TUNING TESTS

TWR BMWs: 535i and 335i

THERE is souse irony to be found in these attractive Tom Walkinshaw Racing (TWR) conversions of the BMW marque. Back in 1977 Walkinshaw was perhaps the driver who ended Jaguar's hopes of winning with the Broadspeed XJC coupes, for it was Tom who held the immaculate Alpina BMW CSL coupe no the lead of that year's Tourist Trophy through a showery closing hour, leaving Rouse to crash the Jaguar whilst trying to score its first European Championship victory. One more race, at ZoIder, and the troubled "Big Cats" were withdrawn.

Yet today Tom Walkinshaw is winning races for Jaguar in that European Championship — the XJS we featured earlier in the year winning both the Czech round on the magnificent Brno street circuit and the Nürburgring, the latter despite the attentions of works BMW men Hans Stuck / Dieter Quester in the best 528i that could be found. The Walkinshaw business also prepares winning Rover V8s and sells Dunlop racing tyres through the DART concern at Silverstone, but the Alpina BMW links remain.

To find out the extent of the Alpina UK business today, I went up to the Dorchester, Oxon, premises where BMWs are modified behind a showroom and forecourt devoted mostly to the sales of Mazda cars! There is one BMW reminder in the showroom, Tom's racing 528i of 1977-78: there is nothing like gaining first-hand knowledge before stepping out to beat an opponent!

As luck would have it there was also a chance to once mom meet Burkard Bovensiepen, "Mr. Alpina," in Germany a few days subsequently so that a thorough background to these exciting cars could be established.

Although some Alpina parts are used in both cars, particularly those of the chassis and exhaust, these are not pure "Alpina-BMWs". Such cars are normally complete road models homologated with the German authorities and produced at the rate of several hundred a year under titles like B6, B7S and so on. As in International saloon car racing every aspect of the car will be changed, using many totally new parts, and the resulting machine will be thoroughly proven by testing that includes days at the Nürburgring.

Such Alpina BMWs are daunting in their Performance. Typical of our recent experience was the 330 b.h.p. Alpina B7S conversion that we tried in Germany last month. Costing under £25,000 it offered an instant 140 mph. with a capability of over 150 m.p.h. All at a price not so different to the British market level for the standard 635 CSi, but German taxes of only 13 per cent. make a big difference at such price levels.

No less impressive were the two cars TWR offered for test, but in totally different ways. First to arrive was an example of the new BMW 5-series range equipped with a modified 3½-litre engine. Since the latest BMW 5-series inner offered with the largest BMW straight six — and if there is such an animal on the stocks it will presumably appear with the new 635's reduced bore 3.4-litre — and since the old 535i was so popular in Britain, this is a conversion that made a lot of commercial, as well as driving, sense.

TWR will convert an existing 1982 model 528i to "535i" specification for £5,215 plus VAT. The lest car had been converted at the beginning of its life, and since it carried all the expensive options such as the computer, sunshine roof and a set of Alpina alloy wheels it was not surprising to learn that it represented "about £18.000 retail for a complete duplicate, including the cost of a well-specified new 528i". We are told that the 3½-litre engine could also be installed in the 525i if the car has the improved semi-trailing arm rear suspension that comes with a Michelin TRX option from the factory.

Beneath a subtly altered BMW body the heart of TWR's 535i was an engine offering a 56 h. h.p. bonus over the normal 528i's healthy 184 b.h.p. TWR are not content to merely ape the 218 h.h.p. that comes with a 735i or that used to be offered in factory 535s. The conversion work thus takes in not only remounting a 3,-litre six where 2.8-litres rested, but also features a TWR modified cylinder head. The latter carries larger valves and a 300 degree camshaft timing, the ports handmatched and cased to fit an Alpina freeflow exhaust system, ending with a distinctive oval over the usual twin pipe layout. Although a more vigorous camshaft is employed TWR say that peak power of 240 b.h.p. is developed at little more than production peak r.p.m. for the 3½-litre engine.

The car we tried had few other alterations: a firmer action for the Bilstein gas dampers and front strut inserts, plus 7J x 14 Alpina wheels, were the only relevant roadholding changes be the production 195/70 Michelins were retained. This demonstrator had also used the Pirelli P7 tyres with 73 x 16 in. wheels at the front and 8J x 16 in. at the rear. Excluding 15 per cent. VAT such a wheel and tyre conversion is sold by TWR at £1,245.

