Well, not the results I had hoped for. 3rd in BSP. I was in a really tough class - one competitor was Tony Kloosterman, a former Targa Newfoundland winner. Top three in BSP managed to beat the MOD classed cars both days.

Turns out I was was far too conservative on Saturday and lost 7/10th to the BSP class leader. I was much more agressive on Sunday and won BSP and came 2nd overall raw time. Unfortunately, I lost too much time Saturday so my cumulative results and a National title didn't go my way. While it sucks to not achieve what I hoping for, it was a valuable learning experience which will only help my pace down the road.

The FTD on both days was GJ Dixon driving an '04 Corvette Z06. He's the 2005 National SCCA D/S Champion (BMW 330i) and 2005 SCCA Solo rookie of the year. This guy can flog a car! The closest I got to him was 4/10ths on Sunday. Considering my moderately prepped BSP 350Z is not much of a match for a properly setup Z06, I was pretty pleased.

Here's a couple of links to pics.

The first one shows that my Koni SA and hotchkis springs might be at their limits...

http://www.pbase.com/klin/image/64748197

http://www.pbase.com/klin/image/64748103

 

WOW! Great job! I think you and I are in the same boat with the springs. I have some RSR TI springs and they do the same squating as your hotchkiss. Keep representing the Z! I am trying to work my way up to the Nationals level as well, but you can't be competative on Street Tires so it looks like some V710's are in my future.

Vince

 

What spring rates are you running? From the look of the picture I would guess you need to up your spring rates by 50% all around (if the Konis are valved for it) and maybe reduce your front anti-roll bar by 1mm. Balance looks good and so does rear camber. It looks like you can put the power down well.

 

Hotchkis spring rates are 340/330 lbs/in f & r.

I agree with your assessment. I'd like to keep the soft springs (for the street) and run dual adjustable dampers but that's a bit of a band-aid and is also an expensive solution.

50% stiffer springs are one of the more feasible options I was considering. Perhaps 500 lbs/in f&r. Eibach has an extensive custom catalogue.

I called Koni and apparently the dampers are setup to a max of 100% more than OEM - so they can handle stiffer springs.

 

Is there a results page?

 

Doesn't the Nismo T2 spring kit have rates in the low 600s? For me at least (later this year or early next) that will be the starting point for a BSP build. Pretty much everyone that I deal with in the racing world has moved to the big spring/little bar/expensive shock philosophy. One of my customer's DSP BMW E36s runs front springs around 900 lb. in. and rears around 700 lb. in. with little ARBs.

 

when i spec'ed out my bsp build, it seemed liek the t2 springs were the most feasible option. i think they were around 600/550 IIRC.

 

More pics coming in from the weekend. A buddy combined two pictures in the same area to show me first lifting the front right tire then lifting the rear left. Pretty cool.

I'm a little worried about the streetability of the T2 springs. I've had JIC FLT A2 with 10kg front and 9kg rear and found the ride to be pretty harsh.

Final results are here. I didn't realize that the difference btw me and 1st was not 7/10ths, but only 4/10ths.

 

A lot of the stiffness people feel has to do with the compression damping of the shocks, not the springs. Typical street performance shocks are designed to work with OEM or slightly stiffer springs so the compression damping is increased a lot to give the driver some initial response in transitions. That's exactly the opposite of what you want when going with 100% or more stiffer springs. When the spring rate is increased significantly then compression damping can be reduced to OEM or even softer levels because the spring has more control over the wheel in bump. Rebound damping needs to be increased significantly to control the increased spring rate in droop.

When I went from Koni SA 8610s in my 240Z to Penske TA 8760s I was able to drop the compression damping by 50% while retaing a lot more spring control. I was able to significantly increase compliance, the car stuck much better in bumpy corners, I could drive over corner curbing without upsetting the chassis, and the car rode a lot better. It was still very firm but it felt like a push over bumps instead of an impact.

 

betamotorsports, thanks for the info.

I noticed you referred to the use of smaller (use OEM instead?) sways. Is that to offset the spring rate increase that stiffer aftermarkets ones indirectly contribute?

 

Anti-roll bars (ARBs) are installed on cars to affect the rate of body roll and are but one component of a vehicle's roll rate. The other components are:

1. Installation ratio (wheel center rate).
2. Spring rate.
3. CG.
4. Track wdith.

If you increase the spring rate, lower the cg, increase track width, or shorten the installation ratio, the need for additional roll rate control provided by ARBs decreases, assuming you want to maintain the same roll rate. Also, ARBs, to some degree, reduce the independence of an independent suspension.