Carb to EFI

[ender2664]

For everyone that has switched from a carbed set up to an EFI...
1-How do you feel about the decision? Do you feel, in your opinion, that it was worth the money?
2- What are the biggest differences you have noticed after the swap?
The engine i am going to order has a decent price upgrade to fuel injection. From what i understand this is helpful in that you get aprox 10% better mpg, a wider power band, easier start up and better throttle response. Are their any benefits that i am not taking into consideration?
The low point is that it is harder to tune and fix. Are their any draw backs that i am not considering?
Thank you very much for your help, experience and opinions.

[joyridin']

My brother just put the FAST EZ EFI on his neighbors 66 Corvette. It is amazing how good it runs. It has a hand-held tuner so you do not even need a laptop. The only hard part was getting an EFI pump mounted in the tank. They could have gone with an external pump, but they wanted the factory look.

You cannot even tell it has EFI.

[blykins]

I would argue against the throttle response and power band.

I do agree with an easier start.

Gas mileage? Really?

[olddog]

EFI encompasses many different technologies.

Throttle body - pretty much an electronic version of a carb.
Multi-port - an individual injector at every intake port.
direct injection - the newest from the manufactures.

But how is it controlled?
Speed density - MAP sensor to estimate the air flow
Mass Flow - a meter to directly measure the mass air flow
Alpha-N - a wild ass guess at what the air flow is based on rpm and throttle position

The most important question of all is what is the tuners access to collect data, and what is the tuners access to change tune parameters? If you cannot tune it yourself, how many tuners are there that can work with your system.

Many respected experts with real experience on this site will tell you that a carb will make more power than EFI, even though the EFI will give better overall behavior/manors.

From my perspective, theoretically if the AFR and timing is the same, the only way for an engine to make less power is if it flowed less air or burned less of the fuel. A carb must have some pressure drop to work, and fuel/air mixture flows through the entire manifold. Where MP EFI needs no pressure drop across the throttle body and the intake runners are dry. So in theory the MP EFI should flow more air, unless the injector is causing a flow disturbance at the port. If combustion was less complete for EFI, you would tend to think the manufacturers would not have went to EFI for better emissions. But cruising and WOT max Hp may be totally different results.

Once you get access to the EFI CPU, you have so much more control over the fuel and timing parameters than the old school carb and distributor, that you are in a totally different league. You can fine tune the fuel and spark over the rpm range. You certainly should be able to improve the torque curve over a carb, even if you cannot make the same peak Hp. I don't understand why you could not make the same peak Hp, but respected people who tried failed to.

I will say this. You can sit at the London Ohio Cobra show and watch the 1/8 mile burnouts. You will hear quite a few carb cars stumble bad after the launch. I expect its the fuel sloshing in the bowls, and there are things that can be done to prevent it. You will see a lot of carb issues. The EFI engines seem to run perfect every time. True a good carb tuner could correct the problems, and you can screw up EFI. I do feel EFI tends to run better.

[bobcowan]

Assuming that both EFI and carb are properly tuned, you do tend to get better gas mileage, simply because the EFI is more accurate at part throttle cruising. I routinely get 18-20mpg.

More power? Peak power will be about the same. As long as you're comparing apples to apples, the peak power will be so close to the same that it won;t be worth talking about. But you'll get more power under the curve. Again, simply because the EFI is more accurate there.

IMO, the big advantage is drivability. On single day, I might see temps range from 70's to 30's, and altitudes range from 5,000-11,000' ASL. Some times I'll drive as high as 14,000' ASL. Last time I did that, the temp was 28*. With closed loop operation, the computer constantly adjust the fuel feed for the available air. When we were ready to leave, I just turned the key and drove away. Some of the carbed cars had a little trouble getting going.

And that's where EFI really shines, IMO. It compensates for weather and altitudes really well. A well tuned carb just can't do that.

Another bonus is it's ability to compensate for radical engines. If you install a radical cam, the engine typically doesn't like to idle well, or run well on light throttle cruise. Even with the biggest cam in the CC catalog, my engines idles nicely at 800rpm's, and will cruise all day long at 2,000. With port injection, you don't have to worry about maintaining intake charge velocity, or keeping fuel in suspension.

Another bonus is the ability to switch between pump gas and E85. I went to Moab a few years ago. It was really hot. Like, Africa hot. And, of course, we're all stuck in traffic at the construction zones south of town. Not a problem for me. Engine runs really well and cool with E85. There's a cruise event in Aurora every year. If it's a hot day, I'll run e85. Even in stop and go traffic, it never gets hot. E85 smells good, too.

The down side to EFI is, of course, cost and complexity.

[olddog]

I forgot cost.

Fuel pump, fuel lines, fuel filter, pressure regulator, cost more for EFI than a carb.
A set of injectors costs as much or more than a carb.
The cpu and wire harness is the big cost for EFI.

Getting the right stuff the first time for EFI is critical because replacing EFI parts is costly.

I do like EFI. My preference is Mass Flow. It is a better overall running engine. No worry of vapor lock, fuel bowl boiling dry, etc. But is it worth the cost? I would have to say, if I were building a new Cobra from scratch today, I would go carb, unless my budget was big enough that it didn't matter. Now if I could pick up the right EFI setup used at a good price, I would jump all over it.

