Words Paul Wager | Pictures Total BMW

The twin-turbo 335i makes a refined alternative to the M3 and with the right modifications it can be made even quicker...

The current M3 is an impressive creation, no arguments from us on that score. But ever since we’ve tried the first example we’ve often had a nagging feeling that the M3 faces stronger competition from further down its own model range rather than from Ingolstadt or Stuttgart.

The M Power V8 showcases what BMW is best at and the soundtrack and sheer pace of the M3 mark it out as a very credible contender, but one step further down the range you find the unassuming 335i. Without even a sniff of an M badge, it quietly packs a 306 bhp punch and a pace very similar to the previous generation M car. In many ways it has more M Power about it than the M3, since myth and rumour suggests that future BMW M models are likely to build on the turbocharged approach controversially introduced with the X5 M and X6 M, moving away from the normally aspirated engines.

What’s more, a twin turbo motor needs nothing more than an expert with a laptop to release a hefty dollop of extra power, whereas getting more from any M Power engine is an expensive business.

ENGINE

The reason you want a 335i and the key to its appeal: the twin-turbo N54 was the first engine to adopt BMW’s TwinPower technology and offers up its 306 bhp with superb refinement. Surprisingly, it has more in common with the earlier M54 3-litre than the normally-aspirated N52 used in the 330i: the older block was deemed to be stronger than the aluminium-magnesium block as used in the newer engine and so was more suitable for the stresses of forced induction. Think of it as a twin-turbo’d mildly updated version of the E46 330i lump and you get the picture.

Using two smaller turbos means a distinct lack of lag and although it’s less powerful in absolute terms than the M3, its torquey nature makes it easier to get the best from it than the high-revving M Power V8.

Until the 335i appeared, BMW hadn’t made a production turbo petrol motor since the sharknosed 745i in the early ’80s, but the N54 is as good as they come and apart from a few niggles is a very reliable unit.

We spoke to Poole-based independent BMW specialist Kartechnic (01202 677455, www.kartechnic.co.uk) who pointed out that there are a couple of things to watch out for though: the first is a rattling noise from the turbos which will be noticeable at idle and is caused by the wastegate assembly. The two turbos on the N54 engine us a conventional pushrod-actuated wastegate and over time the wastegate itself can rotate on its pushrod and then flutter against its housing, causing a terrible rattle. As Kartechnic’s Kevin Orchard explains, the actual fix is simple but the labour involved can amount to a day’s work or more, since it involves removing both turbos. One is accessible but the other definitely isn’t and the total bill can amount to over £700. It’s not the sort of job you want to tackle at home, either so if the car you’re looking at suffers from this problem then get a quote for the work and use it as a bargaining tool. Don’t panic if it starts happening to your own 335i though: the noise may sound horrific but it won’t damage the engine if you need time to gather the funds to have the work done.

One well-publicised issue with earlier cars was the failure of the high-pressure fuel pump but as with so many things, it pays to take online forum talk with a pinch of salt: one remapping specialist we spoke to reckoned that out of all the cars they’d seen, only a handful had a fuel pump issues – and at Kartechnic they’ve not yet encountered a car with the problem.

tech spec

Model                    Saloon    Touring    Coupe    Convertible
Engine                  2979cc twin-turbo N54B30
Power (bhp)        306 bhp at 5800 rpm
Torque (lbf.ft)     295 lbf.ft at 1200-5000 rpm
Economy (mpg)   29            29            29           28
0-62 (secs)          5.6           5.7           5.5          5.8
Max speed (mph) 155          155         155         155

For the complete buying guide including overall verdict and prices see the July 2011 issue of Total BMW
Back issues available here