- 12 Min Read
- By: Christian Schaefer
European Cross-Plane V8 Engines You Should Know About
The cross-plane crankshaft has been at the center of some of Europe’s all-time great V8s. Whether turbocharged or naturally aspirated, small or big displacement, the V8 has remained a seldom-found option across the pond, making it a particularly special animal. Now, with the advent of EV tech and a conscious effort to reduce carbon emissions, it seems like we’ve reached the end for the big engine. In an effort to numb the pain, here’s a look back at some of the best to reach customers’ hands.
When someone speaks of Yamaha, what do you think of? Is it two-stroke dirtbikes and jet skis or their record of building more than a few of the best production car engines in the world? I wouldn’t blame you if it were the former, nor could I if you did not know of their involvement with major manufacturers. But it is true. Since the eighties, Yamaha has been contracted by the likes of Ford, Toyota, and Volvo, culminating in extraordinary engines. Yes, even the swedes contracted Yamaha, and the resulting 4.4-liter V8 in the XC90 was an absolute peach.
In 1999, Volvo Group needed financial help, so the Big Blue Oval out of Detroit bought its automotive division and began consolidating parts and engineering. Around this time, Volvo was preparing to get in on the SUV boom of the ’00s, and with the Americans’ help, they could deliver a stylish and traditionally Volvo-safe seven-seater. However, early engine options left the XC90 relatively underpowered by its European rivals, the X5, Cayenne, GL, and Tiguan. In typical American fashion, a V8 was deemed necessary for the Volvo to compete, which meant a new engine.
Volvo’s safety is world-renowned, which wasn’t going to stop with Ford’s acquisition. The XC90’s engine bay existed as part of Volvo’s Structural Beam Network, and while very safe, it came with some size restrictions. Ford’s 90° V8s were too big to be mounted in the proposed SUV, so the project manager looked elsewhere for engineering. Yamaha and Ford shared a lot of success with the Taurus SHO’s V6 and V8, both longitudinally-mounted, so Yamaha was contracted for engine design. The resulting B8444S took up every last available inch of space in the XC90’s engine bay without any modification and produced the power, sound, and luxurious feel everyone had hoped for.
To fit in the XC90, Volvo engineers gave the B8444S a 60° vee-angle and a weird cylinder bank arrangement. All non-inline engines have offset cylinder banks, it’s the only way they can work, but because of packaging restrictions, the Volvo V8 had to forego tradition and place the left bank ahead of the right. Could they have fit a 90° V8? Probably, but not without the four-valve, dual-overhead-camshaft cylinder heads utilizing variable valve timing on the intake and exhaust camshafts. Today, that’s commonplace, but it was a wonder back in 2005. Inside the aluminum cylinder block, the final displacement measured at 4.4-liters, or 270 cu in. It wasn’t necessarily the most powerful engine that Yamaha had the task of developing, with 311 horsepower and 325 lb-ft of torque all it would produce throughout its seven-year service in the XC90 and S80. It would’ve been a shame if the B8444S’s story ended, but thanks to a few different companies, it lived on.
Volvo wasn’t the only manufacturer to use the B8444S in a production car. There was one other, a microscopic outfit based in Leicester, England, in the business of building the best driving cars you’ve likely never heard of. Designer and engineer Lee Noble started his namesake company in 1999 and quickly established itself as a respected small-volume manufacturer. A decade of success led them to the M600, a model they continue to produce today. Mounted in the middle of the M600’s carbon body is a modified variant of the 4.4-liter Yamaha V8. Three hundred horsepower was nowhere near enough for Noble, so they fettled with the rotating assembly to make it stronger and then slapped on a couple of turbochargers for good measure. The power-supporting fundamentals included in the original design made the V8 an ideal starting point and resulted in a power output above 600 horsepower.
The V8 also saw some life in professional racing at the hands of the Polestar team. Their entry into the V8 Supercars series meant the B8444S was needed. The final product was a 5.0-liter that replaced the production cross-plane crankshaft for a flat-plane piece. Running on E85 and pulling through individual carbon fiber throttle bodies, the race engine wasn’t close to the XC90’s engine by any means, but they did share the same basic engine block.
Today, many XC90s are still rolling around with their V8s in good shape. Very little typically went wrong with them, though the earliest engines had an issue with a balance shaft bearing that would eventually cause the engine to jump timing, destroying itself. Engines part-way through 2006 through the end of production had a permanent fix. Other smaller issues like power steering pump and alternator failures occurred regularly, but enough to cause worry. Don’t be surprised if you find them in an XC90 or S80 with well over 200,000 miles; they’ll run for a long while if you take care of them.
