Originally Posted by Pete_vB
There is no doubt that the Metzger motor is powerful, reliable, and one of the best motors ever built, and I do love mine. But everything gets old... The '07 GT3 cup motor in the back of my car is 480 lbs dressed. The street motors add emissions and a bunch of other stuff and weigh a lot more. Now compare that to a Carrera GT, for example- a street motor that weighs 8 lbs less than my race motor at 472 lbs, but has 184 more hp. And this is an older motor (2003) that was also designed for endurance racing and has a dry sump- I don't think anyone doubt its reliability.
The reason is pretty obvious when you take a GT3 motor apart- every time they added power they also added weight. That flat power curve? Bolt on variocam and a three stage intake. Bolt on emissions controls, water jackets for pistons, water passages and water pumps, etc, each with it's own separate castings and bolts. So the newest GT3 motor is also the heaviest. In contrast to Porsche's slow evolution, BMW has been pushing engine technology every generation of M3. Using clean-sheet design they were able to make the S65 V8 33 lbs lighter than the S54 it replaced while still gaining over 80 hp. They've been pushing the use of lighter materials, and advanced concepts like valvetronic. The result is an engines that are both more advanced and have higher power to weight ratios than their porsche counterparts; I know some porsche race engine designers and the freely admit to this.
Of course this is about to change, and the CGT reminds us of what Porsche can do when they put their mind to it. Porsche will drop a huge amount of weight from the tail of the car with a clean-sheet design when they go to the next gen GT3 motor while still gaining power. In the end that's why you mess with success...
My original point was not to sell BMW engineers short here- they are on the very cutting edge on engine design, and we've seen what they can do as well. When they don't blow motors up, that is (early S54s, etc)...
The next gen. GT3/RS aka 991 GT3/RS will use a variant of the contemporary 9A1 engine. Although it will make more power and be pushed a few inches closer to center than its predecessor, it'll unlikely sustain a major weight loss if at all evidenced by the current 9A1. So, very likely 480-490 hp with a 20-25 lb reduction for engine weight; likely more-so total weight loss. Not that that's not bad, but you won't see major revolution just evolution as the Porsche people say. Hey, I could be wrong.
I agree though that BMW does make some of the best engines and does push the design envelope.