1st season of Autocross...

[Crawleyscobra]

A couple of observations after 1st season of Autocross...

1) First observation is I need more seat time and some instruction. I only got four events in this year. I’m going to try to attend one of the local training sessions next year and get to more events.

2) Second observation is my MK III roadster (As is most if I understand correctly) has lots of oversteer and likes to spin. I understand that a lot of this can be induced by the drivers braking and throttle habits (See item #1). But I’d like to, “Tune” the car to induce understeer to hopefully reduce the amount of oversteer that my limited driving skills create till I can improve my skill set.

My current setup is as follows:

FFR tubular in front with FFR IRS in rear (poly bushings on Knuckles and solid bushings on pumpkin).

FFR Koni coil-overs – 500lbs springs in front, 750lbs in rear (Came with Kit).

Coil compensators on all 4 shocks.

All 4 shocks damper rates set to 2nd firmest.

Front VPM anti-sway bar set at firmest setting.

Rear VPM anti-sway bar set at softest setting.

SAI kit on SN95 spindles.

FFR Bumpsteer kit with FFR rack extenders.

Hydroboost power steering and power brakes.

Alignment:
Front Rear
1/16 “ toe in 1/16 “ toe in
-1 * camber -1 * camber
7* caster

Tires – Goodyear F1s DSG3 255/40/17 front 315/35/17 rear.



So… At my last Autocross a fella asked me what my spring rates were. I told him and he said that part of my problem was I might be over-sprung in the rear with the 750lb springs and an anti-sway bar. He suggested putting the 750s in the front and the 500s in the rear. Or get some 500/600 for the rear. Or possibly disconnect the rear sway bar. Or both (get 500/600lbs and disconnect the sway bar).

Anyone have any opinions? Keeping in mind I would like to induce understeering.

[CraigS]

While I haven't autocrossed an IRS FFR, I have driven a couple on the street. And I have autocrossed my solid axle FFR since 2007. My take is that your rear springs are fine but I would bump the fronts up to 700 or more. I run 800 fronts but I have Breeze QA1 double adjustable shocks. These allow me to adjust very easily and quickly so I have a street setting and an autocross setting. The rears stay very close for both but the fronts get a huge increase in front bump for autocross. For you, I would crank up the FFR FRONT Konis to full hard along w/ the stiffer springs. I would also back the rears to full soft and see how that works. Disconnecting the rear bar is definitely an option also. I am not familiar w/ your rear bar setup, but I would want to do things so that is easily reversed. On my rear bar, I can disconnect the link and wire tie it out of the way. So I have a few wire ties and a pair of snips in the door pocket. I can either disconnect or reconnect in < 5 minutes. One problem you have is running only 4 events limits experimentation. I run 15-20 per year and have found that I can't judge a change as being pretty much permanent until I have run 2-3 events. The pavement is different, the weather is different, so back to back scientific experimentation is not possible. BTW, what are "coil compensators"?

[Pylons]

I haven't autocrossed a FF, but I've got 15 years dodging cones in other vehicles.

I'd definitely try disconnecting the rear bar first...that should have a pretty decent effect and should be easy to do.

Soften the rear shocks and/or stiffen the fronts should help...and is free :)

If you're still not getting satisfaction, put some more toe-in in the rear (especially if you're getting loose on-throttle).

If getting loose under braking is an issue, maybe adjust the bias toward the front

You can mess with tire pressures as well, but that'll likely have the smallest effect.

Spring rates should be very effective, as described above by Craig...but I'd probably try all the free stuff you can first.

[Crawleyscobra]

While I haven't autocrossed an IRS FFR, I have driven a couple on the street. And I have autocrossed my solid axle FFR since 2007. My take is that your rear springs are fine but I would bump the fronts up to 700 or more. I run 800 fronts but I have Breeze QA1 double adjustable shocks. These allow me to adjust very easily and quickly so I have a street setting and an autocross setting. The rears stay very close for both but the fronts get a huge increase in front bump for autocross. For you, I would crank up the FFR FRONT Konis to full hard along w/ the stiffer springs. I would also back the rears to full soft and see how that works. Disconnecting the rear bar is definitely an option also. I am not familiar w/ your rear bar setup, but I would want to do things so that is easily reversed. On my rear bar, I can disconnect the link and wire tie it out of the way. So I have a few wire ties and a pair of snips in the door pocket. I can either disconnect or reconnect in < 5 minutes. One problem you have is running only 4 events limits experimentation. I run 15-20 per year and have found that I can't judge a change as being pretty much permanent until I have run 2-3 events. The pavement is different, the weather is different, so back to back scientific experimentation is not possible. BTW, what are "coil compensators"?


Craig, coil compensators I think can be describes as like Thrust bearings for the Coil springs.

Here is a link take a look:http://www.hrpworld.com/store/default/chassis-components/shocks-springs/shock-spring-tools-accessories/seals-it-coil-spring-compensator.html

[CraigS]

WOW, those are nice. I have used the Torrington bearing type but they didn't even get through a year of use. I have to say I never thought about the spring needing to wind and unwind slightly. I just got them to make adjustments easier.

[skullandbones]

Hi,

I don't know if you have considered this or maybe you already have this device on your PS. I have a Heidt's valve that can modulate the PS dramatically. I haven't turned it all the way to see if it mimics manual but I have been able to restrict the pressure to the pump enough to allow me from experiencing an over sensitive PS and therefore allowing me to induce much too much input for the particular situation. I have not AXed with the roadster but have driven it on track at speed. I have also AXed with other cars like at Bonnderant in a 2014 Camaro. The feedback I've gotten from one instructor on the track was that I might be over driving the car (roadster). Besides the suspension changes that others have suggested (I like the idea of disconnecting the rear sway bar), you might find an improvement in your technique by modulating your PS input. The neat thing is you can change it on the fly and adjust it up or down according to your improved experience and track conditions.

Good luck,

WEK.

[Crawleyscobra]

Hi,

I don't know if you have considered this or maybe you already have this device on your PS. I have a Heidt's valve that can modulate the PS dramatically. I haven't turned it all the way to see if it mimics manual but I have been able to restrict the pressure to the pump enough to allow me from experiencing an over sensitive PS and therefore allowing me to induce much too much input for the particular situation. I have not AXed with the roadster but have driven it on track at speed. I have also AXed with other cars like at Bonnderant in a 2014 Camaro. The feedback I've gotten from one instructor on the track was that I might be over driving the car (roadster). Besides the suspension changes that others have suggested (I like the idea of disconnecting the rear sway bar), you might find an improvement in your technique by modulating your PS input. The neat thing is you can change it on the fly and adjust it up or down according to your improved experience and track conditions.

Good luck,

WEK.


As a matter of fact I do have the Heidts valve, but I have not tried adjusting it yet. Honestly, I forgot I had it installed. That is another thing I need to experiment with.

Thanks for the suggestion.