The world’s most controversial car engines

This might not mean that they were bad, though some undoubtedly were. Others may have been generally excellent, but flawed in some way, or used in the wrong car, or introduced when the world wasn’t yet ready for them.

Here are 30 examples, offered for your consideration in alphabetical order.

Once described as “a horrible engine, but free from bugs”, the B-Series was designed by Austin and powered a great many mid-sized British saloons, as well as sports cars such as the MGA. Some examples of the latter were fitted with a special version which had two camshafts mounted above the cylinders rather than just one placed alongside them.

Far more powerful than any other B-Series, it made the MGA very successful in competition when running on high-octane race fuel. On the petrol available to ordinary motorists in the late 1950s, it was exceptionally fragile, and threatened to do so much damage to the car’s otherwise splendid reputation that MG abandoned it after building just over 2000 cars, from a total MGA production run of more than 100,000.

“Fascinated by its own successes and in unbridled euphoria about performance, BMW had built a car that contradicted the spirit of the times like no other automobile had ever done before.” These are BMW’s own words about the 2002 Turbo, the only model powered by the M31 engine, which was a forced-induction variant of the long-running four-cylinder M10.

Producing 170bhp, it could accelerate the car from 0-62mph in under seven seconds, a remarkable statistic for 1973. On the downside, the Turbo was expensive, suffered from prodigious turbo lag and used an enormous amount of fuel, which made its launch right at the start of a global oil price surge particularly unfortunate. Production was cancelled in 1975, after just 1672 examples had been built, but this once controversial car is now celebrated as a true performance classic.

BMW’s second automotive V12 won the over 4.0-litre category in the 1999 International Engine of the Year awards. A year earlier, it appeared in the short-lived Rolls-Royce Silver Seraph, an application which has been regarded as a mistake.

The 5.4-litre M73 produced its maximum power and torque at relatively high revs, which was fine in BMW’s 7 Series and 8 Series since they were expected to be bought by enthusiastic drivers. A Rolls-Royce was more about making progress in an unflustered manner, and the M73 wasn’t ideal for that. Notably, when BMW took over Rolls-Royce, one of its first moves was to develop another, larger V12 more suitable for the luxury cars it was now responsible for, and Rolls continues to use it today.

As its name suggests, this engine was a V8 which could run on six or even just four cylinders in situations where fuel economy was more important than power output. Cylinder deactivation had been tried mechanically in the first decade of the 20th century, but in 1981 Cadillac attempted to achieve it by electronic means.

Today, that isn’t a problem. More than 40 years ago, electronic technology wasn’t sufficiently advanced to make the system work well. Swamped by complaints that the V8-6-4 didn’t run properly no matter how many of its cylinder were working, Cadillac withdrew it very quickly, though not before writing letters to owners warning of “unwarranted adverse publicity” in the media.

PICTURE: Cadillac Coupe De Ville

Ingenious though it appeared to be on paper, the Chevrolet Vega developed a reputation for unreliability soon after its 1971 launch. Many, though by no means all, of its numerous problems were related to its 2.3-litre four-cylinder engine.

Its block, made of an aluminium-silicon alloy, was vulnerable to warping if the engine overheated – which, for various reasons, often happened. Improvements were made, but not soon enough to overcome the controversy.

The engine in the Chevrolet Series M of 1923 was actually air-cooled, but earned its nickname because its cooling fins were made of copper. GM insiders were so confident about it that they felt water-cooled engines would soon be obsolete, and foresaw monthly production of 50,000 units before the end of the first year.

In fact, only 759 Series Ms were ever built, and many of them were scrapped immediately. The engine was very difficult to build, and cataclysmically unreliable. GM killed the project so quickly that the controversy did not extend far beyond the factory gates, which is one of the few good things that can be said about it.

Although the Chevy smallblock is often regarded as one of the wonders of the automotive world, it’s difficult to find anyone with a good word to say about the 4.4-litre 267 version. Briefly produced around 1980, during what has been called the Malaise Era of US car design, it was an adaptation of the famous engine intended to provide decent fuel economy and acceptable exhaust emissions.

