[MatthewKlein]

Originally Posted by Formulajones

The one thing I'll give fuel injection is that it's much easier to tune and I can get a bit more precise with my changes. But in the end I can pretty much accomplish what I want with a carb and be perfectly happy. I don't have engine longevity issues or drivability problems. They are simplistic and cheap.

The issues really these days is that it's a dying art, with people less interested in them and few people around that even want to understand.


I guess where I'm a bit confused is when you say "over fuel" I'm not sure I'm understanding that correctly. I mean, an AFR number is an AFR number no matter how it's metered. I guess I'm trying to simplify this for those reading.

In other words, if I have the carb dialed to cruise at 14.0 AFR, and I have the other car with EFI programmed to run a 14.0 AFR, where is the over fueling?

As an example, we have 2 cars here with Holley EFI. These engines want what they want for fuel. One makes best power at WOT with a 12.4-12.6 AFR so that's where I have the EFI programmed to run. They also cruise with an AFR of about 14.0-14.2 and that returns respectable gas mileage while not going overly lean. I can basically set a carb up to do the same or very similar. Where the carb loses is the drastic elevation changes we deal with. While atmospheric pressure will change how the air pulls across the boosters and compensate this to some degree, it's not a cure all. EFI with it's ability to change on the fly is wonderful in that respect. EFI has a few drawbacks too, cost and complexity being a couple.

But I've had no issues with over fueling with carbs, as far as the tuning aspect goes using AFR numbers and reading spark plugs. My oil analysis don't show excessive fuel.

Is there another aspect of this I'm missing that you're trying to explain?

The whole time the engine runs on choke it over fuels.

I don't know how you track the air fuel ratio but unless you have a data logger I'm not sure how you know what the ratio is at all times. Every time the accelerator pump discharges its messy and over fuels.

The only time a carb runs at a constant air fuel ratio is at a steady load. Similar to an aircraft carb. Or a stationary pump.

The constant transitions in engine load an automobile requires to accelerate from a stop, pull hills, etc make it impossible for the carb to provide tight enough fuel control to maintain stoichiometry and not to contaminate the oil.