OMG Beaver, what planet did you come from. I´m sorry, I feel slightly insulted by your comments. I hope its just from lack of experience.
The DOHC heads are more volumetrically efficient and will ALWAYS be more efficient in stock form. The limitation of a SOHC head is like 65%(unless you have a cool HO head like the yamaha´s on an 89-95 SHO)
Base VE for a DOHC is like 75%. Percentages may not mean that much to you but a different of 10% increase of VE on a DOHC head on high revs can be up to like 70HP ! Just think if I increased the VE to 95% of my 1.8L I would be gaining as much power as a pretty high mileage 1.9L puts out total!!!
Most higher VE DOHC heads require better balance in the motor, that´s why they rev to like 7k - (1G MR2 hits -->
7.8k revs.
Under boost it makes a HUGE difference too. A DOHC head because of naturally being able to flow a higher VE will produce gobs more power if you keep the pressure the same between both test motors.
Realize too that the main reason why nitro motors are using big block displacement and pushrods is because; THEY CAN´T RACE IF THEY DONT. When you get into Nitro (top fuel, etc.) racing they dont even allow you to use an ECU, PCM, whatever you want to call it to control the motor...only for data collection to better tune the motor.
If there was some law saying you couldnt drive a car on a public highway unless it used big displacement, and 40% efficient motors and got 11 gallons to the mile then I guess you´d be right on.
But I can´t argue, with low efficiencies those cars are still producing upwards to 8000 HP to the ground! Its INCREDIBLE. But still apples and rotton oranges for a comparison.
Back to the Geo Metro comment. the Suzuki Swift is a rebadged Metro with a 1.3L DOHC j-spec motor. There´s a Swift on SpeedOptions.com that was car of the month for Dec. On 20psi it put out over 350hp. Dont knock a turbo´d metro if you see one.
<img src=http://mercury.pr.erau.edu/~bladej/escortweb.jpg>
Jason Blade, 93 EGT Turbo
[ This message was edited by: TheBlade on 05-01-2003 15:08 ]