Fuel Injection vs Carba

Grand Poobah said:

Well I have to say gentlemen (or ladies, but I'm assuming we're all males here) my mind has been both blown and educated.

It seems that a carb is then a perfectly reasonable choice for balancing performance with mileage.

I was wondering it'd be possible to get ~380 net horse power out of a stroked Windsor 302 (stroked to 331 ci) and yet achieve ~10-13 mpg avg.

Click to expand...

I would think you could do that without even stroking the engine. You can also help the mileage out by installing an OD trans to lower cruising rpm.

I get 15city/19hwy with the car in my sig. my opinion, EFI is the best all around.

I guess since you asked for opinions the responses you're getting are to be expected. I won't try to tell you what is best, but I can tell you what my experience has been with two different carbs on two very different engines.

In '98 I drove my 69 Mach 1 from Southern Maryland up to Wash DC, then to Dallas Tx. At the time I had a mildly warmed over 351W; Trick Flow heads, mild Crane cam (.496 lift intake and exhaust) Performer intake with an Autolite 600 cfm 4100 carb freshly rebuilt by Pony carbs. I bolted the carb on without making any adjustments except to the idle. Behind the Windsor was a T5 trans and 3:70 rear gears. I was able to get a best of 23 mpg at 65 mph. The car started as good as any EFI car I've ever owned. I used it as my DD for two years, so the fuel in the bowls never evaporated. As long as I wasn't going through the mountains, this was very repeatable. Driving around town the mileage dropped considerably and varied wildly (13 to 17) depending on how much I played with the throttle.

This past April I drove the same car from Las Vegas back to Southern Maryland. The engine is now stroked to 408 (see sig for details). The 735 Holley was a re-issue of the 428 CJ carb and has annular primaries. The only change I made was to increase the size of the primary main jets from 64s to 66s. I drove between 70 and 75 mph From Vegas to OK City, and averaged just a tad over 17 mpg. An OD trans is an absolute must if you drive at all on the highway.

I've been modifying the suspension since August, so I only start it up once a month to keep the seals lubricated. Since the fuel evaporates, I do have to turn it over to get the carb full, but once it has fuel, it lights off without a problem.

Is it possible that I could eek out another fraction of a mpg with efi? sure.
Is it possible I could pick up 1 or 2 more HP with EFI? maybe, but I doubt I would be able to tell from the seat. Without putting on cats and a smog pump, the efi wouldn't make a measurable difference in emissions either.

Everyone has their own experience and therefore opinion on what's better/best. Personally, I would never go through the hassle of converting to efi when I already have my cake and I'm eating it too.

It was interesting that EFI did not have any luck at Engine Masters this year, but don't worry, the rules for next year almost guarantee an EFI victory. Carbs make plenty power and with a WBO2 and some tuning they can get MPG on par with EFI. Most people don't tune past the jets and squirters.

people have done hundreds of tests, every single time EFI comes out producing more power and runing smoother, its just the nature of the beast, I know carb guys dont want to accept it, having owned both carbed and FI 289s I can tell you EFI starts easier, gets better mileage and makes more power, even with the older non-roller engine, as for wanting to keep the carb look...easy with a TBI setup...using megasquirt or powerjection, or AEM, or your standalone of choice...personally I dont think keeping the look is worth the loss in effeciency you would take passing up a better intake manifold

wicked93gs said:

people have done hundreds of tests, every single time EFI comes out producing more power and runing smoother, its just the nature of the beast, I know carb guys dont want to accept it, having owned both carbed and FI 289s I can tell you EFI starts easier, gets better mileage and makes more power, even with the older non-roller engine, as for wanting to keep the carb look...easy with a TBI setup...using megasquirt or powerjection, or AEM, or your standalone of choice...personally I dont think keeping the look is worth the loss in effeciency you would take passing up a better intake manifold

Click to expand...

But you have to ask yourself this question: Is the little bit extra (the difference isn't that much) worth the added cost of an aftermarket EFI system ? As for the "look" of a carb setup, yea, single four's are pretty ho-hum there, just as is an EFI setup. But with multiple carbs (and look alike multiple TB fuel injection setups), you NEVER get a ho hum reaction when you pop the hood. And "easier starts? You need to meet my 89 Ranger on a 25* morning. It'll completely change your mind about that statement.

I am not convinced that EFI makes more power. The top finishing EFI engine at Engine Masters Challenge had 11 carbureted motors in front of it. You would think they would know what make the most power. Next year carb combos will only be allowed to use dual planes and limited throttle plate that will flow less than 800cfm while EFI will be allowed any single, dual or four blade throttle body and any intake including converted 4 barrel single plane intakes. It is funny how few EFI engines were there this year. I am sure next years rules will force everyone to use EFI.

