Carbs vs. EFI
 

I'm having an argument with a friend regarding EFI versus carburetors...

This stems from the fact that I paid several hundred bucks to have my Nikki rebuilt by Sterling (Spec 7... I HAVE to run the damn thing.) yet, I could have easily built a MegaSquirt and run that.

I also had to throw out two weed wackers, a snow blower, and three lawnmowers including a nice Self Propelled Cub Cadet with Kawasaki engine and caster style front wheels. (Valued at over $400 Although I didn't pay for it.) All ot the engines above had compression but had bad carburetors.

One of the mowers, a Briggs and Stratton, I had to rebuild the carb four times (at $20 a rebuild kit) before it actually ran... Even then, it was a PITA to start and would leak fuel out the intake when I shut it down. The fuel would soak the air filter, so I had to run it without an air filter or it'd choke itself. It eventually caught fire before I threw it out. I partially repeated this process on another mower, rebuilding the carb twice and having it leak both times before deciding it was futile to rebuild a carb and just gave up and bought a brand new mower.



I don't believe I'm stupid or don't understand carbs. I am completely aware of what was wrong... The needle valve wouldn't seal properly allowing the bowl to overflow and fuel the run out the jets. The jets were also clogged so the fuel wouldn't atomize properly.

But when you've replaced the needle valve and seat gasket, and blown through the fuel line and moved the float by hand and found that the needle valve seals air tight... Then adjusted the float as per the manual and blown all crud outta the jet with compressed air and examined the jet under a magnifier, you kinda take all possibilities out of the equation.



My friend's argument is that carbs are so simple. A carb is not a part, it's the complete system all self contained...



My argument is that whenever ANYTHING goes wrong, you have to rebuild the ENTIRE system.

With EFI, you can test parts... Use an ohm meter on Coolant Temp sensors, or an oscilloscope on a Crank Angle Sensor or hall effect sensor in a distributor... If you need to, you can desolder a part in an ECU, solder in a new one, and you know it'll work.

If injectors fail, it costs $30-$40 each to send them out and get cleaned and flow tested.

I've had two FB carbs fail in the same manner as the mower carburetors... They'd just DUMP fuel down the barrels and it'd pool up on the throttle plates.

I've never had to rebuild an ECU and replace all injectors and stuff on any of my EFI cars... Usually it's a quick ultrasonic cleaning of the injectors and I'm passing emissions with flying colors. I usually know about it before the injectors get bad because the O2 sensor says I'm running rich.

I don't just go to start the car one day and it just floods out.

I understand how both work, I just think that repair and diagnosis of a carb is harder because I can separate and see all of the parts of an EFI system... You don't know if a jet or needle valve is any good until you put it in a carb and get it to run.



1st gen technical because we're the only gen that comes with carbs or EFI stock and because there are many threads on problems with 1st gens where the solution is "Rebuild carburetor"...
Discuss.

As general driving goes, EFI is better since it can easily compensate for a wide range of altitude, temperature, load, RPM, etc..of course, it is only as good as your tune, though.

For reliability, both setups can be just as reliable. I've seen 15-20 year old carb setups that have probably never been rebuilt work just fine. EFI can also be quite reliable. It comes down to how well the system is designed and how well it is maintained. For instance, neither setup will work well is you ran no fuel filter and were using a rusty gas tank..or trying to use gas that has been sitting in the carb/tank/lines that is 2 or 3 years old.

It also comes down to if you are more mechanically or electrically minded. For electrically minded folks, EFI is better. They understand the signals, the solenoids (injectors), pulsewidths, duty cycles, etc. Mechanically minded people do better with carbs. They understand how the different jets, floats, emulsion tubes, etc. work. They do not like dealing with wires, sensors, and so on.

Just use what fits best for you. Overall, EFI can give better MPG and emissions, but only if your tune is good. Same with a carb..if your tune is crap, your MPG and HP will suffer. Both systems can produce about the same HP and MPG (assuming similar intake, throttle plate sizes, etc.). The EFI system is able to produce that same good MPG, emissions, etc. over a wider range of conditions, though. The carb would really need to be re-tuned for optimum performance (say if altitude changed dramatically, etc.).

So, you could argue either way as to which is better, but what really matters is what is best for you.

the way you put it, efi is better, but to me, i would be better ar rebuilding a carb, then dealing with solder a part on an ecu.

Exactly. Do what works for you. There is no use throwing on an EFI system (to get better MPG), if you do not understand it, don't feel comfortable fixing it, etc. You can learn the EFI, but it is best to learn how it all works before you decide to change over. If you like/understand carbs better, then use a carb. :)

I would think a properly tuned EFI system makes more average power over the rpm range, as you can fine tune fuel and timing points at different rpm points across the board. However, peak power would be the same if you've tuned the carb to make optimal peak power.

EFI unless rules force a carb. Otherwise the carb gets the "floatation test", take it down to the closest body of water and throw it as far as I can, if it floats, its a good carb.

i find i can work on both, but efi is simpler/faster to fix if theres a problem. (ie when you're trying to get the 2 su's in the tr3 to cooperate!)

also in my 1st gen carb experience, ive rebuilt a couple and the problem has ALWAYS turned out to be something else.

as far as carbs vs efi, if the throttle plates are the same size for both, efi will make more average power, and because of the venturi's restriction, efi might beat it up top. also efi doesnt stumble in corners, it starts cold etc etc

I shoulda gotten the Lawnmower with electric start simply so that I could EFI convert it when the carb craps out... It's got an alternator in it.

Though I suppose I could just add an alternator to my current lawnmower.

You could run a megasquirt on a total loss system without an alt. Just keep the battery charged between mowings. I can show you a bunch of race cars that don't have alts and run EFI, mine just has a big battery. The problem would be in spinning it fast enough to trigger the ECU to think the engine is running. IIRC you can change that rpm # on the megasquirt.

Well, my buddy did a carb swap and then back to stock efi on a s4 rx7. The efi performed as well as the carb on topend, gave better economy, easier starting, and was over all superior in all driving characteristics.

Its digital versus analog. EFI is all digital and relies on a computer and the carb is all analog and relies on mechanical signals to run. Like gsl-se addict said its whatever your comfortable with. I work with computers all day so I like the fact that my car doesn't have one or use one (I don't count the emmissions ecu and its disabled anyway).

I also grew up with carbs and actually know them a lot better than EFI systems. Although the EFI systems are sometimes easier to diagnose and fix as long as your wiring isn't 30 years old and is reliable :-)

efi engines work without gravity.
carb engines work without electricity.

steam engines work without either, if you want reliablity and redundancy you have to get real old school.

I vote for efi because of the attention to detail in the chemistry of combustion.

Why not have ITB's. Best of both worlds.

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