Carbs VS FI, Which is better? Options

[TheCabinetmaker]

Edit: delete accidental double post. Damn fat fingers.

[dflesburg]

We have two 1970 cars both with 2.0 motors, one with stock FI and one with dual two barrel dells. Wont have both running togeather for about four years. Will let you know.

[So.Cal.914]

Low end power? Bow to FI as it has better low end power.

That should be spelt BLOW
With the FI that came with the car the low end sucked. On a slow corner I would have to go for first. With the Webers I only need to go for first when I stop. The FI also had a 'Lag' at take off.

But the fuel milege was great, LA to San diego on a half a tank.

[TheCabinetmaker]

Low end power? Bow to FI as it has better low end power.

That should be spelt BLOW
With the FI that came with the car the low end sucked. On a slow corner I would have to go for first. With the Webers I only need to go for first when I stop. The FI also had a 'Lag' at take off.

But the fuel milege was great, LA to San diego on a half a tank.

Your FI was seriously out of tune. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/stirthepot.gif)

[Dave_Darling]

Which is better?

Yes--yes they are.

Really, what do you know? If you're happy synch'ing carbs, blowing out jets, and tweaking mixture screws, carbs are better. If you're happy just driving until something decides not to work, then troubleshooting that, then go with EFI.

Carbs seem to have the potential to make the most power; they don't really care about cams, for instance. EFI has the potential for far better driveability.


...Just as long as you don't go with the crappy single-Weber setup, either is cool.

--DD

[Bleyseng]

Low end power? Bow to FI as it has better low end power.

That should be spelt BLOW
With the FI that came with the car the low end sucked. On a slow corner I would have to go for first. With the Webers I only need to go for first when I stop. The FI also had a 'Lag' at take off.

But the fuel milege was great, LA to San diego on a half a tank.

Your FI was seriously out of tune. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/stirthepot.gif)

Vacuum leaks or majorly out of tune as FI has better throttle response than carbs (IMG:style_emoticons/default/chair.gif)

[So.Cal.914]

With what I put into that FI it should have levitated, When it worked it worked fine

other than being gutless at low end. Other than cleaning the jets once and awhile

and an occasional synchronization carbs have never let me down.

Carbs may suck but that FI blows. At least mine did...And a whole shit load I have

read about here (and other sites) over the years.

[Justinp71]

I like carbs because I'm mechanical... but when I had fi my car didn't smell... (IMG:style_emoticons/default/laugh.gif)


I would say carbs are a good replacement for any 30 year old injection system that isn't running well...

[Rand]

My FI starts promptly, idles flawlessly, and runs as strong as possible at all elevations and temperatures.

If I was to build a 2270 then I would need a different system. I could go with dual Dells and that would be great. But I would sacrifice some of the benefits listed above. Or I could go with a modern FI system like SDS and have the best of all worlds.

Depends on the engine.

In general terms (across the board, not just 914), assess which modern and competitive cars run FI vs carbs and why.

[EyeTrip]

[quote name='Bleyseng' date='Sep 16 2008, 06:25 PM' post='1080296']
[quote name='EyeTrip' post='1080266' date='Sep 16 2008, 05:52 PM']
Love the sound of dual webers
Once setup, carbs are more reliable than the 40yr 1st gen injection
Very clean install over injection

Now, I would like to megasqirt a 1911. I think that would be fun.
[/quote]

[quote]Love that sound? cuz thats all you can hear carbs are soo loud. I have a CD player and like to listen to music driving not that sucking sound[/quote]

Sissy, A real car will talk to you and make you feel the road. I have a cd player too, but most of the time I find it off so I can enjoy the ride

[quote]Once setup? yep, and then they go out of sync again and again.[/quote]

The only resons I find them out of sync is bad linkage or vacuum issuse.

[quote]Clean? Stock FI is really clean and reliable as its still going strong.[/quote]

Out of the box carbs will have issues but a tuned set of webers are very clean and more relaible dont be fooled

[quote]Low end power? Bow to FI as it has better low end power.[/quote]

HAHA low end? If you want carbs to performs that way you can.... but I prefer the whole range.