Magazine test are not usually a fair fight, and neither is TV. Living around middle TN I have met a few of the powerblock tv people and have heard that companies pay to have their products on the shows. It would suck to hear their product is inferior to the baseline now wouldn't it. Now that I think of it a recent magazine I have was testing cams and the carb made more power than EFI with every cam they tested. Funny how when test cams the carb makes more power, but when testing carb vs EFI, the EFI makes more power. It is almost like who ever pays to have their product tested, wins.

brianj5600 said:

I am not convinced that EFI makes more power. The top finishing EFI engine at Engine Masters Challenge had 11 carbureted motors in front of it. You would think they would know what make the most power. Next year carb combos will only be allowed to use dual planes and limited throttle plate that will flow less than 800cfm while EFI will be allowed any single, dual or four blade throttle body and any intake including converted 4 barrel single plane intakes. It is funny how few EFI engines were there this year. I am sure next years rules will force everyone to use EFI.

Magazine test are not usually a fair fight, and neither is TV. Living around middle TN I have met a few of the powerblock tv people and have heard that companies pay to have their products on the shows. It would suck to hear their product is inferior to the baseline now wouldn't it. Now that I think of it a recent magazine I have was testing cams and the carb made more power than EFI with every cam they tested. Funny how when test cams the carb makes more power, but when testing carb vs EFI, the EFI makes more power. It is almost like who ever pays to have their product tested, wins.

Click to expand...

this is very true...its all about money....what isn't about money though is the fact that EFI is infinitely adjustable....hundreds of time more adjustable than eve the best carb on the market...how can you not make more power if you are able to keep your engine at a perfect 12:1 AFR under wide open throttle? i'm sorry, but there is absolutely no logical way a carb will ever make more power than a properly functioning EFI setup...especially when you bring the intake manifold design into consideration...carbs by their very nature limit the intake manifold design...the majority have to sit above the manifold and so hood space becomes a limiting factor(sidedraft carbs might be an exception, just don't know enough to say)....so what we really have in a carb setup is poor fuel control(in direct comparison to EFI) and limited intake manifold design and you want to tell me a carb is going to make more power? Now I will fully admit the difference in peak power is not likely to be very much when you have say 289 carbed using the stock intake(or aluminum carb intake) and an EFI setup using a stock intake(or aluminum carb intake) that has been modified for port injection(though with sequential injection, the efficiency below 3k RPM on the EFI will definitely be superior)...which brings us to the point of peak power...yes you can tune a carb to give you 12:1 AFR at wide open throttle at whatever your peak power RPM is...but by doing that, its off the ideal AFR elsewhere...meaning the power curve is not going to be optimal...there is no way to tune a carb to adjust fuel every 20RPM(or less) like you can with EFI. As or extra cost...yes of course it cost extra to go EFI..but dont we pay extra anyway for better power? its not like the cost is that much anyway...let me break it down for you real quick, I'm going to with Megasquirt as an example here

Megasquirt, 2 options
1 assemble it yourself...pretty easy(Ive done it) $250
2 buy it pre-assembled $400
wiring harness $50
misc sensors, injectors, injector clips, etc $300(I could do this part for much less but lets just say 300)
inline EFI pump$105(just bought a 255lph pump myself for this cost)
5.0L intake manifold...depending on what you want, aftermarket or used stock, these range from $25-$500

so what we have is $1305 on the expensive side $725 on the low end(this cost could be driven down simply by getting used 24lb/hr injectors from a mark viii in the junkyard, would knock it down to $525) now realize of course this includes a better flowing intake manifold...whether stock or aftermarket, either will flow better than a stock 4v manifold(though maybe not better than a aftermarket aluminum) I think when you throw in the cost of a new intake manifold and a better carb yu really come out just about even

there are other costs that I did not add in...like a laptop to tune with...most people these days have a laptop anyway, other misc cost I didnt include are things like lengths of fuel injection hose...fuel injection hose clamps, etc etc...regardless, when its broken down it really isnt much more expensive...though it is more work to install, and with megasquirt the learning curve is steep...more so if you dont have an EFI experience, so its definitely not for everyone...of course there are a lot of other more expensive EFI systems out there...in which case just add $1000 onto the cost

There were only 2 EFI engines at Engine Masters Challenge and a third that used a carb and efi. 27 entries used only carbs. They test from 3000-7000 so peak is not the focus of the build. I can't imagine why carbs are so popular, but they seem to do very well over a large rpm sweep. I would think that the tunability of EFI would make it a no brainer. I can not tell you why top engine builders can make more power with carbs, but they do. Maybe fuel injection injects fuel too close to the combustion chamber. It certainly seems to help us blow through turbo guys. How much do you think the A/F ratio changes between 60* and 100*?