Styling changes that between them contributed to an outstanding feeling of security in the diabolically wet weather conditions of an English "summer" (standing lakes rather than puddles) comprised front and rear spoilers, plus the four-spoke Memo steering wheel made for Alpina. The front glassfibre spoiler was by TWR and, like the door mirrors, was sprayed in to match the body colour unobtrusively.

Although the 2.5/2.8i Bosch jetronic manifolding is carried over to a new home, and there is a new camshaft to consider, the TWR 535 drives in exactly the smooth manner that customers rightly demand of the standard product. Starting, cold or hot, is instant, and the relaxed way the six pulls the substantial 5-series body through traffic in third or fourth gear is an education in itself. In fifth 85 m.p.h. is displayed as a 3,000 r.p.m. amble and a three-way check on m.p.g. — my own overall calculation; the computer and the sophisticated economy meter that is not just a vacuum gauge — revealed a tuned 3½-litre of astonishing economy. At a steady 85-87 m.p.h. some 25 m.p.g. was still possible and it took a lot of full throttle motoring to pull consumption into the 20-21 m.p.g. range. I recorded 21.2-26.9 m.p.g. outside town with 19-23 the urban overall figure.

Performance? Exhilarating and sophisticated: the noise levels are confined to the odd murmur of wind noise until more than 5,000 r.p.m. is demanded, in which case the engine note takes on an urgency that betrays this is not just a comfortable carriage but a car capable of excellent cross country performance. The handling did surprise me in the wet, being much less prone to sudden oversteer under duress than the production 528i tried briefly at sunny Donington earlier this year.

TWR claim 0-60 m.p.h. should occupy 6.2 sec. and a top speed "in excess of 140 m.p.h.". The latter is extremely likely, for the production 535i of the old series would reach close to 140 m.p.h. on less power with an inferior aerodynamic shape. So far as the acceleration figures were concerned there was no chance of an independent test in the period and weather we suffered, but a French magazine's experience with the higher compression Alpina 535 would indicated that a time of seven to eight seconds is more likely for such a sprint. Either may the acceleration of the test car was as inspiring as every other aspect of this thoroughly appealing conversion: as a former 528 owner I envied the customer who purchased this 535 at the conclusion of our test. He or, quite possibly, she has purchased a blend of sporting dash, secure handling and long distance comfort that I could always accommodate, should £18,000 suddenly burn a hole in my pocket! Far more radical, and a lot less appealing to this driver when forced to part with 535, was the insertion of a standard 3½-litre engine in what had been a 323i! I have driven some similar large engine small cars to use a sa comparison: Alpina’s 2.8-lire 3-series (which the factory rightly frowned on when 328 was the mooted badgework!) and a number of unfortunate Escorts that found themselves with V6 or V8 power in the early seventies.

In fact the 335 was a lot more civilised than any Escort of the original series whatever the power plant, and I have it back with real regret. TWR had genuinely turned it into a thoroughly enjoyable weapon for the man who finds even the Alpina C1 2.3-litre conversion (170 b.h.p. instead of the standard 143 horsepower) a little anaemic.

Although the engine was standard in this case, its mounting had to be new of course. To prepare a 232i for such a transplant the front panel work has to be cut around to accommodate a larger radiator: even then the engine fits so tightly that the distributor rests virtually on the radiator and the complete engine bay appears to be occupied by the six cylinders. Other mechanical changes were needed, such as a special Alpina casing for the Getrag 6 and 7-series rations, avoiding the need to cut the floorpan and central tunnel area in order to accommodate a gearbox of sufficient torque capability. A production 3.45 final drive is retained but it is accommodated beneath a finned and immensely strong central differential cover, which picks up on a two-bolt mounting to the floorpan, and trebles oil capacity. A 323i has a production single bolt attachment. Linking gearbox and axle is a unique and shorter propshaft.

