LSD Break Away Touque...??

New posts disabled. Archived technical discussion about the Datsun PL510
User avatar
Byron510
Moderator
Posts: 12658
Joined: 01 Jul 2003 23:06
Location: Maple Ridge, BC

LSD Break Away Touque...??

Post by Byron510 »

Or any other rally type guys. I'm looking to shim up my LSD for my ice race car. I'm guessing that I should set the break away torque higher than the current 35 lbs. I've always run a welded diff in the ice racer, so this is new to me with the LSD this year. I've yet to be on the ice with it,(going in two weeks) but I was driving around this week on Yokohama gravel tires on the street, and it was fairly easy to get the inside wheel spinning. I know there is more traction on wet pavement than on ice, but I don't think the diff is shimmed up enough. The diff is an R190 with 4:44 gears; power is LZ 2.2 producing about 130 or so HP, but fairly good torque.
Any ideas on what the diff should be set to anyone?

Byron
Last edited by Byron510 on 25 Jan 2005 21:40, edited 1 time in total.
User avatar
bertvorgon
Supporter
Posts: 11996
Joined: 04 Aug 2003 20:45
Location: White Rock, B.C. Canada

RE: LSD Break Away Touque... Baz??

Post by bertvorgon »

Hi Byron,
My diff is set to about 50 lbs, for what that is worth. If you are spinning the tire at that setting, I do not think you would be too out of line to get close to this.
"Racing makes heroin addiction look like a vague wish for something salty" - Peter Egan

Keith Law
1973 2 Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1971 Vintage 13' BOLER trailer
User avatar
Baz
Posts: 521
Joined: 13 Jul 2004 07:34
Location: Lonsdale South OZ

RE: LSD Break Away Touque... Baz??

Post by Baz »

Hi Byron,
I believe the factory spec was 43 lbs.
So Keith is pretty close.
My preference was for 70lbs with the 2 way.
Better control on light throttle without having to "shock" load the diff to
lock it fully.
Check that the ramps are still smooth.
Baz
User avatar
bertvorgon
Supporter
Posts: 11996
Joined: 04 Aug 2003 20:45
Location: White Rock, B.C. Canada

RE: LSD Break Away Touque... Baz??

Post by bertvorgon »

That was kind of our theory also, Baz. When we put the really sticky slicks on for slaloming, we wanted the transition on corner exit to be relatively smooth at that part throttle point, minimizing more understeer. I am pulling my diff out this winter just to see how it is all doing in there.
"Racing makes heroin addiction look like a vague wish for something salty" - Peter Egan

Keith Law
1973 2 Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1971 Vintage 13' BOLER trailer
User avatar
Byron510
Moderator
Posts: 12658
Joined: 01 Jul 2003 23:06
Location: Maple Ridge, BC

RE: LSD Break Away Touque... Baz??

Post by Byron510 »

You know, I've never disassembled an LSD - so I'm in new territory. I'm told you can shim the clutch pack to make it a bit stiffer, but how much shim do I start with? .005", .010", .020??? I guess this will be a bit of an experiment. I don't want it to be shimmed up to tight, as I'll be on a slippery surface, and I'd like to keep the turn in under control. I've already got a locker, and I don't want to go that far with the LSD.

Byron
Love people and use things,
because the opposite never works.
User avatar
RWD_NissanMan
Supporter
Posts: 870
Joined: 01 Oct 2003 14:13
Location: Poncitlan, JAL, Mexico

Re: RE: LSD Break Away Touque... Baz??

Post by RWD_NissanMan »

Byron510 wrote:You know, I've never disassembled an LSD - so I'm in new territory. I'm told you can shim the clutch pack to make it a bit stiffer, but how much shim do I start with? .005", .010", .020??? I guess this will be a bit of an experiment.
Byron

I think you are right, it is a "trial and error" exercise - I have never seen a formula for shim width to break away torque. Probably because there are a lot of variables (condition of disks, type of gear oil used, etc.). First come up with a way to take a measurement of what you have now so you have a baseline reading to start with - then make a change and recheck it. Otherwise, you are just taking stabs in the dark and your likely to get all messed up.
1969 Datsun 510 4-door (donor shell for below)
1973 Datsun 510 SR20DET (sort of broken right now)
1998 Suzuki Escudo (JDM Sidekick Sport) 2.0TD 4x4 (daily driver)
2006 Ford Explorer 4.6 V8 3V 4x2 (wife's ride)
2005 & 2006 Targa Newfoundland Entrant
User avatar
Byron510
Moderator
Posts: 12658
Joined: 01 Jul 2003 23:06
Location: Maple Ridge, BC

RE: Re: RE: LSD Break Away Touque... Baz??

Post by Byron510 »

I was just reading through the Original copy of the Bible (How to Hotrod and race your 510,610,240Z) and it started that .030" in a R190 with 4:44 gears (what I've got conveniently enough), and their net result was 90 Lbs break away. I'll start with .010", and go from there.

Byron
Love people and use things,
because the opposite never works.
User avatar
Byron510
Moderator
Posts: 12658
Joined: 01 Jul 2003 23:06
Location: Maple Ridge, BC

R190 LSD

Post by Byron510 »

For the enlightenment of all, I took a bunch of photos in the process of shimming up the LSD. Break away torque started at 27 LBS. For each pair of .005"
shims (one on each end of the clutch pack), about 11 lbs of torque was gained. So I added .010" to each side in the end. A consistent 49 LBS of torque was achieved - just what I was searching for.
Thanks to Baz and Keith for getting back to me with some specs.

