Originally Posted By: supton
Originally Posted By: veryHeavy
Originally Posted By: jayg
Carburetor cars don't have feedback sensors reporting to a computer telling it exactly how much or little fuel to inject based on the temperature outside? It's done mechanically that has no way of knowing air intake temp, coolant temp (to an ecu), barometric pressure etc.... so instead the choke (electric or manual) gets you pretty close until it's warm enough that you don't need it.
Thank you. I've never owned one, so never had to deal with that.
Also, the fuel goes into the intake manifold (also applies to throttle body injection / aka TBI) with the air. Unlike port (or direct) injection. This makes a difference. Liquid gasoline does not burn, it has to be vaporized. A carb is a fancy fuel leak and as such the fuel goes into a cold space, with cold air rushing over it. The gasoline has a hard time turning into vapors that can be burned. Idling can help heat up the intake manifold; many intakes had an exhaust crossover passage for that purpose.
Port injection squirts just ahead of the intake valve, which is going to be warmer (closer to the cylinder) and offers a straight(er) shot into the the cylinder, with less places for the gasoline to drop out of the air. Also, due to higher pressures, the fuel is "forced" into smaller droplets, unlike a carb. [TBI setups were also hindered if the injectors were above the throttle valve--the fuel had to hit the mostly-closed flap, which of course was being cooled down the incoming air--that couldn't have helped.]
Carb and TBI setups often had a heat riser setup, offering heated air coming off an exhaust manifold. There would be some fancy covers on the exhaust manifold, and a piece of tubing (sorta like dryer hose) going to the intake cleaner housing. Inside that was a bimetallic control which would switch from cold air (the other intake location) to this preheated air (all of this ahead of the air filter). Not sure if I've seen a PFI setup with this, but I'm no mechanic and have worked on very few setups.
Yeah , my Ford Capri has a heat stove on the exhaust header and it also has a water operated aytomatic choke, works quite well in the cold really, it doesn't take more than 2 attempts to start the car in any temperature, although in the summer it often vapor locks because of fuel evaporation.
Originally Posted By: veryHeavy
Originally Posted By: jayg
Carburetor cars don't have feedback sensors reporting to a computer telling it exactly how much or little fuel to inject based on the temperature outside? It's done mechanically that has no way of knowing air intake temp, coolant temp (to an ecu), barometric pressure etc.... so instead the choke (electric or manual) gets you pretty close until it's warm enough that you don't need it.
Thank you. I've never owned one, so never had to deal with that.
Also, the fuel goes into the intake manifold (also applies to throttle body injection / aka TBI) with the air. Unlike port (or direct) injection. This makes a difference. Liquid gasoline does not burn, it has to be vaporized. A carb is a fancy fuel leak and as such the fuel goes into a cold space, with cold air rushing over it. The gasoline has a hard time turning into vapors that can be burned. Idling can help heat up the intake manifold; many intakes had an exhaust crossover passage for that purpose.
Port injection squirts just ahead of the intake valve, which is going to be warmer (closer to the cylinder) and offers a straight(er) shot into the the cylinder, with less places for the gasoline to drop out of the air. Also, due to higher pressures, the fuel is "forced" into smaller droplets, unlike a carb. [TBI setups were also hindered if the injectors were above the throttle valve--the fuel had to hit the mostly-closed flap, which of course was being cooled down the incoming air--that couldn't have helped.]
Carb and TBI setups often had a heat riser setup, offering heated air coming off an exhaust manifold. There would be some fancy covers on the exhaust manifold, and a piece of tubing (sorta like dryer hose) going to the intake cleaner housing. Inside that was a bimetallic control which would switch from cold air (the other intake location) to this preheated air (all of this ahead of the air filter). Not sure if I've seen a PFI setup with this, but I'm no mechanic and have worked on very few setups.
Yeah , my Ford Capri has a heat stove on the exhaust header and it also has a water operated aytomatic choke, works quite well in the cold really, it doesn't take more than 2 attempts to start the car in any temperature, although in the summer it often vapor locks because of fuel evaporation.
