Like other supercars, McLarens are rarer than Sasquatch-fur coats. It’s hard enough to steal a glimpse of one at an auto show, but the chances of seeing one on the street are about as good as commuting to work on the back of a Pegasus.
But even more difficult to spot than the cars themselves are their engines. Mounted behind the passenger compartment, the powertrain of a P1 of 12C for instance is exceedingly difficult to appraise with your eyes. They’re buried in the hidden depths of a tightly confined engine bay. Fortunately one of these alluring twin-turbo V8s was on display at the 2014 SAE World Congress trade show in Detroit.
As for the basics, it displaces a fairly petite 3.8 liters (3,799 cubic centimeters to be precise) but that small cylinder capacity is augmented by a pair of turbochargers. In the 12C it puts out 625 PS and 600 Newton-meters of torque. In figures that may be more familiar that works out to about 616 hp and 443 lb-ft of twist. Yes, it’s very well-endowed with horses.
Like many V8 engines it features a 90-degree angle between the cylinder banks, but one area where it differs from the typical thundering American small block is in the design of its crankshaft. It benefits from a flat-plane layout that reduces mass and pays other performance dividends.
According to Bruce Woodrow, project director, engine product group at Ricardo, an engineering firm based in the United Kingdom, the flat-plane design allowed them to do some special things with the dry-sump lubrication system. Because of how the pistons move up and down in the cylinders relative to one another, this V8 only has three scavenging pumps for the oil and one pressure pump.
And that brings up one very interesting fact about this powerplant. It wasn’t designed by McLaren; Ricardo actually did the development work. Woodrow said “they [automakers] give you the specifications” and then Ricardo goes to work, designing to the OEM’s weight, performance, vehicle size and packaging requirements.
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And they’re capable of doing all kinds of engineering from analysis work on existing products to clean-sheet designs. “We work on an anything from really small engines [on up]” Woodrow said. Ricardo has been involved with powerplants used in unmanned aerial vehicles to gigantic marine diesels you can literally stand up inside.
But just because this 3.8-liter V8 isn’t 100 percent McLaren don’t think it’s not capable. It features dual-overhead camshafts, four valves per cylinder and variable cam timing. Redline clocks in at a warp drive-like 8,500 rpm. With such speed it’s no surprise this powerplant is quite over square; the bore is 93 mm while its stroke is just 69.9 mm. The compression ratio is a surprisingly low 8.7-to-one, though this is because of the
exhaust-driven hairdryers turbochargers hanging off each cylinder head.
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Appropriately for a supercar Woodrow said “it’s quite lightweight,” but he couldn’t share any specifics about how heavy it is. He also was unwilling to comment on how the valvetrain is actuated, though we suspect it uses roller-finger followers.
Staying topside for a moment, the intake manifold features a very direct port design for a laser-straight shot right into each cylinder. This is a design element usually reserved for high-performance naturally aspirated engines, not forced-induction ones. But Woodrow said “it provides some tuning.” The look is somewhat like the intake that sits atop the Ferrari California T’s new force-fed V8, which is similar in many respects to this British bruiser.
But despite of all this advanced technology, one cutting-edge feature is missing and it’s something you can get it on an entry-level Hyundai. Engineers decided to go with port instead of direct fuel injection, a very curious omission.
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According to Woodrow “fuel consumption was not a big want with this engine… though it is very efficient.” He also added that port-injection is much more cost effective and vastly easier to tune, noting that with direct “the whole process takes longer.”
Curiously the folks at Ricardo had one issue with this engine during initial testing. “The drivers complained there wasn’t enough noise” Woodrow said. Ameliorating this admittedly non-essential dilemma, engineers added a special sound amplifier to the intake manifold. It pipes pleasing noises right into the car’s cabin for enhanced driver enjoyment.
Hiding the Guts
Moving down, all of its ancillaries are driven off the sides of the block. Woodrow noted that “you don’t have room at the front of the engine” to fit a conventional accessory-drive assembly. Saving tons of space the air-conditioning compressor, water and oil pumps as well as the alternator are snuggled into the cozy spaces on either side of the engine underneath the turbos.
For maximum rigidity the “the oil pan and bedplate are made in one casting” Woodrow said. Interestingly, no steel or iron is used in the main bearings. They integrated larger bearing surfaces in the aluminum bedplate to carry the load. This saves weight, though probably not very much.
A seven-speed dual-clutch automatic transmission puts the power to the ground and helps the 12C accelerate like shrapnel from a hand grenade. Summing it up, Woodrow described it as “a race engine designed for the road.”
GALLERY: McLaren 3.8-Liter Twin-Turbo V8 Engine
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