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Same engine, different output

india Updated: Aug 28, 2009 11:19 IST
Grease Monkey

I received a question from a reader not too long ago, asking me why the R1 with its four-cylinder, naturally-aspirated 998cc engine develops about 160 bhp, while the petrol Logan, despite a 400 cc advantage, musters only 72 bhp. This power output depends on what you want from your engine.

For example, Skoda India offers the Octavia RS in 150 bhp guise while the same engine develops 180 bhp in Europe. Pete’s Performance, an Indian tuning house, has successfully upgraded this engine to 300 bhp.

Extreme machines
Automobiles that participate in racing are the most extreme things one can imagine — anything that will add weight or use power is thrown away.

You will find no CD player, no air-conditioning and no carpeting, either. All the essentials are made of stronger yet lighter material, including parts of the engine.

The clutch, for example, is quite heavy, and it is made of different pieces that engage and disengage frequently. If one could reduce the mass, the momentum will reduce as well, which in turn means that less energy will be required to accelerate or slow down the parts of the clutch.

The same rule can be applied effectively with pistons — they have to keep moving up and down several times a second, so if they’re lighter, you can conserve energy. However, there’s a fine line that you shouldn’t cross — power and reliability don’t go hand in hand, which is why you see mechanical failures in racing.

The Logan’s engine is designed for a really long life, about 100,000 km, with service intervals that won’t let you become a familiar face at the service station. While the automobile market has been growing exponentially over the years, the engine oil manufacturing space isn’t a good place to be, because the amount of oil sold is gradually decreasing due to longer service intervals.

Torque tales
For example, a diesel car usually has its first service at 5000 km, but the VW Jetta needs to be serviced for the first time at 15,000 km! This reliability is what gives the Logan its comparatively low power output.

Another reason is torque. You can have an engine that develops a lot of torque over a wide rev range, or you can have a lot of torque bunched at one end of the spectrum. A truck engine will produce lots of torque as early as possible, but it won’t rev willingly to its redline. On the other hand, that R1 develops more torque the more you rev it, but is comparatively listless at low engine speeds.

Road cars usually find a balance between the two, to satisfy both the customer who commutes to work everyday, and the other who prefers Sunday morning blasts on his favourite stretch of tarmac.