My first tuning project - Questions how to adapt to more Power - Mazda Eunos Roadster

[KAlex122]

Hi,
I tried my first tuning project. A Mazda Eunos Roadster '89. I took the stock setup + racing suspension + LSD. Did laps at Tsukuba plus some at Spa and the Nordschleife. In the end it felt ok and laptimes at Tsukuba improved by more than half a second. Of course it's probably not perfect but at least im feeling a difference.

My question now is:
After this initial suspension and LSD setup i improved power to 450PP and the cary especially the rear got way more loose than i imagined it would be at 127kW.

What would now be the general direction of my suspension and LSD tuning? As i plan to get the Roadster up to 550 (power, sports tires, maybe brakes), 580 and probably 600PP (definitely needs permanent upgrades like weight reduction and permanent motor upgrades) i would be happy if you could point me in a direction.

 

[bread82]

As you increase the power it is helpful to upgrade the tyres in order to manage the power. It is possible to keep low grade tyres and try to control the power with just suspension and LSD settings, but some cars quickly become very hard to handle - this is a case by case basis. Suspension settings to limit rear wheel drive oversteer would generally be softer rear anti roll bars, a lower rear natural frequency, and less LSD Accel.

Weight reduction is a good move in general and I don't find I need to adjust the suspension too much after doing it. You corner, accelerate, and brake better with a lighter car.

In general stickier tyres can have stiffer suspension and more aggressive LSD settings. Your LSD accel of 35 is reasonably high so I suspect that'd be OK for sports tyres, and you might want to experiment with 15-25 range for comfort tyres.
One very important point to consider with LSD settings is: "can my car easily spin up the rear wheels?". If you are able to spin the rear wheels, a lower LSD Accel can help, because it will reduce oversteer when you exceed the traction limit. It lets the inner wheel spin a little while preserving the important outer wheel. A more locked LSD will spin up both rear wheels which gives massive oversteer.

 

[KAlex122]

Thank you for everything written!

I didn't mention it but i thought moving fromCM to CS wheels would be enough of a compensation for the kW going from 87 to 127.

As of this project, learning tuning i try not to bury all balance problems under too good tires, you know what i mean.

 

[bread82]

Yeah, CS tyres should be fine for your power level. I often use them up to 350BHP which is about 260kW, although you could start using SH from lower than this if you wanted.

Your natural frequencies are quite soft, which I like. Many people always use over 2Hz "because it's sporty" but I get better control with softer frequencies on comfort tyres and road cars.

If you can comfortably drift your car a little, switching back to grip driving as and when you want to, then this means you have good control at the limit, therefore a good tune.