i am curious to see what kind of fuel economy folks are getting with an FI slant six...and how it compares to the carb they had on it in the first place.

i have a 71 dart with a 225 and 1 barrel, so i'm just curious at this point.

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My Dart
GO VOLS!
It's not rocket science, we're just splitting atoms.

I am new to the site, but I am curious about this as well. I just bought a 71 duster, factory AC car with an automatic, that I plan on using as a daily driver. It has a rebuilt engine with an RV3 cam. I am wondering how much of an improvement in mileage EFI would gain me.

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71 Duster, Factory AC, auto

Hi Guys, Assuming your carbureted car was in excellent shape with top flight ignition, carb, and engine mechanics(compression etc), you can get near 20 MPG with a carbureted single barrel carb. Some have done better. The 904 is strong, but inefficient and cost at least a 10% hit on MPG. My car went from 18 MPG to 22 when I changed over the transmission to a manual. To compare an EFI system to carbureted, you would have to assume the same things: that the engine was in good shape, that the EFI was set up and calibrated well, and that the ignition was in good shape. All things being equal, it seems as if you can expect another 10% gain. But, it is not that easy to get there. You must put in the time to learn, and then to calibrate your system. There have been several really successful attempts at EFI slants that have tracked the MPG. Dart270 is one of them. He was getting in the low 20's with an auto matic '68 Dart he drove pretty agressively, (at least when I was with him). He has stated that he improved upon this by running a leaner fuel mix, so my guess he is getting between 22 and 26 MPG now with this car. MPG MIke claims 44 MPG with a carbureted car, which he atributes, in part, to clever head and valve work. I think that would be a simpler way to go if MPG is your only concern.

Words of advice: the simpler the better. The more complex the system, the more variables to tune, the less likely you will ever have it really right. The ECM that has gotten good reviews on this site is SDS. Do a search here on this site for their Web site address. Several have had good success with Mega Squirt, a DYI system available on the internet.
Sam

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