Quote:
Originally Posted by oil pan 4
Does this carburetor you are going to use have a primary and secondary setup?
Or is it single barrel?
If its just single barrel with a metering screw adjustment then you are only going to be able to tune your idle air fuel ratio a little and you will be stuck with one air fuel ratio that stays fairly consistent through out your entire operating range. Unless you get creative. If the single barrel carburetor has a metering rod and spring setup then you will have some ability to tune cruise, part throttle and wide open, but you wont be able to run lean cruise, then go a lot richer for WOT like you want to.
The primary and secondary carburetors give you more built in ability to tune cruise, part throttle and then accurately dump much larger amounts of properly portioned fuel and air mix into the engine at WOT when you need power.
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This is a single barrel Solex 34PICT-4 carburetor with a 26mm venturi and a 34mm base. Besides adjusting the idle mix I can get very finely incremented pilot jets that affect off idle AFRs. Also there's a wide variety of main jets to choose from. I can also possibly source three different sized acceptable used air correct jets for this carburetor, which basically are a replaceable air bleed for the main jet. There's also an "auxiliary jet" which in reality is a separate jet that runs the idle circuit while the pilot jet mainly runs the off idle circuit.
The power fuel system is quite different on this particular carburetor. It is designed to run at stoichiometric at part throttle but then enrich to around 12.7:1 at full throttle and high RPMs. It simply consists of two "high speed enrichment" jets (actually three if you include the accelerator pump outlet as a third jet) that are situated above the venturi. They're not activated by any mechanism off the throttle shaft nor from a vacuum diaphragm. They simply get their own venturi effect at high air speeds.
So yes, it seems like this carburetor is better suited for one AFR across the board. Most VW guys usually jet these to run 13:1 or rich across the board. A few ecomodding types can get them to run around 16.5:1 to 17:1 at low throttle and then enrich to 13:1 or so at high throttle. What I'd like to know is if I can get it to run 17:1 to 18:1 across the board and use something other than extra fuel to control high EGRs and detonation at high load.