2.2 Liter Engine Enhancements
Beginning in the 1997 Model Year, the 2.2 liter engine for 1997 Legacy and
Impreza models has had internal and external changes that yield an approximately
10% increase in power and 3% increase in fuel economy. Accomplishing this
involves many factors, one of which is engine friction reduction.
The piston, a major source of engine friction, has been coated with a friction
reducing agent called Molybenum. This thin coating not only allows smoother
travel through the cylinder, but also reduces cylinder wall scuffing.
The skirt of the piston has been reshaped and the overall weight has been
reduced by approximately 100 grams. Compression ratio has been increased to
9.7 to 1 by reshaping the crown of the piston. This eliminates the clearance that
was available between the piston at TDC and the fully opened valve. Piston pin
offset has been changed to 0.5 mm. Piston to cylinder wall clearance has been
reduced by increasing the piston diameter.
Another source of high engine friction is the valve train. Hydraulic lash
adjusters (HLAs) are always in contact with the valves. The hydraulic pressure of
the lash adjuster must be overcome during operation and during the most critical
time of engine start. To overcome this situation and to contribute to the total reduc-
tion of friction loss, 1997 and later SOHC engines have solid valve adjusters. The
scheduled service of this valve train is set at 100,000 miles. SOHC engines now use
an adjustment screw to adjust valve clearance.
Tools required for 2.2 valve adjustment include a thickness gauge, 10mm
wrench, stubby standard screwdriver, and crankshaft wrench.
Follow the instructions below for set up and adjustment.
• Remove the right bank camshaft belt outer cover.
• Rotate the engine until the arrow on the camshaft sprocket is at 12 o’clock.
Remember that the camshaft sprocket has an arrow and a mark for the timing belt
timing. Make certain that the arrow is used for valve adjustments, not the mark.
Standard valve clearance:
Intake valves 0.20 ± 0.02 mm
Exhaust valves 0.25 ± 0.02 mm
•
Using a standard thickness gauge to measure the clearance of the intake
and exhaust valves in cylinder 1 only. Adjust the clearance by loosening
the locknut and turning the adjustment screw until the proper clearance
is obtained.
•
Rotate the engine until the arrow on the camshaft sprocket is at 3 o’clock.
Check and adjust the clearance of the intake and exhaust valves on
cylinder 3 only.
•
Rotate the engine until the arrow on the camshaft sprocket is at 6 o’clock.
Check and adjust the clearance of the intake and exhaust valves on
cylinder 2 only.
•
Rotate the engine until the arrow on camshaft sprocket is at 9 o’clock. Check
and adjust the clearance of the intake and exhaust valves on cylinder 4 only.
Solid Valve Adjusters
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