In modern terms, it wasn’t good in either respect, but most of the criticism concerns its performance. As fitted to the ‘80 Camaro, it was rated at a mere 120bhp, only 5bhp more than the 3.8-litre V6 engine at the bottom of the range – a poor show for a V8 version of what was meant to be a car for enthusiastic drivers.

PICTURE: representative 1981 Camaro

The LH was a 2.7-litre V6 introduced in 1998 and fitted to several models including the

Chrysler Sebring (2007 Cabrio pictured). It became notorious for a phenomenon called oil sludging, in which the oil is contaminated and becomes an ineffective lubricant, leading to devastating engine failure.

Various explanations were put forward. Chrysler said owners were at fault for not maintaining their cars properly, which went down very badly. Another, more persuasive suggestion is that water leaked into the oil through a failing gasket.

In 1969, when Wankel rotaries were being seen as an important part of the future of motoring, Citroën introduced the M35, a derivative of the Ami with a single-rotor engine. Never officially sold, it was instead offered to members of the public for trial purposes, and was warmly received.

Four years later, the company fitted a twin-rotor engine to a version of the successful GS and called it Birotor. Unlike the M35, it was a disaster, to an even greater extent than the BMW 2002 Turbo but for similar reasons. By GS standards it was unbelievably expensive and very uneconomical, factors which would have been unwelcome at any time but especially in the early days of a global oil crisis.

Calls for specific cars to be banned have been extremely rare in the 21st century, but the most powerful version of the 2018 Dodge Challenger inspired just such a thing. It was powered by the Demon version of Chrysler’s 6.2-litre supercharged V8 engine which, on suitably high-octane fuel, produced 840bhp.

Because of this startling figure, a respected industry magazine described the car as “inherently dangerous to the common safety of motorists” and “the result of a sequence of misguided corporate choices that places bragging rights ahead of public safety”. Oddly, there has been less fuss about the 2023 Challenger SRT Demon 170, which produces 1025bhp.

Initially designed by Navistar and first used in the 2003 model year, the 6.0-litre turbo diesel V8 in the line-up known as Power Stroke proved to be exceptionally expensive for Ford. According to one employee, it accounted for only 10% of the company’s engine production, but approximately 80% of its warranty payments for engines, and around 25% of its warranty payments for all issues combined.

Ford lost even more money compensating aggrieved customers of Super Duty trucks (pictured), Econoline vans and Excursion SUVs, in a series of class action lawsuits and individual court cases.

Available in capacities ranging from 1.1 to 2.0 litres, the CVH was a four-cylinder engine with hydraulic lifters and a hemispherical combustion chamber, intended as a replacement for the long-running Kent unit in European models such as the Escort (1981 XR3 pictured).

Although it was introduced in 1980, 21 years after the Kent made its first appearance, the CVH was barely a step forward in terms of refinement, and was once compared unfavourably to a Moulinex food mixer. The far superior 16-valve Zetec (formerly Zeta) engine family which came along in 1992 showed what Ford could do if it tried.

In the 1960s, Ford’s British and German operations both introduced V4 petrol engines, a layout which has since disappeared from the motor industry. The former, known as the Essex, was acceptable enough in the Transit van, but when it replaced the Kent in the Corsair (pictured) during 1965 there were complaints that the car was now noisier and less economical than before, and (thanks to increased nose weight) no longer handled as well as it used to.

Despite this, Ford persevered with the V4 in passenger cars well into the 1970s, using it in the Capri, Consul and Zephyr. Fittingly, though, it survived longest in the Transit, the vehicle to which it was most suited.

The 255 was to the Windsor as the 267 was to the Chevrolet smallblock – an unfortunate example of an otherwise great engine created in an attempt to reduce fuel economy around 1980.

Not particularly appealing in any model, unless you really wanted a V8 no matter how it performed, it was especially disappointing in the Mustang (pictured), on account of producing only around 120bhp. By the early 1990s, you could have more power than that in a Fiesta.

Although it was created by the Pontiac division, the 2.5-litre four-cylinder Iron Duke powered models in every GM brand except Cadillac, as well as many AMC vehicles including the Jeep CJ (1980 Wrangler Renegade pictured).

