Wednesday, July 24, 2013

Just a few little psi

Those of you who have read this blog will know, I can't stop tinkering with stuff.

About 3 years ago, I bought the Kawasaki ZRX1200R as the basis for a future project.  I figured, I wasn't ready for the project, but I could ride the bike in the meantime.  What I discovered was that the ZRX series had a reputation for being a poor handling bike and, upon riding it for a while, I had to agree.  Going in a straight line, everything was fine, but go over a dip in the road while cornering, you better hang on.  And don't even think about squeezing on the throttle in a turn.

The guy I bought the bike from told me I should make sure to run the factory tire pressures at 36 front/36 rear.  So that's what I did.

Trying to improve the handling, I messed with every suspension setting I could think of.  I managed to move the handling in the right direction, but she was still scary and I still wasn't confident.

One morning, on a pure lark, I decided to blow the tires up to 40 psi.  WOW!  What a difference.  Suddenly, you could feel the front end and the rear would follow the front.  When I got home, I googled ZRX tire pressures and found that lots of other people had discovered that the factory specs were just wrong.  They said that the right specs were 36/42.  I gave those a try, along with 40/42 which I settled on as best for me.  Now I can go through a dip with confidence.  Now I can squeeze that throttle on at the apex and track the bike smoothly out of the corner.  I had a little surprise when an oncoming car crossed into my lane on a corner.  Grabbing the front brake to slow and tighten my line caused a minor steering reaction, but well within control.

How amazing it is that a few little psi could change the character of a bike.

That got me to thinking.  What had probably been happening is that the contact patch of the tire in a corner was moving laterally when the vertical load changed going through a dip.  There just wasn't enough tire pressure to keep the tire's shape under different loading.

Of course, the current style is big, fat, wide tires on bikes.  I guess people think they look good.  But doesn't the fat tire cause the contact patch to move laterally when the bike leans?  Wouldn't the bikes handling be more consistent if the contact patch didn't move laterally as far in roll?  It always has seemed that skinny tires are the best handling on a bike.  I can't say it is the whole reason, but I can say that the KLR has skinny tires and keeps up with just about any sport bike ridden at the same skill level.  So keep your fat tire style.  I prefer skinny any day.

P.S.  Note to self.  Always Google any question that comes to mind.  There is often useful knowledge there and the factory spec isn't always right.

Sunday, July 21, 2013

Guido with an 'e'

When I bought my Fiat 500 a couple of years ago, I named it "Guido" as slang for an Italian American.  Besides, the name "Luigi" was already taken by one of the development cars.

A few days ago, one of my coworkers asked me to drive a Fiat 500e and give him my opinion on the steering tuning (nice - by the way).  The 500e is the battery electric Fiat 500 that was just introduced.  Although pure electric drive cars have limited range and, therefore, limited ability to replace a normal car, I knew it would have more than enough range for an overnight drive, so I took it home and out for a spin.

I didn't take any of my own pictures because, as a prototype, these cars are sometimes not up to production cars for appearance, but I downloaded a few shots from the Fiat website for you to see.

First, a couple of cool things unique to the electric 500 as compared to the gas 500.

It was a very hot day.  Since the AC system is a separate system from the motor, the AC was busy cooling the car down, even when I got out of the car to get things from Guido.  The drive motor is doing nothing, but the AC is cranking away.

The "shifter" is replaced by a row of buttons.  This is not only clean and uncluttered, but gives me some extra knee room that is appreciated.

The Drive Home

Since I wanted to evaluate the steering on the highway and on some twisty roads, I decided not to baby the car on the way home.  There is plenty of torque and power, subjectively more than Guido, so some of the time, there is a little wheel spin on hard launches until the traction control can handle the wheel spin into a nice launch slip.  Pretty soon, I'm running along with traffic in the left lane of the freeway at speeds approaching 80 mph without drama. 

That reminds me of short story.  You see, electric cars have 100% of their available torque at zero speed.  It seems that some of the Fiat guys were demoing the 500e at a press event and decided to enter the car in an autocross.  With its low center of gravity and low end torque, it finished quite well, in spite of its low rolling resistance tires.  Imagine how much fun that could be with good autocross tires.

Anyway, I finished my drive home on some twisty for Michigan roads and enjoyed the handling and torque out of the corners.  When I got home, the display told me that I had used energy at a rate of 2.9 mi/Wh.  My calculations suggest that I would have about 55 miles range to 20% state of charge, all the while beating on the car and not thinking about saving the environment.  20% state of charge is a typical "empty" for battery vehicles, so my calculaitons use 80% of the 24 kWh battery pack capacity.  That said, I don't have any information whether that capacity is usable capacity or total capacity.  It could be that there is another 20% range available.

Other than its silence, in no way did the 500e let me know it was an electric car nor limit me in driving or comfort or other features.

Back to Work in the Morning

That 2.9 mi/Wh is pretty efficient, so I decided to see how little energy I could use on the way into work.  I kept off of the freeway to keep my average speed down.  I coasted to stops and accelerated gently when traffic would allow.  Since the computer was remembering my aggressive drive home the night before, the displayed range leaving home was 60 miles.  By the time I got to work, the displayed range was up to 64 miles and the energy usage was 4.7 mi/Wh.

Think about that.  Just by changing my driving style, I was able to lower my energy usage by almost 40%.  Of course, that is true of normal gas cars, not just electric cars.  You want to save money on fuel, start with your driving style.

Doing the same calculation to 80% state of change suggests that I should have been able to travel 90 miles by trying to save energy.  Now my driving wasn't extreme.  I still accelerated with traffic and drove at 60 mph (5 over) for more than half of the miles.

With a mileage range of 55 to 90 miles, I could use a 500e and have enough range on many days in my life.  Of course, it couldn't replace a regular car on longer trips.  I remember Alan Cocconi having a motorcycle engine and generator mounted in a small trailer.  He towed the trailer and recharged his battery along the way whenever he wanted to take his electric car on long trips.

Anyway, its good to keep an open mind because the 500e is a much better car than expected.  If I had a need for another car or could get a range extender trailer, I might be tempted.