[quote]Tuneable? Bolt on the stock parts and its tuned or if you have a 2056 w/ mild cam adjust the MPS and forget about it.[/quote]

I think thats cool. But your still in the realm of carbs.

[quote]Plus you can get 30mpg with Djet / Ljet and FI has built in altitude adjustment for those up into the mountain road days.[/quote]

Thats great, I have never felt much difference going up Donner summit @ 7200 ft other than running out of air.

If you want the best you need to go for a modern FI, not a 40yr old fi. The new ones are so much more accurate and stable (not to mencheon the parts cost and availibilty) But don't discard the carbs because you don't understand them.

[Bleyseng]

I'll be running carbs on the next engine, 2.4L till I get a FI system.

[Mark Henry]

I voted FI, but d and L-jet sucks....SDS baby

I've messed with weber's for years and it sucks compared to PEFI (P as in programmable) The only thing carbs beats PEFI on is the price.

But then I think anything stock sucks (IMG:style_emoticons/default/biggrin.gif)

[Cevan]

I voted FI, but d and L-jet sucks....SDS baby

I've messed with weber's for years and it sucks compared to PEFI (P as in programmable) The only thing carbs beats PEFI on is the price.

But then I think anything stock sucks (IMG:style_emoticons/default/biggrin.gif)

For stock motors, I'd go stock FI based on my own experiences. I've put about 4500 miles on my L-Jet 1.8 in the last year and it doesn't suck. Starts every time, warms up great, doesn't stall, doesn't stumble, runs the same in hot or cold weather, humid or dry. I'd rather spend the $$$ an SDS system would cost on tires, suspension and gas. (IMG:style_emoticons/default/biggrin.gif)

[DBCooper]

If you're going to compare then you need to compare apples to apples. The ONLY people who prefer carbs to fuel injection are people who didn't have correctly adjusted fuel injection. On a stock engine there is no way that correctly adjusted fuel injection doesn't outperform correctly adjusted carburetors in any way you compare them, at high altitude or sea level; hot or cold; idling or acceleration; power, mileage or tractability. No how, no where, no way. Not possible in theory, nor in practice.

The only advantage carburetors have is the vroom vroom sound. (IMG:style_emoticons/default/rolleyes.gif)

Thinking about carburetors? Fix your fuel injection. Simple enough, and problem solved.

(IMG:style_emoticons/default/stirthepot.gif)

[SirAndy]

Carbs VS FI, Which is better?

No ...

[SGB]

I like carbs because people talk about "good carbs" and sometimes "bad carbs" but NOBODY wants to talk about "good fi". Maybe "good Hi-Fi" or maybe "Sci-Fi". But not "Eff-I". Although when I asked someone at the beverage store, I was told "Eff-U" but I think they were confused. Nope. I'm going with carbs.


Besides, mine are SHINEY. (IMG:style_emoticons/default/smile.gif)

[So.Cal.914]

For all of you that think injection is the best, I give you this. It is long but very well written by a expert from Pro Systems who has worked heavily in both areas.



Carburetion Vs. Injection

One of the most often asked questions is why do carburetors make more power then EFI and why do the car manufacturers use EFI if carburetors make more power?

A few years ago we used some contacts at General Motors to verify some simple facts from some dyno data we had received from a head to head comparison.

An engine was being constructed for Comp Eliminator style racing and the program was going to be electronically fuel injected. Well the system was giving the engine shop some questionable numbers. The shop removed the EFI system and installed some of our Pro Stock carburetors on the EFI manifold top so they could quickly compare systems.

The engine responded immediately with much faster acceleration rates and a 5 percent improvement in power.

The EFI designer was brought out to the site and try as he might he could not out perform those carburetors. When the session wrapped up carburetors were king by 24 horsepower.

I've heard similar stories and similar claims when comparing systems.

So when we analyze this information it really comes down to a simple fact. Carburetors and Electronic Fuel injection are two completely different systems. They share no concepts and each has a different theory.

