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Thread: Help with cams for turbo m50

  1. #1
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    Help with cams for turbo m50

    I got a offer of some cams with this spec:
    260/240 duration 9.5/9.2 lift

    Im currently running m54b30 intake cam, and m50b25 non vanos intake on the exhaust. Which has 240/240 duration.
    But aftermarket cams measure duration from 0.05 lift right?

    Im looking for a better overall powerband, and no loss in spool.

    Will these be worth the upgrade?

    Cost wise it is not a big step.

    Thanks for any inputs.

  2. #2
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    Almost all cams for european and Japanese motors have the cam duration measured at .1mm, not .050" like american v8 cams are measured. It should be a sizable power gain on a larger displacement motor like a 2.8 or 3.0. Probably not a huge gain on a 2.5L


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

  3. #3
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    Quick specs.
    Stroked m50 to 2.8
    9-1 comp
    Ported head, with bigger valves and vanos.
    Hp goal around 700whp.

    Will there be any downsides to upgrade to 260/240?
    Also the lift on my current cams is 9.7 on both cams, so more lift then the 260/240 cams.
    Is that a good thing on a fi engine? (less lift)

  4. #4
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    One more question:
    Should the duration of the exhaust cam be greater? Or is that much less duration ok on a turbo engine?

  5. #5
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    Quote Originally Posted by s50b30 View Post
    Quick specs.
    Stroked m50 to 2.8
    9-1 comp
    Ported head, with bigger valves and vanos.
    Hp goal around 700whp.

    Will there be any downsides to upgrade to 260/240?
    Also the lift on my current cams is 9.7 on both cams, so more lift then the 260/240 cams.
    Is that a good thing on a fi engine? (less lift)
    My personal car I have a 2.8L non vanos with a ported head that was making right around 800 whp. I went from running 240/240 cams to US S52 cams, which are 252/240. There was a very worthwhile improvement in power for me which I could see because my trap speeds went up about 3 or 4 mph at the same boost level. To really see the complete implications you would need to measure and graph both cams to see the area under the curve. You can make two different cam lobes with the exact same lift and duration figures but one could still have more area under the curve because the ramp rates could be different. So it will be impossible for anyone to tell you for certain if the cams your referring to will be an improvement or not because you don't have enough information.

    With that being said if the new cams have similar ramp angles to the stock 240 cams (they are most likely as aggressive or more aggresive on ramp angles) then I as certain as I can be that you will have a net gain in power even with the lower total lift. The flow on an M50 head does not get much better past 7 or 8 mm due to the inside diameter of the valve seats being the restriction. How much gain is anybodies guess. Mabey 20 to 30 whp?

    - - - Updated - - -

    Quote Originally Posted by s50b30 View Post
    One more question:
    Should the duration of the exhaust cam be greater? Or is that much less duration ok on a turbo engine?
    No, the only engines that really work well with more exhaust duration than intake are ones with really poorly flowing exhaust ports. Cams for alot of 2 valve V8's use higher duration on the exhaust but that is because they have to make a compromise on the size of the intake and exhaust valve to fit in the cylinder head. The typically use a much larger intake valve, sometimes with almost twice as much flow through the intake as the exhaust, so they have to use more exhaust duration to get the total flow required. This logic does not apply to a 4 valve head like an m50 where the exhaust port flows 80% as well as the intake.


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

  6. #6
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    That was a very informative reply! Thanks!
    Do you mean 20-30 whp gain up top, or the most of powerband? How do you think it will affect spool?

  7. #7
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    The power gain will be mostly 5000+ rpms. The affect on spool will entirely depend on how you time them.


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

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