An injection of pace: fuel-injected Aston Martin DBS vs its V8 sibling

By Martin Buckley

| 19 Mar 2019

Classic & Sports Car – A pair of forgotten Aston Martins

It’s not only six versus eight with these two DBSs – it’s time these forgotten Astons stepped out from the shadows

There cannot be many nuggets of post-war Aston Martin history that have not been obsessively picked over, but the six-cylinder AE Brico injected cars of 1969 to 1971 never seem to merit much more than a dismissive footnote.

Offered as a no-cost option on the DB6 MkII from late 1969 (supplementing triple SUs or Webers), it got a troublesome reputation early on.

And it seems that most of the 46 cars were converted back to carburettors to placate owners who were having problems with fuel-pump pressures, transistors and solenoids; not good business for Aston at a time when its cars were as much everyday transport for sportily inclined tycoons as they were exotic enthusiasts’ toys.

What is less well known, however, is the fact that 15 six-cylinder DBS Aston Martins were also Brico injected.

The de Dion rear gives fine grip in corners

Gleaming after a bare-metal repaint in Silver Birch, Martin Duckworth’s 1970 auto, chassis number DBS6FI/5592, is thought to be the sole injected DBS still running with all its original parts.

The only outer giveaways are the ‘FI’ badges on the wing vents. He has owned it twice: the first time as cheap non-runner in 1976, then again in the late 1990s when he rediscovered it, needing sills and an engine rebuild, at an auction.

Today is the first time he has driven the car in 20 years.

“It was only six-years old when I first had it; I insisted that the deal included a factory workshop manual. After some head-scratching I got it going on Easy Start and worked out that all it needed was a £6 temperature sensor.”

This is the second time Martin Duckworth has owned this Silver Birch DBS

By way of comparison, and also as a way of illustrating just how schizophrenic the three-body/two-engine Aston Martin range was in the early 1970s, Steven Prevett’s 1971 DBS V8 joins us as an elegantly brutish counterpoint to the more gentlemanly ‘six’.

With a top speed of 170mph, this was the world’s fastest four-seater of its day, the flagship product of a Buckinghamshire factory where its cars were hand-produced at the rate of 80 a month.

These early and rare injected Astons represent a period of transition between the stability of Sir David Brown’s 24-year ownership and the much more uncertain 1970s.

With interest in the DB6 in decline (there had been a savage £1000 price cut to clear stocks in 1967), the DBS was the new sensation the firm needed.

Steven Prevett has owned his 1971 DBS V8 for nearly 20 years and enjoyed 40,000 miles in it – and counting

In some ways, William Towns’ modern, wide-bodied DBS coupé, first seen in 1966, was a natural home for this advanced electronic system, subject of seven years of development by Brico of Coventry.

Aston had been flirting with mechanical injection since the early ’60s, but the Brico system was the first all-British electronic set-up.

It had sensors and control valves, and squirted high-pressure fuel into the induction ports on the say-so of an ECU that pulsed the solenoids at precisely the right moment for any given load or speed, having taken account of manifold depression, throttle opening and temperature readings.

This was sophisticated stuff in 1969 (only matched at the time by the new Bosch electronic injection on the latest mid-sized W114 250E Mercedes-Benz), although it was really a response to the looming threat of American emissions regulations rather than a way of liberating more urge.

If anything, the Brico cars had less power, with tamer cam profiles (to take account of a peculiarity in the timing of the fuel delivery), although engineering director Dudley Gershon reckoned that he clawed back much of the loss with better manifolding; his ’75 memoir does not give a figure and Aston had, in any case, given up advertising power outputs in protest at other manufacturers’ boastfulness.

The small 'FI' badges are the only external giveaways

Only Aston offered the system commercially (Jaguar, Rover and even Ferrari were testing it), and might have continued with it had Brico not sold the rights to Lucas in 1971.

With £8m owed to the company by Rolls-Royce (then in administration), AE Brico realised it didn’t have the funds to complete development.

When it was clear that Lucas was going to shelve the Brico injection in favour of its well-established mechanical system, Aston had little alternative but to return to carburettors only on the 4-litre Tadek Merek-designed straight-six.

The service problems of the 1969 DBS V8 meant Aston was probably losing its appetite for injection. With its distinctive 19-inch ram pipes and beautifully engineered ball-and-roller throttle linkage, this 345bhp quad-cam powerhouse showed, in testing, every sign of being reliable. Developed closely with Robert Bosch of Stuttgart, this mechanical fuel injection had governing parameters of throttle position, engine speed, water temperature and altitude, and should have been bulletproof, given that similar hardware was found on lots of Mercedes.

