Birds B1-3.5 conversion 375bhp 2012 BMW 135i Coupé E82
When physics teacher turned groundsman, Tony Jennings, brought his E82 135i Coupé to class, we stopped skylarking and faced the front. The punchy N55 in a lightweight package with a low centre of gravity… now that’s pure physics!
Words: Graham Leigh
Photography: Jason Dodd
Physics Lesson
The E8x series of cars were produced between 2004 and 2013 and the 1 Series M Coupé was the poster child of the E82 Coupé variant. With its blistered arches, 335hp, LSD and widened track, it was the baby M car the world had been waiting for. Fast forward to 2022 and you will need £40k for an average one. In fact, there’s currently a delivery mileage example available for a cool £79,995 so it’s fair to say that the range-topper has become the preserve of the serious collector. For those with a more modest budget, the starting point for the E82 135i is less than £8,000, with prices rising to £17k for absolute low mileage minters. Of course, the skinny-bodied sister car isn’t as “full fat” out-of-the box but it’s not as far removed as the gulf in prices would suggest. It’s a fantastic car in its own right.
The 1 Series M Coupé is powered by the twin-turbo N54 straight-six. The 135i Coupés produced between 2007 and 2010 shared the same engine albeit in a slightly detuned 302hp format. The later 2010 – 2013 cars had the single twin-scroll turbo N55 powerplant. The horsewpoer figure and torque of 295lb ft remained the same. As to which one is the best is a difficult question to answer. The change to the twin-scroll N55 was emissions led but the move also set to address reliability issues that were associated with the N54 which had marked BMW’s first foray into petrol forced induction in decades. Power delivery is very similar; N54 peak power comes along at 5800rpm but importantly the 295lb ft stays constant from 1300rpm up to 5000rpm meaning that low-end grunt always feels plentiful. The N55 produces peak torque 100rpms earlier than the N54. In standard guise, both cars feel alike, with minimal lag and a modern feeling responsiveness. The N54 is over-engineered from the factory and takes well to tuning owing largely to the fact that there are two turbos to uprate. The engine is often referred to as the “German 2JZ” and as such is ripe for off-the shelf enhancements.
The Birds B1-3.5 375 conversion is a serious commitment but it is transformative...The issues with the N54 are usually external to the engine itself. One of the reasons that the N54 is such a popular engine with tuners is that its internals and timing chain system are very robust. Problem areas for the N54 can include the electric water pump and thermostat. The water pump will need replacing between 60-80k, thermostats are usually good for a while longer but it’s worth changing the pair together for peace of mind. Factor in £800 for parts. It’s a two or three hour job. N54s can suffer from carbon build-up on the intake valves. BMW recommends walnut shell blasting the intake valves every 40k. Expect to pay around £350 for a specialist to carry out this process. If the High-Pressure Fuel Pump (HPFP) hasn’t been replaced with a receipt to prove, for the sake of £200 (plus labour but it’s straightforward for a DIYer), it’s worth addressing. When the HPFP is not at its most efficient it can cause long crank, hesitation and, obviously, breakdown if it fails completely. N54 injectors received numerous factory redesigns. Intermittent misfire and loss of power are good indicators of issues here. The Oil Filter Housing Gasket (OFHG) can leak internally which creates an oil and coolant mixture or externally which can allow the oil to drop onto the belt drive components. Failing serpentine belts can be an issue due to this leakage, the results of which can be catastrophic. Regular monitoring of this is essential. The turbos run 8 PSI on factory settings but can cope with 15 PSI reliably. However, they’re not without their weaknesses. Wastegate arms can become loose and, in turn, rattle.
Birds B1-3.5 375 conversion raises power to 375hp while tweaks to the chassis supportThis can lead to a significant loss of boost. Although replacement or refurbishment for the turbos is now readily available and affordable, the job is labour intensive and includes subframe and downpipe removal.
Boasting a forged crank and rods from the factory, the N54 is the tuner’s favourite. However, the N55 is still ripe for modification (as our featured car will testify) and is, generally speaking, a more reliable choice where BMW set out to right some of the predecessor’s wrongs. However, hardware issues such as valve cover gaskets and water pumps plague both choices. N55s can also suffer leaking OFHGs, VANOS solenoid failures and HPFP issues. With recalls and redesigns particularly concerning injectors and high-pressure fuel pumps, a well looked after N54 will not be the stuff of nightmares that some would have you believe. As with any high-performance car, good service history, evidence of recalls and a wad of receipts are preferable with either choice. Another deciding factor between an earlier or later car could be the choice of transmissions with the N54 coming with either a six-speed manual or automatic gearbox. N55 cars had the option of either a six-speed manual or the excellent seven-speed DCT.