It has been widely reviled because it is not interesting, though this is not a necessary attribute of a successful engine. There is, however, a case for taking offence at the fact that it was fitted to the third-generation Chevrolet Camaro, for which its sub-100bhp output seems quite unsuitable.

Unlike the Mini, its most obvious rival, the Imp and its variants were powered by a very adventurous engine. The all-aluminium unit, available in road-going models with capacities of either 875cc or 998cc, was designed by Coventry Climax, and featured all-aluminium construction and an overhead camshaft, both quite foreign to the Mini’s BMC A-Series.

The little engine could be tuned to produce enormous amounts of power for its size, leading to great success in motorsport. Unfortunately, it also reacted very badly to being overheated, which led to a reputation for disastrous reliability – unfairly so, since it can last for a very long time as long as it’s always kept within the optimal temperature range.

It seems almost incredible now that a manufacturer would develop a V12 engine specifically for a mid-priced model, but that’s what Lincoln did in 1936. The unit designed for the Zephyr was less expensive to create that it might have been, since it was derived from Ford’s flathead V8.

One unfortunate part of the design was that the exhaust was ported through the cylinder blocks, where its heat was transferred to the water system. Reliability suffered, leading to comments that “a lingering puff of smoke at a stoplight meant a Zephyr had just left”, and although Lincoln made improvements while the car was still in production its reputation for unreliability lingered too. Its life ended in 1948.

A brilliant and innovative car in many ways, the Ro 80 was powered by a twin-rotor engine. For the first few years after its launch in 1967, this was miserably unreliable, a problem which turned what should have been one of the most admired European cars of its era into one of the most controversial.

NSU, which should have sorted things out before the Ro 80 went on sale, in fact did so while it was in production. The car survived for a full decade, but the reputational damage to its maker was so severe that NSU itself was discontinued in 1977, and now lies dormant in the depths of the Volkswagen Group.

Oldsmobile’s diesel engine was based – too closely, as it turned out – on an existing petrol V8. The designers failed to take sufficient of the higher cylinder pressures (diesels have a much greater compression ratio), and this led to tremendous reliability problems.

Necessary changes were made, and a related V6 was much better right from the start, but public perception was so negative that production was abandoned in 1985, just seven years after it began. The V8 has since been blamed for American motorists’ long-term refusal to accept diesel engines in passenger cars.

PICTURE: second-generation Buick Regal, one of many GM cars available with the Oldsmobile Diesel

The CIH (for ‘cam in head’) family included many inline four and straight six engines, including a 3.0-litre 24-valve version of the latter fitted to the Opel/Vauxhall Carlton and Senator GSi. Some Carltons left the Opel factory in Rüsselsheim in standard form and were transported to Norfolk, where they were converted by Lotus into the right-hand drive Vauxhall Lotus Carlton or the left-hand drive Opel Lotus Omega.

This process included increasing the capacity of the engine to 3.6 litres and adding twin turbochargers. The resulting 377bhp power output was shocking for a saloon car sold in the early 1990s, and made the Carlton so fast that there were calls in the UK press for it to be banned. As often happens in these cases, the controversy came to nothing as calmer voices observed that many other companies made powerful cars too.

Until 2016, all Porsche Boxsters and Caymans were powered by flat six engines. For the current generation, known as 718, these were replaced by 2.0- and 2.5-litre turbocharged flat fours. This led immediately to cries of protest from people who didn’t think that a Porsche should sound like a Subaru Impreza.

A 4.0-litre flat six was added to the range in 2020, but the flat fours remain available on all but the most expensive versions.

There was plenty for the traditionalist to become upset about when the 911 entered a new generation (codenamed 996) in 1997. The body, though similar in profile to previous 911s, looked different, the headlight units were of such an unusual design that they were caustically referred to as fried eggs – and then there was the matter of the engine.

More than 30 years after the introduction of the original model, Porsche had finally decided to cool its flat six with water rather than, as before, with air. Air cooling was by now as historic as tail fins and starting handles, but that didn’t stop people complaining that it had been abandoned. “Porsche enthusiasts look the other way,” we suggested, because the 996 “represents a betrayal of everything the car maker had hitherto stood for, they tell themselves.”

