View Full Version : tuning side draft webers
05-27-2004, 04:38 PM
i was wondering if any one knows of a place that tunes side draft webers in ontario
05-27-2004, 05:23 PM
Paul At Neetronic's in Etobicoke started out tunning carbs if memory serves me (he does mostly EFI stuff now) ... Give him a call to see if he can help ...if not he should be able to provide a reference to somebody who can
Chris Tapp in Ottawa is another good tuner that may also be able to help you
05-28-2004, 08:27 AM
You might try Rick Bye ,he runs a "Porch" shop in St.Kitts .If he can't help you,he may know someone that can.
Have a look at this web site, there is a good Weber primer on it
05-28-2004, 08:38 AM
They aren't that hard. Chris Tapp knows little about carbs. We had our Jetta (fed by twin Mikuni 44 PHH carbs) on his dyno, he ran the dyno, and we tuned the carbs.
It's actually quite easy once it's hooked up to the wideband. The principles are the same. What sort of 'tuning' are you in need of? I assume that you have the car running already and you just need to get the ultimate A/F ratio right? You can do this on any dyno with a wide band and a BIG box of jets.
I would start by reading this page if you have not already to get your baseline, venturis, emulsion tubes picked, mains, etc... http://www.powerpage.dk/just_karb/webers.htm
Once you've got that set, then get an EGT gauge. This will help once you've been to the dyno especially.
Then go to the dyno, get on it, and pull and change jets until you've got the right mixture. It's really not all that hard. The idle/low speed stuff should be no problem to set, but to get good progression off the pilot jets you may have to play with it a bit. Basically, once all that is done on the dyno, you'll be able to read your EGTs on your last pull with the settings that your going to use on the track, that will give you the EGTs that your setup expects given the mixture that you chose - so if it gets hotter on the track you'll want to richen it up a bit, cooler, lean it out... and then of course, monitor your engine every now and then with a plug cut.
Syncronizing the carbs is also pretty easy to do with the one on this page: http://www.empius.com/c/carburetors.html
Where are you at in your project at this time?
05-28-2004, 10:14 AM
ya i have the car running but the main problem is that it is running way to rich and it fouls the spark plugs with in like 2 hours or driving and then i need to replace the plugs i just want to find some where that tunes the carbs that have the jets on hand because i dont have the money to keep buying jets and then buying new ones if they dont work .
05-28-2004, 10:58 AM
Well if it fouls the plugs when cruising, then I would check the operation of your pilot jet system. Your mains really don't operate much until the loads are much higher. You need to adjust your pilot screws, or possibly change your pilot jets.
Your idle adjustment screws should be 1-1/2 to 2-1/2 turns out from full lean. If they are far outside this range, your idle fuel jet is the wrong size. Increase jet size to reduce the number of turns, decrease jet size to increase the number of turns out from full lean (all the way clockwise).
Here is a great page with lots of information:
This is a nice page as it describes the flow, and which parts you'll be looking to adjust for the various paths.
read this section on tuning:
05-28-2004, 10:58 AM
Blatant cut and paste from the tuning page:
During highway cruise the throttle plate is near the progression holes. Changing flow through the idle fuel jet and idle air holes will thus most significantly change cruise mileage.
Modification would involve:
1) Increasing the size of the idle fuel jet may allow more power at a given throttle opening, increasing the load at which the transition to the main jet occurs. If you have large main fuel jets for good power at higher RPMs, you will find more fuel economy at lower RPMs by staying off the mains, and on the progression holes.
2) If indeed you have enough fuel to stay off the mains, but still have low economy at cruise, you have either too large an idle fuel jet, or too small an idle air jet. Increase the size of the idle speed air jet hole.
How do you determine all this rot? You need to see what your mixture is at your normal cruise speeds. The only way outside a dyno is to do plug cuts after sustained operations at those speeds. This means you turn off the engine and take it out gear after a sustained test at speed. Coast to the side of the road and pull the plugs... comparing color. You are looking for a chocolate brown or dark grey for all results. White is too lean, and black is too rich. Light brown/grey is also somewhat lean.
A note on plug cuts. High-performance spark plugs such as Champion Gold and other high temperature, anti-fouling plugs, can make it hard to read plug color. You want to have the standard temperature range plugs installed for thest tests. In addition, oil fouling will mask true mixture color. If you get oil fouling on your spark plugs, fix >that
The following test assumes the idle mixture adjustment screw has been properly set. The speeds are representative, and should be altered for your cruise gearing and desired RPM (on the MGB this corresponds to about 2K, 2.5K, 3K, and 3.5K RPM).
One method would be:
5 minutes at 35, check plug color
5 minutes at 45, check plug color
5 minutes at 55, check plug color
5 minutes at 65, check plug color
If the plugs are pale at 35 and 45, and go progressively darker at 55 and 65, your idle jet is too small, or your idle air jet is "too large", or you are transitioning to the main jet too early.
If the plugs are black at 35 and 45, and go towards brown or stay black at 55 and 65, your idle fuel jet is too large for your idle air jet. Increase the size of the idle air jet hole. In extreme cases you might have to reduce the size of the idle fuel jet (check the recommended size for your engine).
If your idle fuel jet is extremely small, you may be already on the mains at 35 mph. This is unlikely. You would have noticed this in the benchmark step when your idle adjustment screw was several turns out from full lean.
When you have a relatively even color across the speed/RPM range, fill the tank with gas and drive normally. With luck you will have increased your part-throttle cruise mileage noticably! Your mixture control will be better across the operating range and your engine will be happier because of it.
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