Byron
Attachments
Note how stub shaft has it's own bearing - not like the R160, 180 or 200
Note how stub shaft has it's own bearing - not like the R160, 180 or 200
Shim
Shim
Clutch pack
Clutch pack
User avatar
Byron510
Moderator
Posts: 12658
Joined: 01 Jul 2003 23:06
Location: Maple Ridge, BC

Post by Byron510 »

More pics
Attachments
Diff assembly with stub shafts set in place
Diff assembly with stub shafts set in place
Testng torque - thanks James for the photo
Testng torque - thanks James for the photo
Tool made for checking the torque
Tool made for checking the torque
User avatar
bertvorgon
Supporter
Posts: 11996
Joined: 04 Aug 2003 20:45
Location: White Rock, B.C. Canada

RE: R190 LSD

Post by bertvorgon »

I think you will find that setting very good for most situations.
"Racing makes heroin addiction look like a vague wish for something salty" - Peter Egan

Keith Law
1973 2 Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1971 Vintage 13' BOLER trailer
User avatar
icehouse
Posts: 3885
Joined: 17 Jul 2005 17:06
Location: Everett Wa

Re: LSD Break Away Touque...??

Post by icehouse »

Byron!!! Well I haven't checked the breakaway torque on the R190 I installed yet but it did great on the track in the rain so I'm not in a hurry to adjust anything.

I was wondering how does the LSD breakaway work exactly? We put a H165 LSD in Sam's wagon, it didn't seem to work so we swapped in the other one we got (we scored 2 of them) it had the same issue. One thing we didn't think about till after the race, was that the coilovers we put in the back to increase the spring rate don't allow any droop. Yes we know its bad but the reason we installed those is another story. So my question is..... If one wheel lifts does the LSD not really work? Does the tire off the ground get full power and the other tire only gets 45lbs of torque?
"People don't like it when shit doesn't match their rule of thumb." Sam
User avatar
funwithmonkeys
Supporter
Posts: 1336
Joined: 05 Sep 2013 09:34
Location: Vancouver, BC

Re: LSD Break Away Touque...??

Post by funwithmonkeys »

Here is a nice page explaining it all.
http://www.ppi-ats.com/LSD/LSD_basics.html
If no one from the future comes back to stop you from doing it then how bad of a decision can it really be?
User avatar
Byron510
Moderator
Posts: 12658
Joined: 01 Jul 2003 23:06
Location: Maple Ridge, BC

Re: LSD Break Away Touque...??

Post by Byron510 »

That’s a good article Norm.

Jeff, the last paragraph addresses your question. Break away torque on the bench from one side to the other gives you a mark to gauge and work from, but the actual breakaway measurement when considering the parameters of the drivetrain and wheel diameter is measured in percentage of lock. I’m unsure how this could be calculated as the gear ratio itself would change this reading, as would the diameter of the tire. I would think that placing the torque wrench on the diff input and locking one side of the diff would give you the actual breakaway torque required from the drive line to operate the LSD through the differential itself. But again the tire size would change the actual reading between the diff input and the tire on the ground as it’s diameter would certainly change the applied torque to the ground. A quick reference to this is that Jamie picked up nearly 20hp on the dyno by dropping from his 23 1/2” tall 15” wheels to his 20” tall 13” race slicks.
Maybe someone out there can piece this together :-) But for now it would be interesting to note what your actual breakaway torque is Jeff. It’s a good benchmark to move forward from.

Byron
Love people and use things,
because the opposite never works.
User avatar
bertvorgon
Supporter
Posts: 11996
Joined: 04 Aug 2003 20:45
Location: White Rock, B.C. Canada

Re: LSD Break Away Touque...??

Post by bertvorgon »

Just as a comment, for what it is worth, I hate the "lag" on my G35 with the VSLD. There is a most and disconcerting time lag from when you jump on the throttle, to when the car actually reacts to the diff locking up.

As I can drive both cars, my 510 and the G35 back to back, I see it right away. The 510 reacts right away, but with the G, there is a moment where the rear feels like it is going to step out from under me....THEN...it plants the rear end.

If there was a choice for a 510 IMO, I would try to put a conventional LSD in there.
"Racing makes heroin addiction look like a vague wish for something salty" - Peter Egan

Keith Law
1973 2 Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1971 Vintage 13' BOLER trailer
User avatar
funwithmonkeys
Supporter
Posts: 1336
Joined: 05 Sep 2013 09:34
Location: Vancouver, BC

Re: LSD Break Away Touque...??

Post by funwithmonkeys »

Here is a question for you guys. What is better a high or low breakaway torque? From what I am reading low is better for low speed partial throttle. Ramp up to locking is important and lock % also. I have a choice between 2 LSD's. 1 has low initial and one has high. The low one has a much longer service interval and everything else is the same. They both have adjustable lock % and ramp up. They can also both be set to 1.5 way or 2 way.
If no one from the future comes back to stop you from doing it then how bad of a decision can it really be?
Post Reply