I've got 2 questions...
1. Maybe someone knows what is that big air plastic box on the top of original Punto 16V engine for?
http://img13.imageshack.us/img13/2662/dsc03046a.jpg
Is it just to stop "air vibration" in inlet system?
2. If I blocked "charcoal canister" blue pipe, does it affect engine idling on cold engine? I also don't have valve....if I get one I might connect it just to stop recording fault by ECU. Does anybody know what is exactly function of that device? Is it only to reduce emission?
Thank you
1. The box in the inlet system is to reduce intake noise only.
2. As I said before, the charcoal canister stores fuel vapour. It uses the adsorption potential of the "charcoal" to stick to the surface of it, rather than be absorbed, where it would be difficult to extract again. There will be two valves in this system. One allows the vapour to pass from the inlet manifold to the canister and is normally on the manifold and another is on or near the canister to allow that vapour to go back into the inlet to be burnt at a later stage when the canister reaches a pressure threshold and the engine conditions are suitable (hot). On many FIATs, both are electronic valves controlled by the ECU, but some have one electronic and one vacuum operated valve.
The purpose of the device is to prevent loss of fuel for environmental reasons, which the manufacturers have had to do by law for a while. It will improve economy in theory too of course, but I expect the improvement would be minimal.
In older cars, you would simply have a vent on the fuel tank, which would let out fuel vapour and air as required- simple, but messy in environmental terms. It could cause problems if you blocked up a modern car's system since the whole fuel system is completely sealed and relies on pressure release.
If you are able to use your car for any extended period, then you don't have a breather problem and you can forget all this. If you are experiencing vacuum pressure build up in the tank, then that would manifest itself as an inability to start or run/idle after a while until the pressure in the tank drops naturally through leakage or by opening the fuel cap (you would hear a hiss as you did this). It
might explain your recent problems with trying to accelerate.
Although I did hook up the system in my Panda which did have the later sealed setup with a canister already in the wing, I haven't in my Uno track car, which simply has a mechanical vent on the tank and there are no ill effects on that.
Woops! It would run out of fuel and then backfire with a loud bang! Now it has a 3 Bar injection pump (a bit excessive I know but fuel injection is the next step so all is ready). Fuel pressure is then regulated down to 0.2Bar for the carb!
