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Location:
Hornsby, Sydney
Registered:
October 2002
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Weber jets on a TA22
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Tue, 04 February 2003 08:11
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I have twin DCOE webers 45mm with 30mm chokes on my 2TG. i dont know what size jets are inside and it wasnt set up for a 2TG. i use an excessively lot of fuel. Iknow my jets are way too big. I was hoping that someone with the same setup has over come this problem and could tell me what size jets i should be using for good power? I know they will always vary from every motor and all conditions but any ideas have to be closer than what
i have at the moment.
cheers Roadrunner.
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On Probation
Location:
North East NSW
Registered:
December 2002
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Re: Weber jets on a TA22
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Wed, 05 February 2003 14:28
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there is this thing you do, its called research. usually you go to www.google.com and type in something relating to your subject matter like "weber tuning" or "dcoe jetting", and you go and look up the rules of thumb yourself. you may also find a program called jetting.exe which is very helpful
tuning a weber is more than just fuel jets, you need to look at your emulsion tubes and air jets too, plus your idle jets if you are losing alot of fuel with just sedate street driving. then there are pump jets and chokes and aux venturii, find out how all these work before you go asking questions
your chokes are probably ideal for a 45, maybe a little too small which is a good thing (better to go too small than too big with sidedrafts). maybe try a 140 fuel jet, F9 tube and 180 air jet. idle jets maybe 45, i'm not sure. OR just whatever you're running now just keep buying smaller fuel jets (they're only what 4 bucks each) and/or bigger air jets until it feels nice
if you run too rich your car will bog and pop, if you run too lean it will cut altogether and get hot. the idea is to tune best LEAN at each throttle point. if you can get an EGO meter, about 12.7:1 is optimal power. 16:1 is your optimal fuel consumption ratio, so anything between those two numbers is great. on a carbed engine err on the rich side so you don't pre-ignite (ping), especially if you're still running factory dizzy advance
if you're willing to spend the time and cash setting it up properly (chokes for my dellortos are like $80/pair, i'm not looking forward to putting kits thru them) you can get a sidedraft to be responsive and perform across the entire rev range, unlike a downdraft which usually limits you to good performance in two of the 3 power areas (low, mid, high)
you've basically answered your own question anyway. too much fuel means you need less fuel and more air. learn how your carbs work, experiment yourself and get back to us
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Location:
Finland
Registered:
June 2002
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Re: Weber jets on a TA22
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Wed, 05 February 2003 16:00
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I have no experience with Weber downdraughts. Dellortos yes.
Some downdraught Dell's are 'exhaust emission' models, thus having _fixed_ idle circuitry air bleed (size is 2mm in dia). This is not good. In side draughts same bleed jets are changeable, except models 40H and -F. It makes engines run real lean in low rpm's.
To correct the situation we need to use any means we can come up with to alter air bleed aperature size. I chose to drill & tap said fixed inlets. I manufactured a set of airbleeds in 0,1mm increments ranging from 1,2mm's to 1,9mm's. (I found just perfect allen-key screws from toolshop, only had to drill a hole through 'em and voila!).
So basically yes - fixed aperature carburators can be finicky in idle jet circuitry performance in stock trim.
When DIY altered, they are as freely jetted as their sidedraught counterparts.
BTW, it pays off to go thru carbies in grate detail. For example in my pair the darn butterflies were miles off center. That'll definately scew up progression phase fuel distribution, idle as well.
Fuel levels needed some tweaking as well to get back to OEM manufacturer's manual recommendations.
One more detail: clean, clean clean. Carbies won't tolerate any muck. Install proper fuel line filtering, air filter too.
All in all, so many small little details can be outta order in carbies to make them perfrom badly. There's no other way to make sure what we have unless we take them completely apart.
-A.
[Updated on: Wed, 05 February 2003 16:10]
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