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what's the real issue? Posted by JimBlake [Email]  (#141)  [Profile/Gallery]
(more from JimBlake) on Wed, 30 Jul 2003 07:33:41
In Reply to: OT: Pushrods V. DOHC, nick  [Profile/Gallery]
, Tue, 29 Jul 2003 17:08:39
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Lots of answers about low-rev torque vs. high-rev power, or better breathing, better efficiency, etc...
But really, that stuff has to do with the valve sizes, porting, valve timing & lift & overlap, etc... I'm sure someone could make a pushrod engine with the valves & cam profile to make high revving power, at the expense of low-rev torque. The choice of pushrods vs. OHC comes AFTER the designer decides whether this is gonna be a truck engine or a 9krpm screamer.
How about my former '89 900 DOHC non-turbo; vs my Integra. They're both DOHC, they're both 16-valves. The Saab felt like it ran out of breath long before 6krpm, but the Integra pulls to it's 8k redline. So the n/a Saab had all the characteristics that we're blaming on pushrods. Not only that, but the Saab's oversquare vs the Integra being undersquare - that's backwards...
The Saab had bigger exhaust, and I don't think the intake was really restrictive. I think their behavior had everything to do with valve timing & cam profile. And that's pretty much separate from the pushrod vs. OHC question. Stephen's answer about part count & complexity makes the most sense to me.
posted by 12.28.24...
, Tue, 29 Jul 2003 17:08:39, Wed, 30 Jul 2003 07:33:41 <-- Viewing This Message
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