Alpina, which has been tuning BMWs for 30 years, has come up with a competitor to the new M5. This is the
Alpina B5, which develops the same amount of power, reaches 60 mph in 4.6 seconds and has a top speed of 195 mph – Alpina does not believe in 155 mph limiters for its cars. As a result, it claims this is the world’s fastest production sedan – and not many people would argue. You can also buy a B5 estate car.
Heart of the BMW Alpina B5 – based on the 5 Series, like the M5 - is BMW’s 4.4 liter V-8 with a novel supercharger. BMW’s M Division does not like turbos and superchargers. They argue that you get more pleasant power delivery with a high-revving engine, with the power coming in progressively.
Also, a supercharged engine turns out more torque than a naturally aspirated engine of the same power so it needs a bigger gearbox. On the hand, you have to keep the engine in the 5,000-8,000 rpm range to make the car fly, whereas the charged engine delivers masses of power in the 3,000-6,000 rpm range, which is nearer the revs used when not hurrying.
Supercharger for low-speed powerSupercharger for low-speed power
Alpina thinks that mid-range power is better, and so they have adopted an engine driven centrifugal compressor to boost power throughout the speed range. This produces the same power output as the BMW V-10 – 500 bhp – but at only 5,500 rpm. This is a low speed even for a charged engine, so you can see that this has further potential. Peak power of 500 bhp is maintained up to 6,000 rpm – ah the beauty of electronic engine controls to tailor the power output to what the engineer wants!
This is a mighty powerful engine; at 2,500 rpm it develops 200 bhp, so the character of the engine is completely different from BMW’s V-10. Thanks to the supercharger, there’s massive torque over a big range, with the maximum of 516 lb ft (700 Nm) available from 4,250 to 5,250 rpm – terrific mid-range power. By contrast, the M5 can manage only 383 lb ft (520 Nm) of torque at the high speed of 6,100 rpm. These are completely different engines.
The system of the B5 has a neat twist. At idling and when driving at low speed or load, the compressor does not operate, so gas mileage is quite good. A throttle plate upstream of the supercharger cuts it in and out according to load. This was developed by Alpina.
Lag-free operation
This is a Nautilus radial supercharger, which is similar to the compressor of a turbocharger. Turbochargers suffer from lag, because when you put your foot down, the engine has to develop enough exhaust gas pressure to get the compressor spinning fast.
With the centrifugal or radial supercharger this is not a problem as the supercharger is being driven by the engine so boost is always available. Response at any speed is good.
Many people will find the characteristics more useful than those of the M5. Of course it depends where you drive.
Six-speed Switch-tronic box
The engine drives through a ZF six-speed automatic – this engine develops so much torque that a massive gearbox is needed. The box has the usual manual option, the driver controlling shifts through a pair of buttons on the back of the steering wheel. Alpina does not fit a limited slip diff, which might be an asset with this much power.
The brakes, wheels and tires are all upgraded to suit. The brakes are based on those in the B7, and feature 14.7 inch discs – those at the front are slightly bigger than at the rear. Unusually, the discs are not cross-drilled, as in wet weather the pads are applied automatically to wipe the discs from time to time. This is said to give the same result as cross-drilling. The calipers are Teves' twin-piston floating type, which is a rather lower specification than you might expect.
Michelin Pilot 2 tires on 19 inch rims
To get this massive power onto the road, Alpina has adopted Michelin Pilot Sport 2 tires 245/40ZR 19 at the front and 275/35ZR 19 at the rear – these are just a bit narrower than those on the M5. Of course, the suspension has been stiffened up to suit the extra power.
All Alpina models feature an air dam at the front, which improves drag while allowing extra air flow into the engine compartment and to the brakes. A Cd of just 0.29 is quoted for the B5, so drag is low.
Since the M5 was developed by the M Center, which specialises in the producing BMW's hot cars, you would expect the M5 to be lighter than the Alpina B5. But no. the B5 is just a shade lighter 3,986 lb (1,810 kg), which is a very respectable weight for a fairly large car.
If you fancy something a bit more nimble, try the BMW Alpina B3 S Coupe. It is powered by BMW’s straight six, bored out to 3.3 liter. It churns out 305 bhp at 6,300 rpm. Good for 168 mph and a 0-60 mph time of 5.4 seconds. A true competitor for many sports cars, and of course BMW's own M3.