BMW’s track record of producing straight-sixes is better than anyone else’s by leaps and bounds. They can be found in just about every chassis leading back to the sixties and have more than a handful of sought-after high-performance variants that work just as well on the race track as on the street. But their V8s? Well, in the past two decades, the BMW V8 has become more commonplace, especially among their larger sedans and SAVs. There is one that stands head and shoulders above the rest, though, and that’s the S65.
The S65B40 had some big shoes to fill after the S54, and the E46 M3 led the charge for BMW’s 3-series. M’s first V8 debuted in the E90 and E92 M3, which themselves were a significant departure from the BMWs of old. The new cars were more luxury-focused, dimensionally larger, and heavier than the outgoing 3-series, but the S65B40 ensured they retained the high-strung, naturally aspirated engine people expected from the M badge. At 4.0-liters, the M3’s V8 was the biggest engine fitted to a 3-series and the only time a vee engine found its way into one(excluding the almost non-existent M3 GTR). Love it or hate it, the E90, E92, and E93 M3s are unique among the lineage.
The core of the S65 is its two-piece engine block made from an aluminum and silicon alloy, generally referred to as AluSil. A bed plate with cast-iron bridges made up the lower portion of the case and carried the bottom half of the crankshaft bearings. The upper part was purely AluSil and carried the upper bearing cradle and the rest of the block. BMW’s choice to use aluminum for the block helped keep the weight down in the larger car and was just as strong as the cast iron blocks of the preceding straight-six engines. Inside the case, a forged steel crankshaft and connecting rods worked with the cast aluminum pistons to deliver a rev-happy power band found in few cross-plane crankshaft V8s.
Did I mention it's rev happy? Cross-plane V8s aren’t typically high-rpm performers as they can make gobs of torque low down, eliminating the need for high engine speeds. However, the S65 revved higher than just most engines of the time, hitting its limiter at 8400rpm. That’s 400rpm higher than the S54 straight six found in the E46 M3, making the V8 the highest-revving engine ever fitted to an M3. Helping it achieve that engine speeds are the individual throttle bodies and the dual VANOS system. BMW learned from its mistakes on the S54 and redesigned the VANOS system for the new V8, eliminating nearly all of the problems that crippled the older M3 engine.
The new engine, and the new car, received a lot of praise upon debut. The V8 was a throaty and burbly event at low revs before evolving into a shrieking roar at the upper end of the power band. Of course, the upper end of the power band is where you’d want to live if you’re trying to go fast, as the S65 makes its peak 414 horsepower at 8300. Its peak of 295 lb-ft of torque comes much lower at 3900rpm, but it carries a vast majority of that torque value to redline in a very flat curve. The S65 was a perfect match for the all-new chassis, and though it was a step in a new direction for M, it helped the E90s retain the character synonymous with BMW M and offered potential customers a “family-friendly” sports car.
Although BMW resolved the VANOS faults, the S65 did suffer from new and familiar failures. Rod bearing wear was again a common problem/failure on the V8, but this time they were compounded by a lack of connecting rod clearance to give the S65 some significant bottom-end problems. However, the aftermarket quickly tackled the problem, and fixes have been found. Other trouble spots are associated with the V8, but none are severe enough to warrant complete avoidance. All performance engines can be finicky, it’s part of the ownership experience, and for all of the S65’s quirks, the power and smiles it delivers are second to none.
Over the years, Porsche has built competitive, robust, high-powered engines for themselves and anyone with the right amount of money. Their brand-defining flat-six embodies who they are but never stopped them from experimenting with other configurations. The V8 was set to become the brand-leading engine in the 928, destined to replace the 911, but that never happened. Instead, the 928 played sibling to 911 and offered a profoundly different yet still very Porsche approach to a sports coupe.
Hans Mezger’s air-cooled flat-six engines were around ten years old during the 928’s development and, like the 911, were looked at as an old design needing retirement. The Porsche board room requested a larger displacement engine to power the 2+2 coupe, and after much engineering, deliberation, and planning, Porsche produced the original M28.01 for the first 928. The massive departure from everything Porsche essentially stood for was a risk the company thought it needed to take as 911 sales dwindled. Though it wasn’t as successful as Porsche might’ve hoped, their engineers delivered a high-tech and cutting-edge V8 to take on the luxury sports car market.
