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Mondial 3.2 with Webers - Dyno #2

Discussion in 'Technical Q&A' started by snj5, Jan 6, 2004.

  1. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    Dyno'd the Mondial 3.2 with new Weber carb jetting today (see old threads for history):

    34mm/150/F24/200/idle.55

    Max corrected SAE RWHP: 230.9 hp
    Max corrected SAE RW torque:199.0 ft-lb

    Calculated corrected flywheel hp @18% driveline loss: 281.6hp
    Calulated corrected flywheel torque: 242 ft-lb

    Uncorrected (real produced today) RWHP: 241.4
    Uncorrected calculated flywheel hp: 294.3

    Idle A/F with new idle jet: 14.7 - 15.5

    Goes a little rich as you can see when you dump the throttle - may look at backing off EVER so slightly on the accell pump jet.

    A/F doesn't look too bad - pretty close anyway varying from 12.9@3.5K to max lean of 14.3@6.2K.

    The 36mm chokes arrive this week from Pierce. Will try those next. Got the cam cores in today from trutlands to send to Elgin for reprofiling (255 duration). Will put the cams in in Feb - March.

    I'm having a great time and learning a lot. The car is happy.
    thanks so much to all who have been helping
    rt
     
  2. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    16,557
    USA
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    Hugh G. Rection
    You're already 34hp over stock and still have a little tuning to go? Nice, very nice!

    Thanks for keeping us updated on your progress.

    Dave
     
  3. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
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    Russ Turner
    the scene of the crime.
     
  4. mk e

    mk e F1 World Champ

    Oct 31, 2003
    11,384
    The twilight zone
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    The Butcher
    Hey...I think you used a 17% correction last time :)

    The graph looks very good. 12.9 is a good number, but 14.3 is a little leaner than you probably want to be. It may idle better and transition better with the idle a little richer too, I aim for around 14.0. It looks great though, very smooth.

    I can't wait to see what the cams do for it. I've been thinking about a little more cam too....not sure I need it though, I hope to hit the dyno early march, so I 'll see.
     
  5. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    Mark

    I recently read where the 18% is more accurate for mid engine transaxle cars - really!!

    Am debating what main jet to put in with the 36mm chokes. May bump mains to 145 if I do, or have them ready to swap between runs, as it only takes a few minutes to swap out the whole set if pre-loaded on the emulsion tubes. These Webers are terrific for that.
    On that subject, will probably stick with the F24s although still tempted by the F36s.

    I may be off, but I have a feeling that if I could get more flow through the carbs, there are a few more ponies even with these stock cams - i.e., I have about maxed out the 34mm venturis. Will see if there is any drivability loss with the 36s, the largest size available for the 40DCNF. Am now wondering a little if I should have gone to a 42 or 44 dcnf. Pierce calculated that a 34mm venturi should just support 300 hp. Will see with the 36mm venturis.

    The soon to be installed longer duration intake cams, even with just 30 - 34 overlap (retarded exh) should make a big difference (stock overlap 24). And will also be rolling in 34@3000 advance (stock 32 @5000) which will be interesting. Will be keeping the 9.2:1 comp ratio.

    May hit the dyno again next week or so with the 36s - will keep you posted. Thanks for everything
    best
    rt
     
  6. mk e

    mk e F1 World Champ

    Oct 31, 2003
    11,384
    The twilight zone
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    The Butcher
    So after looking at your post, I went ahead and did the search to see where the nearest dyno is to me...3 of them in a 20 mile radius...ummm and the new injectors should be here any day now....

    What brand dyno are you running on?
     
  7. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    Mark
    Am using a Dyno-Jet.
    $100 for 3 pulls and baseline A/F data.
    You just can't beat it for tuning info. The place I use specializes in supercharged Mustangs, so you guys would have a lot to talk about as they really have a lot of experience with blown v-8s.
    If you (or anyone) want to drive down to do runs and with tweaks inbetween, they have group packages.
    best
    Russ
     
  8. Dopplemax

    Dopplemax Formula 3

    Looks great Russ. We still need to get together. Kendall said I should have the 308 back in two weeks.
     
  9. pma1010

    pma1010 F1 Rookie
    Silver Subscribed

    Jul 21, 2002
    2,556
    Chicago
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    Philip
    Russ
    In the Weber book there is an interesting diagram of (single) cylinder volume versus (single) venturi size for different RPM ranges - from memory there are 3 curves, corresponding to 6000, 8000 and 10000 rpm. I assume all for 2v engines given the timing. As I recall, a 375cc (308) cylinder could support a 40mm [yes, 40mm] venturi at 8000 rpm. Having said that, the issue is sizing the venturi for your use pattern and gaining broadest area under the torque curve.

    In my experience the bigger venturis do tend to cause the air to stall at low velocities (insufficient vacuum above the throttle plate) and produce a "difficult" [to drive] bottom end. Having said that, there seemed to be quite a bit more about 5000 rpm. And did I mention the sound...with the airbox and decklid off [only for tuning obviously], but oh man...

    My advice is to try it. As long as you start off fairly rich you won't hurt anything and you'll generate some data. Also, th 4v heads and the larger displacement of the 3.2 may (will) cause different results from us with "older and smaller" heads.

    Second, you mention increasing the mains to 145 with the 36mm venturis yet your posts seem to be suggesting you are using 150 mains with the 34mm venturis today - am I misinterpreting? FWIW, on my 308 I am running 155 mains (with 185 AC) with the 36s and it is too rich. My gut (and I'll have some data when the weather improves) is the 150s are the right mains for the P6 [290]/36mm combination.

    Keep up the good work. Car looks great in the pics.
    Philip
     
  10. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    Philip, Mark and others:

    Major correction!!!!!!!!!!!!

    I used 140 mains on this dyno run (down from previous 150s which were WAY rich)!!!!
    F24 emulsions and 200 air correctors are correct

    That is why the move to 145 mains with the larger 36mm venturi.

    I am also going to try a K&N, now believing that others' previous reported loss of hp with K&N's was due to mixture changes due to filter airflow resistance changes (thereby changing airbox pressures). I am hoping that the K & Ns will provide more airflow, and I will tune my jetting to match their increased flow. I think the F24s also provide more midrange flow capability than the F36s, correct me if I am wrong on this.

    Sorry about the mis-type confusion - hope this makes more sense

    Philip - I seem to remember that there was no flat spot problem with your 36s? Would also be interested in your accel jet set up. It looks like I go too rich when the throttle is dumped, suggesting too much pump shot or a velocity problem. There is not much seat of the pants indication it is happening.

    thanks
    Russ
     

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