Saturday, January 17, 2009

Real World Driving Tests

I had a chance to take the Civic out for about 25 miles yesterday (two charges) and see how it handles in traffic and on the freeway. Here are some first impressions.

The potbox, being directly under the accelerator pedal, is very sensitive, especially at slow speeds. Since the Warp9 is rather powerful, trying slow moves in reverse gear are tricky. This can be problematic for parallel parking where a sudden lurch might send you into another car. There's a positive feedback loop where if you press just a little too hard while in reverse, the car lurches backward, which makes your body/leg move towards the front of the car and press the accelerator even more, causing an even bigger lurch. Be careful in lower gears!

Given the power the Warp9 and sensitivity of the potbox, starting in second gear seems to be just fine, even on hills. Even starting in third gear works well if you don't need jackrabbit starts at stoplights. Higher gears take the jolt out of moving the car so you get much smoother, albeit a bit slower acceleration. I plan on using third in stop-and-go traffic due to its smoothness.

If I didn't pay attention, very light acceleration in second gear gave me oscillations in car movement. This again was caused by negative feedback between my body/leg mass and the accleration of the motor. If I'm not careful in second gear, light acceleration will cause the car to lurch forward, pulling my body/leg towards the back of the car, releasing the pressure on the acclerator and slowing the car down. This slowing returns my body/leg to a neutral position where I'm accelerating again and... well, you get the point. This is only my first major day driving so I'm sure I'll get trained to the dynamics of the car.

As with many DC motor powered cars, accelerating from zero to 30 mph is great and getting up to 60mph is a bit slower. I can get on the freeway no problem, but it does take a few extra seconds over the original stock Civic. With the Belktronix system, the batteries tend to sag to their low-cutoff point of 10.8V under heavy acceleration. I'm tempted to add an "emergency power" momentary-push button that disconnects the LVP protection to the controller in case I need an extra boost (Think "Turbo" button in Knight Rider) to save my ass when I don't care about drooping down the batteries lower than 10.8V. I'm guessing that Bryan at Belktronix is cringing at this statement, but, hey, they're my batteries and can kill them if I want to.

I'm very thankful that I chose to keep the clutch for this implementation. Shifting is a breeze, both up and down without any delays whatsoever. It just feels so much like a regular ICE car but without the noise and pollution.

Overall, I've been pretty happy and nothing has blown up yet, so we'll see how things go as I break in the batteries and start commuting.

Cheers,
Tim

1 comment:

Mr. Easter Basket said...

Tim,

The sensitivity may be less the potbox itself and more the fact that your throttle pedal has much less physical resistance to your foot, now. Either way, what several have done to create a less sensitive pedal with a more familiar "feedback loop" is to adapt the original throttle body linkage, with all its springs and resistance, to have it actuate the potbox plunger. One way is a cam on the butterfly valve shaft.

Another, simpler, suggestion would be to add a big "puller" spring from the hardware store between the pedal and something under the dash in front of the pedal, again to add resistance and minimize the tendency of the throttle pedal to move in response to every little fluctuation in pressure.

Best,

Jesse.