Efi is better in every way. There may be a learning curve but having an old car that runs like a brand new one is awesome. You will have to drive a lot to get a payback, not sure of your use? A carb can be tuned "good enough" that a seldom driven car will not see enough gain to offset the cost. You can get a carb to run damn close to efi given enough time. Have to retiuch it every so often. When i was younger that was possible. Investing time like that isnt in the cards for me now.

Thanks lots of great info here. I'll probably end up sticking with the carb a little longer and learning how to tune my carter afb. Maybe the price of efi will come down a bit.

I would agree that if you could find and hire a highly skilled craftsman who could:

adjust your present carburetor to an Air to Fuel ratio of 16 to 18 at part throttle cruise,
but 12 to 13 at full throttle

select the best modern sparkplug for your engine,
and set the widest gap your present ignition system can handle when it has worn to the maintenance interval you tell the craftsman you will change/regap the plugs at

adjust your ignition timing at full throttle to the Octane rating of the gasoline you are buying at the highest air temperature/ highest barometric pressure you will drive the car at, then further adjust the vacuum advance mechanism to optimum part throttle settings for fuel economy, which are probably in the 40 to 45 degree range

these "tune up" adjustments should improve highway cruise fuel economy by at least 2, and maybe 4 MPG

i would guess the cost to be less than $600

If it were me i would attribute part of the cost to "education" because a skilled craftsman will explain important details of what he has done, and why

More MPG gains could be had at modest cost by changing aerodynamics and changing to modern low rolling resistance tires

the one thing that you will get from the efi is consistent drivability. you will never have that with an out of the box carb that was basically tuned by swapping some jets or adjusting metering rods. there is a reason every modern car and now nascar is switching over to efi. its modern tech

If you are being forced to re-tune your carb with every temp swing, then you need to review your tuning technique. A/F ratios will change a bit from atmosphere to atmosphere, but if it affects the operation of the car to the point that the carb must be re-tuned then something is not right. Street cars operate in a wide range of environments and conditions and as such the tune must be more accommodating to a wider variety of conditions than a race only application would be.

Dabee spent nearly $3,000 and got a 3-4 MPG improvement. But even he thinks that better timing control accounts for the majority of that improvement. If he is happy with that investment of his money, then that is all that matters because it is his money. But from a practical point of view, most muscle car guys don't see the value.

Another valid point about considering any EFI system right now; it will be totally obsolete in a very short time. The systems are still in the development stage. They will likely mature in time and become a viable alternative. And I look forward to that myself. But today is not the day to drop $2,000 to $3,000 on one of these things.

You can really tell the posters that have a suboptimal understanding of carbs.

You can do a megasquirt for pretty cheap these days. Probably get it all in for 1000 bucks and that will do fuel and ignition.

Even at that cost, I wouldn't do it with the intention of fuel savings paying for it. Sure MPG will be up, especially during cold starts. MPG at cruise may be a bit better but once the engine is up to temp, a carb isn't that bad. It's during warm-up, accel that a carb isn't ideal. An efi system will let you dial in your ignition and fuel to exactly where you want it to be. Throttle response, driveability will all be improved. Ever take apart a factory EFI engine and take a look at the cylinders inside? They look clean and darn near new compared to the carboned up pistons on a carbed job. There are many compelling reasons to go to efi, but if it's just for mpg on a car you drive once or twice a week, take a real hard look to see if it's worth it to you.

First of all, cnxt's calculations showed a 3-year breakeven at 6000 miles per year. That's reasonable, and a good investment.

The one actual user reported a 30% mpg increase. That's huge.

One thing that hasn't been mentioned is how much more fun it is to drive your car when you don't have to think about gas mileage all the time. When my engine swap changed my mpg from 15 to 20-22, it made driving much more fun and I could actually go places because I WANTED to, not because I needed to.

To the OP: Your 1973 Charger is about as bad as it gets with mileage. It's about the worst of the "bad old days". Manufacturers hadn't really sorted out the processes needed to meet emissions regulations, and I remember the result was cars sucked gas bigtime.
From a "normally" tuned 1973 to a modern fuel injected 1973, I am guessing you will see nearly a 50% increase in REAL economy. That's if you buy a system that does the timing as well as the fuel. Reason being the emissions control was done a lot with timing, usually lack of timing. But even using a system that just uses a throttle body injector with an O2 sensor I'm guessing 30%. Most people on this board don't or won't remember how truly awful the 1973-1974 cars were. Unfortunately for us Mopar fans, Chrysler tried to do it without converters for a few more years, resulting in more nearly undriveable cars.

Now, the situation would be much different if you had a chassis dyno to tune carburetion and a distributor machine to get the ignition curve right, it may be only a 10% or less improvement. But your question does not sound like you have the equipment or expertise to do this, and I'm not sure you'd want to pay $125 an hour plus dyno expenses to get it all sorted out.

Back in the day, fuel injection was the unattainable goal. The 1965 FI Corvette was the pinnacle. Few outside of that select club were able to enjoy FI, but we all wanted it.

Chrysler tried it in 1958 with a Bendix system that was a direct forefather of the modern EFI systems, they knew it was best too.
But there wasn't the electronic technology to get it done. Now we have the technology. Why hang on to carburetors? If you're into flathead fords, they make sense. But if you actually want to drive a car on the street, fuel injection is hands-down the winner.

R.

10 or 15 years ago your point may have had merit, but these days, aftermarket EFI controllers have been around for a very long time.

A 50% increase in mileage is what CNXT's calculations are based on, very doubtful you'll see that unless your carbed system was totally hosed before the swap. A simple comparison of OEM EFI systems versus their carbed predecessors sure do not show a 50% increase. EFI was gone to for emissions, not economy.