Steel and iron were the common material for most engines in the mid-seventies. Even if the exterior of the block was aluminum, there were almost always iron cylinder liners for their cost-to-strength ratio. But this was Porsche, and they used magnesium for engine cases for a time before returning to aluminum, so a magnetic engine block wouldn’t cut it. Instead, Porsche chose to use AluSil, a common material in today’s engines; the aluminum alloy was as futuristic as it got at the time. The exotic material kept the engine’s overall weight low and aligned with Porsche’s use of aluminum for the doors, hood, and fenders of the 928. The water-cooled engine, another big change for a Porsche, was then fitted with a set of single-overhead-camshaft cylinder heads made from the same material.
The heads were the subject of clever engineering to keep the hood line low. Although they are overhead camshafts, they sit at the heads’ outer edges. Their positioning allowed the intake manifold to have its distinctive design and spark plugs to sit right at the top of the engine for incredibly easy servicing.
Prototype engines were initially designed as 5.0-liter units, but the production-ready M28.01s and their other variants came in at 4.5-liters. With 240 horsepower and 250 lb-ft of torque on tap, the new V8 was no pushover and far above the anemic V8s that the finest American engineers could produce. Unfortunately for us Americans, though, the M28 was handicapped by our more stringent emissions restrictions, cutting the horsepower to 219 and torque to 245.
As the years rolled on, Porsche continued to improve the M28. A displacement increase followed a change to electronic fuel injection, then several power increases, the introduction of a higher output “S” engine, a doubling of the valve count and camshafts, and two more displacement increases. The final engine, dubbed the M28.50 and found only in the 928 GTS, was a 5.4-liter, dual-overhead-camshaft, 32-valve bruiser of a V8 that could push the GTS up to its 171mph top speed with absolute ease. Now that water-cooled V8s are a staple in the Porsche lineup, the M28 lives on as a testament to how much engineering went into every Porsche product, whether designed for racing purposes or not.
The twin-turbocharged V8 in the current S6 doesn’t feel all that special. Oh, your Audi has one? Well, so do Porsche, BMW, and Mercedes-AMG. Turbochargers have become the norm due to fuel restrictions, environmental effects, and their general reliability. That wasn’t always the case, though, as today’s technology has simplified many vacuum-powered systems that were needed before our advanced computer systems existed. Still, the relative lack of tech didn’t stop Audi from fitting a twin-turbocharged V8 into their C5 RS6, the first car to wear that badge.
Audi’s 4.2-liter V8 has a long and potentially infamous history in the engine bay of many of their models between 1991 and 2013. However, not all 4.2s are the same as the tried and true powerplant underwent significant revisions. The earliest engines had four valves per cylinder and used a large timing belt on the front of the engine to keep all of the internal components spinning in harmony. Eventually, the timing belt engines gained five valves per cylinder before a nearly complete redesign saw the timing belt exchanged for a timing chain mounted at the back of the engine against the transmission. Contrary to what you might believe, the earlier timing-belt-equipped engines are the more reliable V8s, making the RS6 all the more appealing.
The pinnacle of the early 4.2-liter Audi V8s has to be the twin-turbocharged mill internally coded as the BCY. The all-aluminum Audi V8s had been respected and proven engines in their regular normally aspirated guise, but the addition of a pair of Borg Warner turbochargers boosted power to near what Porsche offered from their range-topping 996 GT2. It wasn’t just the pair of turbochargers, though, as the BCY underwent several changes to handle the power Audi was looking for.
A cast aluminum engine block made up the basis for the twin-turbo beast like it did for the rest of its V8 siblings and housed a forged-steel crankshaft. On top were double-overhead-camshaft AluSil cylinder heads cast by Cosworth Technologies of Formula 1 fame, among others. Audi certainly had the resources to cast cylinder heads, but the precision capabilities of such a well-respected company couldn’t be passed on. Inside the head sat a set of camshafts responsible for operating the two exhaust valves and three intake valves. The former were sodium-filled for the extra heat resistance needed in a turbocharged application.
The turbocharges fitted at the factory with a nearly identical pair of Borg Warner K04s to form a “parallel” system. Each turbo was fed by a bank of cylinders and blew through an air-to-air intercooler. Together they produced just 11.6psi of boost, which doesn’t sound like much these days, but it was enough to turn out 450 horsepower and 415 lb-ft of torque. According to Audi, the ZF 5HP24 was the power-limiting factor for the BCY, capable of more power. Still, the peak power figures were immense for the day, besting the 911 Turbo, Corvette Z06, Ferrari 360, BMW M5, and Mercedes E55 AMG. All that power from the BCY connected to Audi’s quattro all-wheel-drive and covered in a big wagon body was as attractive then as it is now.
