My Commuter

I have a Honda Nighthawk (CB250) as my daily driver. It is the only vehicle I own that does not have "Historic" tags. I read it would get 70MPG on average., though on the Yahoo Nighthawk group, some guy in GB said he got 90MPG highway, I didn't believe him.


When I drive it, I have fun. Because the engine is so small (Two cylinder 250cc, you know, 0.25 Liters) , I really feel no guilt in just pouring on the throttle. I'd been driving it hard, always topping out gears before shifting, especially to stay away from people driving cars. When I checked at the pump I was getting 50MPG.

After seeing that, I decided to drive conservatively just to see the MPG I could get. I was not driving super conservative, I was just driving like a car, accelerating calmly, turning the engine off at long lights, and still speeding up quickly to avoid people crazy enough to be driving cars.

I checked again at the pump . . . 200 miles . . . 2 gallons of gas . . .

Yay four stroke engines~!

Electric fan conversion for $20

Why electric fans?

A lot of people want to convert to an electric fan for their cars, either because their stock "clutch-type fan" is dead, to save energy, or to free up space in the engine bay.

Some people say that electric fans do not save energy, the reason being that you lose energy by converting it from kinetic energy into electricity, then back into kinetic energy, unlike the stock fan that is just belt driven without the conversions. This would be true, but only if the electric fan ran at all times. It saves energy by only turning on when it is needed. This is why most modern cars have electric fans. The engine does less work, so you get a little more power and slightly better fuel economy.

I removed my stock clutch fan in my Mazda RX-7 and replaced it with the stock twin fans out of a first gen (Mark I, from the eighties) Toyota MR2, and I did it for about $20. The reasons were simple. The most important reason I did this was that the stock clutch was dead, and a new one costs more then the MR2 fans at a junkyard. I also like having all that room in the engine bay, making it easier to change belts and observe engine operating conditions.

What electric fan should I use?

You can use almost any electric fan you'd like, I would recommend grabbing the twin fans out of a Mark II MR2 if you can, because they are less likely to be rusted out then the Mark I fans, and they look much nicer. The parts are interchangeable, and the motors have been upgraded. In fact, if you have dead Mark I fans, you can get rebuilt motors for the Mark II and turn the old motors in for the core charge.

Installation

This install is on a 1990 Mazda RX-7 Convertible with A/C. Your setup will vary, and you can find a different set of fans (or fan) from another junkyard car, just make sure it covers the radiator well and works with your shrouding.

The dual MR2 fan shrouds are made of metal and fit almost perfectly with a little bending. As anyone who has ever owned an Mark I MR2 knows, everything metal on the car rusts out, so I had to wire wheel and then paint these fans (I did too quick a job on the shrouds, in my opinion). Then I painted the (previously off white) fans black with some KRYLON PlastiCote. I really like the way they came out (scroll down for pictures).

I put regular house weather stripping along the edge of the fan and then set it on my radiator. I cut a few lengths of coat hanger up and then bent them in to create the brackets to hold the fans in place. If you want it to look nicer, you can use zip ties through the top of the radiator. Next, I bent the metal of the fan shroud flat around where the coolant hoses are run (I don't like the idea of my soft rubber hoses touching a vibrating metal fan shroud)

I tested each fan for polarity by applying battery voltage, and then set them to pull air through the radiator. This is important, you don't want the fans fighting incoming air. I then ran the ground wire to the chassis right next to the fans. I used all 8 gauge wire, this is important, you don't want to use too small a wire or it will heat up, and might even cause major issues. The positive wire went to a relay.

Controlling the Fan

Now, you can have the relay powered by a switch that you manually flip (that's no fun, and kinda dangerous if you forget to flip the switch), a thermoswitch (sounds good to me) or an aftermarket ECU (thats what I did). If you don't use an ECU, you can use an aftermarket temperature switch, or just build your own.

I have the The MegaSquirt ECU set to switch on the relay on whenever it sees the engine temperature go OVER 200F (210F is the maximum acceptable operating temperature) and switch it off around 184F.

The temperatures you set will be dependant on what car you install your fans on, and what thermostat you are running. If you're in doubt, just set it to 200F.

Results

When the fans come on, it's insane how fast they cool down the radiator. You can put your hand behind the airstream and FEEL the temperature drop in the air coming off. The coolant sensor input to my ECU hesitates a little, (The waterpump has to circulate the cool water, then the sensor has to catch up) then the display shows the temperature drops 20 degrees almost instantly!

These fans are much quieter then the Black Magic or Flex-a-Lite fans that I have heard. The fans do not over tax my stock alternator either.

Test fitting the fans:


Bending to clear the lower radiator hose:


You will have to bend it on top for the upper radiator hose too.

I would post better pictures, but a bit after I installed these fans, the car was stolen! I hope this writeup has been helpful for you, feel free to ask questions in the comments section!

How to Drive for the Best Fuel Economy: Debunking the Myths, Part 1

In today's article about saving that precious clear liquid that almost all of us world-wide are addicted to, you're going to learn a fun trick: Don't drive slow, accelerate slow (but not too slow, I'll explain)

Driving super slow doesn't save gas, in fact, it wastes it. If your car is not in the highest gear possible, you're most likely not getting the best fuel economy possible. I'm sure you've seen those people in economy cars, driving around at some insanely slow speed, thinking about all the fuel they're saving, but in reality their engines are working harder then they need to, spinning faster and sucking down more gas then the fellow who speeds past them.

It all has to do with the gearing of your car's transmission. When you're in first gear, your engine is spinning rather fast, and the faster it spins, the more air it sucks in. The more air your engine sucks in, the more fuel it needs to balance out the mixture (at least on gasoline engines). So, you shift into second (or your car does it for you, if you're one of those unfortunates with an automatic transmission), and now the engine is doing less work to keep the car going the same speed, or the same work to go a higher speed. Each time you go fast enough to shift up a gear (and do so), the engine spins slower, using less gas and wearing out slower.

So, the first reason going too slow wastes gas: If our car is not in its top gear, your engine is doing more work for less distance.

Now, once your car is in its top gear, going faster and faster will lose you fuel economy once you exit the point that your engine is efficient. This point is different for different cars. For example, my 91 RX-7 got it's best fuel economy at an average of 72MPH on a long highway trip. After that point, if I go any faster, the MPG drops. On regular cars, that spot is a bit lower, around the low 60mph range, depending. On vans and SUVs, the fuel economy "happy zone" is a bit lower, (probably around 50 to 60, depending on your car) because wind resistance is such a factor at higher speeds.

So how can you apply this?

First off, the faster you're in the next gear, the better. The longer you're in a low gear, the more gas is being wasted on going less distance. Though, if you shift too soon, the engine will lug (in older cars your engine might even knock and ping!) and you'll end up having to put your foot down more and more just to get up the tiniest of hills with your fuel economy dropping the whole way.

So, since shifting too soon doesn't work, how about flooring it to get up to speed so you can shift faster? That won't work either, as jackrabbit starts are a huge waste of gas. Ideally, you want the engine to be doing as little total work over the entire course of getting up to speed as possible. A good rule of thumb if you don't know how fast to accelerate, is try to keep the engine relatively quiet. If that doesn't sound scientific enough for you, you can buy a decent vacuum gauge for $36 from Summit Racing (dot com!), so that you can tell how hard your engine is working. If you go that route, try and keep that needle above ~9.

Mentioning "Top Gear" so much makes me think of the TV show, so by all means, have a read about what they have to say about fuel economy at Clarkson's top fuel saving tips, the fellows who brought you this video:




If that isn't interesting to you, you can always read about the fellow pulling 59mpg in a plain old Honda Accord.

I hope this article has been helpful to you, feel free to share what tricks have worked for you in the comments.