Engine Performance
Work Example 23

WorkKey Level: 5
NATEF Automotive Tasks:

Problem:

You are building a racing engine for a customer and he wants more cubic inches. You have an eight cylinder engine with a bore of 4.00 and a stroke of 3.50 inches. You are given the formula for engine displacement of:(Bore/2) squared times p times stroke times number of cylinders.

Facts:
Radius is diameter of bore divided in half
p = 3.14159....(Use 3.14)
Volume of a cylinder= pr² L (L is the stroke length.)

1. What is the cubic inches of the stock motor? __________

2. What is the cubic inches if the bore is increased by 0.120 inches? ___________

3. What is the cubic inches if a crankshaft with a stroke of 3.750 inches is used?__________

4. It costs $160.00 to bore a motor and buy pistons or $399.00 to buy a longer stroke crank. What would you tell the customer who wants more cubic inches but wants it cheap? __________________________

Solution:

1. 351.68 in³
2. 373.97 in³
3. 376.8 in³
4. Go with the bore unless you want an extra 3.8 in³ for an extra $240.