Carbs belong in the trash can.

I remember how I use to "Tune" my car each summer... Something would come up, it would stumble with the carb, I would get it perfect, then I would do it all again next summer as gas changed, weather patterns changed.

After doing my MS3X setup, I have focused on the other stuff I have always wanted to do on it. I can just drive the car now! Sure I am always looking to improve the tune, but now it's fun! I can data log, and adjust stuff while I watch TV at night, Or I can just drive the car.

I just finished getting a check engine light hooked up to the MS3X to do a full sensor check.

I also control my fan with the MS3X now.


Want to change timing???? Bust out the phone, and change it via bluetooth while driving if I want.

I will never run a carb again.


Even chainsaws and other small engines are EFI now.

The carb is dead to me.

That's pretty cheap. How many hours of work do you think is involved in installing?

If you are going Megasquirt and TBI or content running in batch/bank mode, you can go with the Microsquirt for $369 including the wiring harness. Add sensors and fuel upgrades and you are ready to roll.

http://www.diyautotune.com/catalog/micro...ness-p-509.html

Everyone keeps pushing the Innovate WBo2, and especially with MS I would use this one for $125:
http://www.14point7.com/products/spartan-lambda-controller-2

I'd say with some junkyard parts you could be in under $750.

As far as install time, it depends on skill level and what you are trying to do. I would say I had 40 hours doing everything on the W350, but I started with a donor harness and throttle body from a Holley Pro-jection and worked around that. I also had to wire up transmission control. I'd figure if you had all the connectors for the wiring, you could probably get one done in a weekend. Fuel upgrades may take a day. With MS, there are many ways to get to the same point. I've been playing with it for close to 10 years now, and learned quite a few lessons and shortcuts.

Not cost effective for who?

The way you drive or the way he drives? What about that guy over there?
What kind of weather changes?
How many road trips?
What kind of traffic?
What kind of fuel?
How frequently is it driven?
If the street manners improve will it be driven more?
How rowdy of an engine?

You can't make wide sweeping comments like that. What works for one guy might not work for another.

As for me, I want to be able to go anywhere at any time in any weather. I want EFI. It will be more efficient. Eventually, it will pay for itself.

I seen some real poor pay back calculations.

By poor they do not take into account that the payback price is the difference between the car mpg and the efi mpg, if any. If you get 50% better mileage (yeah, right) than at $2.50/gal you are saving $1.25/gal.

If you get 10% better than it's only $0.25 a gallon. And that 25 cents is more likely than that $1.25.

Even with the dirt cheap megasquirt TBI system that $750, if doable for that, works out to 3000 gallons payback. At 10 mpg that's 30,000 miles, at 20 mpg that's 60,000 miles.

If you consider that cost effective, I got some ocean front property for your consideration.

Sounds like the same twisted math I use on my wife every time I 'invest' in another car, a new part or accessory, or yet another must have tool.

She doesn't ever buy it as she does not ever include the 'cool' factor that we usually do,,,which is most likely the most important reason.

EFI will not be cost effective for the OP.
The purpose of this thread is to answer the OP's question regarding increased fuel economy with EFI. Apparently he has made up his mind to pass on EFI, at least for now. And with good reason. Because it simply is not cost effective.

For most us today, EFI is not the way to go. Period. If you like to mess around with electronics, tune with a lap top, can't figure out a carb, or just experiment with the latest and greatest gadget, then by all means go invest in an EFI system. But it is too early in the game for most of us to jump on the EFI bandwagon.

I expect someday to convert my Mopars to EFI. I welcome that transition. But I can tune a carb and ignition that will be hundreds and hundreds of dollars less than any EFI and run as good as it in most instances. EFI's additional expense and complexity is just not ready yet.

I would not discourage anyone who truly gets the advantages and disadvantages of EFI from going that way if they really want EFI. But the OP asked about the additional economy that EFI brings. And the answer is that there is no guarantee the EFI is any more economical that his carb, especially if the carb and ignition are properly tuned.

