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3.2 Weber jetting

Discussion in 'Technical Q&A' started by snj5, Jan 4, 2004.

  1. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    For those hard core few of you following the Weber carb conversion 3.2 saga: To review, we are now putting down about 224 rwhp ( about 270 crank assuming 17% loss )with a way too rich mixture (A/F around 11 and richer - idle A/F is 11.2). The current mix is 150 F24 190 .6 on 34 mm venturis.

    Today's project will be installing new Weber jetting, mostly following David Feinberg, JRV and Philip Airey's great help which follow my reading:
    34mm, 145, F24, 200, .55

    I had a set of F36s ready but broke a tab and will need a replacement. Noticed that the 206/246 and early 308 Dinos used F24s while the later 308s went to F36. Will have a set of 140, F36, 220 pre-made and ready to swap in (or mix and match) by the time I hit the dyno later this week if these are still too rich. As a historical note, F24 emulsion tubes were also used by Porsche Carrera 6 racing cars (with 170 main jets!!!).

    I realize that FI has many advantages, but for all you folks let me tell you - at least for me, these Webers are fun and really give the motor a personality. And did I mention the sound?

    Stay tuned for new dyno numbers when I can get on.
     
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  3. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    Well, after reviewing my previous dyno hyper richness again using 150/190s, put in 140 mains, F24s and 200A/C and swapped idles from 60 to 55. Was very tempted to put in 220 a/c but held off.

    I struggled a moment with the first inside idle jet before I realized it was much easier after taking the fuel line off... I'm slow, but I learn.

    There is a big difference in the F24 and F36 emulsion tubes when you lay them side by side.

    It does very rarely spit a bit at idle but very little. And no blue smoke now.

    The official drive around the block (sans air box) test did not show any noticible flat spots, and really seemed to come on at 4500 - 5000. The transitions from low rpms to the power band is not as smooth as the injection when you dump the throttle, but it responds RIGHT NOW. I thought the 45 accel pump would be too small but so far so good, but may go up a little bit.Pulls all the way up to redline and 3rd gear knocks your socks off from 5 - 7.7K compared to the old Kjet days. Interestingly, did not seem to need to mess with the idle set screws from the previous settings.

    Bolted the airbox back on and will see if the dyno is up this week. I think I'm getting closer to my 230 - 240 rwhp goal and certainly learning a lot and having fun along the way.

    Did I mention how howling loud this thing is, especially with the airbox off and open trumpets?
     
  4. thecarreaper

    thecarreaper F1 World Champ
    Silver Subscribed

    Sep 30, 2003
    16,036
    Savannah
    Full Name:
    I NEED A JOB
    3 cheers for you i love CARBS and will not consider any ferrari in my quest with fuel injection. the other benefit of doing this yourself is you can keep an educated eye out for other things the car may need as you own it, instead of having to take it somewhere all the time for someone else to fix. preventing things before they hapen is way more fun than paying more after the car dies on you. i know this from past expierience. thanks for keeping us posted, i really admire your posts and look forward to future updates. michael
     
  5. dr.mike

    dr.mike Karting

    Oct 31, 2003
    153
    Laguna Hills, CA
    Full Name:
    Mike Adams
    For this kind of tuning, it's hard to beat one of these mini analyzers.

    http://www.innovatemotorsports.com/lm1.php

    It's REALLY hard to beat at the price ( $350 ). Including the sensor, computer serial cable and graphics software. It rides along with you and records your fuel curve. You can download the data to your PC and see the rich and lean spots on the computer graph and adjust the jets/float level/emulsion tubes as needed. You can even see the effect of the accellerator pump.

    The RPM converter ( to make RPM vs mixture plots ) and the exhaust clamps ( so you dont have to weld on your exchast ) are nice ad-ons.


    I'm still not giving up my Colortunes though...
     
  6. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
    2,559
    Chicago
    Full Name:
    Philip
    Russ
    Sounds like you are learning a lot and having some fun too - hard to find a better combination. Directionally sounds like you are headed in the right direction. You might think about the "one step at a time" approach on the jets from here as you get closer to optimisation so that you can feel how each step changes the performance. Some data logging (as Mike mentions) also helps and is likely to save a bit on the dyno time (and cost).

    As I may have mentioned before, the Weber Tuning Manual (Pierce has them) has some excellent tuning protocols to guide the optimization of jetting and I'd (again) recommend it as "required" reading.

    Still debating the bigger carbs...

    Mike
    This does look like a great little unit. I've invested in a similar WB AF unit which also has data logging capabilities (to a Palm or PC) in addition to a display readout. It is installed in the car (which, given there is snow all over the place is in the garage for the next couple of months providing opportunities for all the other winter projects) and I'll post some recording info/data when available in the spring.

    I had a couple of bosses (& plugs) welded in the Tubi (one for 1 - 4, other for 5 - 8) and can pull interchange the WB sensor from side to side as needed.

    My goal is to have some information to inform jetting and tuning at the various tracks and to be able to conceal it/have it be out of sight once done.

    Philip
     
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