Mondial 3.2 w/Webers: cam matching w/ porting | FerrariChat

Mondial 3.2 w/Webers: cam matching w/ porting

Discussion in 'Mondial' started by snj5, Jan 5, 2008.

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  1. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    Through some miracle (thanks, Mark), my heads may be done.

    While not going through the many supporting threads, we've had to re-profile to a less aggressive cam lift set-up based of Webcam's recommendation to meet my over-riding requirement to have a rock-reliable engine with max street torque at the expense of high end power. Laurie at Web found that at lifts over .360 that the chance of throwing a valve shim and excessive cam/shim wear increased dramatically. With my previous lift of .368, there were already lobes that needed repair after 5 years, which was unacceptable. They then recommended based on a test qv/head cam set-up a maximum safe allowable lift of .360.

    To match all of the engine components, this meant that the head porting needed to be reprofiled away from optimum flows at the original cam specification of around .400, increasing lower lift flows to gain .200 - .360 curtain flow and 'area under the curve' (i.e. total air charge mass) at the expense of the 0.400 high lift flow, which was now not being used due to the reliability concerns. So, while the max flow rate number is lower that we had been working with before, the increased fatness of the flow curve (coupled with extremely air high velocities) will optimize performance and reliability. In any event, since this car's main design requirement is street use, I am very interested in the torque from flows 2750 - 7000 rather than an street non-friendly high 9000 rpm screamer.

    Remembering that my previous base maximum qv head flow with 40 DCNFs was about 92/93 CFM @10" at .348 lift, and generated best numbers SAE corrected measured of about 238-242 rwhp @6500 and 203 ft-lb torque ( using std 17% driveline loss, approx flywheel numbers of 286-291 flywheel hp and 245 ft-lbs). The new (and final) flow numbers after the head re-profiling for better lower lift flow are:
    .100" 42 CFM
    .150 69
    .200 87
    .250 97
    .300 102
    .350 104
    .400 105

    So, it's hopeful to note that we are already past the max flow at the stock max .348 lift by a lift of .250; although the flow max CFM is only up by 11 - 12% it all comes in much earlier and for a longer time. Couple with this as said before remarkably increased velocities over stock. So while I do not think the dyno number will be quite as high as would have been seen with the .400 cam, I will gladly trade that for maximum reliabiity and wear characteristics.

    And to recap the other matching changes, we are going with JE 10.5:1 pistons, Weber 44 DCNFs and tubi Euro s/s exhaust manifolds with a true dual system (rather than the previous stock single system). If we stay on schedule, should be tuning in February.
     
  2. rtking

    rtking Formula Junior

    Mar 5, 2006
    703
    Huntington Beach, CA
    Full Name:
    Bob King
    Exciting! Since you're changing pistons, is it possible to bore the cylinder liners a bit larger to increase displacement? Or is there another rod/piston combo that can be used to create a stroker motor? The increased flow through the head and optimized cam seems like it would support larger displacement which should provide significant torque gains.
     
  3. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
    3,930
    CA and OR
    Full Name:
    pit bull
    Russ,

    Your dyno numbers with high compression pistons?

    I finally dyn'd my 2V car . . . really flat tq curve (180 ft-lb from memory) . . . that was high comp pistons but stock .300 lift cams . . . posted the curve in another thread.

    Thanks,

    Sean
     
  4. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    No - the previous dyno is with a US comp. ratio of 9.2:1 and stock cams. Only change was the 40 DCNF Webers instead of K-jet.
     
  5. Dino 208gt4

    Dino 208gt4 F1 World Champ

    Jun 24, 2003
    14,868
    European Union
    Full Name:
    Roel
    Hi Russ,
    all to technical for me but it sounds like you are doing some interesting things;)
     

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