Our photographer Michael Whitestone is convinced that his rattling, shuddering old Citroen XM is the fastest thing on four wheels. But when he was following Ron Creed's 360 bhp Alpina B10 Bi-Turbo off a roundabout and on to a short stretch of dual carriageway, we pulled away from him so quickly he had to rely on his Sat Nav to find out where we were.
This car isn't just fast, it's phenomenal, and although its performance figures and seat-of-the-pants feel are amazing now, just think how fast this must have been back in 1989 when Alpina' brought this monster out into the open.
Alpina are no strangers to the world of building the fastest BMWs and even in 1989 had already been in the business for a quarter of a century. The B10 tag had been applied to a whole host of cars, the last one being the B10 3.5 based on the E34 5-Series and launched in 1988.
Although the normally-aspirated B10 was a good car that improved on the already excellent 535i handling and ride compromise, the 260 bhp that Alpina managed to squeeze out of the 3.5-litre six was only enough to make it usefully faster than the standard 535i, and was in fact slower in acceleration than the outgoing E28 B10 automatic.
A zero to 60mph of 7.4 seconds isn't slow but by the same token it wasn't rocket ship stuff either and when the first of the new M5s started arriving here in early 1990, Alpina had to think again.
The M5 had been available in Germany from 1988 of course and although some might criticise its performance over the later 3.8-litre version, it was still a 155 mph car which could see 60 mph in 6.4 seconds.
To say that the B10 Bi-turbo was merely a turbocharged 5-Series would be to over-simplify matters as it was much more than a crude bolt-on installation. Since turbo-charged cars were first invented, the problem of turbo lag has been with us and the bigger the turbo, the greater the lag, while the exhaust gases get the compressor spinning fast enough to deliver useful boost.
To cure this, Alpina's engineers decided to fit two turbos, but while 'twin turbo' sounds pretty fierce it doesn't always mean twice the power.
The BMW straight-six engine has always used two separate exhaust manifolds, one for each set of three cylinders. This design meant that Alpina could neatly use one smaller turbo for each manifold, with both turbos spinning at the same rate and simultaneously blowing into the engine via linking pipes into an intercooler.
Smaller turbos meant less lag and better response as they didn't need so much time to spool up and deliver the goods and for this, Alpina used twin Garrett T25 turbos. In fact, one way to ruin a B10 owner's day is to point out how the Ford Fiesta RS Turbo used the same Garrett T25 unit.
Many people assume that the Alpina turbo installation was derived from the old turbocharged 745i but they're quite wrong. The two turbo installations are completely different and the 745i was very much a first-generation turbo car without the electronic control the B10 enjoys. The bad old Seven used a single KKK K27 turbo with a 7.0:1 compression ratio and did suffer from some turbo lag, with early cars using separate ignition and Bosch L Jetronic fuel injection as opposed to full Motronic engine management.
The Alpina system was totally different however. Rather than having a large and obvious charge pipe running across the top of the engine, Alpina repositioned the throttle body on the other side of the inlet manifold and ran the charge pipe down by the radiator and out of sight.
With the polished stainless steel exhaust manifold heat shield, crackle-finish cam cover and inlet manifold, the Bi-Turbo engine looks like an absolute masterpiece and if you didn't know that it had two turbochargers strapped to the side then you'd never guess.
Inside the engine, the pistons were 7.2:1 compression Mahle items attached to the crank with special reinforced con rods. The block had special holes drilled into each main bearing housing to spray a jet of oil on to the underside of each piston to cool it down and both turbochargers were water-cooled.
With maximum 26 psi boost selected on the dash-mounted boost setting knob, power was 360 bhp at 6000 rpm with a torque figure of 384 lbf.ft at 4000 rpm. All that power meant that the drivetrain needed to be totally upgraded and apart from a bigger diameter clutch the standard 535i Getrag 280/5 manual gearbox was replaced by the stronger 290/5 type similar to the MS unit.
