8 Valves Cylinder, 16 Valves Cylinder, COMPRESSION RATIOS
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Hi,
wat is the diff between 8 and 16 valves cyinder?? Secondly, is it higher compression ration means more horse power??
i compared the compression ration on NIssan SS and WRX (thou is one heaven & one earth) but seems WRX has lower Comp. Ratio (only 8.0 and Nissan has 10.0). Thot that higher ratio is better??
can help me with this?? -
er... higher compression ratio dun mean higher bhp. a nissan is NS so it has a higher copression ratio, or else e car will feel sluggish. a WRX, however, has a turbo. if u have a high compression ratio for a turbocharged car, the engine is going to blow itself to bits. hence a lower compression ratio.
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HP is derived from torque and RPM. To achieve high RPMs, an engine generally needs to have a relatively larger bore but shorter stroke. Look at bike engine design to get an idea.
Higher compression is directly related to higher torque, not HP. This is why diesels usually have high torque. Add this to the fact that it is not unusual to turbocharge diesels, and you have high torque numbers.
If the compression is too high for a petrol engine, the air fuel mixture might preignite or detonate. This is obviously very bad for the engine, causing melted pistons, broken rods and so forth. There are some solutions such as running higher octane fuel, lowering the in-cylinder temperature such as using water injection, running a less aggressive cam profile, lowering the compression by running a thicker head gasket etc.
Most engines have 3, 4 or 5 valves per cylinder, with 4 valves per cylinder being the most common on today's vehicles. 5 valves are usually found on sports cars like Ferraris and even Audi. There are pros and cons to each design, with higher number of valves generally leading to a more snappy response in exchange for loss in low end torque. -
Hi guys thanks for the info. you guys really solve my doubt.
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Hi guys thanks for the info. you guys really solve me doubt.