AustenW

Are there any technical experts on here that could discuss destroking a zetec turbo engine. (ST170 to be precise)

The Zetec engine is a poorly designed engine from the factory in terms of its stroke and rod length / ratio.

As such I am considering de-stroking my engine to turbo it to get a better rod ratio, freer / higher reving engine etc etc.

The idea is to produce a high power Zetec engine that revs but with reduced torque.

Torque in a car such as a westfield is not needed as they are only circa 550kg.

I don't doubt that I'm making a wise decision, but the main question will be the extent of the benefits I will gain from doing this exercise.

Here is a table I put together last night:

ZETEC Engine Calcs
Stroke Bore Engine Rod length Stroke Ratio
(mm) (mm) cc's (mm)
88 86 2044 140 1.59
87 86 2021 140.5
86 86 1998 141 1.64
85 86 1975 141.5
84 86 1951 142 1.69
84 86 1928 142.5
82 86 1905 143 1.74
81 86 1882 143.5
80 86 1858 144 1.80
79 86 1835 144.5
78 86 1812 145 1.86
77 86 1789 145.5
76 86 1765 146 1.92
75 86 1742 146.5 1.95
74 86 1719 147 1.99
73 86 1696 147.5 2.02
72 86 1672 148 2.06
71 86 1649 148.5 2.09
70 86 1626 149 2.13
69 86 1603 149.5 2.17
68 86 1580 150 2.21
67 86 1556 150.5 2.25
66 86 1533 151 2.29
65 86 1510 151.5 2.33
64 86 1487 152 2.38


Been looking at the 74mm option

Comments welcome


Length of rod / stroke ratio. The vw 2ltr engine have 159/92,8 = 1,713
1,6 - 1,7 is bad.
1,7 - 1,8 is good
1,8 - 2,0 is very good