Booster Plug – What Sorcery Is This?
Let me start by telling you something that all of us motorcyclists experience but never could really put a finger on. The most common ways to describe would be a jerky throttle, sudden jumpy acceleration, stalling, or ‘it just doesn’t feel right!’.
This ‘just doesn’t feel right’ is more evident in fuel-injected motorcycles, especially in the lower revs.
Booster Plug claims to fix this problem. And let me cut it short. It Works! Surprisingly well.
And, if you don’t care how it works, just get one. For details to where and how you can get one, scroll down to the end of the post. You can thank me later!
Read on, I know some of you want to, if want to know how this device works. I’ll try and keep it simple.
Nowadays, with electronic fuel injection, you would expect motorcycle throttle response to be smooth as a hot knife through butter. However, most of the new age motorcycles have a jerky throttle response. Especially at low speeds. It feels like one of those fan regulators which is either full speed or no speed. No linear change in speed. Not only is this annoying but also tricky to get a steady throttle input in corners, often becoming a bigger problem in wet and slippery conditions.
The throttle doesn’t just control the acceleration but also has a major influence on our motorcycle’s handling as well as weight transfer, steering, and stability. If it’s linear and smooth, this is reflected in our riding performance. We expect new age motorcycles to have a smooth and accurate throttle response. But, in fact, the throttle response is worse when compared to even the age-old carburetors.
Why? In one word, emission laws. Right, that’s two words.
Engines are far more efficient and powerful than ever before however the ever-tightening emissions laws also mean that engineers have to run the engine lean at certain speeds where emissions are measured in the power curve.
Of all the strategies to clean up emissions, such as air injection and catalytic converters, the easiest and cheapest method is to reduce the amount of fuel injected into the engine or in other words run a lean air to fuel ratio. An ideal air to fuel ratio is around 15 parts of air mixed with 1 part of fuel. Lower the ratio of air, the engine runs rich. Increase the ratio of air and it runs lean. To achieve maximum power and quick speeding/overtaking, the engine needs a rich mixture. However, to achieve emission norms the engine needs a leaner air-fuel ratio of around 16:1 to 17: 1. This mixture burns slowly and irregularly. Thus, it results in power loss and a jerky throttle response.
This fueling is generally controlled using the Lambda, also known as the O2 sensor in your exhaust pipe which measures the air to fuel ratio while a control loop mechanism in the ECU adjusts the engine’s fueling to match the target mixture. Now you might say, won’t the ECU send in extra fuel when you accelerate suddenly to compensate? Well, it does but there is a delay, and is not fast enough to match the inputs of your throttle response. It doesn’t work linearly when you go through multiple changes of inputs like it happens during a low-speed city ride or sudden acceleration. Remember this ‘delay’ for later.
Now that you know how the Air-Fuel ratio is relevant and how a lean or rich mixture can affect the way your motorcycle runs, let me tell you how the Booster Plug fixes the throttle response issue.
The most important data for the Booster Plug is the Air Intake Temperature and the Closed Loop system. In principle, the Booster Plug alters the Air Intake Temperature part of the equation into making the ECU think it is 20 degrees Celsius lower than the actual temperature. Why 20-degree? Because every fuel injection ECU will enrichen the fuel mixture by 3% for every 10-degree drop in temperature. So, a 20-degree drop will result in a mixture that is 6% richer than normal. This proportion is constant for all modern vehicles because it depends on the density of air molecules and uses the same fuel, which is constant for all vehicles. Why only 6%, you might ask? 6% is the sweet spot that the blokes at Booster Plug figured out. The richer fuel mixture makes the engine run smoother and results in more linear throttle response. But any richer, and you will lose those benefits.
Aren’t you forgetting something? That lambda/o2 sensor? When it detects that the mixture is running rich, will it not tell the ECU to make the mixture leaner and thereby undoing everything that the Booster Plug did? You are correct, it would. Did I not tell you to remember the ‘delay’? The lambda/o2 sensor functions best when at a constant speed. The o2 sensor is not fast enough to act against the richness, at the variable response on the throttle, such as acceleration or overtaking. This is a loophole the Booster Plug exploits. In simple terms, it goes dormant and lets the ECU play its role as tuned when at cruising speeds. This even leads to be a good fuel efficiency due to the lean mix while cruising. As soon as you apply the throttle, the Booster Plug input to the ECU is back in action and you get a richer mix, to go booming again.
Installing the Booster Plug is probably the simplest mod you can ever do on your motorcycle. The units sold come specifically for the motorcycle because it comes with the connectors which match those connecting the ECU to the Air Intake Temperature sensor. The unit simply bypasses the signal sent from the Air Intake Temperature sensor to the ECU. The external temperature sensor on the Booster Plug should be fixed away from the engine heat. I fixed it near the air intake duct. In theory, any Booster Plug will work with any fuel injected motorcycle as long as you can figure out the connectors to bypass the connection between the Air Intake Temperature sensor and the ECU. I mentioned the last point for motorcycles, for which, the Booster Plug is not yet available.
The Booster Plug works as it claims, simple to fix, simply smoothens the experience of riding the motorcycle by fixing the one nagging issue with most fueling systems on our motorcycles. I did not find a drastic change in fuel efficiency either, possibly because of its mechanism to go dormant when at cruising speeds. The instant change you will notice on the Himalayan is that it reduces the stalling issue at cold starts. There is no need to pump the throttle to keep the engine at idling speed. Then the whole smoothness and throttle response, in both trails and highway cruising alike. I even managed to cruise at 135-140kmph stress-free, which was unimaginable on a Himalayan earlier. It does feel like a different motorcycle. Who knew a small change in your motorcycle’s throttle response will go such a long way in getting a better experience.
Those of you who want to drown in more technical reading, head over to the manufacturer website here. Feel free to shoot some comments my way, incase you have any questions.