Stuff You Need to Know Before Modifying Your Exhaust : BikeAdvice

Stuff You Need to Know Before Modifying Your Exhaust

Posted: 24 Jun 2011 11:08 PM PDT

Original Source: Stuff You Need to Know Before Modifying Your Exhaust from BikeAdvice.in

The automobile plays an important role in the transport system of India. With increase in population and living standards, the vehicle population also increasing day by day. There is steep increase in the number of two wheelers during the last few years. All this are increasing exhaust pollution and particularly in metros as density of these vehicles is very high. As we know, more the emission, more the amount of fuel we have to burn in engine.

Fuel consumption is directly depends on working conditions of an engine. Particularly for two wheelers, an extensive analysis of energy usage and pollution shows alternative power systems are still a long way behind the conventional ones. Moreover many bikers uses modification in their exhaust to get so called exhaust tune and sporty look.

Here is the live example of it. He has converted his normal TVS bike into dirt bike and exhaust has been modified to get sound like dirt bike. I saw many FZs, FAZERs and other bikes with modified exhaust like R1. Then I decided to observe the effects of this modification and I had performed one experiment.

Engine does a process called scavenging in between completion of exhaust stroke and starting of suction stroke. This process is for removing the burned gases from the cylinder with the help of fresh charge.

The scavenging efficiency of engine is directly affected by speed of the engine, exhaust valve opening, exhaust port dimensions, exhaust pipe location and position, dimensions of catalytic converter, muffler design. All these parameters finally affect the back pressure of exhaust. Back pressure in the exhaust is required to remove the gases from exhaust pipe.

After completion of exhaust stroke, Pressure in the exhaust pipe becomes more than the atmospheric pressure. Because of this, gases flow automatically from pipe to the atmosphere with high velocity and produces tune that we listen from exhaust.

Now to get the smooth (Nearly Laminar) flow of exhaust gases, designer keep the value of back pressure within limit by introducing slant in muffler (You can observe this slant in each bike above 125 cc), muffler design, path travel by gases etc. according to the capacity of engine. Now at the time of modification, we are influencing following parameters:

First of all we are increasing the total length of exhaust because of which the path travel by the gases increases. Now as the gases have to move long way, velocity developed in the pipe decreases by the time. As per the rule, velocity and pressure are inversely proportional. So finally pressure will increase and flow gets chocked. (Chocking means drop in velocity of exhaust gases drastically. It doesn't mean the zero velocity. If the velocity becomes zero then we can't run the engine anymore. But as we are introducing more and more gases in the pipe after each stroke, the gases finally reaches to the opening of pipe. But the velocity is too low then the required.)
As we are increasing the exhaust pipe length, we are introducing more bends in the exhaust pipe. Each bend causes flow restriction and friction losses in the gas flow. This leads to chocking of flow again.
As this two major factors result in chocking of flow, the next batch of burned gases coming out from cylinder don't find any way to move.
Finally the scavenging efficiency of engine reduces drastically and burned gases remain in the cylinder. These burned gases got mix with the fresh charge and burnt again and again. This process leads to generation of more emission.

Experimental Setup

So to check the above said effects of modification, I performed an experiment. The figure indicated here illustrates the HH PASSION just for outlining the set-up. In real experiment, I used other bike. I increased the slant of exhaust pipe up to 90°.

Because this is the maximum angle likely to be exerted at the time of modification. 3000 to 5000 RPM was selected for the test because in usual driving practice this is the most common operating range.

First, I measured the performance with original angle provided by the company to get the standard data. The next step was to carry out the performance test with various changed angles of exhaust opening. Changed exhaust manifold angles would result as higher fuel consumption, low brake thermal efficiency, and high exhaust emission. Below fig indicates my prediction I made before test and also illustrates the changing angle of exhaust.

The above figures indicates the total experimental set-up used for the test. Now I directly switching over to result I got from this test.

Results

The value of back pressure for 90° is approximately 3.2 times more than the standard value.
Back pressure value increases 0.08 KPa with increase in manifold angle by 1°. This nature of back pressure is applicable up to 60°.
After 60°, the increase in back pressure turns out to be 0.44 KPa with 1° rise in manifold angle.
Fuel Consumption increases 7.93 gm/hr with increase in manifold angle by 1°.
Thermal efficiency of engine decreases 0.17 % with increase in manifold angle by 1°.
HC emission increases 2.60 ppm with increase in manifold angle by 1°.
CO emission increases 0.054 % with increase in manifold angle by 1°.

So guys, here you have the results of modification done in exhaust. I did the modification only with opening angle of exhaust; many other factors are yet remaining to be examined. Many other factors also contribute to these effects.

You can judge the results what if all the factors contribute together. This is what generally happens when we modify our exhaust with local dealers or garages. We blindly are increasing pollution and fuel consumption of our bikes. Many calculators are available on net for calculating correct required back pressure for your bike engine. You have to insert some technical specifications and it will provide you the correct back pressure.

