Driving Impressions

So what's it like to drive this car? Well, it's getting better as time passes by. Any car built from the ground up like this one requires quite a bit of development. A lot of work still remains to be done, but here is a description of the car's current status.

Getting in - You have to be a little careful getting in. It's not that easy to climb over the door bars and you don't want to scratch them with the bottoms of your shoes. But once you are in it's comfortable and there is a lot of head room. Of course all the controls in this car are positioned to fit me perfectly.

Starting - It's a sort of unusual procedure to start this car but it starts right up unless it's very cold weather. I have noticed that if I am wearing any type of MR2 apparel it does not start up as well.

Sound - Right away you notice this car is not quiet. Rotary engines are naturally on the loud side. The big turbocharger quiets it somewhat, the Flowmaster muffler quiets it a little bit more, and the baffled tail pipe reduces the noise a little more. But the exhaust exits in front of the rear wheel, on the passenger side of the car, and it can be clearly heard from inside the car. Turbocharged cars have a characteristic whistle. This whistle is the sound of the turbocharger turning at speeds in the neighborhood of 100,000 RPM. It is more pronounced in some cars than others. This car does not have as noticeable of a whistle as I had expected. I guess this is because the turbocharger (especially the turbine side) is relatively large, and because the rotary engine makes so much noise of its own. I cannot hear the wastegate opening either.

Throttle - Another thing you notice right away is, the throttle response of the engine is very quick. Tap your foot lightly on the throttle pedal and it feels as though the engine responds at the exact same moment.

Driving - The clutch is fairly light and the car goes into gear and takes off from a stop with a slight amount of slipping the clutch. Just like a normal car.

Steering - The steering may be the best thing about driving this car. It is really quick, but it's still light. It centers itself firmly but not forcefully. At higher speeds it feels very stable. It transitions very quickly, because there is no rubber in the suspension, and because of the aggressive alignment. The small diameter, thick, suede steering wheel feels great in the hands too. Thanks for breaking it in, Geoff.

Brakes - The brakes work very well and the pedal is very firm, maybe too firm. I have not yet done any development on the brake balance. It's still set by eye with the balance bar centered between the master cylinders.

Suspension - The compliance of this car's suspension is surprising. It has relatively soft springs and you can tell it. The ride is not harsh, especially considering this car's light weight and its roll stiffness. I haven't done any development on the anti-roll bar balance. The rear bar could probably be adjusted stiffer because it feels like it understeers, but for the time being I am leaving the anti-roll bars adjusted like they are. They are both at their softest settings. The car has very little roll in fast cornering but the balance isn't perfect yet. I am playing it safe.

Acceleration - When you press the throttle pedal on this car, you can immediately hear the turbo spool up. But like any high-output turbocharged car, if you aren't in the right rev range it feels a little disappointing. All fixed turbochargers are a compromise between low-RPM response and high-RPM power (low backpressure). I like to think this one is a little bit biased toward the high RPM power but not excessively so. I have an extra turbine housing which is slightly smaller than the one currently installed (A/R of 0.58 compared to 0.69) if I want to try it. In the past I have judged this by really silly method: wheelspin (if you get excessive wheelspin at low RPM's, go to a larger turbo). But this car with its sticky 12" wide rear tires, doesn't tend to exhibit any wheelspin. It just accelerates. It seems to get enough boost to open the wastegate at any setting I have tried (5 to 10 PSI) at under 4000 RPM, usually less, depending on load. That gives a full-boost rev range of 4000-7000+ RPM so I am more than satisfied with the power band. If anything, maybe it needs a larger turbo!

Traction - There appears to be absolutely no problem with traction. I haven't even seen any wheelspin while shifting, although I have not done any serious power shifting with this car, and for that matter, I don't plan to either. The vast majority of the tire width touches the ground at almost any tire pressure because the tire sidewalls are very stiff. So I don't think tire pressure is going to have much effect on traction.

Gearing - The RX-7 5-speed gearbox has nicely spaced gear ratios. The differential ratio I selected was a good choice because the car accelerates well in all gears at the proper speeds. The theoretical top speed in fourth gear is 135 MPH at 7000 RPM, which would not be attainable due to the power-to-drag ratio. So fifth gear is needed only for cruising, not for performance driving.

On the road - This car gets a lot of attention. With its bright yellow, ultra-smooth body, full roll cage, and massive rear tires, I guess that's not surprising. The usual Mustangs and Hondas wisely don't seem anxious to race me.