UPDATE Dec 2016: Deana Kelley wins the 2016 C Street Ladies SCA Solo National Championship! My interview with her here:
Early 2016: First big WIN for FCM Elite customers in the new 2016 Mazda MX-5 Miata!
WOO HOO!! First big SCCA autocross event with our FCM Elite tune and both our C Street and C Street Ladies drivers WIN! Congrats to Jeffrey Bandes and Deana Kelley on their success at the 2016 Crows Landing Championship Tour.
TL;dr – My interview with Jeff and Deana after their Crows Landing Tour wins is at the bottom of the post.
Note the C Street class had 17 drivers, so a very strong showing and competition that came down to the last couple runs!
Our path to unlocking the Miata’s potential as a Street-class autocross car
The new ‘ND’ Miata is an improvement is essentially every way over the earlier 3 models (NA 1990-1997, NB 1999-2005, and NC 2006-2015). Lighter, better power-to-weight ratio, good brakes, great suspension geometry. However, the front camber gain at stock ride heights is very limited, so the tires tend to roll onto the sidewall when driven hard especially when grippier-than-stock compounds are used. In SCCA autocross, the 2016 Miata goes into C-Street with minimal useful modifications such as dampers, air filter, alternate brake pads, and changing one sway bar.
With the help of Travis and Deana Kelley, already running their ND in C-Street, I made a series of measurements on their Club package. The data and analysis helped me understand what the behaviors of this new-and-improved chassis would be in terms of spring rate, sway bar stiffness, bump stop interaction, and damper tuning.
Fat Cat Motorsports – Characterization of ND Miata suspension behavior
Per Street class rules, you can change one sway bar, but not both. Since the rear-wheel drive Miata needed help putting power down in competition driving situations with much sticker-than-stock tires, additional front roll stiffness was needed to keep the rears from working too hard. Travis and Deana had already installed a larger diameter tubular Progress Technologies front sway bar (28mm vs 22mm for the OE) and had been using the soft or middle setting due to the added understeer with the factory bump stops and dampers. With some further changes to bump stops, I was able to get them to use the middle stiffness setting on the Progress bar even with the OE dampers. The car had more grip and was faster in comparison to other cars, but there was still room for improvement in damping. Because there was no aftermarket Bilstein HD or Sport damper (ready to take-apart) available, we had to machine and ‘de-crimp’ a second set of factory crimp-top Bilsteins then make our intelligent changes to that set.
The initial gas pressure was quite high on the original monotube Club package Bilsteins, about 60-65 lb. This was far higher gas pressure than the dampers needed to prevent cavitation. The phenomenon of cavitation refers to localized boiling of (in this case) hydraulic oil due to a pressure drop above the vapor pressure of the oil caused by insufficient pressurization of that oil. Twin tube dampers get around the problem of cavitation due to the valve design which regulates pressure drop. A standard de Carbon type monotube damper as used by Bilstein, most Penskes, Ohlins, etc. has to rely on sufficient nitrogen gas pressure in adjacent chamber to prevent cavitation and keep the damper working efficiently. However, we’ve found success in terms smoother initial damper response by reducing that gas pressure and carefully monitoring damper behavior. We were able to achieve resultant gas forces nearly half the OE values which creates a much more fluid, responsive damper with less tire shock from the high initial resistance to start of damper motion.
FCM’s innovative Ripple Reducer upgrade
We also, per the Kelley’s request, incorporate our Ripple Reducer and KBO (Kerb Blow-Off) technologies into their build. Ripple Reducer involves a modification you might find in off-road dampers, where the piston has been drilled with carefully-sized holes to allow a more direct flow-path for hydraulic oil during small displacement, high frequency events, such as you experience on any real-world world. Many dampers rely on shim displacement or flow through an adjustable needle valve to create low-speed ‘bleed’, but the more turns the oil makes, the more resistance the damper builds. Ideally, you do not want the damper to have any resistance to very high frequency motions beyond controlling wheel hop which is usually in the 6-10 Hz range. Ripple Reducer is a customized thru-hole bleed that combines with minimal or no shim bleed to noticeably reduce the damper’s resistance on ‘road rumble’ while still providing enough low-speed damping force for good ride and transient control. It’s a win-win!
Our novel and proprietary Kerb Blow-Off (KBO) Technology, v1.9
I’m also very proud of our KBO technology, nearing its third year of continuous development and refinement. KBO allows us to separate low-speed compression forces (which are very useful for improving transitional response and optimizing tire grip, especially in dirty, wet, or rougher surface conditions) from high-speed compression forces (which can often ramp too high and cause grip loss as the tire ‘launches’ away from the road). We do this by use of a precisely-machined and toleranced spring-loaded assembly in place of the compression shims. You can see graphs below in the video plus the feedback from one of our most experienced customers, Jeff ‘Goji’, for his turbo MazdaSpeed Miata. We’ve heard similar comments from all our KBO customers, where we seem to ‘cheat’ and ‘chop the top off of bumps.’ From what I’ve seen, there is no one other than Penske with their Regressive Valve who is able to create this kind of ideal, optimized damping behavior. I will discuss this more in future videos and blog posts.
First revision – tested by Malcolm
With these changes in mind, and noting that the Kelley’s work and racing schedules were compressed, I was able to rely on our second ND C Street customer, Malcolm K., to give feedback on our initial valving. For that recipe, I went on the side of more rebound with the intention of providing more neutral handling with that the stiff Progress front bar would induce. Malcolm said that configuration was too edgy so I had to revisit the proportion of bump and rebound damping, a parameter I’ve also paid close attention to the past few years. Instead of going firmer on rebound (like people used to think years ago when tuning for Stock class with even stickier R-compound tires), I went back to what I knew from experience and logic: jacking down almost never a good idea unless it’s VERY controlled and very specifically done!
The second revision is what Jeff, Deana and Travis and been experiencing and doing so well with. Their setup isn’t jacking down, even up to 19 ips. I recall the comment in our interview below, that someone else noted how bumpy the course was and Deana shrugged her shoulders saying “I have no idea what you’re talking about!” Sounds like my conversations with Sam Lee, who was the first Street-class customer we had, in his H-Street Mini Cooper, and loved how smooth and fast his FCM setup was.
Results from the Crows Landing Championship Tour event
Jeff found he had to learn to trust the car, since there was so much grip. His 2nd run on Sunday (Day 2) was blisteringly fast! We don’t have video from that run but here is the one before it at 65.3 vs. the 64.7 for the 2nd.
Deana’s 1st run of the second day is here, a 67.5. Her best was a 66.4 on the 3rd run:
I did a short testimonial video a few hours after the event to capture their experience while it was still fresh – enjoy!
Want to join the Elite? Get in touch with us!
If you’re interested in an FCM Elite suspension for whatever your application, I invite you to contact us via our consultation form: