A Look At Fuel Injection Controllers

Fuel Injection Controllers


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Most ATV manufacturers are increasingly using electronic fuel injection systems. Among the many advantages are better performance, decreased fuel consumption and elimination of the need to modify carburetor injectors according to season or altitude. For those quad riders who want more from their rides and already have dealt with the usual mods (exhaust, air box…), better performance can also be achieved with certain other changes. The subject covered here will concern fuel injection controllers.

There are many products on the market, but specifications and applications can vary greatly. Product choice and price will be affected by your needs and the type of ATV. Certain products are geared for high performance and will necessitate excellent knowledge of fuel injection operation. You will need a computer to reach optimal settings or your local dealer should be equipped to do so. Even with more simple systems, where no computer is necessary, I still recommend installing an Air / Fuel ratio sensor to adjust the controller, in order to avoid damage to your ATV.

In my opinion, a very important factor is the Air / Fuel ratio, since a bad mix can cause considerable motor damage, with overheating, backfiring, difficulties in starting… In other words, whenever considering the purchase of an injection controller, one should plan the acquisition of a wideband Air / Fuel sensor. The Air / Fuel ratio is a measure that analyses the mix of air and fuel, the perfect ratio being 14.7 :1, meaning 14.7 units of air are mixed to one unit of fuel. This balance is not easy to acquire, the important point being to come as close as possible. According to your driving style and your type of vehicle, you can proceed to different adjustments. Certain racers adjust the ratio by either decreasing or increasing the quantity of fuel according to their type of racing. When decreasing the quantity of fuel compared to air, the motor will seem more nervous, more powerful, but will more easily overheat. For those riders into racing or those who like to ride at full throttle for long stretches, the tendency will be to choose a higher amount of fuel compared to air, in order to avoid engine overheating.

Injection systems installed by ATV manufacturers do not allow modifications of fuel demand when you have added performance parts to your vehicle. These aftermarket parts might necessitate a larger demand in fuel.

In other words, an injection controller will allow you to reach a good Air / Fuel ratio and thus obtain higher performance from your ATV after modification. Certain controllers will permit electronic decrease or increase in fuel demand without having to remove any parts on your ATV. It’s like changing the injectors on the carburetor without getting your hands dirty!

All controllers are programmed for a certain type of vehicle, data bases being different. Make sure to purchase the controller that suits your ATV.

How to choose your controller?

For the purists who own ATVs equipped with more aftermarket parts than stock parts and, of course, with a computer, here is a new product offered by Yoshimura, whose reputation for performance is already known.

The PIM-2 and the Data Box are now available and your injection controller and Air / Fuel ratio sensor can be bought from the same manufacturer. The PIM-2 comes with 400 adjustment points, two basic settings: the first for those equipped with a Yoshimura muffler and the second for those equipped with a complete exhaust system. Different injection curves can be found on the Yoshimura Website, according to the modified parts added to your ATV. The Data Box allows you to set your own Air / Fuel ratio, it will calculate the necessary fuel adjustments for all engine speeds and all positions of the throttle, allowing the desired Air / Fuel ratio. There is no limit to progress!

The Dynojet Power Commander V is also a controller designed for those hard-core ATVers bent on modification. This company offers a wide range of products and also proposes an Air / Fuel ratio sensor with a new system called Autotune, which affects adjustments on the controller while you drive. Several curves are available on their internet site according to your type of ATV and your modified parts. In this company’s case, a solid reputation for quality is also well established.

These two products are designed for those with considerable experience in the preparation of competition engines. The process can be very complicated for the beginner and the projected goal of such an intervention can be difficult to attain.

For those who really want to improve their ATV’s performance, but are less injection system savvy, Dynatek now offers an alternative, which does not necessitate the use of a computer for adjustments. Their injection controller uses three curves of settings based on the level of modifications done to your vehicle. Following installation, all you have to do is adjust the quantity of fuel with a potentiometer for low, medium and high engine speeds. The Dynatek controller allows you to decrease or increase the quantity of fuel to the engine on these three levels independently.

For some of our readers, modifying their ATV should not be a puzzle and should not entail exorbitant expenses. The Dobeck TFI should suit their needs, being one of the most simple injection controllers. Dobeck proposes a system that allows only the increase in fuel. In my opinion, this type of product is destined to customers with less experience in engine and injection system modification who, nonetheless, wish to improve their rides. Setting suggestions are included with installation instructions.

We could continue reviewing more controllers as there are many makes and models on the market, but our main objective is to help you in your choice, according to your capacities. So we have decided to play the game and have chosen to go through some testing for your benefit.

In order to do so, we equipped a Suzuki 700 KingQuad with an injection controller and an Air / Fuel ratio sensor. Our test machine has already undergone certain modifications: the exhaust and the air filter are not stuck, the air box has been modified and the clutch system has been redone by our mechanic. Starting with the Air / Fuel sensor, we choose the AFX model from NGK, reputed for the quality of its sparkplugs. The AFX is capable of reading Air / fuel ratios from 9.00 to 16.00 AFR (Air / Fuel Ratio), with a precision degree of 0.1 AFR. Installation requires drilling a hole through the exhaust and welding on the sensor support. This modification must be done by an expert welder, forget the handyman’s torch; this here is more serious business!

Figure a clearance of 4 to 5 inches for the good sized sensor. Once installed, wiring must be run from the sensor reading to the display. Also figure some space for the display wiring, which is quite long since this model is used for racing and for automobile customization.

NGK provides a threaded nut that will allow you to fill the hole left when the sensor is not in use, as it is recommended not to leave the sensor in place permanently, in order to avoid premature wear. Connection of the display dial goes to the battery and an added switch is necessary (not included). It is not recommended to turn on the sensor without the motor running. We follow all these installation instructions very closely and now we have to find a place to locate the display dial. The support proposed by NGK comes down to a small piece of Velcro of about 2 inches included inside the box. Bear in mind that your dial will come loose on the first bump you hit if you use the model proposed. We choose the Velcro system anyway for simplicity’s sake, but we use a more resistant commercial version.

Now that our sensor, our dial, and our switch are installed, we are onto the controller. For our test, we chose the Dynatek model, simply because I consider it as a mid- range product, not necessarily lacking in quality, but because  it’s not the most simple, nor the most complicated, just in the middle of both extremes. It will allow us to increase or decrease fuel injection with its three different injection curves, without the need for a computer. Installation of this small housing is done through a few connections, without welding or important disassembly, but of course, it will necessitate certain knowledge of the electrical components of quads. As for all modifications, we recommend dealing with professionals. The controller should be installed within easy reach, which will allow for easy settings without constraints.

Ready for a few tests, we first try to set the controller without using the Air / Fuel sensor to verify if its purchase is justifiable. I can confirm to you immédiate, that trying to set the adjustment of the Air / Fuel ratio by trial and error is almost impossible; how do you know if your settings are exact? Furthermore, you are risking damage to your ATV engine. In order to insure that no damage is done to our KingQuad’s motor because of overheating, we added a heat sensor with a dial placed just below the 12 Volt outlet on the front right fender, a small low cost addition (approximately $60) to verify that the KingQuad’s engine remains at the right temperature.

After hours devoted to testing dozens of settings, we come to the conclusion that the Air / Fuel sensor is indispensable, if your controller is to be adjusted for good performance. I now understand why Yoshirama or Dynojet include this indispensable part in their catalogue. The sensor dial allows us to visualize whether the ratio is right. The ideal setting is between 12.5 and 13 AFR and even with this tool, the manipulation of the controller potentiometers was very touchy, since only a slight change in the position of any potentiometer will affect the ratio of the motor speed it controls.

Now here comes my favorite part of ATV modifications, on track testing! I met with Alain, our editor-in-chief on a Sunday morning for a good coffee and a fine joyride. This long awaited day is not the best weather wise, it’s raining, it’s dark out and it’s cold! But the whims of Mother Nature will not stop 2 thrill seekers such as we are. The 12 kilometer circuit where our testing occurs is beckoning us. After warming our engines, we decide to push the King a little harder. Honestly, the difference felt from the controller appears more evident at low and medium engine speeds, the engine pickups on the KingQuad are superior and we experienced no difficulty in sliding the rear just by pushing the throttle in turns. A small thrust on the throttle just before a bump will send you flying over on the back wheels without difficulty. There is so much water that we have trouble keeping our protection goggles on, water is even seeping all the way to my ears despite my helmet, but we keep on going relentlessly. I keep on checking my Air / Fuel ratio as often as possible and, to my great surprise, in spite of all this water, it still keeps on functioning properly. NGK claims the instrument resists splashing, but is not waterproof.

In short, an injection controller and an Air/ Fuel sensor are 2 necessary parts for modifying an electronic fuel injected ATV, but bear in mind that the cost of the set will be quite high, say anywhere between $500 and $800, something to consider! Just as importantly, do not miss the next issues of ATV Trail Rider, as we will present a very interesting product that could compete with fuel injection controllers, that’s all I will say for now…