Gearing, final drive, trick differential...etc.E46 in Philly said:The Hartge version is a lot better looking than RD's cheesey knockoff (at least as pictured in that link - with the two tone exterior).
I saw a comparison on MotorTrend Television a while back where Hartge's 3-series failed to outperform the M3 (there was another conversion involved - I can't recall whose). I was surprised. When it comes to acceleration at least, you'd think the M5 engine would give the Hartge car an edge. I don't recall seeing any top-end figures though, which is where I suppose the V8 would really make a difference.
I wonder how many of those Hartge actually sells.