The Op originally only asked about mileage, we have inserted "economy" into the fray, not sure we can assume that requirement. Everyone else has also inserted their own benchmarks, but bottom line, hard for any carb tuned by any tuner to exceed even the basic tuned EFI for street driven mileage alone, which was pretty much the OP's original question.

I bet most carb guys have three or four carbs laying around that they could sell to cover the entire cost of an EFI setup. I know I did.

Clearly opinions vary

I'm definitely interested in EFI. I think I'll jump on board once I can make the entire conversion, everything included, for around 500$.

Just to be clear, I'm not talking about fuel economy because I can't afford to drive the car. I was just trying to find out if EFI was worth it from a fuel saving standpoint. The for and against camps seems to be approximately the same size which is telling me that it's almost there.

I agree with the OP, EFI is not a good value today. But when it gets to about the same cost of a carb ($500 +/-) I will be in, too.

Opinions would turn into more accurate "guestmates" if we knew how the eight cylinders of your engine vanied in air fuel ratio.

Find someone who already owns a wide band oxygen sensor who would bring it over for an afternoon.

Get some brake line about six to ten feet long.

Cut an approximately 3/8 inch diameter hole in the exhaust pipe just below where it attaches to the exhaust manifold on each side of the V8.

Try "fishing" the brake line up into the interior of the exhaust manifold several times, each time bending the brake line a bit so that eventually you can get the end of the brake line into each exhaust port.

Once you have this custom bent cylinder "probe" to your liking, take it to an exhaust shop and have the other end welded to a two foot long ength of exhaust pipe large enough for the wide band oxygen sensor to slip into.

You might also want to have the exhaust shop weld oxygen sensor "bungs" where you made your holes in the exhaust pipes so you can screw in plugs later.

Get the volunteer to bring over the wide band and test each cylinder.

Load the engine a bit by jacking up the rear axle of the car and applying the brakes.

Pay most attention to the air to fuel ratios in the 1500 to 2500 RPM range from one quarter throttle to half throttle.
This range dominates what MPG you get,
unlike full throttle and rpm above the Torque peak that determines acceleration performance.

All cylinders need to be above 14.7 AFR in the economy range.

With typical EFI the cylinders will not vary more than 8 %

Once you know what cylinders run richer in this economy range you can do some port grinding in the intake manifold and cylinder head runners to increase airflow and (hopefully) lean out the mixture getting to that cylinder. I say "hopefully" because wet airflow can be complicated and does not always follow " common sense".

You also have the alternative strategy of drilling and tapping holes into the runners of the intake manifold which will allow you to use an adjustment screw to partially block and reduce airflow in a lean cylinder to richen it. Obviously this can slightly reduce full throttle performance and is less desireable in that regard to improving wet airflow to the rich cylinders.

Tweaking this way in theory can get your engine very close to the economy of EFI.

Do not think that the "tiny droplets" of fuel injection spray is a big secret of economy compared to the typical droplet from a carb.
Its another long story but this is the all too common
"Myth of the 200 MPG Carburetor"
and was proven untrue years ago,
both by GM fully vaporized gasoline experiments
and by natural gas fuelled spark ignited engines.

I spend the last 10 years daily driving my car with a 440 and thermoquad. I eventually put a wideband o2 sensor on it, spent some time tuning and had the choke setup real well. The MPG was good for what it was considering I was doing all town driving, lots of short trips as well as pointless cruising. It did really well and IMO the thermoquad can be a great carb for daily driving, if you take the time to set it up well.



No "kit" per say, but but off the top of my head here's what I bought:

$250 - megasquirt-2 unassembled kit. MS-2 has the self-tuning features and does fuel plus spark. It is a batch fire system, not sequential. Newer MS units do sequential, which IMO is of little value on our cars. Toss in a couple hundred more dollars if you want one you don't have to sodder together yourself.

