BMW Z4 with 550hp M5 engine

There's still some fun to be had in the old BMW Z4. German tuner Hartge used the good 'ol American tradition of stuffing little cars with engines of their big brothers and transplanted the BMW M5's V10 into a Z4. If that wasn't enough, Hartge upgraded the 5.0-liter engine from 507 hp to 550 hp. That's not bad considering the M Roadster comes with 330 hp. All this extra power comes at a price, about $137,700 at current rates. (...)

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