Engine displacement v/s power output

Hi,

I know this is sometimes very obvious to say that a higher engine displacement would lead to a higher power, but rarely I have seen same engine displacement giving same power output in cars.

To simplify, consider Swift with a 1.2 ltr engine, giving you an output of 85 bhp, compared to Punto 1.2 ltr engine, giving you less than 80 bhp.

Does fine tuning of engine, reducing vibrations etc are the only factors that cause difference in engine displacement?

Can somebody throw some light on this? Any concrete information will be grateful.

Thanks,

Harsh

CC Refes to the total volume of an engines cylinders combined, not including the combustion chamber/s. BHP is the measure of an engine's horsepower without the loss in power caused by the gearbox, generator, differential, water pump, and other auxiliary components. Thus the prefix "brake" refers to where the power is measured: at the engine's output shaft, as on an engine dynamometer. The actual horsepower delivered to the driving wheels will vary.The term "brake" refers to the original use of a band brake to measure torque during the test (which is multiplied by the engine RPM and a scaling constant to give horsepower).

More "horsepower", and/or larger "cc", will typically make a vehicle faster. For Example a 1600cc of SX4 produces 102Bhp while Honda City's 1500cc Engine produces 118bhp. While Honda will be faster on the tracks, SX4 will have enough puff left on the straights.

If two cars have same displacement say 1248; one has power of 75@4000 and the other 90@4000 which one will be better (also in terms of mileage and resale value)?

It surely would be the 90@4000 since it is giving you a higher output. But nonetheless, there would be some implications as to why the two cmoapnies are offering a differential output. Could be a relation to more refined pistons, cyliinders, and other mechanical equipments that have a say in the engine.

Hey Joel,

I am still not very clear as to how is it possible for same engine displacement to churn out different power outputs.

Is it because of fine tuning and other mechanical moving parts that an engine has?

Is it because the engine has more better dynamics (small piston thickness, but a highly efficient material, which in turn enables more fuel available for combustion).

There must be some distinct factor that causes this difference. I would be really keen if you could throw some light on this.

Harsh

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@Harsh,

The same engine can have different power/torque at the same RPM because these are dependent on fuelling. The ECU is what controlls fuelling using "fuel maps" - change the map and you change engine behaviour. Also, the gearing plays a vital role here - gearing made to put out more torque at a given engine RPM will also reduce available speed at that RPM.