Limited Slip Differential (LSD)

Which drivetrain to choose, so many choices, 4-cyl? 6-cyl? NA? Turbo?
AndreasMergner
Posts: 19
Joined: 05 Sep 2013, 12:28
Anti-spam question: 4
Are you a spammer: No
Location: Albany, NY

Limited Slip Differential (LSD)

Post by AndreasMergner » 19 Sep 2013, 05:43

I've read that an LSD makes a significant difference in the handling of a car. I didn't give LSD much thought until I found out it seems pretty rare on a cheap donor. That, and it seems that a decent aftermarket LSD is at least $800. I keep researching donors and it looks like maybe a Civic or Accord would be good choices as I could get one for maybe $1000-1500 from what I have seen on Craigslist. I plan to buy a running donor so I know the drivetrain works and then using it for the Midlana build as is. I can rebuild the engine if anything goes wrong or the next Winter. I can put in an LSD then too.

I know Kurt has tried both the Quaife (Kimini) and the Wavetrac (Midlana). Kurt, could you comment on what you like better?

Anyone else want to comment on whether an LSD is desirable or donor sources that have LSDs? I mean, I could get a sportier donor with LSD, but they all come with a premium price AT LEAST $1000 more....and they all seem to be slammed with custom rims and ground lights. I somehow don't think they are that well taken care of. :roll:

Midlana1
Site Admin
Posts: 3048
Joined: 19 Dec 2008, 16:44
Anti-spam question: 4
Are you a spammer: No
Location: Southern California

Re: Limited Slip Differential (LSD)

Post by Midlana1 » 19 Sep 2013, 07:14

It all depends what the car's for as for whether an LSD is needed. Even if you do plan to track the car, one data point is the Lotus Elise people who claim that due to the rear weight bias, their car's don't need it (it comes without from Lotus). On the other hand those who autocross the Elise claim that it does need one so who knows. The point is that it's all about how you use the car - a cruiser doesn't need to worry about any of this.

That said, there were three modifications that make a huge difference when I started autocrossing my old Datsun 1200: lowering it, adding a rear bar, and the LSD.

I cannot offer insight into the differences between the Quaife and the WaveTrak until I track the car. However, I expect them to act the same since the WaveTrak allegedly only has an advantage if and when the rear tire gets into the air. With the rear weight bias I don't expect that to happen. (I only bought the WaveTrak since the Quaife at the time had become hard to find and the WaveTrak appeared to offer more for the same price.)

WickedOne
Posts: 129
Joined: 01 Jan 2009, 08:51

Re: Limited Slip Differential (LSD)

Post by WickedOne » 19 Sep 2013, 16:28

I have 3 friends with Elises who all added LSD and all 3 removed it at a later date.

Yes, you can smoke them out of the tighter corners without the LSD which might cost you some time, but the understeer that was added after the addition of the LSD, which is exactly what Lotus says will happen, cost them much more time than the small amount of traction loss.
Last edited by WickedOne on 20 Sep 2013, 17:12, edited 1 time in total.

Midlana1
Site Admin
Posts: 3048
Joined: 19 Dec 2008, 16:44
Anti-spam question: 4
Are you a spammer: No
Location: Southern California

Re: Limited Slip Differential (LSD)

Post by Midlana1 » 19 Sep 2013, 18:49

Hmm, interesting. I may quote you in the book on this, depending how my car handles on-track.

AndreasMergner
Posts: 19
Joined: 05 Sep 2013, 12:28
Anti-spam question: 4
Are you a spammer: No
Location: Albany, NY

Re: Limited Slip Differential (LSD)

Post by AndreasMergner » 20 Sep 2013, 21:10

How would something like the Racelogic traction control (http://www.enginebasics.com/Advanced%20 ... ntrol.html) fit into the mix with an LSD?

jaxmadine
Posts: 44
Joined: 02 Jul 2013, 04:51
Anti-spam question: 4
Are you a spammer: No

Re: Limited Slip Differential (LSD)

Post by jaxmadine » 24 Sep 2013, 04:13

Cutting fuel in my experience is a very bad thing.