The Billancourt was developed for Renault’s first post-War car, known in France as the 4CV and in the UK as the 760 (and later 750). It was a perfectly good engine, but in 1962 introduced the more modern and more powerful Cléon-Fonte. The Billancourt remained in the Renault 4, though, and when the 6 (based on the 4, but larger and heavier) was introduced in 1968, it must have seemed reasonable to use it in that too.

Controversy immediately followed. The old engine was too weak for the new car, which was in turn too slow even by the standards of a cheap French model of the late 1960s. Renault saw the error of its ways and added the Cléon-Fonte to the line-up in 1970, though the Billancourt remained available for customers who didn’t need to get anywhere in a hurry.

The K-Series first appeared in the Rover 200 in 1989, and was later used in many Rover and MG vehicles, along with cars produced by Lotus (Elise S1 pictured) and Caterham, among others. It was impressively light, and could be tuned to produce very high outputs for its size.

Its reputation has been blighted by a tendency to suffer from head gasket failure, though not necessarily because of a problem with the gasket itself. Replacement is difficult because the cylinder head bolts extend a long way down the engine, which therefore has to be disassembled to a greater extent than usual in order to reach the gasket.

The Saab B engine was a redesign of one designed in the 1960s by Triumph. From 1978, it was fitted with a compressor in the 99 Turbo, which therefore postdated the BMW 2002 Turbo by five years but was produced and sold in far greater numbers.

For its time, the car performed very impressively, but it also introduced the concept of turbo lag to drivers who had previously never heard of it. For nearly half a century, it has been almost impossible to have a conversation about the 99 Turbo without this, its most unfortunate feature, being mentioned at some point.

In its original form, the EK was a 356cc two-cylinder two-stroke which first appeared in the tiny Subaru 360 in 1958. This car was well suited to Japanese motoring conditions, and remained in production until the early 1970s.

It became controversial only in 1968, when imports to the US began. A spectacularly damning report published the following year included harsh criticism of the EK, which “simply cannot accelerate the car fast enough to keep up with today’s faster-moving traffic”.

In order to continue selling the popular Midget sports car in the US, MG had to make many changes in the mid 1970s. One of these was to replace its 1.3-litre BMC A-Series engine with the 1.5-litre version of the Standard SC, a choice “guaranteed to cause controversy” (in the words of the MG Owners’ Club), since it was already being used in the Triumph Spitfire.

MG and Triumph had been under the same ownership since 1968, but enthusiasts of the former considered the Spitfire to the Midget’s natural enemy. The fuss eventually died down, and the 1500s, immediately identifiable by their large rubber bumpers, are now considered to be ‘real’ Midgets.

Triumph’s 3.0-litre V8 engine was a derivative of the company’s slant four, and made its debut in the only production model it was ever fitted to – the attractive Stag sports car – in 1970. The Stag’s reputation was trashed almost immediately because of the V8, which could fail spectacularly and was dizzyingly expensive to repair.

The pity of it is that none of this had to happen. The V8’s problems are now understood and can be avoided, and current owners of well-maintained Stags report that they run reliably.

This was a straight six engine measuring either 3.6 or 4.0 litres and fitted to many TVR models, including the Sagaris (pictured) in the first decade of the 21st century. An excellent performer, if not necessarily as thrilling as TVR’s V8s, it soon became controversial because of its unreliability.

The designer of the prototype engine came up with a ‘performance and reliability upgrade package’ intended to solve the problems inherent in the one produced by TVR, though it should be pointed out that some people had no trouble with the latter.

There was nothing wrong with the basic design of VW’s EA189 diesel engine, known to customers as the 2.0 TDI and fitted to many VW Group vehicles including the Jetta (pictured). Indeed it seemed at first to be extremely successful, delivering zestful performance, a relatively smooth operation, and impressive economy. But it hid a dark secret that would cost its parent $40 billion.

It housed a cheat device which made its exhaust emissions greatly smaller when it detected it was undergoing official testing than they were when a car fitted with it was driven on the road. Dieselgate, as the scandal became known, led to similar revelations about other engines produced by several manufacturers, but the mud has stuck more tenaciously to the EA189 than to anything else.