How to

Performance Tuning

Performance tuning is a subject that has been written about, argued upon, concluded upon, sworn upon, cursed upon, given up on and eventually, once in a while, savoured by generations of motorcyclists. Most of the people think that if they enlarge the exhaust port and install a free flow silencer, their bike will fly. The slightly smarter ones know that a filter and a big jet are needed too. Spare a thought to the intelligence of the manufacturer. They would have done it themselves, no?

It’s like the great equalizer. Any country, any race, any era. A boy with dreams of building the best engine goes through the same lessons, the same mistakes, the same epiphanies and the same moments of exasperation, the same moment’s adrenaline-rush. And the next generation does it all over again. And it’s so much fun, no one complains.

In this series of articles, I shall attempt to outline what you should know about getting into this controversial yet delectable world of increasing the punch in your motorcycle. It does not include everything and does not turn you into an overnight tuning champ but is intended to give you a an excellent platform to start with, and saves you the time of learning the mistakes that people have learnt thousands of times already.

Let’s first, ever so boringly, look at the building blocks of power and its basic aspects. You can’t come out with a work of genius with just knowing what you are doing. You must know why you are doing it too.

Performance:

Its how a thing performs. If the performance of an engine is good or bad, is a matter of opinion, or rather, function. The track racer won’t appreciate the fact that a motorcycle is so efficient in using fuel that it gives you 75 kilometres on a litre of petrol. It is still good performance. Yea, pretty obvious so far, but read on.

Power v/s Efficiency:

This is not to say an efficient engine is a low powered one. Engines that produces a lot of power, say a 100bhp and still wastes a lot of it is low in efficiency. And one that gives the same 100bhp with lesser fuel consumption is higher in efficiency but equally powerful. The reason this needs to known is that in a low efficiency engine one can gain power by modifying the engine to reduce wastage. On the other hand, expect an increase in fuel consumption if you have set out to increase power in an engine that already scrounges for the last drop of petrol. It would help to note that generally high-powered engines tend to be lower on the efficiency front.

BHP: The number preceding the letters ‘bhp’ pretty much decides the amount of respect one has for a motorcycle. So what determines this bhp? Apart from the obvious fact that a big engine and bad-ass tuning will give you lots of power, let’s delve deeper into what builds power, since we are planning to make some ourselves.

Let’s look at the term. Horse Power. In its original crude and raw sense, it’s the number of horses that are pulling your motorcycle. So in the real sense, what is producing the power? The blast above the piston? The spin of the flywheel? Since we are going to work with technical terms, let’s put them each in their place as relevant to a motorcycle

Power: Well, technically speaking, power is a product of force, time and distance. In the layman’s term, it’s simply the ability of an engine to do some work. It’s obvious that pulling a train and riding at 300kph both are a lot of work. But both are still so incomparable. All right, let’s get down to the details so we can sort this simple yet unclassifiable concept.

Power = Work * Time

Power = [Force * Distance] * Time (Work = Force * Distance)

Work: It’s a known word, yet technically we need to define it within its limits of usage.

Work = Force * Distance

Force: Force is a “push or pull that can cause an object with mass to accelerate.” In engine terms, called the MEP, or Mean Effective Pressure.

THIS IS THE PUSH AT THE PISTON CAUSES BY THE BLAST THAT IS CAUSED BY IGNITION OF PETROL-AIR MIXTURE.

All right, now we are talking! Let’s reverse-engineer these boring formulae. So your plug ignites a blast that produces the force(1). The piston moves from top to bottom. Distance!(2). And finally this takes some time. The faster it moves up and down, the higher your ‘rpm’(3) is.

There we go. The next time you want power, go for one of these three things. Let’s make these formulae a bit more relevant.

Motorcycle power = MEP(Force) * Stroke of the Piston(Distance) * rpm(Time)

Now that we have these things in perspective, we can get technical and get down to the facts instead of guesses whenever we need to know why something is losing out on power.

Well you still can’t step out to the garage and make the bike fly huh? Well for that we need to get down to the details of how and what to do in order to boost these three pillars of power.

Brace yourself for the second part of this article on Motorcycle Performance Tuning, which would be posted soon.

Performance Tuning – part 2, Fluid Flow
Performance Tuning – part 3, Ignition
Performance Tuning – part 4, Power Transmission

2 Comments

  1. Man, U r just AWESOME,
    Thnx for guiding us.

  2. Pingback: Performance modifications for Yamaha RX 135 - India Travel Forum, BCMTouring.com

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