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Discussion Starter · #1 ·
Here's a link to Sports Compact Car's Project 350Z, and their handling setup.

http://www.sportcompactcarweb.com/tech/0404scc_350z/

Project 350Z has just become our second project car in a year to reach the once fanciful goal of 1.0g on street tires. Like making 100 hp per liter on pump gas, pulling a street g is slowly working its way from theoretical fantasy to everyday reality. Doing this with a Z turns out to be relatively simple in terms of raw parts count. We changed only four parts to bring the Z from 0.88g to 1.0, and only three of them were probably strictly necessary. The only real trick was to ignore what everyone else was doing with the Z and look at the car's strengths and weaknesses on their own.
Interesting article. I'm kind of glad that (by accident, and some advice from wiser people) my handling modification path hasn't varied enormously from what they've done.

And now I'll definitely be looking for a new LSD once I sort out the rims / tyres.
 

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Came across the same article a while ago. This would be a good set up for a track Z with competant driver.

Did you manage to avoid / limit the stagger with your new wheel / tyre combo?
 

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Yeah I read that one a while ago too, I kept waiting for them to do something interesting to the motor but they still havnt.

After having driven a RWD car with an aftermarket diff, I now consider it a compulsory mod for a RWD performance car. It makes a huge difference to handling. Upgrading the suspension would be needed first to keep the side to side weight transfer more evenly distributed over the wheels when driving hard making the most of the available grip. I can notice this at the moment as my rear springs are almost stock rates.
 

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great read

i was planning on buying the hotchkis tvs kit with the new wheels, and was unsure what setting to put the bars on - middle on both ends - easy

how would running 20s effect the stock diff ????
 

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TPIACE, I don't think 20s would require a new LSD, since they are kind of an anti-performance mod.
 

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Discussion Starter · #6 ·
From what people have said, its not the diameter that gets you, its the width (and thus the wider rubber you run).

When your tyres start gripping a lot more, the LSD doesn't have the strength to lock up, and so it acts like an open LSD.

I'm of two minds as to if this is a bad thing. An open diff tends to be less understeery than an LSD, and if you've got so much grip from the new rubber that you can't overwhelm the tyres anyway, the traction benefits of an LSD are moot.

Of course, I might be missing something else...since the SCC guys like running wide, grippy rubber with the LSD (even without a massive increase in power).
 

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scathing wrote:
I'm of two minds as to if this is a bad thing. An open diff tends to be less understeery than an LSD, and if you've got so much grip from the new rubber that you can't overwhelm the tyres anyway, the traction benefits of an LSD are moot.

It might technically be a little more understeery, technically speaking, but I dont think your objective is to create a car with the least amount of understeer at the cost of greater handling and increased control. If you can go through a corner at a higher speed with greater control then the fact that it technically creates a little more understeer is moot. The idea is to tune the car as a whole anyway so if an aftermarket diff will technically create some understeer then you should setup the rest of the car to accomodate. Same goes with all mods which affect handling, tyres, wheels, springs, shocks, sways, diff. Race cars and supercars etc dont suffer from adverse understeer and they all use LSDs. The benefits of LSDs are proven over open diffs.

Getting bigger tyres will give you more grip overall but they wont give you so much grip that the car cant over power one of the tyres, they wont help if one wheel goes over hole and spins, or if the weight shifts off one wheel and it spins, or if one wheel goes over some gravel and spins etc etc etc, this is all it takes to over power an open diff as the wheels are independant of one another. They are useless in anything to do with performance.

Of course, I might be missing something else...since the SCC guys like running wide, grippy rubber with the LSD (even without a massive increase in power).

Although an LSD will allow you to handle a massive increase in power but this is not its only function. After running a RWD car with and without an aftermarket LSD i can tell you its definately a handling modification which allows higher cornering speeds and greater level on control irrespective of power levels.
 

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hmmm might have bitten off more than i can chew re lsd

ill just keep the stocky, afterall i dont track, and that axle tramp is enough deterant not to light up the rear wheels anyway
 

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Interesting....why do you think wider tyres create more grip? For a given car weight the contact patch between the tyre and the road is the same size, regardless of tyre width ;)
 

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Discussion Starter · #11 ·
Interesting....why do you think wider tyres create more grip? For a given car weight the contact patch between the tyre and the road is the same size, regardless of tyre width ;)
I was thinking more of doing a total "tyre upgrade" package. Getting better tyres that are wider and have stiffer sidewalls, so I can run a lower pressure. Which gives me a wider track and a greater contact patch.
 

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Discussion Starter · #12 ·

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Here's a link to Sports Compact Car's Project 350Z, and their handling setup.

http://www.sportcompactcarweb.com/tech/0404scc_350z/
Interesting article. I'm kind of glad that (by accident, and some advice from wiser people) my handling modification path hasn't varied enormously from what they've done.

And now I'll definitely be looking for a new LSD once I sort out the rims / tyres.
Two things stand out as things I totally agree with and experienced -- both before handling mods and after:

The before mods observation:
... a stock Z can be frustrating. Throttle inputs have minimal effect on the car's attitude and the front tires take all the punishment. Many a twisty road attack has ended with us wishing for that elusive neutral balance.
And the observation I also had after I changed wheels, tires, springs, and sways:
...easily balanced mid-corner with the throttle. Lift off the gas and the tail should step out slightly. Ease onto the gas and the front tires should [now "do"] slowly start to slide. In a properly balanced car, the transition to oversteer is so gradual and predictable you can hang the car right on that transition point as long as you want. [I feel that describes what I now have] ...
The Z's handling behavior is now exactly what we had hoped for. Turn-in is crisp and immediate, the steering is precise and predictable, and the limit is approachable, controllable and perfectly neutral.
 
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