Todd00

Having driven and/or owned the same style car with 4 different diffs in it, I feel that I can comment on this.

1) 97 GSR, open diff
2) 00 ITR, OEM LSD
3) 98 ITR, Quaife
4) 00 ITR, 1.5 way clutch type.

The jump from the OEM ITR LSD to the Quaife is slight, but not earth-shattering. The jump from the OEM ITR LSD to the 1.5 way clutch-type *is* earth-shattering. I cannot begin to describe how much it transforms the car in every situation, especially on turn-in and pulling through/around a corner.

A mechanical 1-way is a mechanical 1-way. They are good, but they can only get so good and they will always have their drawbacks. A 1.5 way clutch-type is the ideal LSD for a FWD car that sees track/autox use. Not so good for a daily, though.

Anything is better than an open diff.

Robin6

^^

Presidential_Detail

Thanks for sharing Todd!

xotic_crx

Awesome feedback, thanks for sharing! I thought just going from an open diff to my OEM ZC diff was a big enough difference, I can't wait to step up to a 1.5 clutch-type. What brand did you use?

RagingAngel

A 1 way Plate differential is ideal for road racing/autoX.

The reason for this is because it is only active during acceleration.

1 way = 100% lock OPEN during decel/braking
1.5 way = 100% lock going forward, 50% lock during decel/braking

That said, the experienced racers prefer the 1 way lock only because under braking and decel, this allows the wheels to move at a different speed effectively enabling the driver to place the car where they want to.

This is important in wheel to wheel racing because you cannot always drive the ideal line due to traffic/going for a pass etc.

With 50% lock under braking/decel, this can cause a degree of understeer that is obviously undesirable for a front wheel drive car.

However, less experienced racers/track go'ers have gone faster with a 1.5 way due to some understeer when they are driving at THEIR limit. This acts as a bit of a safety net.

Some more information found here:
http://www.motoiq.com/MagazineArticl...rivetrain.aspx

FlewByU352

some real good info being brought up in this discussion!

Franshow

Damn it Chris, Now you have me wondering if it would be worth replacing my OEM ITR LSD for an "upgraded" MFactory LSD as well lol. The car definitely seemed faster last event. Just wondering if I should buy a bigger rear sway bar and decrease rear grip or upgrade my LSD and increase front grip... decisions decisions...

Franshow

Agreed

RagingAngel

It is definitely worth doing.

The majority of the racers since 2009 in Honda Challenge etc. have reportedly gone as much as 2 seconds faster per lap with the plate differential ONCE THE REST OF THE CAR HAS BEEN matched to the diff (alignment settings etc)

Drivers such as Renan Bayar, 2009 NASA HC champ and Edo Stepanyan continue to go faster to this day.

Much like tires, not all limited slip diffs are created equally.

If you are using the car exclusively for track, you really can't go wrong with a plate diff.

A little humor in the truth....

xotic_crx

Sorry for the ignorance, but what settings changes would you make going from open to a diff? I'm looking to go with an mFactory diff this offseason after I get the new engine is in and I decide on which trans to run. I think I'll go with a 1-way myself after reading your posts. (Sorry for the threadjack).

10cjennings

iTrader: (1)

IMO, always change one thing at a time. Get the LSD and continue to test/tune from there.

xotic_crx

Yeah, I just didn't know what kind of changes would you expect to make going to a nice diff. I guess what I'm asking is how will the diff change the handling of the car? I know when I went from open diff to the ZC diff I could plant the power earlier in the turn.

10cjennings

iTrader: (1)

You'll be able to get on the throttle much earlier with less on-power understeer. It also allows you to use the throttle more effectively/consistently to control oversteer.

Franshow

Exactly... I wouldnt say that a good LSD aids in turning the way a rear sway bar would (should*) by helping your car rotate better. What it does (IMO) is help initial turn in drastically by increasing grip while going on throttle. This applies to 1 way lsd's.... 1.5 and 2 way do that and more, which can be a good or bad thing. (If that makes sense)

Aquafina

iTrader: (3)

It isn't just initial turn-in. You can be mid turn with an LSD and give it more gas and it will pull the car even more in the direction you want to go as long as you have enough traction.

