ICAR AIEEA-PG — Agricultural Engineering & Technology (Major Subject Group 10) · India · National Testing Agency for ICAR
Original practice questions written to the published syllabus · not past papersHow tractor engines work and how their performance is measured — the single most reliably examined farm-power topic.
In the exams: GATE AG Section 3 (engine performance asked in all 8 papers 2019–26); ICAR AIEEA-PG Unit V; ICAR AICE subject 39 Unit 4; NCEES PE IC engines; RPSC AAE
ICAR AIEEA-PG — Agricultural Engineering & Technology
Unit V farm power: engine systems (fuel, cooling, lubrication, ignition, governing), cycles, performance terms and tractor testing; more recall than GATE, with short calculations.
How our questions for ICAR AIEEA-PG spread across the units of Tractor & Automotive Engines (IC Engines). Difficulty: 20 easy, 26 medium, 4 hard.
| Fuel properties | 6 | |
| Engine performance: IP, BP, FP and efficiencies | 5 | |
| Engine classification and terminology | 4 | |
| Two-stroke and four-stroke engines | 4 | |
| Combustion and knock | 4 | |
| Governing | 4 | |
| Emission norms | 4 | |
| Otto, Diesel and dual cycles | 3 | |
| Engine components | 3 | |
| Lubrication system and lubricants | 3 | |
| Engine testing | 3 | |
| Air intake and turbocharging | 2 | |
| Ignition and electrical system: battery, starter and alternator | 2 | |
| Diesel fuel system: injection pump and injector | 1 | |
| Cooling system | 1 | |
| BSFC and heat balance | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Which statement about SI and CI engines is correct?
B. CI engines use higher compression ratios because the air must be hot enough to ignite the injected fuel
A CI engine needs a high compression ratio (roughly 14–22) to reach the fuel's self-ignition temperature, and it controls load by fuel quantity, not throttling. SI engines are limited to lower ratios by knock; petrol has a high octane, not a high cetane, number.
The correct sequence of combustion stages in a CI engine is
D. ignition delay → rapid (premixed) combustion → controlled combustion → after-burning
Fuel mixed during the delay burns rapidly; later fuel burns as fast as it mixes (controlled); reactions finish during expansion (after-burning).
Further reading: Heywood, Internal Combustion Engine Fundamentals
In the pressure (forced-feed) lubrication system of a tractor engine, oil reaches the big-end bearings through
C. drillings in the crankshaft from the main bearings
The pump feeds the main gallery and main bearings; drilled passages in the crankshaft carry oil from the mains to the crankpins. Dippers belong to splash systems.
The governor normally fitted to an agricultural tractor diesel engine is
C. an all-speed governor
The tractor governor holds whatever speed the hand throttle sets, from idle to maximum, so PTO machines run steadily. Constant-speed governors are for generator sets; min–max governors were used on road vehicles. This is also called a variable-speed governor.
Hunting of a governor means
A. continuous oscillation of engine speed above and below the set speed
An over-sensitive governor over-corrects, so speed keeps swinging about the set value. A steady fall of speed with load is droop.
Load control in a diesel engine is called quality governing because
D. the air is not throttled and only the fuel quantity (hence mixture strength) is varied
A diesel takes a full charge of air at all loads; the governor varies fuel, so the air-fuel ratio (quality) changes. SI engines throttle the mixture quantity at near-constant ratio: quantity governing.
The two reference fuels originally used to define the cetane scale are
C. n-hexadecane (100) and alpha-methylnaphthalene (0)
Cetane (n-hexadecane) = 100 and alpha-methylnaphthalene = 0; current practice uses heptamethylnonane (15) as the low reference. Iso-octane/n-heptane define the octane scale.
Further reading: Heywood, Internal Combustion Engine Fundamentals
Straight-chain paraffins, compared with aromatics of similar boiling range, make
D. better diesel fuels (higher cetane) but poorer petrol (lower octane)
Straight chains break down and self-ignite easily: good for CI, bad for SI. Aromatics and branched paraffins resist self-ignition: good octane, poor cetane.
Further reading: Heywood, Internal Combustion Engine Fundamentals
At constant speed an engine has BP = 40 kW and FP = 10 kW. If the load is reduced to BP = 20 kW with friction power unchanged, the mechanical efficiency becomes
C. 66.7%
At 40 kW: ηm = 40/50 = 80%. At 20 kW: IP = 20 + 10 = 30 kW, ηm = 20/30 = 66.7%. Mechanical efficiency falls at part load because friction stays roughly constant.
A rope-brake dynamometer has a 0.6 m drum and a 20 mm rope. At 1,500 rev/min the dead load is 400 N and the spring balance reads 50 N. The brake power is closest to
C. 17.04 kW
BP = (W − S)π(D + d)N/60 = 350 × π × 0.62 × 25 = 17043 W = 17.04 kW. Ignoring the rope diameter gives 16.49 kW; adding W and S instead of subtracting gives 21.91 kW. Using T × N/60 without 2π gives 2.71 kW.
Ten here, 50 in the app. The Laisha app has every practice question we have written to ICAR AIEEA-PG in this subject, marked as you go, with timed papers, a jump-to-unanswered list and a certificate when you pass at 70 per cent.
Free for ten days, then one subscription of US$10 a month. We would rather say so here than have you find it later.
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