Dyno Test: BMW 335i and 335is – N54 vs. N55 engine

Interesting | September 12th, 2010 by 14
BMW 335i 335is dyno test N54 vs N55 torque 750x500 Dyno Test: BMW 335i and 335is   N54 vs. N55 engine

Automobile Magazine compares BMW’s single-turbo twin-scroll N55 engine to the twin-turbo N54. Which engine has less lag? What about power output? Let’s have a look. …

Automobile Magazine compares BMW’s single-turbo twin-scroll N55 engine to the twin-turbo N54. Which engine has less lag? What about power output? Let’s have a look.

“A few years ago, we were among the first to get a brand-new BMW 335i on the dynamometer. We don’t often dyno cars, but we couldn’t resist. Before the first 335i was delivered to a paying customer, the rumor mills were bubbling about the 335i’s twin-turbo straight-six being underrated.

It turns out those rumors may have been right. The 2007 BMW 335i’s N54 twin-turbo six is rated by its manufacturer at 300 hp and 300 lb-ft of torque. And when we put the first 335i coupe on the rollers, it laid down a very impressive 275 hp and 300 lb-ft of torque. In awful conditions, too: 92 degrees of humid, Fahrenheit heat.

Remember — the power measured at the 335i’s rear wheels should be lower than the engine’s rated power. Some of the engine’s output is lost to friction in the transmission, driveshaft, differential, axles, wheel bearings, and tires. The dynamometer we used to measure the 335i’s output is a DynoJet model, and DynoJets tend to read higher than other dynos, but the output was a good bit higher than we expected.

BMW 335i 335is dyno test N54 vs N55 655x491 Dyno Test: BMW 335i and 335is   N54 vs. N55 engine

The new engine, the N55, is different from the N54 in that it uses only one larger turbocharger in place of the N54’s two smaller turbos. To keep lag to a minimum, BMW used a twin-scroll turbo and its Valvetronic throttle-less, variable-valve-lift system. On the street, after driving N54 and N55 cars back to back, it’s definitely safe to say that the N55 suffers from even less turbo lag than the N54 did. And that engine set the benchmark.

BMW’s quoted output for the N55 remains 300 hp and 300 lb-ft, which raises a question: what if the N55 actually does only make 300 hp? And, given the simultaneous appearance of a 335is (which uses an even more potent, 320-hp version of the N54) we couldn’t help but wonder: what if the 335is didn’t actually make any more power than the old, underrated 335i?

There’s only one way to find out, right? Call the dyno shop.

To answer the questions quickly: BMW isn’t hiding anything. The 335is put down 293 hp and 343 lb-ft, beating every previous N54 we’ve tested by a big margin. And if you look at the torque curve, the midrange overboost function BMW promised (rated at 369 lb-ft) is definitely alive and well.”

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  • http://www.bimmerboost.com BimmerBoost.com

    This is an extremely interesting comparison. The main thing is, motors vary a bit. Automobile found the N54 to dyno higher than their N55. We found the exact opposite, the N55 with slightly more peak power: http://www.bimmerboost.com/showthread.php?1458-First-N55-Dyno-283-whp-91-octane-293-whp-94-octane&p=16261#post16261

    The thing is, the fuel used and how the motor is broken in can greatly affect the output. We also found that higher octane fuel, 94 octane vs. 91, resulted in 293 whp vs. 283 whp stock, on a dynojet just like Automobile used: http://www.bimmerboost.com/showthread.php?1458-First-N55-Dyno-283-whp-91-octane-293-whp-94-octane&p=16129#post16129

    These types of comparisons are great to see.

  • BIMMER1

    The ONLY thing that is better about the N55 is it’s 10% more efficent than the N54, which means CAFE will not fine BMW as much $$$ based on their fleets MPG rating this year. And it’s only more efficient at lower RPM’s. Drive it hard like most BMW owners will and you’ll get identical results from the N54/N55 when it comes to MPG. So yay for politicians dictating our lives! BMW also knows the N55 is handcuffed at the stock 300hp/tq rating. From what I’ve been told by several reputible sources there is not much tuning potential at all in the N55. You basically are stuck with 300hp/tq as that’s what the single turbo can manage. Otherwise, the iS models and the new 1MCP would have come with an N55. With Dinan getting 384hp/421tq from just a software download on the N54, I think we can safely say that the N55 single turbo is not up to the task of those #’s.

    From another standpoint, BMW may intentially be trying to make the N55 have less potential. They are losing sales on M cars because a stock 135 N54 with Dinan software is faster than a M3 and you just saved yourself $15,000 by buying the 135 instead.

  • Eric

    The numbers look nearly identical but the N55 would be the one to get. One less turbo to worry about, better MPG, better response, same power, etc.

    From what I’ve read the N55 was ridiculed with issues so I’m glad they’re getting rid of it.

    • Daniel

      I think you meant to say that the N54 was riddles with issues (Frequent High Pressure Fuel Pump and turbos failure). They increased the warranty to 10 years on the N54 HPFP to compensate for the embarassment.

    • Daniel

      I think you meant to say that the N54 was riddles with issues (Frequent High Pressure Fuel Pump and turbos failure). They increased the warranty to 10 years on the N54 HPFP to compensate for the embarassment.

    • Daniel

      I think you meant to say that the N54 was riddles with issues (Frequent High Pressure Fuel Pump and turbos failure). They increased the warranty to 10 years on the N54 HPFP to compensate for the embarassment.

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