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Fuel atomization: Carb vs. EFI
#2722175
12/06/19 11:21 PM
12/06/19 11:21 PM
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Joined: Jun 2016
Posts: 903
Washington
hemienvy
OP
super stock
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OP
super stock
Joined: Jun 2016
Posts: 903
Washington
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There are discussions about which is faster, which is easier, which is cheaper, which is.............etc, etc.
My question is: Which system will atomize the fuel better (I suspect EFI) ?
How can this be measured ? Two otherwise identical engines, one carb, one EFI, So which will produce the most power ?
Or alternately, if both engines can be adjusted to the same HP output at the same RPM, which engine will use the least fuel ?
Not sure if it's feasible (for us hotrodders) to measure unburned hydrocarbons, but that would indicate lack of fuel atomization.
Now, I read that carbs can be tuned run extremely efficiently in a certain RPM band, but likely not idle - to - peak RPM.
Of course, if the engine in question produces highest HP with a rich mixture, meaning there will be unburned hydrocarbons,
both carbs and EFI can do that, but which system can achieve that power level with a lower BSFC ?
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Re: Fuel atomization: Carb vs. EFI
[Re: hemienvy]
#2722206
12/07/19 12:37 AM
12/07/19 12:37 AM
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Joined: Aug 2003
Posts: 43,096
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,096
Bend,OR USA
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You know the answer already, it depends of course on the engine, EFI system and the tuner on the carbs  You can make a carb really good if you have the time, tools, knowledge and know how on what and where to tune on the carb, same thing on EFI I learned that a good O2 wide ban system is a great aide on tuning all the circuits on carbs, not just the WOT results  I like to see around 14.8 AFR or leaner on hot idle, 12.8 to 13.5 AFR on light accelerating part throttle cruise and as lean as possible(15.3+) on steady light throttle cruising RPM ls far as atomizing the fuel if you mounted the EFI injectors up high in the tunnel ram intake runners instead of down low at the manifold flange you might be pleasantly surprised on those results  I hear comments on fuel droplets falling out of the air in the manifold and I wonder what size hole that fuel is coming out of 
Last edited by Cab_Burge; 12/07/19 12:43 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Fuel atomization: Carb vs. EFI
[Re: hemienvy]
#2722209
12/07/19 12:52 AM
12/07/19 12:52 AM
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Joined: Apr 2008
Posts: 117
Aus
hysteric
member
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member
Joined: Apr 2008
Posts: 117
Aus
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There are discussions about which is faster, which is easier, which is cheaper, which is.............etc, etc.
My question is: Which system will atomize the fuel better (I suspect EFI) ?
How can this be measured ? Two otherwise identical engines, one carb, one EFI, So which will produce the most power ?
Or alternately, if both engines can be adjusted to the same HP output at the same RPM, which engine will use the least fuel ?
Not sure if it's feasible (for us hotrodders) to measure unburned hydrocarbons, but that would indicate lack of fuel atomization.
Now, I read that carbs can be tuned run extremely efficiently in a certain RPM band, but likely not idle - to - peak RPM.
Of course, if the engine in question produces highest HP with a rich mixture, meaning there will be unburned hydrocarbons,
both carbs and EFI can do that, but which system can achieve that power level with a lower BSFC ?
From my understanding when Bruce Robertson aka Shrinker was still alive and posting on the Motorsport Village Forum he stated that Carbs were better because there was a constant supply of atomized fuel in the plenum as soon as the valve opened this column would fill the chamber with a homogenized mixture. With injection the injector cycles on and off to limit the amount of fuel but in so doing there will be parts of the air column which wont be completely saturated with atomized fuel leading to pockets in the chamber that are leaner that other areas. A 5 gas analyser would tell how well the mixture is being utilized. Its all about the quality of the mixture. Hope this helps.
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Re: Fuel atomization: Carb vs. EFI
[Re: hysteric]
#2722215
12/07/19 01:34 AM
12/07/19 01:34 AM
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Joined: Aug 2011
Posts: 2,853
Pattison Texas
CSK
master
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master
Joined: Aug 2011
Posts: 2,853
Pattison Texas
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There are discussions about which is faster, which is easier, which is cheaper, which is.............etc, etc.
