Is it time already?

After more than half a decade, is it time that we'll part our ways?

You've taught me a lot and we went through even more together...

Memories of the time we spent together can never be erased...

As we part ways, I hope that you can look forward to a better companion who is able to take good care of you. To experience the freedom of the highway, giving a good workout to yourself as well as him.

Not longer is 200km/h the baseline for cruising... No longer is 100km/h achieved in a single gear... No longer is a twist of throttle like a jab of adrenaline into the body...

I remember the time I was still confused on how a simple change of exhaust will affect the power delivery. To the point where the engine was laid out in pieces for a major rework for the transmission to the cylinder block, to the cylinder head...

Having been with you for so long, with all the refinements that we worked through. It'll take a long while before something that will come close to what you are comes along as a stock production bike. It'll be quite hard to look at another Hayabusa without remembering how different you are.

Together, we experienced the hot, the cold, the dry, the wet, the dirt, the dust, the highways and the trunk road. You have even been there on the most important day of my life, my marriage and was featured in the video during the wedding dinner...

Go forth and spread your wing, Peregrine Falcon, or as what we know you as Hayabusa - 隼! Dominate the straights and the bends! Let no other bike show you otherwise. For the stronger and nimbler you; can dance like a butterfly and sting like a bee! Be that Ultimate Predator, my friend!

Good bye, Hayabusa K Spec II

Till we meet again!

Vapour Lock

Owners of the 1999 and 2000 model of the Suzuki Hayabusa may face this problem when they were to increase the engine compression (in one way or another); resulting in higher ambient temperature under the fuel tank. Add to that equation a in line fuel filter, it's a very good recipe for vapour locking the fuel system.

According to wikipedia,

Vapor lock (also known as vapour lock) is a problem that mostly affects gasoline-fueled internal combustion engines. It occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient loss of power or complete stalling. Restarting the engine from this state may be difficult. The fuel can vaporise due to being heated by the engine, by the local climate or due to a lower boiling point at high altitude.

The 99-00 model of the Suzuki Hayabusa utilises the external fuel pump as opposed to the in-tank fuel pump from 01 model onwards. This provides the opportunity for vapor lock to occur. The external fuel pump runs 2 fuel lines, 1 inlet and 1 return line. The inlet is gravity fed and is not pressurized. This allows the fuel to vapourize when the engine compartment temperature rises too much due to heat soak.

The fuel pump when moved to the interior of the tank helps prevent vapor lock, since the entire fuel delivery system is under high pressure and the fuel pump runs cooler than if it is located in the engine compartment. Under high pressure the fuel will be harder to vapourize and thus vapour lock is almost unheard of in K1 models and above.

What are the causes of vapour lock?

A vapor lock is more likely to develop when the vehicle is in traffic because the under-hood temperature tends to rise. A vapor lock can also develop when the engine is stopped while hot and the vehicle is parked for a short period. The fuel in the line near the engine does not move and can thus heat up sufficiently to form a vapor lock. The problem is more likely in hot weather or high altitude in either case.

What are some solutions if you have a vapour lock issue?

1. Rerouting of the fuel lines away from heat generating components,
2. installation of a fuel cooler or cool can,
   
3. shielding of heat generating components near fuel lines,
4. and insulation of fuel lines.

Amongst the above suggested solutions, you can also consider swapping to an in-tank fuel pump which requires the replacement of the entire fuel tank, fuel pump some fuel line fittings. I have personally tried items 3 and 4 with good results.

If you have a fuel problem, do check if it is caused by vapour lock. You would want to be caught stuck in traffic with a stalled engine and unable to start due to the vapour lock issue.

Signs of not riding enough

Doing long distance rides is an endurance sport. It requires a certain level of physical fitness as well as the mental alertness.

Physical fitness comes in the form of core muscle strength; to maintain in the fully or half tucked posture. Neck muscle to sustain the forces exerted by the wind on the helmet.

Mental fitness to concentrate and to react to the environment. Especially when things come hurling towards you at crazy speeds.

Just went for a relatively short touch and go trip today. Distance back and forth was barely 200km. But by the time I'm back. I could feel the ache on the back and neck. What used to be a ride in the park can really take a toll on you if you are not adequately acclimatized to it.

All in all it's the body's way of reminding me the importance of constantly riding to keep the physical and mental endurance in check. Not just the above, it'll also allow for the practicing of the skills essential for a safe ride.

Till then, have a safe and fun time on the road.

Shell's transparent car

A rare glimpse of the interior of an engine as it is running and lubed by the engine oil. Real big budget production by Shell.

Finding time to ride

What used to be an integral part of life, riding has since taken a step back in the long list of things to do in this hectic life.

Excuses for not riding includes tiredness, bad weather; too cold, too hot, non enjoyable route to ride, need to bring car out for ferrying large items, and it goes on and on.

Week in week out, the weekend objective is to ride my bike. To date, the success rate of meeting out the objective is 50% at best.

Today, after a week of rest for the bike, it out again. Hitting a short highway before reaching the Upper Thomson road prata shop. It has now become the futile attempt to put in some decent riding mileage.

As far as it goes, such short sprints like this, are still keeping the fun in riding until some decent trip comes along.

Till then, enjoy the freedom and breeze of the highway that riding brings.

BMW S1000RR

One of the most challenging circuit in the world. Used as a benchmark for many automakers. The BMW S1000RR challenges the Nürburgring Nordschleife.

Exhaust Performance and Scavenging

A very clear and concise explanation of the process of exhaust gas scavenging and how it's affected by exhaust size, length and cam timing.

