Comparing two-stroke and four-stroke engines Which of the following statements about two-stroke versus four-stroke engines is incorrect?

Introduction / Context:
Two-stroke (2S) and four-stroke (4S) engines differ in how often a power stroke occurs and in their mechanical complexity. Misconceptions are common regarding power output, mass, bulk, and cost trends.

Given Data / Assumptions:

• Engines compared at similar displacement and speed.
• Conventional naturally aspirated designs.
• General market trends for cost: diesel vs petrol.

Concept / Approach:

In principle, a simple crankcase-scavenged two-stroke engine has one power stroke per revolution, whereas a four-stroke has one power stroke every two revolutions. Thus, for the same size and speed, the 2S can develop up to about twice the power (ignoring scavenging and thermal differences), not the 4S. Two-strokes also tend to be lighter and more compact for a given power. In common practice, diesel engines are more expensive than similar petrol engines due to higher compression ratios, injection hardware, and structural strength.

Step-by-Step Solution:

Verification / Alternative check:

Textbook comparisons and manufacturer data support higher specific power and lower weight for simple 2S designs, and higher purchase price for diesels due to injection systems and robustness.

Why Other Options Are Wrong:

Option (e) ignores that (b) and (c) are also wrong.

Common Pitfalls:

Assuming modern emissions-compliant 2S designs always keep the historical power advantage; scavenging and aftertreatment can alter practical results, but the conceptual comparison holds.

Final Answer:

All of the above statements are wrong.