Most dramatic in their transformation of handling and braking are comprehensive chassis changes which include replacement coil springs front and rear from Alpina and Bilstein. All the production rubber bushings in the rear semi-trailing arms and associated mounting points are replaced by harder bushes; progressive rate springs are employed front and back. Because the production 3-series can be quite a handful, particularly in the wet, I would add that these modifications were outstanding in providing superb high-speed handling, even when provoked with a sudden variation in throttle or high braking loads. The only penalty is the kind of firmly absorbent ride that you would expect, given that Recaro sports seats and low profile P7s are employed. Under-pinning a radical set of modifications, we find that wheel and tyre sizes are different front to back: the 6J BBS carry 195/50 Pirellis at the steering end and 7J with 205/50 aft, all of 15in. diameter.

The rear brakes remained as in production but larger 335 mm. ventilated front discs were fitted at the front, although the normal callipers were retained. A long range fuel tank of 20 gallons occupied a little more boot space and might well be just the thing that owners of standard 3-series who are in the habit of commuting to Scotland. Even with the bigger engine installed it was impressive to see the best part of 200 miles recorded while the fuel gauge showed that nearly half the fuel tank’s contents remained.

Again front and rear spoilers and a Momo wheel were employed, but this time Recaro seats made a rather too firm intrusion on comfort and the front spoiler was an even higher quality Alpina unit, which costs nearly £100. The large capacity exhaust system (worth 7-10 b.h.p. itself) with its massive separate tailpipes is an Alpina product too. Reaching as far as the manifold downpipes it costs £369 plus £48 for fitting. The strongly recommended suspension improvements are priced without VAT at £246 for the Bilstens, £137 for the springs and £55 for the heavy duty rubber mounting bushes; labour to fit those items would amount to £72.

The complete conversion price of the car we tried? Some £10,000 beyond the price of a new 323i! Now £10,000 is a substantial amount of money to buy a complete car, never mind as a conversion cost but, as in Germany, a market exists. The C1 conversion referred to earlier for the 323i sold 17 complete cars in 1980, but since then TWR BMWs have been sold only in converted form for legal reasons (a complete guarantee with breakdown service is supplied). They have delivered ten of the 535s in new bodies with five on order. Just two more 335 machines are ordered in addition to the one tested here.

Of course the dominant impression of a 3-series equipped with over 200 flexible horsepower is that of sheer performance. As you rush to 48 indicated m.p.h. in first, 75 m.p.h. in second and over 100 m.p.h in third it’s very easy to accept that this awesome device is capable of reaching 60 m.p.h. from a standstill in under six seconds – as Walkinshaw himself demonstrated at Silverstone recently – and that the speed with which 130 m.p.h. comes up makes he cost of this conversion almost reasonable!

The charm lies in having the power, handling and brakes of a competition saloon, allied to complete docility and unheated progress through traffic jams. The car has a distinct character that does slowly grow on you: from the gruff double burble of exhausts to handling that convinced me BMW ought to be made to try some of the chassis modifications themselves in any new 3-series.

It is very pleasant not to have any qualms at all about safely enjoying a very high level of performance indeed. Of course the P7 is a remarkable tyre, but the balance of the car remained intact despite the heavy engine bonus in the nose. We took the 335 our first in floods where any heavy application of power in third and fourth would produce wheelspin, yet the TWR 335 could always be skated in the right direction albeit with the real wheels understandably out of line under power. When full power from 2,000 r.p.m. in third produced a gently controllable tail slide over sodden tarmac I knew that the ensuing few days of usually wet motoring would provide memorable, and they did.

However, the car was also used to provide more than 22 m.p.g. in a brisk tour up to GPA Models at Radlett, chugging through thunderstorms and suburban traffic with all the well ventilated civilisation that a BMW ownder would expect, only the heavier brake and clutch pedal action a reminder of the power behind those now subdued exhausts.

I was prepared not to like the 335. The wipers lifting from the screen at 115 m.p.h., the occasional over-run surge from the injection cut-off fuel system and combination of ride and seating that left one more fatigued than necessary, I did make it some time before I appreciated the sheer exhilaration of such a cheeky Q-car once more.

However, my applause is reserved for the 535i, the tuning work seemed to have added another dimension to what is already an exciting proposition without inflicting an unjust fuel consumption penalty. The BMW business is liable to prosper chez Walkinshaw. . . but I can’t wait for him to start offering sportier Jaguars! J.W.