If you’re looking to get your hands on a BCY, you’ll have to find an RS6, which isn’t the most challenging task in the world. Forums are the best places to find them with good ownership, but they aren’t uncommon on used car websites. You’ll want some maintenance history on it, though, because there are a few trouble spots. The significant issues aren’t engine-related, but the BCY has its list of weaknesses. Oil leaks, turbocharger failures, and short timing belt service intervals are all costly regular occurrences. More minor things like EGT, O2, and coolant temp sensors tend to fail with age, and the C5 engine makes nearly every job one that requires engine removal. As a whole, the car is regarded as a money pit, even by enthusiasts, but that doesn’t mean the BCY isn’t unique.
Mercedes M100 6.3/AMG 6.8
V8 engines, as far as I’m concerned, are synonymous with Mercedes vehicles and, more specifically, AMG. Their best-driving and well-known models all sport twin-banked eight-cylinder engines arranged in a vee, giving them a distinctly German muscle car feel that few can rival. The M156 engine that powered the large majority of AMG models made in the last 20 years is mainly responsible for that reputation, but the true beginning of the Mercedes muscle car extends back much further. No, no, not the 560SEC AMG “Hammer,” either, earlier than that, way back into the sixties.
The first small sedan with a big V8 was the 1968 300SEL 6.3. Mercedes engineers were looking to go faster in the sixties, and one of them, Erich Waxenberger, took it upon himself to shove their biggest engine into their W109 chassis. The car would become the world’s fastest sedan, bring the names Aufrecht and Melcher (the A and M in AMG) into the public eye, and deliver a legendary race car for Mercedes. However, the star of the show was the engine, Mercedes’ M100 V8.
In the era of carburetors and pushrods, the M100 was a fairly advanced engine, though nothing new for Mercedes. The V8 used a cast iron engine block to house its fully forged, over-square rotating assembly. In its earliest form, the M100 displaced a monstrous 6.3-liters, but the size was strictly necessary. Mercedes’ most luxurious model of the day, the 600 “Der Grosse,” was a 7000-lb behemoth of a luxury vehicle, and the M100 was designed specifically to push it around. With around 300 horsepower and about 370 lb-ft of torque, the M100 struggled wasn’t a “performance” engine in the 600, but the 300SEL was a literal ton lighter.
Along with the large displacement, the V8’s ability to produce good power was down to its cylinder heads and injection system. The Kugelfischer mechanical fuel injection, later engineered by Bosch, was the best fuel injection system of the era and came as standard equipment on the 6.3-liter M100s. Its accuracy and reliability put carburetors to shame and surpassed many carburetors as the injection system of choice on BMW and Porsche race cars. The MFI was right at home spraying through the V8’s aluminum single-overhead-camshaft cylinder heads on the Mercedes and gave the Germans aspirations of racing.
Most famously, the M100 powered Mercedes’ iconic “Red Pig” of 1971. Three years after the 300SEL 6.3 went on sale, Mercedes-Benz engineers Hans Werner Aufrecht and Erhard Melcher built entered a modified example in the 24 Hours of Spa. At the end of the race, the Red Pig, riding on air suspension, was sitting first in class and second overall. It was an impressive feat, but not without some hefty modification.
The AMG founders punched out the M100 to 6.8-liters, nearly doubling the size of competitors’ engines. Supporting modifications included lighter connecting rods, new pistons, larger camshafts, stronger valvetrain components, and reshaped cylinder head ports. Still mated to an automatic transmission, the modified V8 produced over 400 hp and nearly 500 lb-ft of torque on race day.
After its racing success, the M100 continued to be used in Mercedes street cars until the early eighties. In street trim, it grew to 6.9-liters in 1975 for the 450SEL 6.9 and received a dry sump oiling system for packaging and reliability reasons. Early Bosch “K-Jet” electronic fuel injection was the last of the major upgrades. In 1981, the once highly-advanced V8 was something of a relic and was finally retired by Mercedes. Since then, Mercedes and AMG have produced a handful of great V8s, but it’s hard to imagine where the company and its vehicles would be without the 300SEL 6.3 and the M100 V8.
Each of these engines was a significant step in their respective manufacturer’s legacies. They all represented and powered legendary vehicles that have become points of passion for untold numbers of people. If you’re one of those people, you’re in luck because we can do more than just bring you content here on the DIY blog and on our YouTube channel.
Owner of a flat-six swapped 1998 Impreza 2.5RS and a 1973 Porsche 914. Horizontally opposed views, only.