Hypermiling, Maintenance and Costs

Since I bought the Kawasaki Ninja 500, two weeks ago, I’ve been riding quite regularly between Melbourne and Orlando, using the Some Highway and No Highway routes that I talked about in my last post. In that time, I’ve clocked almost 1000 miles, which is a lot more than I used to ride in the past! Most of my riding was in the early mornings to get to work around 9 am, or at night after work at about 7 pm.

The first thing I have to say is that the weather in March has been amazing for motorcycle riding. The air was cool and dry, meaning that I wasn’t sweating up a storm in my leather riding suit, nor was I freezing to death or wet. A couple of times, when I was only wearing a single t-shirt under my jacket, I was feeling a little too cold, but that was easily fixed by adding a second t-shirt.

I did an odometer check for the two routes that I take between Melbourne and Orlando to see what their actual length was compared to what Google Maps had predicted.

• Some Highway: 76.4 miles (Google said 75 miles)
• No Highway: 76.9 miles (Google said 74 miles)

I was surprised to see how close the two routes were in distance. Google’s estimate may have been a bit off, but to be honest, I deviated a bit from the original routes. I’ll try to follow that slightly different route to see if it is actually a little shorter.

As expected, taking the No Highway route added time. Since the distance is the same for the two routes, but on the Highway route I’m doing a constant 65 mph with no stopping, while on the other route I’m doing between 35 and 55 mph with traffic lights and turns, it’s no surprise that the No Highway route takes a lot longer.

Hypermiling

It turns out that I’m pretty good at driving economically. My 2005 Chrysler Town and Country is listed at having 19 mph mixed (23 mpg highway), and I can usually get about 25 mpg mixed (perhaps because a lot of my driving is on the highway?) The guy that I bought the Ninja 500 (his name is Rich) said that he got around 50 mpg, riding it to work and back. I’ve been able to get 67 mpg regularly. Again, this may be because I’m doing mostly highway type riding — long stretches at a constant speed.

My understanding of the way to get good fuel economy is pretty simple and has three basic elements:

• Keep the RPM counter as low as possible all the time. That doesn’t mean that you have to be going slow. You just shift to the highest gear you can get to without stalling the engine. At 55 mph in 6th gear, my Ninja runs at about 4400 rpm. I can go down to about 2500 rpm before the engine starts to struggle. Beware! Riding at low rpms can be dangerous, since you have very little torque at low rpms. If you have to speed up quickly, you’re going to need to shift down a a gear or two first.
• Avoid changing speeds. Of course if you hit a red light, you need to stop, and then accelerate when the light turns green, but if you see a red light in the distance, try to slow down sooner so that the light turns green when you get to it. Any increase in speed is going to cost fuel, and if you can slow down less by slowing down sooner, you won’t have to accelerate as much when you need to go again.
• Avoid going fast. The other thing that is going to cost fuel is the drag due to air resistance. The slower you go, the less drag there is and the less fuel you use. (See below for a discussion about air resistance.)

An electric vehicle is going to be subjected to the same speed issues as a gas bike, but I expect that the effects of keeping the RPMs low will be quite different. (More about that in another post.)

Maintenance

I did my very first oil change over the weekend, and amazingly, the bike still runs! It’s something that I wanted to do for a few reasons.

• It keeps the costs of ownership low.
• I can do it over the weekend in an hour at my own house, rather than having to go to a repair shop and wait for them to finish.
• It’s something that I believe that I should be able to do. (How hard can it be, right?)
• I’m going to appreciate not doing that when I get an Empulse!

The Ninja manual says that I should do an oil change every 7500 miles, but people on the motorcycle forums that I read say 3000 miles while a couple of people I have talked to swear that an oil change is needed ever 2000 to 2500 miles. Their logic is that changing the oil is good for the engine, and the proof is that their engines are running fine. It’s true that the cleaner the oil, the better, but considering the manual’s recommendation, 2000 miles seems way too low. Also, none of the forums that I read had tales of engines that seized up when following the official oil change schedule. So I decided that I’m going to change the oil every 4000 to 4500 miles. If things start to go wrong, I’ll let you know about it and change my schedule.

Based on a 4000 to 4500 mile oil change schedule, I was able to calculate that I’m going to need to do three or four oil changes before October, which is the earliest that I could hope to get the Empulse.

It turns out that changing the oil of a bike is quite simple, and cost me about $30 and 30 minutes (plus the time to dispose of the old oil). I did my first oil change under Rich’s watchful eye. He did all of his oil changes, and was willing to teach me how to do that. He also taught me the joys and tips for washing a motorcycle, which I’m going to do more often that I used to. (I.e. never! My old Ninja got washed when I rode it in the rain. Poor thing.) I want to get into some good habits so that my Empulse will look great all the time.

