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Notes from the Field -- 2012/13 KB GT-4 CS/RS Mustang
Submitted by bgrissom on Mon, 06/11/2012 - 17:01
Autobahn Test 05/18-20/12
We recently had a really good 3-day test of my emerging GT-4RS Mustang performance package at Autobahn. Our continual development program for the 2012/13 KB GT-4 Series Mustangs is providing valuable data, upgrades, new products, and components for our current and future customer cars. Combine that with the technology transfer we have with the Paul Brown/Tiger Racing team in the Pirelli World Challenge series, and we are positioned to build the best track-day Mustangs this generation has ever seen.
In the GT-4 Series of Mustangs, I offer multiple levels of equipment and performance to suit the needs and intended use of our customers. The GT-4 Series consists of; the base model GT-4 for street or occasional track, GT-4 CS (Club Sport) for open track and motorsports country clubs or aggressive street performance, and the GT-4 RS (A heavily optioned CS) is one step below the full race GT-4 RSR.
Ruby started as a GT-4 CS "Autobahn Edition", for Autobahn Country Club members who wanted to step up from the popular Miata series, and have a more cost effective option to the European counterparts. The GT-4 CS package testing went so well, we are already upgrading Ruby with options and equipment moving her smartly towards a full GT-4 RS Mustang.
A couple of new items worth mentioning that will make its way into our system from the recent testing, are the custom single adjustable JRZ shocks and a new torque sensing differential. After urging from myself and Paul, JRZ is now making a custom series of “Club” shocks based on the development we have done with JRZ on the #50 championship-winning Boss 302S Mustang. The double adjustable JRZ’s are already in the system for the competition cars and experienced track-day customers that are ready for higher spring rates and slicks. The single adjustable JRZ shocks showed great control and very acceptable ride, that I would have no problem putting them on a performance street application as well as track. The on-track performance was great, a lot of control and they made the car faster. The single adjustable feature is a great tuning tool without getting too complicated as the next step above our current H&R Club Sport spring and shock packages.
The new differential worked really well on the car. The issue I have with the Torsen, is an unsettling “wiggle” at the back of the car with power off and down-shifts after full throttle, as the differential shifts from side to side looking for traction. The new differential reduced the wiggle quite a bit to almost barely noticeable and it is still torque sensing for great traction. The new unit will become standard on the GT-4CS and RS Mustangs.
Both the JRZ shocks and the new differential are now available through Kenny Brown Motorsports.