Franshow

Ok I said "In my opinion" (OR my personal experience) a good LSD helps turn in drastically but that is not to say that it doesnt help you out in other phases of a turn. Where an LSD helps you all depends on your driving style, where you put down the power (or let off) and how much power you have (or dont have). You saying how an LSD will perform "as long as you have traction" further amplifies what I am trying to say, various setups will react differently to various LSD's which is exactly why I made sure to include the fact that what I said was an opinion and not necessarily fact. But yes a good lsd can help you mid corner if need be....

Todd00

I found that one of the largest improvements the 1.5 way from the mechanical 1-way gave me was indeed the ability to put power down mid-corner (much earlier, too). With that, some of my push went away (with zero other changes to the car). I was amazed the first time I drove the car how much better it behaved with only a diff swap (and how much faster I got on the autox course).

Franshow

I actually drove "C10Jennings" car at our last event and the difference from my OEM ITR LSD to his upgraded MFactory helical was very noticeable. Even more impressive is the fact that my factory LSD could barely handle putting the power down mid corner with a B18C where as with his MFactory Helical I could pretty much go WOT mid corner and have it pull me through the corner in his more powerful K-swapped EG. Yesterday was the first day I had driven in something other than an OEM ITR LSD and I would say it was pretty noticeable. Not only that but it also made me realize how conservative I had been driving in my car mid corner because of my inadequate LSD. I can only imagine what a proper clutch type LSD would do...

Todd00

I had to re-adjust my driving style with the new diff. It's amazing how it changes the handling dynamics, but it does. I also felt that after the new diff, my springrates could probably be changed as well as I didn't need to rely on rate as much to get the car to rotate.

10cjennings

iTrader: (1)

I had the opposite thought process. From an autox perspective I felt like I could set the car up even looser with the LSD (vs open diff), because the throttle could be much more effectively used to tame oversteer. 1st event with new rates (from 500/550 to 600/750), and the 2nd with the LSD it took a whole practice session to get the car close to what I'm looking for, still a lot of fine-tuning to do but it felt pretty good.

RR98ITR

This is Crazy talk if you're suggesting softening the rear or stiffening the front, ie taking weight off the inside front. You up the bias ratio and are so happy that you lessen the value that it multiplies.

Scott, who refers you to my next post below...

RR98ITR

SUPER KEY thing to keep in mind - having a front end that hooks up gives you a front end that can outrun the rear end...it's a machine...it's a system...

Scott, who admits that while it is a machine...and a system..."it's a very bad design"...

Todd00

I was quite a bit higher than 600/750 with the OEM LSD. I was going to drop down to something like that.

It's all about perspective

Todd00

Are you speaking from a "track" perspective or a ~50mph autox perspective?

In autox, there is (almost) no such thing as being too loose in a FWD car...unless you can't control it in a slalom or something.

Unless...you have a proper LSD that does a better job of controlling what the front wheels do, as we all know that if you can get the front pointed where you want it, the back will usually follow along properly and you don't need to apply the same amount of "trickery" to get the back to behave.

Again, autox perspective. I don't disagree with you though.

10cjennings

iTrader: (1)

Yeah, My thought process was to set the car up too loose, and back off from there. I wasn't really sure I'd find that but 1st couple runs out with the new rates and everything else the same, the car was definitely too loose (at least for me, and I think I really prefer a loose car. With the slow manual rack it was challenging for me to keep the rear in control in transition between slalom-like corners which both require shuffling to achieve enough steering angle. This was a much different course then I typically run as well), Putting the RSB on soft and softening the rear shocks a little hit the balance I was looking for, faster rack going in before the next event and keep testing, probably try the bar on stiff.