Picking up where we left off last time, the chassis and drivetrain for the FC RX-7 has plenty of potential with minimal modifications. Chassis bracing is a good place to start.
CorkSport offers strut braces for the front and rear strut/shock towers. Some people have questioned the effectiveness of the tower braces in the FC. Speaking from first hand experience, they work very well, and they make a big difference. I have e seen the aftermath of a car hitting a guard rail at highway speeds sideways and what saved the car from crushing itself sideways was the front strut brace. The front is a simple bolt in, and while the rear requires some extra work and includes trimming some metal, it is well worth it.
For underneath the car CorkSport sells the AutoExe Member Brace Set. Think of this is an over the top strut tower brace set for the under side of your RX-7. The chassis brace set ties together multiple points of the suspension to make the chassis more rigid, including tying up the rear differential sub frame to the chassis.
AutoExe Member Brace Set
Next up is lowering the car. Lowering the car gives it a lower center of gravity and you should also stiffen the dampening of the suspension to go with the springs. Tokico Illumina shocks combined with Eibach springs are a good combination for street driven vehicles. With the installation of lowering springs you will need to address the camber for the rear suspension. The design of the RX-7 suspension requires a camber adjustment kit which CorkSport offers as well. The rear camber link kit adjusts the rear sub frame correcting the camber on both sides of the car.
Rear Camber Adjuster
If you are seeking maximum performance out of the suspension you can change out the suspension bushings with polyurethane parts. The good part about the bushings is the upgrade to urethane makes the suspension work without extra deflection. The trade off is extra vibration from the stiffer bushings into the chassis. CorkSport offers the Prothane bushing kit for the RX-7.
Drivetrain mounts will also need to be replaced. It is not really a choice anymore, the engine, transmission, and differential mounts will be worn out after ¼ century. CorkSport offers Mazdaspeed replacement mounts for all of the drivetrain. The stiffer rubber used in the engine and transmission mounts limit engine movement to help cope with the extra power and put the power out the drivetrain instead of moving the engine around. The rear differential mounts are needed to deal with the increased torque load of the drive train under hard acceleration. We have seen cars in the past come into the shop with a clunk noise from the rear end of the car only to find the front differential mount broken.
Mazdaspeed Engine Mounts
With the increased power made from the engine modifications in the first blog you will need to upgrade the clutch. For a street driven RX-7 the ACT street clutch kit is hard to beat. The reason for the street version of the clutch is that puck clutches tend to chatter when engaged from a stand still and make driving in stop and go traffic a pain. With the installation of the clutch a lightweight flywheel is a good idea as well. ACT also offers lightweight flywheels in two varieties, Streetlight and Prolight. The reason for a lighter flywheel is engine response. With a lighter flywheel the engine has less mass to spin and because of this engine revs build faster. The difference between the two is the weight. The street version weighs more which helps with keeping the inertia of the motor going. This is helpful with making smooth starts and stops while on hills. I would choose the pro light myself. Having a rev happy rotary engine just makes me smile. When purchasing a lightweight flywheel it is important to get a counterweight. The stock RX-7 flywheel has the counterweight built in but the aftermarket flywheels do not.
The last piece of the drive train puzzle is the shifter. It is something you are constantly using in the RX-7 and CorkSport offers a short throw shifter. The short throw shifter decreases the distance you have to move the handle to change gears resulting in quicker shifts. The CorkSport shifter includes all new bushings and seals which are a must since most RX-7s we have seen need to have all of the parts replaced. If you are wondering what I am talking about there check out the shifter in your RX-7. If you can move the shifter left to right while in gear, and it feels loose and vague when shifting, or it doesn’t return to the center while in neutral you need to replace the bushings and seals at a minimum.
CorkSport Short Shifter
Well, that is it for the chassis and drive train. In the next blog post I will cover the brakes and styling for your RX-7.