The DOHC engine doesn't have as much torque as the 3V does. The DOHC design is more for higher rpm HP than for low end torque. The new 3V with variable cam timing and special flow controlling flaps in the intake manifold, provides 15 more lb/ft of torque over the 2V engine (365 vs 350), but the 3V has 80% of it's torque in by 1000rpm. This will give superior power to get moving from a dead stop. The 3V also has 40 more HP than the 2V engine.
I'm interested in this, I have a 5.4l DOHC in my Ford Falcon XR8. The Falcon is a 4 door sedan produced in Australia which is similar in size as the Taurus was. It's a 5 speed manual rear driver. For the present model which was produced in 2002 Ford Australia decided to ditch the Windsors and increase cubes and power/torque. They made up their own version by mating the 5.4 block with the same DOHC heads as in the 4.6l DOHC Mustang. The result is 260kw and 500nm of torque, the GT Falcon has 290kw and 520 nm. I'm interested in what you guys are doing because there's not much modifications available yet due to the newness of this motor. I did have a Vortech supercharger kit on it for a while but removed it because it was noisey, not refined. The power was great, about 400kw, which is about 540hp. I'm presently on the look out for a Powerdyne supercharger setup, they're much more quiet. We also fully import the 3v 5.4 single cam engine, it has about 220kw(295hp), it's in the less sportier models.
290 kw=389 HP
520 Nm=384 HP
SOunds a lot like the last Mustang Cobra R motor
You guys in Australia really get some kick *** cars compared to what's offered here in the US. There are no Ford cars with anything bigger than a 4.6 here.
The DOHC is also designed for premium fuel. I didn't realize that the Navi was getting the 3v for 05. It'll be interesting to see how it compares to previous years.
The engine going into the 2005 Navigator is basically identical to that of the 2004+ F-150's 5.4L SOHC V8 w/3-valves per cylinder and offers the same amount of horsepower and torque. Against the outgoing Navigator's 5.4L DOHC V8, the new engine (the 3-valve V8) matches its horsepower at 300 but actually has a torque advantage of 10ft-lbs; 365 versus the DOHC engine's 355. All of this goes on top of the fact that the 3-valve engine doesn't require premium fuel like the DOHC engine, which is another plus. It should also be mentioned that Navigator's corporate sibling, the 2005 Expedition, will also be getting the 24-valve 5.4L SOHC V8. In addition, it'll be the only engine offered, at first at least, replacing both of the 16 valve V8s offered before, the 4.6L and the 5.4L.
An added bonus is that with the flapper valves in the intake, the Variable Cam Timing and the drive by-wire throttlebody, it has 85% of it's total torque @ 1000rpm. That's 310lb/ft. Great for getting heavy loads rolling from a dead stop. Something that my 2V 5.4L is lacking. It doesn't really start pulling good until about 2500rpm(peak torque).
4v with all of that would cost even mroe to make ... more parts and machining on top of all the ellaborate stuff, possibly to minimal gains in factory form. the three valve allows them to tune the engine to low end grunt off the tow valves, and allow the third valve to increase upper end flow when needed for horsepower.
Not sure about the first 2 options but we definately have drive by wire. Ford Australia import the block and heads seperately. I believe the block is the same as the one in your trucks, the heads are the Mustang 4.6 DOHC heads. They have a small V8 engine production line devoted to these engines. They mate the heads with the blocks and then add locally sourced parts such as the intake, manifold, plenum, throttle body and cams. The Falcon GT blocks are totally gutted, higher compression pistons and other goodies are installed. It ends up looking like a Mustang engine except the rocker covers are black and the plenum is larger with inlet the Aussie passenger side. If you go to my website http://craigwarden.tripod.com/ and click on my cars you see the engine on a stand.