Sunday, November 21, 2010

ECR Ride - Alamparai and Pondy

"The journey is in itself a destination." This quote was experienced first-hand yesterday.  The ride through the ECR (East Coast Road) to Pondicherry which is about 130 odd kilometers may be a routine thing for many bikers in Chennai and a total of 300km ride in a day is definitely not a "Saddle Sore" ride. But the different weather conditions which we encountered along the way in such a short distance was awesome. Torrential downpour, sunny sun, sandy sand, knee deep water, wet roads, damn roads, bone dry roads etc.

The day started for most of us at 5.30am and everyone one where geared up and ready at the starting point (Besant Nagar beach). As everyone ready to leave the heaven's opened. We waited for 15 mins there was no sign of rain stopping. We decided to start anyway and Amith on his C500 took the lead followed by Siva on his C350, Ramkumar on his C500, Mothi and Selvam (pillion) on TBTS, Rajesh on his spanking new Apache RTR 180 and I was in the sweep. Before we could hit ECR we had to ride through almost knee deep water at places and everyone got wet to their bones in the first few kilometers itself. We hit ECR and the within 10 minutes of riding the rain stopped but the roads were really wet. We road on a single file formation. We took a couple of breaks in-between. I was forced to ride behind Rajesh and he couldn't go more than 60kph because he was running-in his bike. It was very frustrating and finally we reached Mahabs were we had a decent breakfast.

We were in no hurry and slowly puttered our way back to ECR from Mahabs and kept riding. The roads were damn neat, damp and so no dust and pleasant weather but overcast but all of us were still wet. And 60kph speed didn't help the drying process either. After Kalpakam I lost my patience and ripped. The Megaphone was roaring to glory and comments I got from the fellow riders was that even their listening to music and riding at 60-80kph the only thing they heard was me zipping past them. Maybe thats when I realized that Megaphone was a bad idea for group rides as its prone to irritate others. But that being said "Loud pipe does save lives." I saw people crossing the rode at intersections and when I was riding slow I had to blow my horn considerably to alert my presence. But that also didn't help sometimes because these folks are used to blaring horns. Different story when I ripped. People were running for their lives and no one in that vicinity had the balls to step on the road.

Reached Alamparai Fort by 10ish. Scouted the place for few minutes and decided to take the bike up the sand path up to the backwaters. Here where all the fun started. About 400m of off-roading. The bikes slipped and slided. It never for once go in a straight like and the OEM zappers are no good for off-roading. By this time Amith and I reached the backwaters and headed back on foot to help the others. Everyone struggled except for Mothi :D. All the bikes picked up sand and sprayed it on the brand new Apache. But eventually everyone made it to the top and were satisfied.

The location was perfect and the sun started to shine. Perfect place to relax and dry our clothes. Some explored took a swim in the backwaters, some explored the fort and some just lazed around. We spend mre than an hour and next time we have to buy some ration before coming here.

We started to Pondy and reached Promenade by 12.30pm... Relaxed for while at the Leather Bar and headed towards "La Terresse" for pizzas and sizzlers. We tanked up the bike and by that time we were ready to head back it was 4.15pm. We decided to have just one re-grouping point at Kalpakam. Mtself and Amith maintained and good speed of 80-90kph while Mothi was at a brisk 70-80kph and Ramkumar at a sedate 60kph and Siva didn't have an option and had to tag Ram. Myself and Amith stopped at a backwater for some final snaps of the trip and reached Kalpakam for the re-grouping. 

Now it was officially dark and we could see thunderstorm at the horizon. Me wanted to get back home at the earliest because a headache started to creep up. Switched on the driving lights which proved to be a life saver  when traffic from the opposite side were on high-beam. Ripped through the damp roads and then it started raining for a bit. The headlight glare was blinding but didn't give a damn. Concentrated hard and reached home by 8. Within 30 minutes everyone reached their home safely. Me had after effects. The food at La Terresse made me sick and had to throw up what ever I had for lunch. Grr.. I guess the meat was not cooked well and decieded not to go there from here on and stick with Promenade or Rendevous for food.