I personally suggest you not to modify your exhaust ever. Because it is optimum design provided by the manufacturer and designed by their best designers. Even then if you are so passionate about noisy bikes (there is vast difference in tune and noise), first you get the calculated back pressure and then get the correct dealer for correct exhaust.

- Dhruv Panchal

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YikeBike – The New Face of City Commute

Posted: 24 Jun 2011 10:05 PM PDT

Original Source: YikeBike – The New Face of City Commute from BikeAdvice.in

The days are gone when it was only difficult to park a four wheeler in a busy street or in some vague corner of the city. The difficulty is now the same in parking the bikes as well. How good would it be if you can fold your vehicle and take it along with you? Above all, if you can put your vehicle in a bag and take it along with you wherever you go? Adding to it, if it doesn’t need fuel to run, wow, its just amazingly great to think. Well, these are not my mere imaginations. It's a live product available in many countries. Wanna know what that product is? Well, it is the YikeBike. YikeBike is World's first super light electric folding bike.

To mention a word about the manufacturer, The Christchurch Company which makes YikeBike won the Dell Innovative Hi-Tech Hardware Product award at New Zealand recently. YikeBike comes into two versions: Carbon aka the high-end one and the Fusion aka the low-end bike. The bike was also featured at #15 in TIME magazine's list of top 50 innovations in year 2009.

This electric bike has a running range of 10 km with the capability of attaining a top speed of upto 23 kmph. The YikeBike weighs just 10.3 kg and is made of carbon fibre composite frame and is powered by an electric brushless DC motor. The source of power is a LifePO4-40 min re-chargeable battery. The YikeBike can be folded or stretched to its original form in less than 20 seconds. The front wheel is 20 inches and the rear 8 inches in size. In the folded form, it occupies a volume of 43 litres

"We created the YikeBike to dramatically change urban and suburban transportation, providing users with a fast, safe, cost-effective, eco-friendly way to navigate their cities and towns," said YikeBike CEO Grant Ryan. "The original, upscale, carbon fiber YikeBike generated tremendous interest among early adopters when we unveiled it in late 2010. This led us – in record breaking time – to design the more mainstream YikeBike Fusion, which uses conventional materials to make it more appealing to both cost-conscious and energy-conscious consumers."

This bike is pretty similar to the Segway in terms of catering its purpose. Both are ideal only to be used within the city and for a short distance only. But, this is differentiated from the Segway in terms of its design concept.

The YikeBike is an ideal bike to be used at night times also. It comes fitted with High Vision built in LED lights which will be constantly glowing always. This enables the rider and the bike to be noticed by the passers irrespective of it being day or night.The YikeBrakes are also known for their safety being offered. Thought these are very small machines capable of carrying just one rider, safety is given a top priority at the time of conceptualizing this bike. This is proved by the very fact that the YikeBikes comes fitted with anti-skid regenerative brakes. This enables the rider to ride the YikeBike even on wet roads without compromising on the riding confidence.

But, why does the YikeBike need a special mention at this point of this. I'll tell you why. At this perid of time, when we hear of petrol price being hiked every now and then, the YikeBike costs you a meagre US$0.01 for every km that you ride on it. It is hardly 45-50 paise for every km. This is, of course fine to use in roads, but wondering how to carry this once you reach your office, school, college or whatever? Its very simple. You gotta fold it and either put it in the bag which is given exclusively to carry it or you can even fold it and take it along with you just like that. That's how it is designed. (This even reduces the expense of buying a lock for it!!)

The large 20 inches front wheel is capable of taking any bumps or small pits in the road without much strain andl even worrying about reducing the speed at which you are commuting.

The bike is ideal for those who are interested in reducing their Carbon footprints thereby leading a sustainable life with a Green Badge to promote eco-friendliness.

The interesting point is the price at which you can get your hands on a YikeBike. The YikeeBike Carbon which is made out of Carbon Fibre is priced at US$ 3795. This is the one which weighs the above mentioned 10.3 kg. In Indian currency it is (just) around 1.78 lakhs and the YikeBike Fusion which weighs 14 kgs cost US$ 1995, which comes to around INR 93,765 (only).

When you book a YikeBike, you get a Charger, a Charger Cord suited to the delivery country, a user manual, a carrying strap with which the YikeBike can be carried along with the user and a toolkit along with tyre inflator and the keys.

The YikeBikes are available in a range of 6 stunning colours. The colours available are Carbon Fibre which is the standard colour, Silver, Red, White, Green and Blue. Many corporate giants including Google are customers of YikeBike. Apart from this, YikeBike is featured in many magazines and have received great reviews too.

The company claims that every YikeBike comes with complimentary telephone/email support for two years. In addition there is a full 1 year warranty where the company takes care of the pickup and return courier of your YikeBike. There is also a full range of service videos online so you can easily replace tires, adjust steering, etc.

Also, the company offers global delivery of these YikeBikes is the form of a package straight to the doorstep irrespective of the country where it is to be delivered and the delivery period is just one week.

So are you all set to book one! Is it worth the price? What is your say on the YikeBike. Have your word below.

Regards,
M.Naren.
Author – BikeAdvice.in

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Saturday, June 25, 2011