The Alpina B3 S Biturbo is the marque's take on the 335i. The renowned BMW fettlers have tuned the B3 S’s 3.0-litre, twin-turbocharged six-cylinder engine to produce 395bhp, almost 90bhp more than the current 335i, and 398lb ft of torque, a rise of more than 100lb ft. That means that even in convertible form, as driven here and which is some 200kg heavier than the saloon, the B3 S will hit 62mph in 4.9sec and go on to an unrestricted 185mph.
However, comparisons will doubtless be drawn with the M3 as often as with the 335i, and it’s worth noting that while the B3 S is two cylinders and 25bhp down on the V8-engined BMW, it delivers a remarkable 103lb ft more torque – and it isn’t restricted by a speed limiter.
Chassis-wise the B3 is way softer than the M3’s, and that’s an entirely deliberate decision on Alpina’s behalf. Apart from Alpina’s own, lighter 19-inch wheels and bespoke Michelin Pilot Sport tyres (235/35 at the front, 265/30 at the rear), the B3 is virtually identical to a 335i Sport in set-up, and is none the worse for that. Notably, the lack of runflats do give the B3 S’s ride a suppleness and civility that’s pretty much unmatched by any 3-series, without any major sacrifice in body control.
The only obvious omission is the absence of any form of limited slip diff from the B3’s spec sheet. The B3’s open item makes for poorer traction on less than perfect surfaces, and rules out the 200-yard power slides you will be able to pull off in the M3 with it’s awesome M-diff. Which, you could argue, is a pity, but it’s perhaps also a good indicator of the greater maturity of the B3’s typical driver.