I asked that question on the sts forum and didn't get a clear reply. After trying the d3r here's my answer to the zx12 mega v.s sts d3r
The x12 is a screamer of an engine. It winds and i have no problems seeing that engine hit 35000+ rpm. At the track 50% of the guys run the zx12.
My D3r is not a screamer put a super torque engine. I guess it winds around 28000 - 32000 rpm. At first i thought i had made a big mistake on buying it. This thing i thought had no top end. On the sts forum everyone was saying to gear up and don't worry -- the d3r will pull . They where right. On my G4 I went from 19th to 20th and 24 to 25 on second gear. My RB v12 had problems with that setup. To say the least, i can keep up and i'm just as fast as any Zx12 on the track.
The only odd thing that i have to get used to is the sound. My rb v12 screamed and on the back straight, you know you where moving !!! With the d3r, the rpm's are so low -- you have the impression you're not moving but it's just an impression. I'm going as fast or even faster than before -- it's just an odd feeling.
Now the question is -- how's the endurance on this motor. I have not had the engine long enough to say anything about that.
One guy at the track kept pestering me about the d3r ( don't buy that - it's crap, buy my JP modified for 500$ canadian, it's made in taiwan, i know a guy who knows the guy who makes them and...... etc... I guess you know what people can say). He was pretty quiet about the engine after the race