It is now well known that its downfall was over-fuelling and bore-wash, with disastrous consequences for bearings if the oil was not changed regularly, ideally every 2500 miles.

The diluted mixture would glaze the bores, knock out the oil pressure and leave dealers in the embarrassing position of having to sort smoky engines in £8000 motorcars that had done few miles.

This rebuilt 4-litre ‘six’ is one of just 15 to have Brico injection from new

David Jacks of Aston Engineering in Derby feels the lack of familiarity with injection at that time, plus the fact that the injection pumps take ages to settle – coupled with the natural human urge to fiddle – are as much to blame for the V8’s early reputation as anything else.

“The general mechanics of the day didn’t understand the system,” Jacks explains, “and both the Brico- and Bosch-injected cars are typical of Aston in that they wanted to push the boundaries, but didn’t make the cars in high enough quantities to sort them out.”

The first official carburetted V8s are associated with the single-headlight cars post-1972 (although there were a few single-headlight Company Developments injected crossovers), but Jacks recalls that the factory converted at least 10 quad-headlight DBS models to carburettors for customers in period, using a very restrictive flat-top airbox that cost the quad-cam all-alloy V8 as much as 30 horsepower, but meant the flat bonnet could be retained.

Prevett’s DBS V8, one of only three in Oyster, is a pleasingly sorted and regularly exercised manual example that he has owned since 2000.

“I paid £14,000 for it,” he recalls, “but it was painted bright red then. I had a TVR Griffith – in fact I still have one, I love TVRs – but I needed a classic with four seats for my children.”

The big V8 is still strong when properly set up

We are humming along, dodging April showers and keeping an eye in the rear-view mirror for Duckworth in the Brico car, who is having problems with his windscreen wipers.

The quad-cam V8 is smooth and sonorous, rippling with torque having been uprated to 5.6 litres during its previous engine rebuild and gaining an instant 30bhp from the ‘rocket’-type four-into-one exhaust manifolds that are now an accepted upgrade on these cars.

Early V8 tests talk of disappointing torque below 2000rpm, but it feels as if it would pull down a gable end just above tickover, which is perhaps a bonus of the four-into-one system. Prevett admits it had issues in period but, with care, his car is reliable and often used daily.

He likes that, even after a good thrashing, it always idles nicely, thanks to the injection.

Duckworth's 1970 car has an automatic gearbox (left); shortened ZF gearlever in the V8

Somehow, the 70-profile tyres (on 7in-wide GKN alloy rims) give the V8 a more bullish stance than the ‘6’ on its glinting centre-lock wires, but the chisel-nosed fastback bodies are identical (complete with MkII Cortina front indicators and Hillman Hunter tail-lights), as are the cabins where you sit fairly low in seats that don’t quite support the thighs and are more boardroom than grand tourer.

There is clear, workmanlike instrumentation (the oil-pressure gauge is directly in the driver’s sight), and the aroma of leather helps you to forgive the slightly scatty minor controls and the hard-to-fathom heating and ventilation.

There is more room in the back seats than you might expect and the boot makes up in depth what it lacks in length, but neither is at it best in town, with their supertanker turning circles, big three-quarter blind spots and, in the case of the V8, a hefty clutch, although its smooth engagement and feel is some consolation.

Prevett has shortened the gearlever and maybe that’s why the change is particularly sweet on what is usually a meaty-feeling, ZF-supplied gearbox that doesn’t like to be rushed. Neither car is silky or cosseting, favouring handling over absolute comfort, so you can hear and feel the hum of the road and the slap of the tyres.

Soon the feeling of great width fades and you sense the impressive margins of stability in these Astons, which are viceless and easy to place, with a de Dion rear that digs in on sharp corners and gentle understeer to lead you safely through fast, long ones with a relative lack of roll.

The six-cylinder car pulls well

These were big GT cars with sports car instincts, but there are predictable differences in straight-line urge. The V8 weighs 250lb more than the ‘six’ but, given clear roads, it would turn the 4-litre car into a speck in the distance.

It accelerates with a suave savagery that makes any overtaking manoeuvre a breeze, any clear stretch of road its rightful own in a reverie of sophisticated quad-cam rumble and fearless solidity, communicated through the carefully valved power steering.

Put into figures, the high gearing in the intermediates gives the potential for 80 in second, 110mph in third and 135mph in fourth with another gear to go.

At that speed, the DBS6 would be flat-out even in manual form: given that the BorgWarner Model 8 ’box tempts untold numbers of horses from their proper place – and has but three forward gears – we can assume a top speed (as if it mattered) the wrong side of 130mph.