EFI's claim is this: I will supply sprayed droplets of fuel at the proper air to fuel ratio all the time.

Carburetors claim: I will supply a pre-emulsed froth of fuel and air into the engine at a preset ratio.

The results proved the analysis of the concepts to be correct. In this case, the carburetor was supplying the engine in question with the proper air to fuel ratio, so the EFI's advantage was gone. Remember, EFI has a computer to tune the engine. You have you. If you know how to tune you'll have the advantage. Carburetors (at the risk of sounding chauvinistic) are a man's game. Guessing rarely works. You have to know how to actually tune an engine.

Remember a carburetor is an atomization/emulsion machine. An injection system is a proper air to fuel delivery ratio machine. Two different concepts. If a carburetor can be designed to supply the perfect air to fuel ratio all the time it should consistently outperform EFI. Its design lends itself to have an unfair advantage in atomization.

Obviously adiabatic expansion is the next question on the list. So if we take a good look at the carburetor we see its not only a perfect machine for atomizing fuel, it also has another advantage. The joule-thompson effect.

Tests performed using quartz plates and infra red sensors located in the plenum area beneath an NHRA Pro-Stock engine revealed an intake manifold temperature drop on a 85 degree day of almost 20 degrees as a result of the the carburetor creating this effect.

So when your neighbor with EFI is ingesting 85 degree air, your power-plant could be ingesting 65 degree air.

That's a nice advantage.

But let's not skip over the atomization advantage. In a high end designed carburetor the fuel is emulsed to lift it. Its a controlled froth. I won't kid you, it's very difficult to control. Its much easier to build a carburetor that operates on a vacuum to ratio concept. But the fogging advantage is gone. So when a customer asks, why is this carburetor more expensive than that builders carburetor as they look basically the same. Most of it is all in the emulsion package and the time spent flowing it and tweaking it to do its job. Remember in a high emulsion design .001 of an inch is a big deal. They're difficult to balance and require sophisticated equipment that many shops have never seen. Also, don't go poking things into the metering block passages to inspect them or look around. You might just lose 10 lbs of torque.

The disadvantage of carburetors used to be restriction. I remember back 20 years ago before booster technology really took off you had to size carburetors to operate on 1-2 inches of vacuum in the plenum at the starting line. The restriction alone was probably costing these engines a 2-3 percent power loss.

Tests we performed at Sonny's racing 5 years ago showed us numbers of about .6 in the plenum and spikes of about 1.1 to 1.3 in the runner at the finish-line. That's a pretty huge decrease and just for dynos sake when we built carburetors large enough to reduce this number by on average 40 percent we saw an increase of only about 3-5 horsepower on an IHRA Pro-Stocker. SO that advantage for EFI is now also gone.

Now that these same engines can operate on as little as .5 hg of vacuum at the starting line and only 1-1.2 at the finish-line, the restriction is nil. Really it all comes down to getting the air to fuel ratio correct. If a carburetor can do that, it should win the race every time. After all, by design, it's a superior emulsion machine.

Thanks for reading.

[749142]

fi becuase,
better gas mpg
its original,
and setup up properly Ljet is the most reliable thing ive had so far.
i heart ljet becuase i never could get the djet to run right. bad narnesses.
djets are good too i just never had any success becuase my harnesses were cracking and breaking. brittle wires.
but oh well carbs arent my style

[DBCooper]

Pro Systems, you mean the drag-racing carburetor manufacturer? Do you suppose they have a point of view? And do they have any concern other than wide-open throttle? Do you drive your 914 at anything less than wide open throttle? If you do then that information is irrelevant.

Ljet and Djet may be primitive compared to more modern fuel injection technologies, but they still deliver better ratios throughout all driving conditions than even more primitive carburetors can. It's easy enough to see that for yourself, how do your carburetors adjust for cold running temperatures? For higher elevations? For higher temperatures?

[Spoke]

I like FI because I could sell my used dual Weber IDF40's for $400 in one day.