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tuning Question for MK E or anyone with similar experience

Discussion in '308/328' started by 328turbo, Jan 5, 2010.

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  1. 328turbo

    328turbo Formula Junior

    Jun 15, 2009
    306
    nyc
    #1 328turbo, Jan 5, 2010
    on another thread, fuel injectors and power potential were discussed and sparked some tuning questions.
    because i did not want to hijack someone else's thread, i decided to start another
    ___________________________________________________________________________
    Originally Posted by 328turbo:

    w/ 42#inj, your turbo 308 should be tunable to 520-600hp -if you can push the appropriate fuel and air.

    response by mk e:

    Not on a QV or 328. The way the heads are flowed the the cams selected a lot of air goes out the exhaust when you add boost and it takes a lot of fuel with it. My QV was making right about 540 crank hp and I needed 55# injectors with the fuel pressure cranked up to 60 psi running 85% Duty cycle to do it. N ow, the air flow chart for the blower said I was pumping about 800hp of air....and that matches the fuel flow but not the result.
    _____________________________________________________________________________

    are the cams timed like that to create a syphoning effect for the intake stroke? wouldnt this be unnecessary in a forced induction application and could this be corrected by adjusting the overlap or lobe separation between the int. & exhaust cams? or is this a dumb question?
     
  2. mike996

    mike996 F1 Veteran

    Jun 14, 2008
    6,872
    Full Name:
    Mike 996
    #2 mike996, Jan 5, 2010
    generally speaking, high overlap, long duration, high lift cams are a liability with forced induction unless you are talking about a competition-only application. The beauty of forced induction is that the engine can remain perfectly streetable but have a great deal more power throughout the rev range.
     
  3. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,742
    The twilight zone
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    Help me get this thing finished! https://gofund.me/39def36c
    #3 mk e, Jan 5, 2010
    Yup. The QV/328 engines have relatively long duration cams for a 4V and a pretty narrow LSA at 107 for the US and 109 Euro…112-114 is a better boost number. My car was a US and I did change from 107 to 109 but saw no really difference on the boost gauge (I was running a blower not a turbo). I planned to try 114 the next time I messed with it but moved on the V12 project instead so I don’t know for sure what the result would be.

    Another problem is the head flow. The intake flow is kind of low which is why the longish duration is required, then the exhaust flow is up around 92% of intake instead of the more normal 70-80% to again help the weak intake flow a bit.

    The stock engines work pretty well and make decent hp but it’s an odd combination, odd to the point that the simulation software I have (dynomation5) chokes on it a bit and gives worthless results below 4000 and misses the peaks by 500-1000 rpm. Add boost to it and all these little things start working against you and create a really air/fuel pig that makes decent hp but you need a turbo/blower and injectors that are quite a bit bigger than you would think you’d need.
     
  4. 328turbo

    328turbo Formula Junior

    Jun 15, 2009
    306
    nyc
    #4 328turbo, Jan 5, 2010
    wiill lobe separation angle affect the powerband or redline on these engines?

    thanks for the input/adivse/opinions/experience, guys.

    as far as injectors i am a big believer in bigger being better. your shared insight on sizing is a big help.

    i am in no rush to do anything as far as tuning right now, but i figure why not ask while its hot on my mind.
     
  5. 328turbo

    328turbo Formula Junior

    Jun 15, 2009
    306
    nyc
    #5 328turbo, Jan 5, 2010
    i am kinda new to the board, is the v12 308 the same as the supercharged one?
     
  6. Hans

    Hans F1 Veteran

    Feb 17, 2006
    7,734
    Hilversum, Netherlands
    Full Name:
    Hans Teijgeler
    #6 Hans, Jan 5, 2010
    "tuning Question for MK E or anyone with similar experience "

    Yeah, right. Like anyone has experience similar to Mark's!!! ;)
     
  7. mk e

    mk e F1 World Champ

    Oct 31, 2003
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    #7 mk e, Jan 5, 2010
    Same car, different engine...for the 3rd time becasue I can't leave well enough alone....much to my wife's dismay.
     
  8. TURBOQV

    TURBOQV Formula Junior

    Mar 6, 2003
    838
    NV and Utah
    #8 TURBOQV, Jan 5, 2010
    amen to that! i love the power band, smooth and linear from 3k to redline!

    Cheers
     

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