Somewhat lost in the massive engine bay, the straight-six, with that unfamiliar Brico plenum chamber, has a warm hum to it once under way and a lusty character with one foot still in the 1950s; a trait that would have made it the choice of Aston’s more traditional customers.

Which is not to say the DBS injection is slow. It churns its torque converter off the line, but has a brisk feel with refined mid-range pull. I felt it was slightly quieter and smoother than a DBS on carbs and Duckworth was pleased that the hot starting on his car was better, firing at once, while the V8 spent five seconds turning over.

Duckworth has only just rekindled his affair with his DBS, but Prevett has run his V8 for 18 years and 40,000 miles, and watched the market wake to its charms. He finds insuring it for £220k a bit of a worry.

The upside, I suggest, is that people like him are more willing to restore these once-unloved models, which is good for the cars, but only if people actually use them.

Images: Tony Baker

Specialist advice

Former Aston man Andy Chapman knows the foibles of these systems

Andy Chapman worked for nine years in Aston Martin’s service department, later becoming an engine fitter, a road tester and an engine-shop foreman before branching out on his own as Chapman Spooner in 1975.

“Before leaving Aston in 1970, I aimed to learn as much as possible about Brico and Bosch injection,” he says. “Certainly the Brico system had many niggles. Whatever we did, we couldn’t get rid of its flat-spots. I was led to believe the black box needed more functions. There was a light-throttle problem that was not rectified, but at full throttle it pulled like a train.

“The factory modified the control box and fitted a new inlet camshaft, but this didn’t solve it. Air and water senders were a problem, and if mechanics did not replace the ‘O’ rings when injectors were removed, they leaked into the manifold.

“There were also problems with a vacuum pipe to the control unit – which kinked – and bad electrical connections. A later thought I had was that the mixtures were too weak to overcome the drying out of the manifolds at idle. But it had so much promise and I think a modern electronic ignition system would help. The DB6 MkII auto was very lively to 60mph with Brico.”

“The Bosch system on the V8 also had its problems,” Chapman continues. “They needed careful setting up; when this was carried out the cars ran well. The injection pump was in the middle of the ‘V’, with engine heat affecting the settings. The Opus ignition system was not up to the job and the engine ran rich at high revs.

“The tappets also needed to be adjusted regularly to hold tune. Even then emissions regulations could not be met, and Weber carbs proved more successful.”

A brief history of electronic fuel injection

The Mercedes-Benz 300SL had the first production mechanical direct-injection set-up

In the 1950s, America was booming and was the world’s richest country, with hard-won innovations from WW2 trickling into the consumer market. Stuart Hilborn, who had served in the Army Air Corps, started experimenting with aviation-derived mechanical fuel injection for cars.

General Motors clocked the benefits that Hilborn’s system – and others – offered compared to a carburettor, and Chevrolet’s mechanical ‘Ramjet’ fuel injection came in 1957, giving its C1 Corvette electrifying pace. GM wasn’t the first to use a production mechanical set-up – that was Mercedes’ direct-injection system in the 300SL – but home-grown rivals didn’t like GM’s new technical edge.

Fortunately for Chrysler, US specialist Bendix was busy getting ahead of the curve. Mechanical injection required pricey precision equipment and, in cars, could sometimes be outperformed by a finely fettled carb. In Bendix’s ‘Electrojector’ set-up, each cylinder had its own electronically triggered injector. Impressed, Chrysler made it available on some models.

The date 28 September 1958 marked the official production introduction of an electronic fuel injection (EFI) system. Sadly, if predictably, the optional $637 Electrojector (over £5000 in today’s money) was ruinously unreliable. Only 35 Electrojector cars were made and most were later retrofitted with carbs.

Even today, an Electrojector system wouldn’t be unfamiliar to those used to EFI, and it wasn’t a new idea: in 1940, Alfa Romeo tested a prototype 6C-2500 on the Mille Miglia with Ottavio Fuscaldo’s simple EFI system, before war got in the way.

Chrysler bailed out of the partnership, but Bendix persisted and licensed its patents to Bosch in 1965. Bosch delivered its first ‘D-Jetronic’ EFI set-up in the 1967 Volkswagen 1600.

Better hardware and falling costs meant a wider roll-out of the technology and, as emissions controls tightened in the 1970s, EFI rose to dominance due to its improved drivability, efficiency and precise mixture control. By 1990, electric fuel injection had finally found its feet and became practically standard across the board.

Additional words: Lewis Kingston

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