Given data :

No of stroke = 2

No of cylinders, n =1

Bore = D = 75mm = 0.075m,

Stroke = L= 90mm = 0.09m,

Speed = N= 1200rpm ..........Two stroke

IMEP= P = 7.5 bar = 7.5x10⁵ N/m²

Mean brake diameter =1m,

Net brake load = 500N,

Mechanical efficiency

$\mathrm{B} . \mathrm{P} .=\frac{2 \pi \mathrm{NT}}{60}$

$\begin{aligned} \mathrm{T} &=\text { Net brake load } \times \text { Radius of Drum } \\ &=500 \times 0.5=250 \mathrm {N} . \mathrm{m} \end{aligned}$

$\mathrm{B} \cdot \mathrm{P} .=\frac{2 \times 3.14 \times 1200 \times 250}{60}=31400 \frac{\mathrm{Nm}}{\mathrm{Sec}}=31400 \frac{\mathrm{J}}{\mathrm{sec}}$

$=31.400 \mathrm{KJ} / \mathrm{sec}$

$\mathrm{I.P}=\frac{\mathrm{nPLAN}}{60}$

$=\frac{1 \times 7.5 \times 10^{5} \times 0.09 \times\left(\frac{\pi}{4} \times 0.075^{2}\right) \times 1200}{60}$

$=5964.117 \mathrm{J} / \mathrm{sec}$

$=5.96 \mathrm{kJ} / \mathrm{sec}$

$\eta_{\operatorname{mech}}=\frac{\mathrm{B} \cdot \mathrm{P}}{\mathrm{I.P.}} \times 100 \%$

$=\frac{31.4}{5.96} \times 100$

$\eta_{\text {mech}}=532.2 \%$

Mechanical efficiency $=532.2 \%$