Well, I finally cracked and invested in some track goodies. Mainly addressing the suspension, grip, and track-readiness.
The early-model AP1 is extremely loose and snappy from the factory. It has a tendency to bite the driver at the limit. Last year, I addressed that by swapping an 06 rear swaybar in place of the very stiff AP1 bar. Rear bar stiffness was reduced from 427# to 311#. This tweak changed the car’s wheel rate ratio from 1.16 to 1.28. I felt that the car was pretty comfortable on the track, but that it was a little on-edge still. In the long-run i think that in order to get faster the car probably will need to be even more neutral at speed, but a little looser at low speed wouldnt hurt.
The CR S2000 has a stock wheel rate ratio of 1.45, which has been described as a bit understeery. So I think that a wheel rate ratio of between 1.35 and 1.4 would be ideal.
Springs and Dampers
The springs and dampers are the basis of the build. Without properly matched springs and dampers, the car’s behavior cant be optimized. This was the biggest decision that I had to make, and ultimately took the most thought.
Ive always been a huge fan of Ohlins, due to their ability to be a true dual-duty suspension with incredible track results. Unfortunately, as far as their kit for the s2000 is concerned, they have some serious design flaws. The biggest one surrounding the low amount of compression travel on the rear dampers. Secondly, due to the rear lower mounting bracket design, the ride height adjustability is limited.
Other options that I evaluated were Fortune Auto 510, AST 4100 and KW V3. Each carry with them their own pros and cons in the mid-range pricepoint. But ultimately I just couldnt deny the streetability that comes with the Ohlins DFV technology.
I eventually decided to work with Sakebomb Garage out of California, a prominent RX7 and S2000 specialty shop, to design one of their FPSpec Ohlins kits for my needs. Theyve done significant track and developmental testing with the S2000, and offer a breadth of knowledge toward determining the right setup. Their FPSpec kit addresses both of my major concerns with the standard Ohlins DFV, and gives the option for valved dampers to match custom spring rates. The FPSpec dampers have a custom long-stroke rear damper (addresses short stroke), along with a passthrough rear cup (addresses ride height limitation). They also come standard with Custom Ohlins Yellow Swift springs. Unfortunately, the FPSpec comes at a 50% premium to the standard DFV kit. But this is truly a kit that I believe will handle all of my track needs, both current and future. This is not an expense that I plan on incurring again.
I chose to go with 12k front and rear springs, with 5k helpers on the rear. More to come on the setup later in this post.
When looking at track wheels, 17×9 squared seem to be the top choice of S2000 owners. The balance between high grip at the limit and low speed rotation is perfect for track. Once I decided on that, it came down to “which wheels am I going to get?”. The new TC105X was a real head turner for me, the weight and price were fantastic but the +49 offset not so much. From the beginning, I had told myself that I didnt want to make any irreversible modifications to the car, which included rolling/pulling the fenders. Which meant the TC105X was out. Due to the ridiculously high offset required by the S2000, my options were quite limited. Advan was a clear front-runner, with a variety of proper offset lightweight cast wheels in several different classic styles; RG-D2, RGIII, RSII, RZII, etc. I had eventually decided on the bronze RZII; cost effective, lightweight, proper offset, good brake clearance. I had all but placed the order when my buddy Will at TH Motorsports hit me with a sweet Black Friday special on some forged Volk ZE40’s. I couldnt resist. The Volks will hold their value much better than the Advans, and save me an extra 1# at each corner. Plus, c’mon, they’re Volks… Every young JDM ricer kid’s dream is to own a set at some point in life.
When installing a Volk wheel that weighs in somewhere in the mid-15 lb realm, Injust didnt have the heart to slap on a cheap set of Muteki lugs. While they would be perfectly fine, my buddy Sam told me about a sweet deal for some titanium lug nuts through STM that I jumped on. They weigh about 3/4 less than a steel lug nut at under 30 grams each.
The objective is to use the springs/dampers to make the car as neutral as possible, and then using the dampers to adjust the balance of the car on the track. Sakebomb recommends a big 32mm front swaybar and a tiny 21mm rear swaybar. Doing so allows the S2000 to maximize wheel independence, with square spring rates on square wheels.
The current front swaybar on my car is a 28mmx5mm, rated at 393lb by Honda. The SBG front swaybar is 14% stiffer, with 3 adjustment slots.
The current rear swaybar is a 25.2mmx4.5mm, rated at 311lb by Honda. The SBG rear swaybar is 16% softer, with 3 adjustment slots.
I have been working with Heath at SBG, and his comment regarding these swaybars was that, “it tunes out the bad S2000 behavior, making it tossable and more predictable like a Miata.”
While “reliability mods” arent necessarily sexy, they are extremely necessary when building a vehicle that not only can perform on track, but still be able to drive home at the end of the day.
Oil coolers are great insurance against boiling your oil. Afterall, the oil is keeping your engine lubricated, and they can only withstand so much heat before they shear and have a change in viscosity while running through a hot engine. Below is a good forum post from BITOG explaining oil shear.
Sakebomb Garage makes a nice bolt-in oil cooler kit for the S2000. You have the option to upgrade to a Setrab unit in either 19- or 25-row configurations. I opted for the 19-row, which is perfectly sufficient for naturally-aspirated cars. The 25-row is really more suitable on forced induction vehicles.
The brake system on the S2000 is a weak point, mainly due to how light the stock rotor and caliper are. There’s not quite enough material/weight to properly absorb and dissipate heat, which can lead to cracked rotors and melted brake pads. Brake ducting is considered a must for avid track S2000’s, and many guys wind up moving to a big brake setup. With the car being used mainly for street, with a handful of track events per year, I would like to avoid ducting.
While I have not fully ruled out a BBK at some point in the future, I chose to move forward with the S2000 Big Rotor Kit from Ballade Sports. The big rotor kit allows the S2000 to run 30mm larger rotors on both front and rear (300mm to 330mm). What this does is greatly increase the stopping power of the brake system, while also using a rotor capable of absorbing more heat. If you think of the rotor like a breaker bar, the longer the handle, the greater the leverage. The same principles are true with the rotor. The larger rotor provides greater leverage, so the same caliper is capable of greater stopping force while also not having to work as hard.
Not to mention, the larger rotor acts as a larger heat sink, which should help the brake system to absorb/dissipate heat more effectively.
I found an authentic OEM AP1 front lip. Since these are no longer available from Honda, they are like finding a unicorn. Good condition ones go for $5-800 pretty easily. I didnt pay nearly that much. Its currently painted silver, so I need to have it re-painted Berlina Black. Otherwise its in great shape. No broken tabs or cracks.
The intake side valve spring retainers and keepers on the AP1 are prone to cracking under high stress. While its not a problem if you dont mis-shift and over-rev the little F20C to the moon, its cheap insurance against dropping a valve and having to replace the engine. Ill likely bring the car to One6 Motorsports to have that done along with the alignment in the spring.
The timing chain tensioner is another spot that is prone to failure. The OEM unit’s worm gear can wear out over time causing slack in the timing chain. Ballade Sports makes a replacement that has a lifetime warranty. Ill upgrade to that before the first event.
i think thats about it for now. Keep an eye out for more updates as parts arrive and get installed!