While a D16 may be able to make 400hp it will have nowhere near the amount of low end grunt of torque that a 400hp LS1 will have. The 400hp LS1 car would handily beat the 400hp D16 car (if you could even get one in a 7, it spins the wrong way and is setup for FWD). The same thing goes for any small displacement engine, even up to things like the 2.4L KA24. There's no replacement for displacement. To get those sort of numbers from a small engine you need lots of boost, and it takes time to spool such a large turbo, which means that you'll have much less low end power. A 400hp LS1 will also be much less stressed than any 400hp 4cyl engine, so it'll last longer and be more reliable.

People bash the LS1 because it's a pushrod engine, but that make it more compact and light than if it were to be OHC. It's actually a fairly advanced engine, despite what people may think, even with it's "sub-optimal" configuration. It's true that it may cause the car to be slightly more nose heavy than before the swap (by that I mean ~50lbs, depends on the car before and the options kept such as AC and PS), but it adds a huge amount of hp to the car, and it's not that much weight anyway, it can easily be fixed by moving the battery or by ditching the PS and AC. How often do you hear people criticise that huge front mount that's half covered by the bumper because they're adding a big weight to the front of the car? Never, because they think it adds power and people don't even consider the weight penalty,or don't think it's very significant. Guess what? The weight balance differerence is probably similiar.

People focus too much on a peak hp number, when that's just the hp at one point in the engines rpm range. What makes a car accelerate is the amount of power it has across it's entire operating range, and that's where a larger displacement car has its major advantage.

 

i love the rotary, without a doubt, beautiful work of art, probably the best RACE engine you can ever build. but after having one for a while and it goin out, i realized, the car could be alot more FUN to drive if it were more reliable, better low end tq, and better mpg. i'm CONSIDERING a ls1/t56 switch for those reasons. i've driven my parents '04 z06 and i loved how it ran, broke the tires loose easily in the lower rpms, and got 30+ mpg on the highway. so i figure if the ls6 can do it with minor changes in timing, fuel map, cam, and intake for a car that weighs just over 3100 lbs, then what would the ls1 do for a car that weighs around 300 lbs lighter, i'm guessing almost the same

 

355 Twin Turbo gets my vote(hence why I'm doing it). Should be pretty interesting.