The Basics

As are most things automotive, the exhaust system is a compromise. It must balance noise and performance. In addition, the exhaust system can be designed to increase performance in the low RPM range or at the top end. All of these aspects must be taken into account when designing the best possible setup for a given application. A larger pipe diameter typically will reduce backpressure allowing the engine to expend less energy pushing out exaust gas. If the system was being restricted, this will result in more power at a certain range of RPMs. The downside to larger pipes is a loss of power in other areas of the power band and increased noise.

Scavenging

At first glance one might think that a maximum pipe size would result in the best performance. It should provide the most flow. This is true for a steady stream of gas. An engine ejects exhaust gas out of the ports in pulses though. This results in a stop-go-stop-go situation as the exhaust valve opens and closes. A properly sized pipe will help to suck the gases out of the cylinder at certain RPMs. Since air has mass and velocity, it has momentum. When in the scavenging RPM, the exhaust charge exiting actually creates a vaccum for part of the exhaust stroke. This provides for a nice boost in power and torque. For ideal scavenging an exhaust speed of 240-260 feet per second is desired. Thus as engine speed increases for a given displacement so must the pipe diameter.

Below is a typical graph of exhaust port pressure vs. piston position:


NOTE: The exhaust pressure during scavenging nets out to be positive. Thus there is not an all around vaccum. Energy is still being wasted pushing exhaust gas out. The scavenging is not "free". Work is still done. Scavenging merely helps to aliviate what would be even more work being done by the engine. Also note that the psi values will vary from engine to engine, but the curve remains approximately the same. Values over 6 psi are generally considered excessive backpressure.

The graph above is a typical representation of what exhaust port pressure looks like as the engine rotates through almost a full revolution during the scavenging RPMs. Exhaust pressure builds as soon as the exhaust valve opens. This occurs before bottom dead center. Most of the torque the engine generates is produced by 90 degrees, thus it is not necessary to keep the exhaust valve closed much past 90. By opening the exhaust valve early, the high cylinder pressure helps to accelerate the charge in the exhaust manifolds. Pressure peaks before bottom dead center and then rapidly falls as the accelerated charge pulls the exhaust out of the engine. As the piston approaches top dead center, the intake valve opens. Pressure drops again and the exhaust gas actually helps to suck the intake charge into the cylinders.

These ideal conditions can only be met at certain RPMs. To do this one can vary the size of their piping to chose what will provide them the best performance. Smaller pipes will move an equal volume of gas at a higher speed. This typically comes at the expense of increased backpressure (resistance to flow) which inturn leads to poorer performance. A smaller pipe will help to maintain the ideal exhaust gas velocity when the engine is running in the lower RPMs. This provides for a torque boost off the line with improved streetability and driveability. For this reason many manufacturers size their pipes on the more conservative side. As the RPMs increase though, the backpressure builds due to the excessively small pipe size. This pushes the velocity of the exhaust gas out of the scavenging range and saps power on the top end, reducing performance in that spectrum.

A larger pipe will maintain ideal exhaust gas velocity on the top end. This will increase peak power. The downside comes with a slow exhaust charge on the low end. Their will not be enough suction to aid in the expulsion of exhaust gas. Torque will suffer in the low ranges for this reason. Too large or too small of a pipe will push the scavenging bonuses out of the useable RPM range and will result in diminished overall performance. It is important to size the piping correctly for the desired application: low end or top end. One should also consider how this will effect the rest of the car. For instance, if the car has an automatic with a stall speed of 1,500 RPMs it won't do any good to have all the power on the top end when off the line performance will suffer terribly. Likewise if the car is mainly driven in the city or through heavy traffic, a lack of low end grunt might make driving more of a chore.

On valve overlap scavenging also helps to draw in the fresh intake charge. The pressure in the exhaust port drops again and the exhaust flows more easily. It should be noted though that too much exhaust velocity on overlap can cause "over scavenging". This occurs when the exhaust vaccum becomes so great, due to overly small tubing, that it actually sucks the intake charge right through. This leaves spent charge in the cylinders and causes a loss in performance.

Common Views

A couple of commonly recommended modifications are increasing backpressure for lowend performance, and the use of equal length headers. Backpressure is almost always a bad thing. The higher velocity of a smaller pipe is what one wants on the low end. Unfortunately this ultimately chokes off the top end to an extent. Since these two go hand in hand (small pipes and top end back pressure), people often consider them the same. They are not. Putting a sharp bend in a pipe will cause high backpressure, but it will have little benefit for performance and scavenging. Backpressure is very useful for quieting an exhaust though and muffling the sound waves. As for equal length headers, companies often claim that they help with scavenging. They are used to line the exhaust pulses up. This can help during scavenging as the exiting charges will not try to occupy the same collector at the same time. Instead, the exhaust pulses will alternate and "zipper" there way into the collector. This results in smooth flow and optimal performance. Equal length headers, or headers designed to take advantage of scavenging in general are a plus. It is important to buy from a reputable company though as equal lengths will not guarentee optimal performance. Dynometer testing is the best way. Most reputable exhaust companies do make use of a dyno which gives some assurance as to what one is getting.

Summation

1. Choose a smaller pipe for better low RPM performance, a larger one for high RPM performance.

2. Remeber that peaks are not everything, as seen in Understanding Performance, thus a proper sized pipe will deliver better results than one that may give the highest peak low end or top end performance.

3. Back pressure is almost always a bad thing.

Article from: http://autolounge.net/tech/exhaust.html