You still need to tune the EFI as well, self tuning units are not cheap and will add to the pay back time, plus who's to know how well they self tune short of dyno time to verify?

You can really tell the posters that have a suboptimal understanding of EFI.


As for retuning the carb with any change in temp or pressure, it must be done to keep everything running in optimal condition.
Why do you see hard core racers with weather stations in the pits? If the day starts getting hotter or the humidity changes you will see them ripping into their carbs to rejet and optimize the settings.

The EFI guys check their datalogs and look for possible improvement. If tuned properly, the computer takes care of all the adjustments.

I ditched the carb for port EFI. I spent quite a bit of money since I went for my custom intake manifold. It was the best money I spent on the car. The drivability was greatly improved. Economy picked up a bit too. My system controlled timing and fuel so I could completely retune by laptop if needed.

Did the system pay for itself?

No.

Did the money spent on the engine build pay for itself?

No.

Did the wheels and tires pay for themselves?

No.

Did the seats pay for themselves?

No.


You see, I didn't do it to save money. I did it to optimize what I had and make the car FAR more pleasurable to drive. Some things just come at a cost. When you're talking about a car that is driven on a somewhat regular basis then EFI is a great idea if you can afford it.

Don't look at EFI as a way to save money. If you wanted to do that, you picked the wrong hobby.

Bullpoop. You are comparing later model O2 sensor feedback carb carbureted cars, not taking into account how bad the '73s were.
I was there, I remember. Between my 1972 and my friend's identical 1973 car, there was a 2mpg drop. (chevy nova 350 2-barrel 2-door bought new, mine was 16mpg, his 14)
R.

I live close to sea level and then drive my car to the track that has a density altitude of anywhere from a best of 2000' to a high of 4000' with 3000' DA being pretty common. I'm guessing EFI would help me out.

For the vast majority of people in the GENERAL forum, this is turd polishing. If this was the race forum where tenths matter, then yeah this is needed. Back when I still had my 64 300 it was my daily driver. When I transferred from the destroyer I was stationed on I had to go to a new radar school in Memphis. I left San Diego in September, returned in March the following year. In that time I went from mild, dry 70's temp to humid heat, snow, cold, ice and rain. Up mountains, into valleys, stop and go and long straightaways. Guess how many carb adjustments I needed to make, zero. I also got 15 mpg making that drive and pretty much nothing changed that environment wise. Once you have it dialed in, and it's not that difficult, all you might need to adjust is the choke if it gets snowy where you live. I had a manual choke so it didn't matter for me.

Now if I had a twin turbo setup EFI might make good sense, but that isn't to say a carb doesn't work in a blown application. They do, but it takes a lot more knowledge of fueling a blown engine, regardless of what is supplying the fuel. Less forgiving for mistuning, whether it's a carb or EFI.

It's turd polishing claims like the above that make noobs think carbs are some sort of PITA to deal with.

There is one thing carbs are better at than EFI, which you glossed over, if you have a problem EFI will tune around it till it's outside it's ability to do so. Carbs will not, so you find problems before they get seriously out of shape with a carb.

Nope, I am not comparing feedback carbs at all. Never really ran one for any length of time. BTW, you are not the only one who's "been there".

I suggest you go to http://www.fueleconomy.gov/feg/Find.do?action=sbs&id=27332&id=5987&id=9257

I compared an 84 1/2 ram with a carb'd 318 to an 89 1/2 ram with a TBI 18 to a 92 1/2 ton ram with a MPI 318. The 92 has OD, the others do not. 84 was as far back as it went.

Combined mileage for all three was 12mpg. City for all three was 11 mpg. Highway varies a bit, 84 was 14, 89 was 13, 92 was 16, which is the OD in effect.

The numbers don't back you up and your anecdotal Nova story could be many things, including loss of compression or retarded cam timing due to emissions which the carb can do nothing about.

I wasn't bashing carbs.

Someone else brought up the experts supertuning carbs. I brought up the examples of where you would need to super tune.

I've put lots of miles on carbed engines and have no problems with them. However, I prefer EFI.

I'm pretty good with an AFB. That's the carb most newbs have trouble tuning for some silly reason. In fact, I run an AFB on the Imperial. The only reason I haven't dropped my EFI on that car is because of the A/C line position. It would run directly across the mouth of the throttle body. Since the system is carrying 84 oz of R12 and cooling extremely well, I don't want to mess with it.

If the A/C system needs to be opened you had better believe that EFI is going on with a Sanden compressor.

Could you link to this 1000$ kit?

Ah, then we are on the same page. BTW, the carb I had on that 300? The dreaded, POS cna't be tuned Edelbrock model 1407, 750 cfm AFB clone. Still have that same carb too since 1988, liked it so much I bought another. Got two 1406's as well.

"Don't look at EFI as a way to save money. If you wanted to do that, you picked the wrong hobby."

But increased economy is exactly what the OP asked about. So we are agreed then that today's self learning EFI systems are not cost effective. That is all I've been trying to say.

You could grab an assembled MSII for about $450: MS-II

If you want it to "self tune" you will need a wide band O2 sensor, about $200: LC-2

Then add a used or rebuilt GM TBI throttle body and a lean burn distributor for timing control.

Then the assorted sensors and harnesses, and an electric fuel pump and fuel lines.

If you shopped carefully you could get everything needed for around $1000. I would think closer to $1200 to $1500 with the fuel system upgrades needed. Of course you will need the fuel system upgrades no mater who's EFI system you use.