# IC Engine Questions and Answers – Engine Performance Parameters

This set of IC Engines Multiple Choice Questions & Answers (MCQs) focuses on “Engine Performance Parameters”.

1. The ratio of indicated thermal efficiency to the corresponding air standard cycle efficiency is called ___________
a) net efficiency
b) efficiency ratio
c) relative efficiency
d) overall efficiency

Explanation: Relative efficiency is defined as the ratio of indicated thermal efficiency to the corresponding air standard cycle efficiency.

2. Compression ratio of I.C. engine is ___________
a) the ratio of volumes of air in cylinder before compression stroke and after compression stroke
b) volume displaced by piston per stroke and clearance volume in cylinder
c) ratio of pressure after compression and before compression
d) swept volume/cylinder volume

Explanation: None.

3. The air standard efficiency of an otto cycle compared to a diesel cycle for the given compression ratio is?
a) same
b) less
c) more
d) more or less depending on other factors

Explanation: In general, the Otto cycle, which is used in gasoline engines, tends to have a higher air standard efficiency compared to the Diesel cycle used in diesel engines. This is mainly due to the higher compression ratio typically employed in Diesel engines, which leads to higher thermal efficiency.

The Otto cycle operates on the principle of constant volume heat addition, while the Diesel cycle operates on the principle of constant pressure heat addition. The higher compression ratio in the Diesel cycle allows for better thermal efficiency, as it allows for a higher expansion ratio and a higher peak pressure during combustion. This leads to more complete combustion and a higher air standard efficiency.

However, it’s important to note that there are several other factors that can influence the efficiency of both cycles, such as the specific design of the engine, fuel properties, and operational conditions. Therefore, it is not accurate to make a general statement that the Otto cycle always has a higher efficiency than the Diesel cycle for a given compression ratio.

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4. The calorific value of gaseous fuels is expressed in terms of ___________
a) Kcal
b) Kcal/kg
c) Kcal/m2
d) Kcal/m3

Explanation: None.

5. Indicated power of a 4-stroke engine is equal to ___________
a) pLAN
b) 2pLAN
c) pLAN/2
d) 4pLAN

Explanation: Indicated power of a 4-stroke engine is equal to pLAN/2.
where p = mean effective pressure,
L = stroke
A = area of piston and
N = rpm of engine.

6. If the intake air temperature of I.C. engine increases its efficiency will ___________
a) increase
b) decrease
c) remain same
d) none of the mentioned

Explanation: None.

7. All heat engines utilize ___________
a) low heat value of oil
b) high heat value of oil
c) net calorific value of oil
d) calorific value of fuel

Explanation: None.

8. An engine indicator is used to determine the following ___________
a) speed
b) temperature
c) volume of cylinder
d) m.e.p and I.H.P

Explanation: None.

9. Fuel oil consumption guarantees for I.C. engine are usually based on ___________
a) low heat value of oil
b) high heat value of oil
c) net calorific value of oil
d) calorific value of fuel

Explanation: None.

10. The thermal efficiency of a diesel cycle having fixed compression ratio, with increase in cut-off ratio will ___________
a) increase
b) decrease
c) be independent
d) none of the mentioned

Explanation: None.

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