Despite the fact that modern cars have amazing power and performance, most of them now use turbocharged engines. For lovers of interesting, naturally aspirated or slightly quirky powerplants, this can be a bit frustrating. The relentless quest for fuel economy and environmental standards has killed some of the most interesting engines ever produced. Here are 5 of my favourite weird engines they really wouldn’t make these days!

BMW M5 S85 V10

This strange engine code represents one of the best naturally aspirated engines BMW had ever produced – the 5.0-liter V10 which was installed in the 2005 to 2010 BMW E60 M5 and E63/E64 M6. This V10 was one of those once in a lifetime engines which combined BMW`s racing heritage with the latest in engine technology. In those days, BMW was very active in Formula One so somebody in the M Performance department decided to transfer racing know-how into a road-going super saloon.

Despite being basically an M3 V8 engine with 2 extra cylinders, the result was the glorious 5.0-liter V10 with a high revving capacity and red line at 8250 rpm which was insane in 2005 and still is today. The power output was equally impressive at 507 HP with 384 lb-ft of torque. With such firepower under the bonnet, the E60 M5 was easily the fastest sedan of its generation and a true modern classic. Unfortunately, BMW decided to go with turbocharging for its successor and killed the V10 magic. It will not be forgotten!

Audi RS6’s 5 litre V10

Audi`s lineup has always been full of unique engines and one of the most interesting is the 2008 to 2011 5-liter turbo V10 unit. Producing 570 HP and 480 lb-ft of torque, with a red line at 7500 rpm, the RS6 engine is really pretty cool. Like many of the great engines, it was built by hand and had specially issued parts and components to distinguish it from similar, naturally aspirated engines in other Audis.

The specifications, exotic materials, and enormous power suggest this was a supercar powerplant which essentially, it was, being also used in the Lamborghini Gallardo as well. Despite the universal praise from the motoring press and unbelievable performance in the RS6 station wagon, Audi have decided to go with smaller and more conventional engines in current models.

Dodge Viper V10

The king of all naturally aspirated sports car engines is the mighty Viper V10. Conceived in the late `80s using basically a truck engine as a starting point, the Viper V10 has evolved into one of the most impressive powerplants, not just for its sheer size but also for its unbelievable power, torque and smooth running. A lot of people makes mistakes and claim that Viper`s engine is the same one you will find in heavy-duty Ram trucks of the early `90s but this isn’t really true to be honest. The Viper`s V10 is made of aluminum and not cast iron, with a totally different bore and stroke as well as the rest of the engine`s components. When it was introduced in 1992, it displaced 8.2-liters of pure American muscle which delivered 400 HP and 464 lb-ft of torque but soon after the power grew to 450 HP.

The second generation brought a slight increase in volume to a hilarious 8.3-liters and 510 HP but Chrysler`s engineers eventually managed to squeeze 600 HP from this beast. The last Viper to be built had an 8.4-liter V10 engine with 640 HP and the rumor was that Fiat Chrysler Corporation deliberately kept the output low because Ferrari was afraid that the Viper could outperform anything coming from Maranello if the engine was given full power. We don’t know if this is true, but its just sad that Chrysler killed the Viper and its glorious V10 engine.

BMW 320si N54B20S

BMW was quite busy in the early 2000s when it came to racing. With Formula One, the GT championship and the ETCC series to contend with, BMW needed a touring car ready for racing. In order to enter, the brand had to produce a few hundred production ready cars, available to the public matching their race car. The result of this was the E90 320 SI. Under the hood though was a 2.0-liter four-cylinder which at first glance is ordinary enough but it was actually pretty much a racing engine.

Assembled in the UK by a specialised engine shop who normally make Formula One engines, the N54b20s was super advanced and largely handbuilt. Interestingly, it came without BMW`s signature Valvetronic system since it restricted the engines ability to rev. The result was a modest 175 HP with 147 lb-ft of torque but with racecar characteristics. Rather like the e30 M3, BMW chose a 4 cylinder because it allowed the weight in the engine bay to be pushed further back, improving handling. Unfortunately, being a British engine, they are unsuprisingly not very reliable!

Audi`s V12 TDI

Most of the time, diesel engines are nothing to be excited about. Oil burners are usually a dependable and fuel efficient choice for people who cover a lot of miles, but not really for car people. That being said, the thoroughbred V12 turbodiesel engine from Audi is something special. With 500 horsepower and an earth moving 740 lb-ft of torque, this engine is definitely worth the attention.

Having 4 times the amount of cylinders as a modern supermini, this enormous unit was not only immensely powerful but physically large as well, meaning that, Back in 2008, it was only suited for Audi`s biggest SUV model – the Q7 V12 TDI. Thanks to massive torque ratings, the 2.6-ton luxury SUV could accelerate from 0 to 60 mph in just 5.5 seconds shaming most sports cars of the period.

Unfortunately, Audi decided to retire this goliath of an engine. Despite all the qualities, the Q7 V12 TDI was a very expensive ride and after the infamous Volkswagen`s Dieselgate scandal in America, the general automotive climate has changed towards hybrids and electric vehicles.

So there you are. What great engines would they really not make anymore? Let me know in the comments.