Very interesting - '07 BMW 335i Dyno results

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Thread: Very interesting - '07 BMW 335i Dyno results

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    Very interesting - '07 BMW 335i Dyno results

    These figures are by Shiv Pathak at Vishnu Tuning (The WRX STi/EVO tuning Guru)

    They're inline with the results by Automobile Mag.


    Dyno'd our new 335i today. The dyno actually reads a bit low for a dynojet. Other dynojets in the area usually read 8-12whp higher. Regardless, the results were better than expected. Yes, the car is grossly under-rated from the factory.

    Shiv
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    Hi guys,

    I've been playing around with our new 335i and found a few interesting bits. One thing I noticed, after much datalogging, probing and head-scratching is its boost control system. It's pretty unique. I haven't seen anything like this employed before in any turbo application, twin turbo or otherwise.

    Unlike other turbo systems (evo included) which have a positive mechanical wastegate pressure (that keeps the wastegate normally shut); the wastegates on the turbo are designed to remain fully extended in its natural state. This means if you disconnected all forms of boost control, the 335i runs 0psi of boost. On the other hand, if you do this to an EVO, it will run 11psi of boost. To get more boost in the EVO, the factory boost control solenoid bleeds off the wastegate pressure so the wastegate stays more shut. If the wastegate signal hose, for some reason, were to pop off or rupture, the wastegate would get no boost signal, and you'd get an engine-grenading overboost condition.

    With the BMW, to get more boost, it regulates a *VACUUM* signal to pull *CLOSE* the naturally open wastegate. During normal off-boost driving, the wastegate is fed 10" of vacuum which keeps the wastegate partially open. During WOT, but before full boost is reached, the wastegate is fed 20" of vacuum, which completely closes the wastegates for maximum boost response. Once full boost is reached, the wastegate sees 3-5" of vacuum used to regulate the wastegate opening for sustaining the desired boost. Once fuel cut is reached, the clever folks at BMW decided that boost needs to go to 0psi so as to not result in a big, uncivilized "bang bang bang" against the rev limiter. To do this, it cuts all vacuum to the wastegates and they go fully open (no boost!).

    The upside to this approach, as i see it at least, is as follows:

    1) During start-up, the wastegates are open and the turbos are effectively bypassed. This means that much of the hot exhaust coming out of the engine doesn't go through the turbine wheel and cool off. Instead, it goes right out the wastegate and right into the catalyst. This gets them up to temp quicker and makes the boys at the EPA happy. This also means that BMW can push the cats back downstream a little bit instead of cramming them right up against the turbo where backpressure effects are most deleterious.

    2) There is no way to induce an overboost since the natural state of the wastegate is fully open. In other turbo cars, something as simple as a wastegate line rupture will cause the car to overboost.

    3) Its just cool engineering.

    The downside to this approach, as i see it at least, is as follows:

    1) It requires the use of a separate vacuum tank that needs to be smuggled under the hood somewhere. This takes up a little bit of space and costs extra money. Not much but we all know how OEMs like to shave off every extra bit of material and cost.

    2) It confused me for a good part of the morning.

    cheers,
    shiv
    And if you want to see Automobile mag's test runs plus videos of both dyno runs (listen to that engine!)

    Articles

    http://www.automobilemag.com/feature...5i_dynamometer

    http://www.automobilemag.com/feature..._dyno_revised/

    Videos

    http://www.automobilemag.com/multime..._bmw_335i_dyno

    http://www.automobilemag.com/multime...ough_the_gears
    Last edited by guitarlix; 09-15-2006 at 04:54 PM.

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    Re: Very interesting - '07 BMW 335i Dyno results

    Sounds very nice indeed.

    I love this car!

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    Re: Very interesting - '07 BMW 335i Dyno results

    So this is rear wheel horsepower, right? Not at the flywheel? Because the engine is rated at 300 horsepower, isn't it?
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    Re: Very interesting - '07 BMW 335i Dyno results

    Quote Originally Posted by 69Firebird400
    So this is rear wheel horsepower, right? Not at the flywheel? Because the engine is rated at 300 horsepower, isn't it?
    Yes it has been talked about before. The 335 is very underated and this tuner already has added 70 hp under the curve by only adding 1lb of boost and taking out the areas that reduce boost, fixing the af ratio and timing.

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