My question is: Which system will atomize the fuel better (I suspect EFI) ?
How can this be measured ? Two otherwise identical engines, one carb, one EFI, So which will produce the most power ?
Or alternately, if both engines can be adjusted to the same HP output at the same RPM, which engine will use the least fuel ?
Not sure if it's feasible (for us hotrodders) to measure unburned hydrocarbons, but that would indicate lack of fuel atomization.
Now, I read that carbs can be tuned run extremely efficiently in a certain RPM band, but likely not idle - to - peak RPM.
Of course, if the engine in question produces highest HP with a rich mixture, meaning there will be unburned hydrocarbons,
both carbs and EFI can do that, but which system can achieve that power level with a lower BSFC ?
From my understanding when Bruce Robertson aka Shrinker was still alive and posting on the Motorsport Village Forum he stated that Carbs were better because there was a constant supply of atomized fuel in the plenum as soon as the valve opened this column would fill the chamber with a homogenized mixture. With injection the injector cycles on and off to limit the amount of fuel but in so doing there will be parts of the air column which wont be completely saturated with atomized fuel leading to pockets in the chamber that are leaner that other areas. A 5 gas analyser would tell how well the mixture is being utilized. Its all about the quality of the mixture. Hope this helps. And that is why they have this, takes the cam timing into account on WHEN the injector sprays fuel. this is my Hilborn sequential EFI on my Charger. .png "Name: Screenshot (37).png
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1968 Charger COLD A/C Hilborn EFI
512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim
2020 T/A 392 Stock 11.79 @ 114.5
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Re: Fuel atomization: Carb vs. EFI
[Re: CSK]
#2722216
12/07/19 01:43 AM
12/07/19 01:43 AM
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Joined: Aug 2011
Posts: 2,853
Pattison Texas
CSK
master
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master
Joined: Aug 2011
Posts: 2,853
Pattison Texas
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Also with EFI I can run it leaner than when it had a carb at cruise rpms, without lean misfires
Last edited by csk; 12/07/19 01:45 AM.
1968 Charger COLD A/C Hilborn EFI
512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim
2020 T/A 392 Stock 11.79 @ 114.5
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Re: Fuel atomization: Carb vs. EFI
[Re: hemienvy]
#2722222
12/07/19 06:02 AM
12/07/19 06:02 AM
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Joined: Aug 2005
Posts: 5,998
Salem
Grizzly
Moparts Proctologist
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Moparts Proctologist
Joined: Aug 2005
Posts: 5,998
Salem
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My question is: Which system will atomize the fuel better (I suspect EFI) ?
You would think carb given the time for fuel to move through a heated intake manifold, but, injection is now direct on some engines................... The Factory must know something if they are moving the fuel closer to the piston.  A Fellow I worked with once told me: " put a few ounces of fuel in a 45 gallon drum, shake it up, leave it in the sun for a week and then throw a match in it. Heat and vapor seem to be the ticket to massive combustion.
Mo' Farts
Moderated by "tbagger".
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Re: Fuel atomization: Carb vs. EFI
[Re: hemienvy]
#2722233
12/07/19 09:05 AM
12/07/19 09:05 AM
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Joined: Oct 2007
Posts: 4,205
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,205
New York
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I see no one understands the question.
Rather than cut-n-paste, read DV on "displaced charge factor" in any of his books.
Last edited by polyspheric; 12/07/19 09:09 PM.
Boffin Emeritus
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Re: Fuel atomization: Carb vs. EFI
[Re: polyspheric]
#2722252
12/07/19 11:11 AM
12/07/19 11:11 AM
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Joined: Jan 2003
Posts: 8,018
Tulsa OK
Bad340fish
master
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master
Joined: Jan 2003
Posts: 8,018
Tulsa OK
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My thoughts, and I am no engine scientist lol. I think a carb vs THROTTLE BODY EFI the carb is better, fuel flows through it 100% of the time there is no pulsing of injectors to interrupt the stream of fuel.
