Inside Optima’s Airstrip Attack 1,200-HP Porsche 3.8L Flat-6 By BBi

Recently we ran across a promotion Optima Batteries is running, where a lucky winner will be given a spot in the passenger seat of an amazing Porsche 911 GT3 Cup car — which has been reconfigured for the Pike’s Peak International Hill Climb — as it takes on the standing 1/2-mile Pikes Peak Airstrip Attack event.

Intrigued by the 1,200-horsepower claim made by Betim Berisha, owner of BBi Autosport, in the promo video, we decided to dig a little deeper into the flat-six engine powering the amazing vehicle up Pikes Peak and to the estimated 180 mph in the half-mile.

While the OEM Porsche GT3 Cup engine is an amazing piece of engineering, 460 horsepower just wasn’t near enough for what was going to be asked of the car. For Berisha’s intended performance envelope, with horsepower measured in four digits, some upgrades would have to be made to the OEM powerplant.

Luckily, BBi Autosports has an in-house machine shop and a talented engine builder on staff, by the name of Jared Deputy, who specializes in high-performance Porsche engines  (which makes sense, since high-end Porsche’s are BBi’s bread and butter). While an extreme engine configuration, this build was right in BBi’s wheelhouse.

Built initially for the Time Attack 1 division of the Pikes Peak International Hill Climb (which is only one step below the top “Unlimited” class), there weren’t a whole lot of rules that had to be considered. “The rules for Time Attack 1 only stated that the engine had to be offered from the factory, so no LS swaps and the induction is free,” explains Berisha.

A Boxer’s Heart

The core of the combination is a factory aluminum sand-cast Porsche RSR engine block. The split-case design features dual oil jets per cylinder which helps keep piston temperatures in check, which is doubly important when running copious amounts of boost in the engine.

To strengthen the block for regularly running double — and sometimes even triple — the OEM horsepower, the first order of business was to machine the block for thicker ductile-iron sleeves. With the new sleeves installed, which is a much more complicated process on a split-case boxer block, the bore was brought to the final bore size of 102.7mm (~4.043 inches), which happens to also be the OEM bore size.

The OEM Porsche crankshaft is a forged steel piece that is more than capable of holding the desired power. Its 76.4mm (~3.008 inches) stroke makes for a high-revving engine, especially once the factory unit is both completely polished and strategically lightened, to aid in the high-revs. The 102.7mm bore combined with the 76.4mm stroke equate to a 3.8-liter displacement (3.797 liters, actually. Or 231.7 cubic inches, if we’re splitting hairs).

The Porsche 911 RSR was developed for FIA Endurance racing and as such has the premier engine block (or case, as it's called in Porsche-speak) out of the entire GT3 lineup. The casting itself is stronger, and it features dual piston-cooling oil jets for each cylinder.

Inside of those bores resides a set of custom pistons built to BBi’s specifications by CP Pistons. Forged from 2618 aluminum, they feature box forging, which moves the wrist pin bosses inward, and adds reinforcing ribs. This minimizes deflection and allows for a shorter and lighter pin to be used. In addition, BBi chose to use a wrist pin with a Diamond-Like Carbon (DLC) coating to minimize friction.

Connecting the pistons to the crankshaft are a set of custom, trick Carillo connecting rods built to BBi’s specs. The 130mm forged steel H-beam rod is no ordinary H-beam rod, however. “When you look at the small and large end, the rod kind of starts to go to an I-beam,” says Berisha.

“We have a great relationship with CP-Carrillo. Being less than ten miles away, I am always popping in to see what’s new and where we can lose weight and pick up strength. This design was all due to a Finite Element Analysis that was done, we were actually able to move the high-stress points to an area that didn’t see much load at all. It’s cool that we were able to distribute the loads more evenly throughout the entire rod.”

Keeping the rods and crankshaft spinning freely at the impressive 9,000-rpm rev limit are Clevite tri-metal rod and main bearings throughout the engine. Oil is provided by the OEM Porsche GT3 dry-sump oil pump, using the factory dry-sump pan. Remember, the factory parts from the 911 GT3 Cup are factory racecar parts, so for some items, the factory piece is the best option on the market.

To handle the immense heat generated by twin-turbos and 9,000 RPM for extended periods, BBi hand-fabricated the turbo manifolds entirely out of Inconel 625 tube.

