I wonder if this is a HEMI engine. Maybe not but it sure sounds and acts like it. Here is an excerpt:

More speed from less torque and more gears
By Greg N. Brown Email
Date posted: 05-17-2006



A faster, less torquey solution
As Inside Line has noted in its review of the ML63 AMG, the new 6.2 is a marvel of an engine. It's lighter, more powerful, cleaner, just as fuel-efficient and, arguably, more durable than the 5.5 it replaces. It's also the first engine in a Mercedes-Benz passenger car to be developed completely by AMG, which fully exercised its motorsport expertise when developing the V8's unique architecture.

In its state of tune for U.S.-bound E63 sedans and wagons, the 6,208cc four-valve DOHC V8 puts out 507 horsepower at 6,800 rpm compared to the E55's 5,439cc three-valve SOHC supercharged V8's rating of 469 hp at 6,100 rpm. Well and good. The newer car should be more powerful. Torque? The bigger V8 twists out 465 pound-feet of torque at 5,200 rpm compared to the (what's this?) 516 lb-ft of torque from the outgoing V8. The E55's torque also peaked earlier, at 2,650 rpm. Sounds like a step backward.

However, there was good reason for the reduction in torque. This allowed Mercedes to fit its new, sophisticated seven-speed automatic in place of the old five-speed. Though the new gearbox is far more efficient than the five-speed, and though it was not built to handle the massive torque of the supercharged engine, its limit of 542 lb-ft, say Mercedes engineers, gives it the required durability to handle the 6.2's far-from-paltry crank twist.

Even better, the loss of torque has had no impact on the car's performance. Let's turn to the factory for this conclusion, which says the 6.2 can launch the E63 sedan from zero to 60 mph in 4.3 seconds. (That's a worthy accomplishment for a 4,035-pound four-door — and it's also probably a conservative figure. Certainly the 514-hp European-spec car we drove in Germany felt much quicker.) To compare, the E55, according to factory numbers, takes 4.5 seconds to achieve the same speed. Race is over; the E63 is quicker. (Just to save you the trouble of looking it up, the similarly sized BMW M5 makes the dash from zero to 60 in 4.5 seconds.) Credit the E63's more efficient seven-speed transmission, improved aerodynamics and, surprisingly in this day of the bloated automobile, a moderate overall weight gain of just 45 pounds compared to the E55 sedan.

 

With 4 valves per cylinder and DOHC? I wouldn't think so.

 

I know but I had to post it as it looks like a good performing engine also from DCX.

 

If I remember correctly, it held on to the same torque amount for a long time. The reason why this probably is because of a wonderful invention called VVT. I believe this engine is supposed to have this. Holding on to a lower torque number for a longer time can be better off than having a high peak. That 7-speed transmission gives it another gear to keep it in the proper torque range. 4 valves per cylinder and DOHC are not impossible to have with a HEMI. There was a DOHC version of the 426 HEMI that they were going to use in NASCAR if Ford used the 427 SOHC "Cammer." I just doubt they did this.

 

any info on that DOHC 426 hemi?

alot of DOHC engines look like a hemi head, because they use the center mounted spark plug..much like the srt4 motor...

 

The info is limited unfortunatley but here is what I found (It is listed as the A925).
http://www.thehemi.com/notable.php?id=010
http://www.cartype.com/page.cfm?id=181
http://www.allpar.com/mopar/hemi/hemi.html
There were only two built and one was destroyed. They didn't need it after NASCAR baned the 427 SOHC, so they didn't build it.

 

It probably has an angled head design, almost definetely not a Hemi however. Hemis have many undesirable characteristics for street vehicles, like carbon build up, inability to meet emission standards etc. You'll notice that even the Chrysler 5.7-6.1 Hemi, really isnt even a Hemi. Its what we call a Semi Hemi. The combustion chamber has a very noticeable flat spot in it to help with the above mentioned issues. The new Hemi is a fantastic engine though, definetely on par with GM's LS smallblocks in design.

 

Those emissions issues can be resolved with Direct Injection, VVT, and other modern technology.

The 5.7-6.1L are above par in comparison to the LS series. They require a lower compression ratio to produce more power. The LS7 7.0L has a compression ratio of around 11.0-11.1 to 1 compression; meanwhile, the 6.4L HEMI produces similar to slightly more hp and more torque while only having a 10.5 to 1 compression ratio and also is significantly smaller. The 6.1L produces 425hp & 420 ft-lbs of torque with a compression ratio of 10.3 to 1; meanwhile, the LS2 6.0L has a compression ratio of somewhere close to 10.9 to 1 compression and only produces 400hp & 400 ft-lbs of torque. Although the 6.1L is larger the difference in cubics is 364 (6.0L) and 370 (6.1L) only leaving 6 cubics which is really insignificant.

 

6.9 - variant of 6.4

 

I bet the increased performance is more attributable to the 7 speed transmission than anything else. Lower gear ratio's and more gears will do wonders for performance.