The 2011 revision was also cosmetic with the E82 undergoing mild surgery with revisions to the headlights, taillights and bumpers. Parts availability is good and is aided by the fact that the E8x range of cars shares 60 percent of components with its E9x 3 Series bigger brother. With its compact dimensions, 50:50 weight distribution and multi-link suspension, the E82 handles brilliantly and that’s before upgrading any suspension components that are well supported by the aftermarket.
Fifty-eight year old, Kent-based Tony Jennings knows his way around a performance car. His back catalogue is as eclectic as it is impressive. Like many of us, it all started with a Mk1 Fiesta in insurance friendly 1.1- litre guise. As the need for speed gathered momentum, the plucky Crossflow-powered Mk1 XR2 represented the natural progression. Staying with the blue oval, a Mk1 Orion 1.6i Ghia brought more space, a radio cassette and fuel injection to the party. After that, variety was the spice of life with a Lotus Elan, Saab 96 V4, Suzuki Cappuccino, Rover 200 BRM (factory diamond-stitched red leather and orange radiator grille surround, anyone?), Rover Mini Cooper Sport 500, Lancia HPE Volumex, Jaguar XJS Coup., Jaguar 3 litre X Type, Ford Puma Millenium and a Mini Coup. John Cooper Works all taking up space in Tony’s garage for varying periods.
Tony is now somewhat of a brand ambassador, owning both the stunning 135i you see before you and an M235i Coup. that he bought first, but why did it take him so long to see the Bavarian-based light? “I have had an interest and an admiration for BMWs since I was a teenager but the public perception and image problem they had back in the 80s and 90s was not insignificant. However, with the ‘BMW Driver’ thing losing some momentum over the years, I felt I could finally enjoy the marque and took the plunge in recent years, For me, the appeal is a combination of the styling, German quality and great driveability. Once I had driven the M235i I was hooked!” After building up a Lotus Elan +2S 130/5 from the ground-up, Tony enjoyed the fruits of his considerable labour and took the diminutive beauty to various shows and meets. However, he found the limitations of the car on longer trips. “I used it to go on holidays but found it too noisy and tiring to drive long distances. I remember a drive down to the New Forest where we took the A-roads. I was shattered by the time I got there! Not easy to hold a conversation or listen to the radio at any speed above 30mph. The seats weren’t the most comfortable and lorries were intimidating when driving on motorways. I sold the Lotus and bought a Jaguar XJS 4.0. I retrofitted cruise control as well as heat pads, lumbar support, and memory modules to the seats. I also fitted a new headlining. I loved the comfort of the XJS but it needed paint and rust is a constant worry with them. Whilst driving the XJS to Cornwall I saw a series 1 Coup. on the Torpoint ferry and thought it looked great. Research told me that the N55 135i was the one to get so I waited until I found the colour and spec I wanted”. With the fun factor present and correct but still boasting an impressive degree of comfort, we can see how the E82 fits in the middle between the twitchy Lotus and the lazy Jag. With the XJS sold, Tony set about his search for a suitable E82. This handsome, low mileage example was found in Bristol. At the time it was completely standard and the impressive factory spec includes Le Mans blue paint with Coral red leather interior, M Sports package, Professional Navigation package, Comfort Access, memory seats, PDC, Xenon adaptive headlights, cruise control and Harman Kardon surround-sound audio system.
Having uprated his Lotus, Saab 96, Lancia and Jaguar X-Type, Tony is not averse to considered modifications. The Birds B1-3.5 375 conversion is a serious commitment at a cool £5463 fitted but it is transformative. As the catchy title would suggest, power is uprated to 375hp but it’s not just the N55 that is improved upon. Springs and shocks and anti-roll bars sharpen up the handling whilst a Quaife LSD tries its best to apply the extra power to terra firma. Tony is delighted and reports that the package “makes it so much more of a driver’s car”. Factory charge pipes can be an N55 weak spot, especially when running increased boost. A Masata aluminium item was fitted to ensure longevity and reduce flex. It is all serious stuff.
Inside Tony removed the original wood trim with a turned aluminium kit that he feels is far more in keeping with the sporting nature of the car. A P3 air vent gauge allows a watchful eye to be kept on those all-important Ts and Ps, whilst a rear view camera keeps lookout aft. Externally Tony was keen to keep the car looking as Munich intended. Tyres are Michelin Sports non-run flats as recommended by many BMW enthusiasts.
The E82 135i represented a return to a smaller, more agile breed of Coup. for BMW. It’s an inspired choice as it blends bygone proportions and agility with relatively modern six-cylinder turbo power and comfort. We’ll leave the final conclusion to Mr Jennings: “The BMW 135i Coup. looks good and drives superbly. It’s different to my M235i…more old-school, raw and feels like a modern Ford Escort RS2000”. Praise indeed. Snap one up now and enjoy as school’s out for summer!