wicked93gs said:

this is very true...its all about money....what isn't about money though is the fact that EFI is infinitely adjustable....hundreds of time more adjustable than eve the best carb on the market...how can you not make more power if you are able to keep your engine at a perfect 12:1 AFR under wide open throttle? i'm sorry, but there is absolutely no logical way a carb will ever make more power than a properly functioning EFI setup...especially when you bring the intake manifold design into consideration...carbs by their very nature limit the intake manifold design...the majority have to sit above the manifold and so hood space becomes a limiting factor(sidedraft carbs might be an exception, just don't know enough to say)....so what we really have in a carb setup is poor fuel control(in direct comparison to EFI) and limited intake manifold design and you want to tell me a carb is going to make more power? Now I will fully admit the difference in peak power is not likely to be very much when you have say 289 carbed using the stock intake(or aluminum carb intake) and an EFI setup using a stock intake(or aluminum carb intake) that has been modified for port injection(though with sequential injection, the efficiency below 3k RPM on the EFI will definitely be superior)...which brings us to the point of peak power...yes you can tune a carb to give you 12:1 AFR at wide open throttle at whatever your peak power RPM is...but by doing that, its off the ideal AFR elsewhere...meaning the power curve is not going to be optimal...there is no way to tune a carb to adjust fuel every 20RPM(or less) like you can with EFI. As or extra cost...yes of course it cost extra to go EFI..but dont we pay extra anyway for better power? its not like the cost is that much anyway.

Click to expand...

You make it sound like the difference between a carb and EFI is huge in terms of the AFR over the entire RPM range. And that simply is not true. And there are carbs and carb setups that DO provide the optimum AFR (or damned close to it) over the entire rpm range. Like the old Predator carbs(which is a variable venturi design) for a single carb application or multiple carbs (like my 3x2) There are drawbacks to both systems of fuel delivery, it all boils down to personal choice in the end here. The ONLY scenario where EFI shines above a carb setup is with big altitude changes. If I lived somewhere where I drove where this was the case, I would choose an EFI setup over a carb.

i'm not biased either way (FI vs carb), but i certainly like the look of a carb and i have never had any cold start issues with my cars. having said that, i have always owned divorced choke Q-jets and although they may have been less that ideal on a track they are dependable and deliver good economy on a daily driver. i'm sure holley or edlebrock carbs set-up right would give similar performance. my go-to car for bad weather used to be a '70 LeMans with a 4V 400 because it was old faithful and drove good in rain or cold.

i would also vote for a carb for a vintage mustang and with a money is no option budget, it would be Inglese induction. since i'm poor, i'm using a E-RPM, a street avenger, and a chrome lid.

the only aesthetically pleasing fuel injection set-ups are aftermarket ITB's and GM's TPI (flame away, but it's true)

I'll admit you probably do get better fuel atomization from a carb setup(assuming a good intake manifold design) as compared to a port injection setup...but with a TBI setup that would not be the case...it would be virtually identical...of course with a TBI(or carb) setup you wouldn't get as good efficiency below 3000 RPM...which may not make much difference for power, but it does make a noticeable difference in driveability(at least every day driving) I guess its all personal preference in the end...except for one other advantage computer control offers....timing advance adjustment that is much more precise...all this of course leads to an overall smoother engine and better gas mileage...as for aesthetics...well, that's very much subjective, the intake manifolds on a lot of EFI applications just look so much better(IE the Ford Taurus SHO) in my opinion than any comparable carb intake...carbs heavily limit the manifold design. I guess these days I much prefer to sit in the seat of my car and press a button on a laptop and viewing an AFR readout then bend over a hot engine adjusting the carb, making a pass and pulling the plugs to see the effect(though I used that method on one of my EFI cars before getting a wideband...it was tedious)

The stack length moved the torque and HP curve around with the Hilborn and Webers. Basically used to tune the engine. They would still work in that regard to some extent with fuel injection. Ford did this with the SEFI systems, only using the runner lengths instead of stacks. The EFI system is adapted to the Hilborn throttle bodies. And yea, it all does work together. Why do this, you ask ? CAUSE IT F--IN LOOKS COOL !!!

D.Hearne said:

Why do this, you ask ? CAUSE IT F--IN LOOKS COOL !!!

Click to expand...

Try and focus on the meaning of this sentence.

ITBs(individual throttle bodies, which use stacks) are still used on a lot of modern EFI engines...take a lot a suzuki GSXr....150HP out of 1000ccs...they are used to increase engine response...but mainly people do it because it looks cool...you could use a single plenum on top of the stacks and a shelby style air filter and lid