Butr whatever the be the case, ride along ECR has no parallels. Flawless roads with beautiful scenery. We never get tired of riding there. As far as I'm concerned, "There is ECR then there are roads". 

Friday, November 12, 2010

Exhaust backpressure myth busted

Destroying a myth.

Some say that "an engine needs backpressure to work correctly." Is this true?

No. It would be more correct to say, "a perfectly stock engine that cannot adjust its fuel delivery needs backpressure to work correctly." This idea is a myth. As with all myths, however, there is a hint of fact with this one. Particularly, some people equate backpressure with torque, and others fear that too little backpressure will lead to valve burning.

The first reason why people say "backpressure is good" is because they believe that increased backpressure by itself will increase torque, particularly with a stock exhaust manifold. Granted, some stock manifolds act somewhat like performance headers at low RPM, but these manifolds will exhibit poor performance at higher RPM. This, however does not automatically lead to the conclusion that backpressure produces more torque. The increase in torque is not due to backpressure, but to the effects of changes in fuel/air mixture, which will be described in more detail below.

The other reason why people say "backpressure is good" is because they hear that cars (or motorcycles) that have had performance exhaust work done to them would then go on to burn exhaust valves. Now, it is true that such valve burning has occurred as a result of the exhaust mods, but it isn't due merely to a lack of backpressure.

The internal combustion engine is a complex, dynamic collection of different systems working together to convert the stored power in gasoline into mechanical energy to push a car down the road. Anytime one of these systems are modified, that mod will also indirectly affect the other systems, as well.

Now, valve burning occurs as a result of a very lean-burning engine. In order to achieve a theoretical optimal combustion, an engine needs 14.7 parts of oxygen by mass to 1 part of gasoline (again, by mass). This is referred to as a stochiometric (chemically correct) mixture, and is commonly referred to as a 14.7:1 mix. If an engine burns with less oxygen present (13:1, 12:1, etc...), it is said to run rich. Conversely, if the engine runs with more oxygen present (16:1, 17:1, etc...), it is said to run lean. Today's engines are designed to run at 14.7:1 for normally cruising, with rich mixtures on acceleration or warm-up, and lean mixtures while decelerating.

Getting back to the discussion, the reason that exhaust valves burn is because the engine is burning lean. Normal engines will tolerate lean burning for a little bit, but not for sustained periods of time. The reason why the engine is burning lean to begin with is that the reduction in backpressure is causing more air to be drawn into the combustion chamber than before. Earlier cars (and motorcycles) with carburetion often could not adjust because of the way that backpressure caused air to flow backwards through the carburetor after the air already got loaded down with fuel, and caused the air to receive a second load of fuel. While a bad design, it was nonetheless used in a lot of vehicles. Once these vehicles received performance mods that reduced backpressure, they no longer had that double-loading effect, and then tended to burn valves because of the resulting over-lean condition. This, incidentally, also provides a basis for the "torque increase" seen if backpressure is maintained. As the fuel/air mixture becomes leaner, the resultant combustion will produce progressively less and less of the force needed to produce torque.

Modern BMWs don't have to worry about the effects described above, because the DME (car's computer) that controls the engine will detect that the engine is burning leaner than before, and will adjust fuel injection to compensate. So, in effect, reducing backpressure really does two good things: The engine can use work otherwise spent pushing exhaust gas out the tailpipe to propel the car forward, and the engine breathes better. Of course, the DME's ability to adjust fuel injection is limited by the physical parameters of the injection system (such as injector maximum flow rate and fuel system pressure), but with exhaust backpressure reduction, these limits won't be reached.

- Adapted from Thomas V.

Thursday, November 11, 2010

The Science of Exhaust Modifications

I chanced upon couple of images which gives a good understanding of exhaust systems.
Click on the images to read it.

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