In any form of motorsport, cars are pushed to the limit. Whether in rally, road racing and even drifting, every component is put under maximum stress. Time Attack is one of the more demanding motorsports. Also known as time trials or super lap, cars strive for the fastest single lap time around a road course. To oust opponents, race teams and drivers must squeeze every ounce of performance from their cars. Time Attack’s intense pressure is what ultimately led Bobby Downes to build this BMW 135i.
Contrary to what you might expect, Bobby’s car history was non-European. Straight out of college, he started a business specializing in off-road vehicles. He became a skilled fabricator and expanded his portfolio into rock crawlers then eventually drag and street cars.
With more opportunities arising, Bobby landed gigs on the Overhaulin’ TV show. He was hired as the general manager at National Speed, which later opened a sister company called Momentum Performance his own company today.
As the owner, Bobby’s aim was to develop intakes, manifolds, exhausts and turbo kits. With all the products thoroughly tested on a road course, Momentum gained a reputation in the Nissan/Infiniti scene. But the noise generated by the BMW 135i expanded Momentum’s horizons to both hardcore racers and European enthusiasts.
I was never a BMW fan, he started. When it came to German stuff, I was into Porsches. But in ’08 when the 135i came out, I looked at its power, handling and weight. It seemed ideal to be an excellent track car.
Two proven ways to get more performance is losing weight and widening the track. Less weight improves not only acceleration but also handling and braking, while a wider track with beefier tires allows more grip and better stability.
Like other teams working with the 135i, Bobby learned that a 265-series tire was the widest he could squeeze under the factory fenders. When you build a dedicated track car, that’s not much tire so a widebody would be needed, he told us.
Right away, the owner picked new wheels and tires for the job. 18x11" front and 18x12" rear CCW Classic wheels were custom-built for 315/40 front and 335/35 rear Hoosier R6 radial tires.
I knew the staggered setup I wanted to run. When I took the car to the bodyshop, it had 3" of tire sticking out of the fenders, he laughed.
The 1-Series was delivered to John Kamler at Axis Power Racing in St Louis, MO. With a background in open-wheel racecars and carbon fiber fabrication, John developed a carbon widebody in a year. It included new bumpers, fenders, rear quarter panels, doors, hood and trunk. I gave them photos of the Rahal Letterman ALMS M3 GT cars as reference, Bobby noted.
Typically, the widebody cars we come across are more show than go, but Bobby’s car would be 100% functional. Each corner was stretched 4" wider to accommodate the bigger tires. From there, each panel was recreated and molded from carbon to lighten the weight.
For example, a 135i door with its glass and electrics weighed around 85 lb, whereas the new Axis Power carbon door only weighs 3 lb.
Although not carbon, the roof was swapped for a European-spec skin with no sunroof. According to Bobby, this saved another 120 lb.
The car weighed 3345 lb when I bought it. Now with the widebody, carbon panels, rollcage, electronics and seats, it weighs only 2540 lb with fluids, he explained.
For heat transfer, all the fenders are vented. Aerodynamically, there’s a flat panel under the car as well as a front splitter, rear diffuser and rear wing for stability.
The 135i was returned in exposed dry carbon, so it took Cannon’s Autobody and Byron Spivey another six months to ensure the panels fitted properly before they were sanded for paint.
Chassis & Cockpit
Developing the chassis is another vital element of a Time Attack car. Bobby started with the suspension and had befriended Anze Engineering. The New York company catered to racecars using Penske shocks and Hypercoil springs the same parts used on many Grand-Am and ALMS cars. Together they developed a three-way adjustable, remote-reservoir coilover setup specifically for the 135i.
Beefier H&R sway bars reduced body roll. Then every rubber bushing was upgraded and E92 M3 front control arms added, while the rear arms were custom-built to offer better turn-in response.
For stopping power, the factory six-piston Brembo front calipers with 13.3" front and 12.75" rear rotors were already over-engineered. With this in mind, Bobby simply added Carbotech pads and Evolution Racewerks stainless lines for a solid pedal feel. Brake cooling was improved with ducts in the front bumper.
Next on the list was an eight-point rollcage and lightweight Racetech carbon seats. The dash remained in the stripped interior but a Sparco steering wheel was added along with a RLC Racing data acquisition system to monitor lap times, track mapping and other performance data.
When Bobby bought the 135i, he immediately visited a dyno. It made a respectable 290hp and 290 lb-ft of torque at the wheels. I wanted to preserve the factory reliability, so I installed simple bolt-ons. With a 2500 lb car, I knew it would have a good power-to-weight ratio but I didn’t want to overwork the motor a bunch at the track, he explained.
A JB3 plug-n-play harness allowed Bobby to switch ECU maps for different levels of turbo boost. Allowing the straight-six to breathe better was an aFe intake, Riss Racing downpipes and a custom 2.5" aluminum exhaust built by Bobby himself.
Twin oil coolers were added to protect the engine, as well as an Active Autowerke front-mount intercooler to chill the intake charge.
Aiding acceleration, the final drive was changed from 3.03 to a 3.46:1 ring and pinion from an automatic transmission. Finally, a Quaife limited-slip diff guaranteed better traction on the road course.
At the end of the day, the N54 engine put down 400hp and 420 lb-ft of torque. And with those numbers Bobby’s perfected the anatomy of a Time Attack car by focusing on saving weight, dialing-in the chassis and getting good power.
The car was finished last July but with the business I haven’t had a lot of time with it. It’s only done 3200 miles but I’ve taken it to the track five times, he said. It’s a glorified go-kart with ridiculous suspension, low weight, good brakes and decent power. It performs awesome but is still a long way from being fully complete
ET Tech Spec
2008 BMW 135i
Owner: Bobby Downes
Location: Wilmington, NC
Occupation: Momentum Performance owner
Engine: 3.0 straight-six 24v twin-turbo with JB3 tuning module, Active Autowerke front-mount intercooler, blow-off valve and speed delimiter, Riss Racing downpipes, Momentum Performance dual 2.5" aluminum race exhaust, aFe dual-cone intake, twin Setrab oil coolers, custom crank breather and power steering reservoir, Momentum Performance solid motor and tranny mounts
Drivetrain: six-speed manual with solid aluminum subframe and diff bushings, Quaife LSD, UUC double shear selector rod, Active Autowerke short shift kit
Brakes: Carbotech pads, Evolution Racewerks stainless braided lines, carbon cooling ducts
Suspension: Anze/Penske triple adjustable coilovers with remote reservoirs, H&R sway bars, M3 control arms and rear lower camber arms, custom rear chromoly control arms with Aurora rod ends, custom front strut bar
Wheels & Tires: 18x11" front, 18x12" rear CCW Classic wheels with 315/40 R18 front, 335/35 R18 rear Hoosier R6 tires
Exterior: carbon doors, hood and trunk, widened fenders, European roof, Aeromotions rear wing, custom carbon front splitter and rear diffuser
Interior: Racetech carbon seats with Schroth harnesses, eight-point rollcage, Sparco steering wheel