Automobile Ignition Question

[tcmtech]

Only old engines with a carburetor have a venturi. It's what draws the fuel from the carburetor bowl into the air stream. Fuel injected engines don't need one since the fuel is injected under pressure.

Yes and from the early 70's well into the mid 90's we had a whole generation of vehicles with emissions systems and that still had carburetors. The conversion from full non emission carburetor to full emissions compliant fuel injection did not happen in one day to all makes and models of vehicles. Many of those transition period vehicles are still on the roads today.

 

[jareeb]

at school im taking a small engine class and on the older engines the use beaker points and condenser they read 2.5 millihenries on the coil with is just a 2 fas the makes like 20,000v, and the condenser made if i can remember it was .85 uf to .956 uf

 

[nigel wright]

So how do modern petrol engine ignition systems work without a capacitor ?
I worked on an ECU for a motorbike and just used a mosfet to turn the coil on and off.

 

[jpanhalt]

So how do modern petrol engine ignition systems work without a capacitor ?
I worked on an ECU for a motorbike and just used a mosfet to turn the coil on and off.

Please show us the circuit that worked for >10,000 miles without a capacitor. BTW, this thread is quite old.

 

[nigel wright]

Its very simple the mosfet holds the coil on for 2mS then turns the coil off causing a big spark.
There are no points in the design.

I also worked on an electronic ignition upgrade for cars that used a transistor to turn the coil on and off. The points just became a switch for the electronics to synch off.