A Two-Headed Monster

Moving up to the top (err…sides?) of the engine, BBi only utilizes two factory components in the cylinder head and valvetrain assembly, and that is the cylinder head castings and camshaft cores — both of which are heavily modified from factory form.

First, the four-valve cylinder head castings get to spend some quality time with BBi’s CNC machine, getting worked over to improve their already impressive flow, optimizing them for use with the twin-turbocharger arrangement. The same is done with the camshafts, where Porsche camshaft blanks are turned into useable bumpsticks with BBi’s proprietary specs.

The bare heads are then outfitted with a set of Ferrea SuperAlloy valves, which BBi has had great success with in their other high-power turbo applications, along with a set of Ferrea valvesprings to control the valves at 9,000 rpm. BBi uses a lightened and DLC-coated lifter arrangement to withstand the monster engine speeds and aggressive camshaft lobe profiles.

Feeding the engine’s intake ports is an awesome intake manifold that BBi designed and then 3D-printed out of aluminum. The aluminum is actually laser sintered which is a slightly different process than what most people think of when they hear “3D Printing,” and makes for a fully-functional part which will withstand significant pressures from the turbos.

Attached to the intake manifold is an 82mm throttle body, which surprisingly, utilizes drive-by-wire. The intake manifold also houses six Injector Dynamics 1,700cc fuel injectors, which are fed by an ingenious six-pump fuel system built in-house at BBi using Protec fuel pumps XRP fittings and hose.

This engine generates an incredible amount of data in addition to an incredible amount of power. Run by a MoTeC M150 ECU, pretty much every system is monitored, if not outright controlled by the ECU, including a drive-by-wire throttle body.

The system utilizes four high-volume, low-pressure in-tank pumps at the corners of the fuel cell to feed what is essentially a surge tank, which houses two high-pressure fuel pumps. The whole system is controlled by a MoTeC M150 EFI system with a whole lot of custom programming, and an Optima Yellow Top battery mounted in the passenger footwell.

Compressing Atmosphere

For Pikes Peak, the BBi team chose to go with a pair of Garrett’s new G25-660 turbochargers with a 0.82 A/R giving them an impressive powerband with which to attack the mountain. To feed the turbos, BBi hand-fabricated a pair of three-into-one turbo manifolds completely out of Inconel 625 tubing. Before entering the engine, the compressed intake charge flows through a custom-built C&R Racing tube-and-fin (chosen over a bar-and-plate core to save weight) air-to-air intercooler.

For the Pikes Peak run, BBi opted for a pair of smaller Garrett G25-660 turbochargers. However, for the Airstrip Attack, there will be larger Garrett turbos fitted in place of the G25s.

Having experience with several engine and turbo combinations, for this build, Berisha opted for smaller turbochargers this go-around. “First I thought going for all-out grunt with a 7,200 rpm rev limit would be good,” Berisha says. “However we ended up going for less torque with a smaller turbo, and a higher 9,000-rpm rev limit. That allowed us to have better throttle modulation with a massive table-top torque band with 680 lb-ft between 4,400 rpm and 7,780 rpm. More or less, we had gobs of usable power from 4,400 rpm to 9,000 rpm.”

While that combination was good enough to set the Time Attack 1 class record, and the second-fastest time up the mountain overall, for the Airstrip Attack BBi will not only be cranking up the power in the ECU but will have also swapped-in a set of larger Garrett turbochargers. “It’s the same engine with larger turbos and wicked-up,” Berisha says. “We typically build this combo to take short bursts of 1,600 horsepower, so 1,200 shouldn’t be an issue.”

While the Optima Batteries Ride Shotgun contest is now closed for submissions, the winner hasn’t yet been announced. That will take place at the SEMA show on Tuesday, November 5th at 2:30 pm in Optima’s booth. So from a class-winning, record-setting Pike’s Peak engine, to a half-mile, 1,200 horsepower straight-line monster, this BBi Porsche engine does it all.

It’s impressive just how much was crammed into such a small space. Through the use of 3D laser-mapping technology, many of the components could be designed and laid out in CAD and checked for fitment before ever being installed.

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About the author

Greg Acosta

Greg has spent fifteen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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