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Old 03-30-2004, 11:31 PM   #1
Racer5
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Have a Nice Day? Another ej18 query, how many valves?

Yes I searched the forum to no answer. I'm new to these boxer engines but it seams to me that a SOHC like the ej18 would be an 8 valve engine just like any other SOHC right? I have people telling me that they are 16 valve engines. Is that the truth?

How many valves does the ej18 have hmmmm?
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Old 03-30-2004, 11:36 PM   #2
marioej18
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well, my impreza says 16 and it has an EJ18
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Old 03-30-2004, 11:43 PM   #3
Hawk296
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Yes, EJ18 is SOHC and has 16 valves.

4 valves per cyl...
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Old 03-30-2004, 11:46 PM   #4
Racer5
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Okay, so what does the DOHC setup on some of the ej25s do? I mean, if all of the ej engines are 16 valves why go to the more complex setup?
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Old 03-31-2004, 07:43 PM   #5
munkis
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DOHC motors allow for more precise opening and closing of valves since the intake and exhaust valves are controlled inpedently, this helps to improve mid range torque.

Among other things.

Jay
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Old 04-01-2004, 12:16 AM   #6
redwagon
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Quote:
Originally posted by McDade
DOHC motors allow for more precise opening and closing of valves since the intake and exhaust valves are controlled inpedently, this helps to improve mid range torque.

Among other things.

Jay
Except that unless you have adjustable pullies, timing shifts between intake and exhaust cams as the belt stretches, which doesn't happen on a sohc motor.
OTOH, dohc does allow direct valve operation, adjustment by shim, less reciprocating mass. All of which in theory allows operation at higher speeds, or with higher valve acceleration, or with lighter springs. If you have adjustable pullies, a dohc setup can have intake and exhaust timing advanced or retarded independantly. Direct valve operation also reduces side thrust on the valve stems which increases life on the valves, guides and seats. On the downside you have extra weight, complexity and expense.
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