82 mpg?
Melting Slicks
Joined: Mar 2008
Posts: 2,989
Likes: 198
From: Meriden CT
You're right; I didn't and still don't understand that; can you explain?
Why doesn't the motor care if the center cylinders are rich as long as the outer ones aren't lean? -Why does it vary from cylinder to cylinder? (heat related?)
How can it generate the same power from a cylinder that's running rich vs. a cylinder that's running lean?
Totally agree for a discussion limited to just 1st gen SBCs that direct injection is not a fair conversation; the issue of higher temps due to no evaporation of fuel when doing port or direct injection is an interesting one as the greater air flow seems to more than makeup for the slight difference in temps; it's also why many of these modern EFI intakes are using plastics or even aluminum, right? (no/ less heat soak) EFI (port) gives them a lot more options that more than makeup for any loss of heat due to evaporation.
Again, I totally agree that swapping a carb for a throttle body EFI system in a well and constantly tuned car would not see a perf increase, but what percent of these cars are in that state? I still think a slight majority would see a perf increase with a current gen TBI+Ignition Control EFI swap vs. a carb.
Adam
Why doesn't the motor care if the center cylinders are rich as long as the outer ones aren't lean? -Why does it vary from cylinder to cylinder? (heat related?)
How can it generate the same power from a cylinder that's running rich vs. a cylinder that's running lean?
Totally agree for a discussion limited to just 1st gen SBCs that direct injection is not a fair conversation; the issue of higher temps due to no evaporation of fuel when doing port or direct injection is an interesting one as the greater air flow seems to more than makeup for the slight difference in temps; it's also why many of these modern EFI intakes are using plastics or even aluminum, right? (no/ less heat soak) EFI (port) gives them a lot more options that more than makeup for any loss of heat due to evaporation.
Again, I totally agree that swapping a carb for a throttle body EFI system in a well and constantly tuned car would not see a perf increase, but what percent of these cars are in that state? I still think a slight majority would see a perf increase with a current gen TBI+Ignition Control EFI swap vs. a carb.
Adam
I didn't say a lean cylinder would make as much power as a rich one, please stop putting words in my mouth. If some cylinders are rich the motor will only burn all the fuel it can with the given amount of air, the rest is wasted, that's why FI gets better fuel mileage. A lean cylinder will obviously make less power, tune so none are lean.
The mixture varies from cylinder to cyl because each intake runner is very different from the others in length, shape, turns, especially in a plane single 4 barrel like most have. The velocity slows and mixture falls out of suspension on the longer ones.
Plastic manifolds are available for carburetors too, I have seen back to back tests but I can't remember the results, so it must have not made much of an impression, but I do remember that they are quite expensive compared to the aluminum .
I could buy a reasonable FI system for $2500 to $3000. How much gasoline could I buy for that money? To gain a few MPG?
