But I'm a skillful carburetor programmer too.
The real challenge is using LPG with a Pierburg 2E3. Which has an auto choke mechanism and engine load dependent second barrel operation. Also there is the distributor itself with centrifugal advance mechanism coupled with vacuum advance unit*. (*= On stock engines. I have R12 distributor) All of those advance mechanisms are tuned for gasoline. LPG advance curve is different.
- Issues with cold start. (<10ºC)
- Issues about switching between fuels.
- Issues about setting up the static advance and advance curve. (Since I have R12 distributor, probe light doesn't work for me! It shows an awkward position on degree marks near the pulley. Because, original Favorit ignition circuit has its own delay!)
- Advance curve and fuel ratio is connected with each other but I can't put at least one variable to a constant with LPG.
- Issues about keeping the carburetor clean. (LPG setup is pouring a black sticky muck right into the carb.)
Think about this; second choke on the carburetor opens at a certain vacuum level from the engine but its movement is blocked when gas pedal is not pressed at a certain degree. Because of this, you can't adjust LPG when the car is stationary. It's useless. (You can over-rev the engine with second choke completely closed, when the car is stationary)
A carburetor is designed to keep the A/F ratio constant under variable airflow but the vaporizer of the LPG unit solely depends on vacuum. It increases LPG output based on vacuum.
Long story short, it's a nightmare to properly setup and use LPG on a Pierburg 2E3 mounted engine. This deserves its own topic.
I have some home brew solutions to address some of the listed issues above but they won't just cut it all. The car can keep 120Km/h on flats with acceptable LPG consumption in the city but I can hear the engine pinking when climbing hills on second gear with revs more than ~3000-3500 (depends on air temperature and engine temperature).
Also, there is evident power loss between LPG and gasoline. You can tell the difference easily. On injection cars, when their LPG installment and ECU programed correctly, there is almost no power related difference between LPG and gasoline.
After some deep dig from past-time Czech sources, the real masters of using Pierburg 2E3 with LPG is no one than Czechs themselves! They are mentioning modifying the second choke operation. Remote controlling some of the parts in the carburetor for LPG use. On top that, they built a system with a SMV (Stepper motor valve) as a LPG power valve, receiving signals from a lambda sensor. They did this in the early 2000s. 😱 WOW! Just WOW!
If you want to up your game, you need better tools. I think, monitoring a lambda sensor value is a good start to see whats going on. (I mean getting some meaningful numbers)
Thanks! Many thanks! That's really what I've needed! A live world experience.
Using the original secondary pipe will save me a lot $$. Now I'll have to decide whether to obtain a wide band Bosh LSU 4.9 or a more basic lambda sensor. Expensive sensors will setback the project for sure. But I'll post info whenever I can achieve some progress.