Project RX-7

So i thought I'd kick start this blog with a little suspension talk.
Thankfully there are a lot of suspension options for the FD, thanks to, by a large degree, the tuners who run the car in touge battles and GT racing.
Fortunately or not, most aftermarket setups tend to be quite hard. While RE-Amemiya and FEED run their cars with 18kg/mm Swift springs front and rear, the other "mild" sport coilover options range from 16kg/mm to 7.4 at the front, 5.8 at the rear.

There is a wealth of suspension information available at FD3S.net with some useful testimonials on daily driven setups.

However (aaah, thought it was that easy did you?)

Seeing that PRX7 will pretty much be a dual purpose commuter weekend racer car, my doubts were as to whether or not a single setup "sweet spot" was appropriate. On top of that, the other recurring questions were: how do the OEM's do it? and is there a way to make the car soak up the bumps and still corner properly? Must... seek... answers....

To this end i had a conversation with esteemed colleague and fellow blogger deamoncynos7 about using harder anti roll bars and softer springs. The theory behind my idea would be using the anti roll bars to sustain some of the axial loading during cornering, while keeping a streetable suspension stiffness for badly paved roads etc.
We both agreed that harder anti roll bars would reduce suspension travel, which can be a problem over bumps. However this could be solved with appropriate rebound valving adjustments. Also, harder bars would oppose the weight transfer during cornering, which can lead to some "interesting" results when pushed hard.

Plan B would be to use a system like the EDFC or the equivalent by Tanabe to electronically adjust damping force with a push of a button. hard when you wanna go, soft when you wanna show, if that's your thing.
I see why it could be useful, but, the truth is that even though there is more than one correct damper/spring setting, having 12kg springs on the softest damper setting wont solve the ride harshness problem. The car will still crash over the bump, regardless of how well damped the crash is.
I'll be giving the subject some extra thought over the next few days, and hopefully run some numbers on some suspension diagrams. Suspension settings are a black art.

When Mazda first released the E-FD3S RX-7 back in 1993, Japan's economy was booming, and Mazda's engineers were on a roll. They had just produced a car with the world's first ever mass produced sequential twin turbo system, a chassis that is competitive even today and given it timeless looks. The only real problem with the RX-7 back then, was its price. It was a massive move upmarket from the previous generation "cheap and cheerful" FC, and owners who opted to trade in their old wankel for the new version left the showrooms understandably shocked. To make matters worse, service costs for the finicky twin turbo wankel engine were astronomically high, with only few specialized centers qualified by Mazda.

A few years later the economy bubble burst, Mazda's monetary problems worsened, leading to the Ford buyout. The RX-7 was pulled from most markets, while it still soldiered on in Japan until 2002 in various versions even after restyling in 1999. The ultimate version was the Spirit R Type A. Mazda sold very few

RX-7's during the entire production run, and only 500 Spirit R's were made, so it's quite rare to see this car on the road. Yet it's instantly recognized by the car loving public. The reason for this is competence more than popularity. Mazda never entered the FD3S in major touring or endurance competitions around the world officially, but independent tuners have been successfully racing them for almost twenty years. The full racing accolades can be found on Wikipedia, along with the full biography if needed.



so what do i plan to do with it?

I've never been a fan of all out race converted street cars. Some people find it gratifying, I don't think it's worth the hassle. Nor do i want a soft and cosy minature luxury car to flaunt at the nearest high class social gathering. I believe that the right solution is a blend of different properties. The perfect car to me is a car that is never out of place or inappropriate, or rather one that doesn't force it's owner to make sacrifices. And with modern technology and a bit of clever engineering, it is possible to fast and frugal, to corner flat and not die over speed bumps, to have downforce and not look like Dom Toretto. I will be approaching and thoroughly re-engineering the car in as many ways as possible to achieve these goals, in all areas from engine to aerodynamics, documenting research and progress along the way. It'll be a pretty long process but the results will be very interesting...