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FWD power understeering

Suspension Tuning & Optimization

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Hello Guys;

I am an Academy member and a racing driver from Portugal.

This year i am racing in a Portuguese "Legends" car championship with a Volvo S60 Challenge.

The car has 375 bhp and a new Quaife Sequential gearbox (with Thorson LSD - that maybe is not that good for competition purpose)

I tested the car last Sunday on Estoril track and noticed a lot of power understeer.

I miss traction out of the corners, slow and even fast corners.

Braking, corner entry and mid corner is OK.

I have dumpers with bump and rebound settings and of course I can change springs.

The car is FWD and has 1300 kg (with driver inside and 60% weight on front axle).

What can I do to improve traction?

Thanks; Nuno

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Have you tried adjusting the front Camber? I would suspect that with a front wheel drive too much front camber would cause power-induced understeer as the compromise would be toward cornering at the expense of longitudinal acceleration.

I would also try softening the front damper rebound if that's possible.

Lastly, you may have to just be patient with the throttle (driving within the understeer limit), and or work on rotating the car more mid-corner (later apex) so that less cornering is required on corner exit, and thus more traction is available for acceleration.

As David said, you may have to work on how you apply power, and maybe try a later apex so you can open up the exit more and that will allow the front tyres to accept more torque - they will have less side load. This comes to mind as it can apply to slow and fast corners, and fits the other points you made.

Failing that, it's a fairly heavy car and the mass is front biased. Worse, you have to work with the tyres you have to control quite a lot of power being fed to them - I'm old enough to recall when they said you could never use more than 200hp with front wheel drive... - and all that is going to put a lot of load, and temperature, into the tyres, which may be overheating them. Does the problem worsen over the first few laps before reaching a stable point?

You could try increasing the rear roll stiffness slightly, as that will load the fronts a little more evenly, but that only works until the inner rear lifts - if you do try that, I'd suggest using ARBs rather than springs, as the latter may cause skipping over bumps.

As David said, you could try reducing the negative camber in half degree steps to see how that works - especially if there seems to be more inner wear.

If you can move mass rearward it may help - oh, I assume it has a rear tank, what difference is there in full, half full, and near empty?

But, as I said at the start, biggest gains may be from a change in driving style?

I'd agree with the comments added so far. Understeer is always going to be the natural tendency of a FWD car at corner exit as you're applying throttle. An LSD that's very tight can result in corner exit understeer as you apply power, however to the best of my knowledge that's not adjustable in a torsen (sorry my experience is primarily with plate-style diffs). Usually softening the front ARB and/or stiffening the rear bar is the preferred technique of dialling out as much understeer as possible, however there is invariably gong to be that natural tendency towards understeer so adapting your driving style, lines and power application are the best tools to mitigate this.

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