$65 - megasquirt engine harness. Optional, it's just a harness with all the sensor, power, injector connections labeled for you to speed up installation.

$100 - walbro gsl-392 fuel pump. Universal, in-line pump supposed to deliver enough fuel for 600hp.

$250 -edelbrock victor EFI intake manifold. Found one used but never installed.

$80 - Fuel injectors. I bought some used factory injectors that should have just enough capacity to fuel 550hp. You can get spendy on injectors if you want to.

$40 - bulk fuel rail extrusion that I had to cut to length, drill for injectors and mounts. Alternatively edlebrock sells the matching fuel rail kit for it's intake for around 100 bucks.

$200 - 4bbl throttle body. Universal EFI 1200cfm unit on ebay. Accepts GM sensors you can snag at the junkyard.

$70 - GM ls1 fuel regulator. Combination regulator/filter you mount back by the tank. GM's spec is 58psi. These work so well and are so easy I used one on my jeep as well when I did the efi conversion.

$200 - Innovate LC-1 wideband o2 sensor with in-dash gauge.

$180 - New Spectra Premium gas tank. This one's not a necessity. My old tank was banged up and leaking bad so I was replacing it anyway. I took this time to add an in-tank sump and switched my fuel pickup over to a 3/8 feed and added a 5/16 return to match the filter/regulator. There are other ways to do this without changing tanks or cutting your existing one.

----------
$1255 (excluding the new gas tank I bought). That also excludes the new fuel line I bought as mine was due for replacement anyway. That is for a fairly high performing system that will do 550hp. Spark is handled by a stock distributor with the advance locked out.


Now if I wasn't looking to make a whole lot of HP and just wanted EFI, some dough could be saved. Another build I thought would be fun would be all the same parts, but minus the intake, throttle body, injectors, regulator and fuel rail. Swap the intake out for an edelbrock CH-28 dual quad manifold. Go to the junkyard and grab a pair of GM 350 TBI's, make adapters and plop them on. I could get those for 30 bucks a piece at the local u-pull. They have a built in regulator, there are resources online that show you the various injector sizes these things came with, but you should be able to do 400-450hp with a pair of them I would think. That would drop the cost down to just under the $1000 mark. Add on another 100 bucks or so to upgrade to the higher flowing GM 454 units. A lower performing unit could be built much cheaper with a GM TBI and a stock intake manifold if you wanted something with stock type performance but EFI. I decided if I was going through the trouble of EFI it would be port EFI as port EFI is superior to TBI in every possible way. Plus the GM TBI's do handicap you in terms of power production due to flow rate(fuel and air).

At the end of this long essay, all my EFI stuff is still sitting in a box as I have the engine, trans and front suspension out for a years long rebuild. My intent with the EFI was to maximize mileage/driveability because once the car is completed I intend to return to using it as a 3 seasons daily driver and hope that will allow me to reap the benefits of going to EFI. If I only planned on driving the car once or twice a week for pleasure cruising, I would have stuck with the thermoquad.

Under part throttle cruising, between engine vacuum and a hot intake manifold the fuel is going to be in vapor form. Many guys have a hard time visualizing dry flow distribution and grasping that dry flow does not equal wet flow.

I thought about EFI for my 69...but I don't drive the car enough to constitute $2500. I put at the most...800-1000 miles per year. Gas is $8/gallon.

I run two 500cfm Edelbrocks. I have been inside and out with them, I have them jetted, metered, and set to my Summer weather here in the Mediterranean ...I don't drive her in the winter. Twin Carbs on a progressive linkage and I am pulling 18mpg...keep in mind this 18mpg is on a 440 with a gear vendors...I am rolling 70mph @2200rpm with a 28" tire.

I'd be lying if I said I didn't want a FAST EFI...but thats two throttle bodies I would have to buy now...plumb new fuel lines, run an electric pump, install sensors, have a custom fuel tank made. Then the endless gremlins and tuning from the beginning all over again.

Maybe when I hit the lotto...