Looks? I like a carb look in a Cobra. Very few EFI engines give me a woody to look at.

[lippy]

If you have a big cam with lots of overlap, you won't be able to run EFI in closed loop mode because the oxygen sensor can't get a good reading with significant unburnt fuel passing through the engine at lower RPM.

[Gaz64]

Originally Posted by lippy

If you have a big cam with lots of overlap, you won't be able to run EFI in closed loop mode because the oxygen sensor can't get a good reading with significant unburnt fuel passing through the engine at lower RPM.

You'll have a better chance with sequential injection, .

[olddog]

Originally Posted by lippy

If you have a big cam with lots of overlap, you won't be able to run EFI in closed loop mode because the oxygen sensor can't get a good reading with significant unburnt fuel passing through the engine at lower RPM.

It think it is more the oxygen, causing a false lean reading. I have not done this, but the tuners tell me to target a lean AFR at idle to get the desired actual AFR.

[lippy]

I think Gaz and Olddog are both right. But the problem then becomes programming in an entire map of AFR vs. load vs RPM. It gets pretty complicated and time consuming, and you need a lot of dyno time. I considered it but for those reasons just went with a carb, albeit a very good one (Braswell).

[joyridin']

If you have a big cam with lots of overlap, you are probably running into problems anyhow.

You can do a heck of a lot with a Holley Dominator system these days. Turbos, supercharged, E85, nitrous, auto, stick... just tell the computer what you want it to do and it will do it.

[twobjshelbys]

If you don't run a closed loop system then all you have is a more expensive carb. There are no advantages. You get the advantage of EFI from the closed loop system. The dilemma on a Cobra is that finding an ideal location for the O2 sensor is a compromise. My original one was in the passenger side tail pipe, but at low RPMs there was enough back flow (air coming back) to give a bad reading. We moved it to one of the exhaust ports but then you are only sampling 1 cylinder but it was still much better than the downstream location.

The real advantage for me was what Bob mentioned - altitude compensation is part of the system. A real big deal in Colorado where I also went from 5000' to 11000+ in a 2 hour period.

[Detroit Bill]

Depending on your viewpoint the simplicity of a Cobra is one of the draws. It is something you can work on. Once you add fuel injection you start going backwards.

Where I live it is relatively flat so some of the advantages are lost.

My thoughts are once by build has settled, find a good carb tuner with a chassis dyno and dial it in.

[ender2664]

I live in southern california, so weather really isnt an issue. 90% of driving will be done from 0-2,000 elevation and once A month or less ill hit 5,300. It sounds like from what im hearing from u all that fuel injection really isnt worth it and having the company that im buying the motor from tune the carb is the way to go.
are there certain features I shoiud be looking for on the carb? I have never used one before.

[lippy]

What engine do you have? I have a killer QuickFuel q-850 in black that I'd like to sell. It's only been on the car for maybe 250 miles. It's infinitely adjustable. Pm me if you want more details.

[ender2664]

I havent ordered the motor yet which is why im asking about carbs. Im either doing a 02 or 383.

[Dimis]

Unless you plan on logging tens of thousands of miles per annum.
You'll see more pain than gain with any Efi system. Imho.

Even IF your mpg shows marginal improvement, you're upto $10k behind to start with. Im pretty sure one can invest $10k to cover the mpg loss elsewhere and not suffer the pain lol.

Further having investigated them at infinitum, those hand held carbed ezy-Efi gizmos just can't be made to work anywhere near as well as advertised. I contest any claims to the contrary (till I see with my own eyes). I've just seem so many that don't work, either at all, or so poorly that a bad carb would be better.

Efi is great for your daily driver, else not so much for your part time drive.


Good luck with it.

[ender2664]

Thank you all for yoir advice and seemingly from saving me money that can be better spent elsewhere!

[mdross1]

Once tried the add on EFI really did like playing with it, the trouble with my setup it was installed in an everyday driver without closed loop. Once in a while I would forget and leave the setup to my liking for hard core 4wd. The wife would take the truck, Oh did she ever complain to me about the way it ran. Finally removed it all and installed a dbl pmp Holley we were both happy after that.

[joyridin']

Originally Posted by Dimis

Unless you plan on logging tens of thousands of miles per annum.
You'll see more pain than gain with any Efi system. Imho.

Even IF your mpg shows marginal improvement, you're upto $10k behind to start with. Im pretty sure one can invest $10k to cover the mpg loss elsewhere and not suffer the pain lol.

Further having investigated them at infinitum, those hand held carbed ezy-Efi gizmos just can't be made to work anywhere near as well as advertised. I contest any claims to the contrary (till I see with my own eyes). I've just seem so many that don't work, either at all, or so poorly that a bad carb would be better.

Efi is great for your daily driver, else not so much for your part time drive.


Good luck with it.

Interesting, yet the ones I have seen work quite flawlessly. The LS1 site I frequent has literally hundreds of people putting various types of aftermarket EFI units on their cars and usually the problems are self induced.

I also do not see any of them running $10k unless you go with some type of stack injection.

No offense, but your argument sounds like the same one horse and buggy owners used when cars first came out.