One valuable piece of advice that I got from Rich but didn’t see in the manual was:

• When screwing the oil plug back into the engine, screw it all the way in by hand first. Only then should you use the wrench to tighten it. His rational was that if you use a wrench to put the plug back on, and don’t set the plug correctly, you can easily damage the thread in the soft aluminium engine with the hard steel plug.

Besides oil changes, the cost of maintaining the Ninja is pretty negligible, and even the oil change is only $30 every month or so. With a 67 mpg fuel consumption, the Ninja is quite economical.

Running cost comparisons

Using the cost of the oil change, my average mpg and other data, I can estimate how much the running cost will be for my van and the Ninja, and compare that to the Empulse.

Vehicle	Van	Ninja	Empulse
Average cost per month	$345.74	$143.68	$44.58
Average cost per year	$3,815.20	$1,474.40	$535.01

Assumptions: Van: 25 mpg. Oil change is $33.37, every 4000 miles. Ninja: 65 mpg. Oil change is $31.22, every 4000 miles. Empulse: 10 kWh per trip. Gas is $3.80 per gallon. Electricity is $0.085 per kWh.

Even though my estimate the gas price is low, and the estimate for the kWh used is high, the Empulse is still clearly the cheapest to run. I would be saving about $940 per year by using an Empulse instead of the Ninja, or $3,280 by replacing the van. Going from the van to the Ninja was already a big saving (the Ninja will pay for itself in a year!)

I didn’t consider any repair costs on the vehicles. I recently had to replace the catalytic converter on the van. It cost over $900! Ouch. The Empulse is better in that it will have less parts to break, but when parts like the battery or the motor wear out, those repairs are probably going to be pretty darn expensive.

Air Resistance: Speed is the enemy of range!

There are a number of things that can affect the range you can get from your battery. The most important one that you can directly affect is your speed. There’s a very clear trade off between how fast you go and how much energy that speed will cost you, and it’s pretty bad. If you double your speed, you increase the energy you use by four times!

Here’s the equation that describes the different things that make up air resistance:

F = ½pv²C_DA

• F is the force due to air resistance (also known as Drag). The bigger this number, the more energy you have to use to keep going at a constant speed. Or you could say, the bigger this number is the sooner you’re going to run out of battery.
• p is the density of the fluid (i.e. the air). That is always going to be the same, so we can forget about that for this discussion. You can also ignore the ½, since that doesn’t change either.
• v is the air speed. Notice how it’s v². That is the reason why speed makes such a big difference.
• C_D is call the Drag Coefficient. This is where good fairings would make a big difference.
• A is the cross-sectional area. Think of it as the shape that drivers see of you in their rear view mirror. The smaller this is, the better. Ducking down makes this smaller, sitting up tall or adding saddle bags to the bike makes this bigger. (Heck, sitting up tall makes a pretty good air brake when you want to slow down on an exit ramp!)

A couple of things about the dreaded v. As long as v is small, v² is no big deal. When v gets bigger, v² starts to matter. To get a feel of that, take a look at these examples. Assume the numbers for v (e.g. 25 x 25) are miles per hour.

• 25 x 25 is 650 ← That’s small fry.
• 45 x 45 is 2025 ← At urban speeds the number is getting significant.
• 55 x 55 is 3025 ← At rural speeds (10 mph more), I’m using 33% more energy.
• 65 x 65 is 4225 ← At minimum highway speeds, I’m using twice (i.e. 100% more than) the energy at 45 mph.
• 75 x 75 is 5625 ← Holy cow! Almost 3 times the energy at 45 mph! That means that if I go at 45 mph I can travel almost 3 times further than at 75 mph.*

* This is just due to air resistance. There are other factor that will affect the actual range that you can get, but this is a pretty good place to start from.

The good news here is that if you think that you’re going to run out of battery, you can go a bit slower and get a lot more range (unless you’re already going at “small fry” speeds!)

One last note about v: Since v is the air speed, if the wind is blowing from behind you, v will be less than your actual speed, and if it’s blowing from in front, v will be more than your speed! Also, if you’re behind a truck, it’s going to be sucking a lot of air behind it, so again, v will be less than your actual speed. Beware! Riding behind a truck is dangerous: If the truck stops suddenly, you could end up crashing into it. Also there will be a lot of wind turbulence behind the truck that will be buffeting you around and that can tire you out. If you’re tired, you’re more likely to make mistakes.