Alpina engineers soon found that all this power was twisting the propshaft too, so an uprated version was used along with a special oil-cooled differential. This used a separate oil pump and cooler with a digital display on the facia which included diff oil temperature.
Suspension was another Alpina forte and this was uprated to a similar specification as the non-turbo B10, using Alpina's own springs, a combination of Bilstein and Sachs dampers and anti-roll bars. Unlike the non-turbo car though, the standard single-piston brake callipers and discs were not enough and to get around this bigger callipers were needed.
Alpina enlisted Lucas Girling in Britain to make a batch of large four-piston callipers with the Alpina lettering and these look very impressive through the spokes of the 17 in spoked Alpina alloys.
As for the rest of the car, it was pure Alpina with special electrically adjustable and heated Recaro seats, the special Momo/Alpina steering wheel, recalibrated instruments and the unique Alpina spoilers and body stripes.
Ron's car was fairly well optioned with air conditioning, cruise control, wood trim and M3-style mirrors, all added while the car was living in Germany. All B10 Bi-Turbos had the larger 110-litre fuel tank, not that the car is particularly thirsty.
The result of all this development was a car that could achieve 181 mph and reach 60 mph in 5 seconds with staggering handling and roadholding and all with the same refinement as a standard 535i. Some 507 cars were sold but unfortunately the twin turbos nestling under the exhaust manifolds left no room for the steering box on RHD cars so they were all left-hand drive.
B10 Bi-Turbos are understandably very rare in the UK and are extremely sought-after as according to Sytner in Nottingham, none were officially imported. Owner Ron Creed bought this one from MCP Motorsport in Norfolk (01263 822481) for a very reasonable £17,000 in March and it's a Brilliant Red example with a full BMW dealer history. The car was originally supplied by BMW dealer Auto Weissmann in Dulmen, near Dortmund and had only two owners in Germany before being imported to the UK.
"It was de-registered by its second owner in September 1998," says Ron. "And it doesn't seem to have been used between then and early 2000. It was absolutely immaculate and as soon as I saw it I knew it was just right. I've also got an M635Csi and I bought this to give the me the kind of performance that the M635CSi couldn't.
"I'm a great lover of the M635CSi and I've had mine for eight years and done a great number of mods to it for track day use. But at the end of the day I couldn't find any way of increasing the power to this level without astronomical expense so I went for the B10.
"I still prefer the 6-Series shape to these later 5-Series and initially I tried to find the twin-turbo B7S Alpina 6-Series but of the ones I found, none were really very nice and would have needed a full restoration to get them up to the condition I want."
Ron bought the 1992 car with just over 50,000 miles on the clock and has since added another 20,000 in the line of business as a project director in the construction industry. "The car came with a three-year BMW Euro Warranty in Germany and I've only used it once when a turbo gasket started to blow. Apart from that, it's been excellent and I have it serviced by BMW dealer Prophet's in Gerrards Cross."
Like the M635CSi, the B10 sees a fair bit of track day action and although the engine and suspension were fine, the brakes weren't. "My first track day at Croft saw me boiling the brake fluid and after that I had no pedal!" laughs Ron.
"I waited for a bit until the pedal returned and drove it to Motoscope in Northallerton, near the circuit, who purged the fluid and replaced it with Castrol SRF Racing Brake Fluid and it was OK then.
"After that, I had some Pagid fast road and track rear pads fitted but because the front callipers are special Alpina ones I can only get the front pads through Alpina at a cost of around £200. They're very good pads but not what I want for track days and Motoscope offered to take my old pad backplates and fit Mintex linings for about £120," says Ron. "The man from Lucas knows the Alpina part number, but it's blocked on the computer, so big thanks to Motoscope for saving the day."
Ron's Alpina B10 is a reminder of the late, great '80s when excess ruled and anything went. Nobody needs to do 181 mph but the fact that Alpina built a four-door BMW that would outperform a Testarossa makes it an absolute classic.