AndreasMergner
Posts: 19
Joined: 05 Sep 2013, 12:28
Anti-spam question: 4
Are you a spammer: No
Location: Albany, NY

Re: Limited Slip Differential (LSD)

Post by AndreasMergner » 24 Sep 2013, 05:24

I hear ya, but this is not a lean mix...it is a full cut assuming you have an injector for each cylinder and the cuts are rotated through the cylinders. I've read some threads on (more powerful) Locosts losing traction on a corner and crashing. Seems like the risk to the engine might be acceptable compared to the risk of a crash...? I mean, turbos and superchargers stress an engine too, but lots of people use them.

500HP Locost with Racelogic demo http://www.youtube.com/watch?v=2BaFhWz_zhY

I'm not an expert. I'm just trying to learn. I'm not associated with Racelogic. :) My plan is to eventually implement traction control in my DIY ECU.

bgkast
Posts: 711
Joined: 17 Dec 2012, 11:33
Anti-spam question: 4
Are you a spammer: No

Re: Limited Slip Differential (LSD)

Post by bgkast » 25 Sep 2013, 21:47

Looks more fun with the traction control off. :twisted:

In all seriousness I can see a traction control unit like that causing more harm than good by making the driver overconfident. Sure it will stop the tail from sliding out if you romp on it in a corner, but will not help in say a throttle lift oversteer situation and could make it worse by cutting power. These types of cars are very powerful and need to be driven with care and respect. (I gained a healthy dose of respect for throttle lift oversteer after smacking a fiero race car into a concrete barrier after lifting in a corner.)

Midlana should have better traction than a typical locost due to the mid-engine configuration.

In reply to WickedOne: the Elise also has skinny bicycle tires in the front that probably don't help understeer. :P

In reply to the original poster: the SRT4 drive train I am using came with a factory LSD. After parting out the car I have a total of $0 into my power plant.

AndreasMergner
Posts: 19
Joined: 05 Sep 2013, 12:28
Anti-spam question: 4
Are you a spammer: No
Location: Albany, NY

Re: Limited Slip Differential (LSD)

Post by AndreasMergner » 26 Sep 2013, 05:51

Well, you can always turn it off! 8-)

I've never been on a track so that is why I'm asking the questions *before* a build. As far as cutting power causing throttle lift oversteer....could it prevent that? If you are adding back power in a turn, you could easly add too much causing the rear end to slide and then taking your foot off the throttle completely causing more rear end sliding. With the TC, you can just floor it all the way coming out of the corner and the car is a bit more stable, even with a highly powered car.

Can TC help with understeer? I don't know if the front wheels are moving at a different rate, which would trigger the TC.

I see what you mean about TC making throttle understeer worse, but TC might make sudden throttle changes less likely...?

Bryan, what did you pay for the donor and what did you sell from it? I have a Copart auction a few miles from me, but everything I've read about them made me think finding an old running Accord for $1000 would be less risk. You can PM me if you want.

bgkast
Posts: 711
Joined: 17 Dec 2012, 11:33
Anti-spam question: 4
Are you a spammer: No

Re: Limited Slip Differential (LSD)

Post by bgkast » 26 Sep 2013, 16:36

Good point about being able to turn it off. ;) In my (limited) experience with RWD and traction control in my RX8 it seems like I'm usually in the process of "catching it" when the TC intervenes. When I autocrossed it I forgot to turn the TC off on a few runs and it was very surprising how much it held me back, even though it was my first autocross. That being said, I'm no Michael Schumacher (see previous reference to crash :D ) and would be very interested to see how a home brew TC system can work. For maximum effectiveness it seems like it would need to be able to control the brakes as well, but that would require ABS and more programming skills than I have!

I got my SRT4 for a bid of $2,300, which turned out to be more like $2,700 after all the fees. The car was hit in the front and rear, but not hard enough to damage the power train. I kept the engine, transmission, shift assembly, steering column, wipers, pedal assembly, fuel pump/sender and several other miscellaneous parts that I thought I could use in the build and sold the rest. To date I have sold $2,500 of parts and still have the doors and trunk which I should be able to get $400 for. I guess technically I have $200 in it at this point, but it should be no problem to break even on the deal.

Copart can be a good source for a donor, but check the fees before you bid. Also check your state laws to make sure that you don't need any special licenses to buy from them.

Post Reply