Change to clutch pack LSD or not

[Icecreamtruk]

So I have a problem that I dont really know how to address but Im leaning towards a clutch pack LSD being the solution.

Basically, the car is kind of stiff (12k springs all around), has quite a bit of aero (estimating around 400-600lbs total or something in the ballpark of that), stock power, entry level R compounds levels of grip tire wise.

On to the problem itself, when the tracks are smooth, its mostly fine, but on some turns, or in really bumpy tracks, when the car hits a bump as I start to accelerate or if I hit the kerb too hard the car will struggle to accelerate smooth and just go up and down in rpm, which Im assuming is the inside wheel spinning freely, or close to anyways. When it does so, the car understeers on turn exit instead of getting the nice rotation I like so much when its just sliding both tires towards the exit. When this problem doesnt happen, I can take most turns with very little steering input and have to even add a bit of counter after I hit the gas, but when the stuttering happens its just understeers and I usually just have to back off or dab the brakes a bit to not run out of track.

The car doesnt lack power to spin both wheels on corner exit, provided im at the very edge of traction, I think with even half the power I would still slide the rear on corner exit, but it only happens on smooth tracks, on bumpy tracks corner exits are frustrating and filled with transitions between under and over as if the car is suddenly losing half its power. What I think the solution is going to be is a clutch pack diff, thinking of an OS-giken specifically. To have both wheels get all of the power all the time, regarding of one being 1 foot in the air or not.

What do other people who have been down this path already think? Am I on the right track? I havent really experienced this before so Im not sure if it is what I think it is. In the ruleset that we use, there is no difference between a torsen or clutchpack type diff, so I would incur no penalties for switching out, so if there's time to be found there, Im totally taking the dive. I know this problem can be driven around, but I'd rather solve and find time if at all possible.

[CSG Mike]

Datalog it.

You have enough equipment where you should have a datalogger. Verify the problem before committing to a fix you may or may not need.

[Icecreamtruk]

Originally Posted by CSG Mike

Datalog it.

You have enough equipment where you should have a datalogger. Verify the problem before committing to a fix you may or may not need.

Working on it, should have something up with ECU + GPS logging and video to correlate, I should have it before the 6th july which is my next day out at the track. What should I be looking at appart from the classic throttle, brake and steering input? Individual wheel speeds? Is it possible to get that over OBDII?

[Racecomp Engineering]

For the problem you are describing, I would want shock position sensors in addition to the usual obd2 data.

- Andrew

[CSG Mike]

Originally Posted by Icecreamtruk

Working on it, should have something up with ECU + GPS logging and video to correlate, I should have it before the 6th july which is my next day out at the track. What should I be looking at appart from the classic throttle, brake and steering input? Individual wheel speeds? Is it possible to get that over OBDII?

I just want wheel speeds, really. Available via OBD2.

[ame]https://www.youtube.com/watch?v=9Jw0yeTx0Ig[/ame]

numbers on bottom right are wheel speeds.

Front Left, Front right

Rear left, Rear right

Observe the rear wheel speed differentials to see when the stock torsen is behaving like a limited-slip, vs open diff.

[Evan55]

If your shocks arent keeping the tires on the ground, it would have the same symptoms, and if you say it happens when the track is bumpy but not smooth, thats would back up that hypothesis.
I would look into shock tuning first

[rice_classic]

Originally Posted by CSG Mike

I just want wheel speeds, really. Available via OBD2.

numbers on bottom right are wheel speeds.

I need this video overlay in my life. How do you achieve this?

[CSG Mike]

Originally Posted by rice_classic

I need this video overlay in my life. How do you achieve this?

Race Render. Additional overlays done in Premiere.

http://racerender.com/Products/index.html

[rice_classic]

Originally Posted by CSG Mike

Race Render. Additional overlays done in Premiere.

http://racerender.com/Products/index.html

What are you using for data logging that you import to racerender?

[CSG Mike]

Originally Posted by rice_classic

What are you using for data logging that you import to racerender?

Aim Solo DL

[Ultramaroon]

Or one could just listen to their engine and deduce the cause for free.


OP, are we talking about washboard like 10 Hz or wavy, say at 3? Could you get away with less rebound damping? I'm with Evan55.

[CSG Mike]

Originally Posted by Ultramaroon

Or one could just listen to their engine and deduce the cause for free.


OP, are we talking about washboard like 10 Hz or wavy, say at 3? Could you get away with less rebound damping? I'm with Evan55.

Can you listen to the engine in my video, and tell me when there's a single rear tire spinning?

[Ultramaroon]

Originally Posted by CSG Mike

Can you listen to the engine in my video, and tell me when there's a single rear tire spinning?

No but OP can hear his so he's working on a way more obvious issue. He doesn't need that kind of sensitivity. How on earth did we ever tune suspensions before the days of electronic gizmos?


edit: actually, I went back and realized why I didn't hear anything. I turned off the sound as soon as I heard that painful intro music. Even in yours there were a few places where it was pretty obvious.


edit 2: And sound is not all of the story. The feels are important too. You know there's a difference between engine surge mid-corner with outside wheel hooking versus surge from lofting.

[soundman98]

Why are you running such stiff springs? Are you trading off for not running a sway bar or something?