there is great confusion regarding the difference in these two NSX LSD's. The difference may be mostly marketing speak. Does anybody know?

Bob

 

[nsx1]

Eddy is correct in regards to the method. I believe he was stating that both NSX differentials have clutch plates (which I also believe is true.)

I have spent almost a week researching this stuff. I still feel I have allot to figure out. One thing I can do is share what I have discovered about the methodological differences as they relate to the comparison of the Quaife and Torsen (Troque Sensing differentials).

The following qoutes are copied directly out of white papers and web sites.

"In cornering, while accelerating out of a turn, the Quaife biases power to the outside wheel."
(ref. http://www.quaifeamerica.com/differentials/diffs.htm)

The above quote fits the definition of the "Torque-reactive" differential.

"The Torsen differential resists transfers of torque between drive wheels in proportion to the torque applied to the differential housing, and this results in a larger proportion of the applied torque being delivered to the slower rotating drive wheel."
(ref. http://www.sonic.net/garyg/zonc/TechnicalInformation/TorsenDifferential.html)

The above quote fits the definition of the "Torque-control" differential.

According to Honda, the "torque-reactive" differential generates ~10% more lateral acceleration force than the "torque-control" differential (0.255 g vs. 0.230 g on a 15-meter skid pad). You can determine for yourself whether or not this is good for racing.

 

[1BADNSX]

NSX1, I think you will find that neither NSX differential in question is similar to a Quaife or Torsen. Helical gear driven differentials do not use clutch packs. Some general comments about these two differential methods from a racers point of view:

1) Clutch pack LSD: Con: operate with slipping between the clutch packs and will always transfer more torque to the inside wheel. They also wear out. Pro: they will still transfer some torque with one wheel with zero traction.

2) Gear drive LSD (both Torsen and Quaife are similar): Pro: transfer more torque to the outside wheel. Con: will not transfer any torque if one wheel loses all traction.

Most racers consider it an advantage to go to a Quaife or Torsen type differential, but from the descriptions above neither of the NSX LSD’s fall into this category.

Bob