Differencials, Front/Rear Torque distrobutions. How do I tune it?

[Stevisiov]

Thats right the variable center differential, I have just bought one for my Toyota Celica GT-4, 96ish road car. Now with my heavily tuned GT-4 I noticed the front tyre wear is pretty heavy in comparison to that of the rear wear. I was also finding a tad of power understeer (I assuming this is due to double the orginal power of the car, therefore more power through front) Now I am aware there are different ways of solving both of these problems however I thought changing the front/rear torque distrobution could solve these problems somewhat, and I also just wanted to have a try with altering it rather than using other methods.

So I got the VCD, ready to make a few swift adjustments, went to configure it, to find a bar slider, giving me numbers 1-50 but giving no clue as to what this number represents, I tried reading the helper on the bottom but its just useless, it goes to quick to read, and just explains stuff I already know but fails to tell me what the bar slider and the numbers represent, it currently is set to 40, (40 what?) am I missing something or am I meant to understand it.

I want to get to grips it so I may be inclined to use it in future (providing it works succesfully) could someone please tell me what these unknown values represent (at least unknown to me), I was planning to set it at rear 70%, front 30%, rather than what it currently is (I am assuming 50/50) or does it not work quite as I stated?

Help is much appreciated. Thank you.

 

[sukerkin]

What the VCD is measured in is percentage of power/torque applied to the front wheel. So if you set it to 30 then you have a 30/70 split between front and rear.

 

[Scaff]

This should help out, from the second of my tuning guides...

...but in a nutshell to get a 70% rear / 30% front split, set the VCD to 30 which will send 30% of the drive to the front end (the VCD figure is always % to the front).


Regards

Scaff

 

[Stevisiov]

Well thank you, I was just missing what the bar meant, it appears that I should really thinking more like 80% rear so I need to set it to 20, therefore 20% front, I think I could have saved a making new thread by searching more efficiently, but cheers non the less

 

[Parnelli Bone]

Personally when i've used VCD's in the past, i'll usually have as big a rear-bias as possible, unless i'm racing in dirt. On pavement, a front-heavy bias just introduces more and more understeer. The front tires are of your Celica GT-4 will still wear faster than the rear ones no matter what, since they are doing

1. all the steering

2. most of the braking

3. a portion of accelerating.

But no matter what, the steering & braking will keep your front tires wearing out quiker.

 

[Stevisiov]

Personally when i've used VCD's in the past, i'll usually have as big a rear-bias as possible, unless i'm racing in dirt. On pavement, a front-heavy bias just introduces more and more understeer. The front tires are of your Celica GT-4 will still wear faster than the rear ones no matter what, since they are doing

1. all the steering

2. most of the braking

3. a portion of accelerating.

But no matter what, the steering & braking will keep your front tires wearing out quiker.

I am aware of this, however when you reach a certain power, or rather Torque level, the rear tires tend to wear quicker than the front ones, just because the rate at which they turn or the amount if power put through them, it is most noticeable on really powerful LM cars, but I can imagine it is still evident in a 500BHP Celica. 20/80 (or 80/20?) should make the difference or at least close the difference in tyre wear.

As for the understeer, While your right, before the car was so powerful, the power understeer was not an issue, so I aim to reduce the power through the front wheels but not kill it completely, therefore I won't (or rather shouldn't) be giving the front tyres understeering problems.

Anyway this is what I aim to find out, all of the above is based on an assumption, but I would expect that having a fraction on the front rather than having just a pure RWD must have its advantages.

I will do a bit of testing and report back anyway, I have not used the VCD before I only have known what it was used for.👍

 

[Parnelli Bone]

I am aware of this, however when you reach a certain power, or rather Torque level, the rear tires tend to wear quicker than the front ones, just because the rate at which they turn or the amount if power put through them, it is most noticeable on really powerful LM cars, but I can imagine it is still evident in a 500BHP Celica. 20/80 (or 80/20?) should make the difference or at least close the difference in tyre wear.

As for the understeer, While your right, before the car was so powerful, the power understeer was not an issue, so I aim to reduce the power through the front wheels but not kill it completely, therefore I won't (or rather shouldn't) be giving the front tyres understeering problems.

Anyway this is what I aim to find out, all of the above is based on an assumption, but I would expect that having a fraction on the front rather than having just a pure RWD must have its advantages.

I will do a bit of testing and report back anyway, I have not used the VCD before I only have known what it was used for.👍

I see. Yeah, report back. 👍 I haven't personally driven a 4-wheel drive Celica since GT2.

 

[BobK]

I generally set the VCD to around 25 on pavement, leave it around 40 on dirt, and 45-50 on ice. You generally don't need the extra traction on pavement, certainly not at the cost of understeer and front tire wear. 40 on dirt is a good compromise between traction and the ability to kick the rear end out in turns. On ice, I'll take all the traction I can get. Needless to say, this does depend on the car.

 

[Greycap]

The LSD settings can be used to really good effect in making the car turn better and are vastly more important in doing so than the VCD. No matter how you set the VCD the car won't turn if the front differential is letting all the power, no matter how little it is, through.

Try (front/rear) initial 50/10, acceleration 50/10 and deceleration 10/10. The rear differential is very open to enable the car to turn better without too much resistance while the front differential is pretty tight to make the front wheels pull the car out of corners. It sounds completely crazy but it works.

 

[Leonidae]

[shameless plug]Or then you could simply try my Impreza settings, that can be found at Mad FinnTuners-thread.. [/shameless plug]

 

[AOS-]

if the thing scrolls too fast, hold L3 to pause the thing...

Your manual says that i think...

 

[Stevisiov]

if the thing scrolls too fast, hold L3 to pause the thing...

Your manual says that i think...

Ahh, cool I never read manuals...👍

Anyway, I tried the settings and found at 20, the understeer is eliminated, so that is good news, bad news is that the tyre wear is still a sizable margine so different front/back combo may be the best solution. As Parnelli Bone said the front wear is going to be the most because of the extra jobs of the front wheels, the car isn't powerful enough to make the tyre wear even even with a 10 on the VCD, however I may find this more effective with higher power 4WD cars.

I am glad that I tested it, I am aware of the other understeer solutions but I wanted to get to grips with the VCD anyway.👍