I think IF port injection doesn't atomize better it at least allows better control of where the mixture goes, and with some EFI systems you can adjust that per cylinder.
68 Barracuda Formula S 340
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Re: Fuel atomization: Carb vs. EFI
[Re: chargerbr549]
#2722275
12/07/19 12:22 PM
12/07/19 12:22 PM
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Joined: Jan 2003
Posts: 30,989
Oregon
AndyF
I Win
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I Win
Joined: Jan 2003
Posts: 30,989
Oregon
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Almost all the race motors we build get fuel injected and go across the dyno, they get broke-in with a carb and then get switched over to fuel injection, engines will almost always make more horsepower with a carb but usually overall driveablility and fuel control is better with fuel injection. Most of the EFI vs. Carb testing that I've done on the dyno shows that a carb has a slight power advantage at peak power, but generally gives up some power in the mid-range. This isn't always true but seems to be true about 80% of the time. I don't worry about it or pay much attention to it since the power difference is irrelevant for the customer. If we were building EMC type engines then we would explore it. The couple of experts I've talked to say it has more to do with the intake design than anything else. The intake for dry air should be designed differently than a wet manifold. Most aftermarket EFI systems use wet manifolds for port injection just because that is what they already have tooled up. Eventually we might see the aftermarket start to design dry air intakes. Once that happens the power difference will swing the other way. The G3 Hemi guys are seeing this.
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Re: Fuel atomization: Carb vs. EFI
[Re: dthemi]
#2722279
12/07/19 12:38 PM
12/07/19 12:38 PM
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Joined: Oct 2004
Posts: 8,165
Left Coast
BobR
master
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master
Joined: Oct 2004
Posts: 8,165
Left Coast
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Purely atomization, carb. Absolutely no doubt about this. Direct injection may change this but that's OEM only right now.
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Re: Fuel atomization: Carb vs. EFI
[Re: hemienvy]
#2722306
12/07/19 02:13 PM
12/07/19 02:13 PM
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Joined: Dec 2003
Posts: 22,695
Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,695
Bitopia
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Not sure if it's feasible (for us hotrodders) to measure unburned hydrocarbons, but that would indicate lack of fuel atomization.
Not sure I agree or if you can support your premise here, and is maybe a separate topic, seems there is a lot more at play in the process then strictly atomization, or that it can be determined by unburned carbons measurement alone.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: Fuel atomization: Carb vs. EFI
[Re: hysteric]
#2722310
12/07/19 02:29 PM
12/07/19 02:29 PM
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Joined: Jul 2004
Posts: 19,317
State of confusion
Thumperdart
I Live Here
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I Live Here
Joined: Jul 2004
Posts: 19,317
State of confusion
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Let's not forget the cooling effect of a "wet" manifold compared to hot incoming air prior to the injectors.............
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: Fuel atomization: Carb vs. EFI
[Re: BobR]
#2722380
12/07/19 06:50 PM
12/07/19 06:50 PM
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Joined: Jan 2003
Posts: 8,160
Plymouth, MI
Blusmbl
master
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master
Joined: Jan 2003
Posts: 8,160
Plymouth, MI
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Purely atomization, carb. Absolutely no doubt about this. Direct injection may change this but that's OEM only right now. Direct injection gets you the benefit of in cylinder charge cooling, and should make more power than a carb, with the obvious tradeoff of complexity. Direct injection is out for racing applications... just not common at the 3000+ hp level you are playing with. Pretty much all F1rally/IMSA/enduro/whatever are using Bosch Motorsport DI fuel systems on them. You can also claw back atomization deficiencies with injector placement. Early F1 fuel injection had the injectors pretty much dead center, aimed straight into the individual throttle bodies. A few OEM's have both port and DI fuel systems on them now, and that is done primarily because of soot production issues at high load. Newer emissions standards depending on the country have a standard for tailpipe soot, which led to the second fuel system.
Last edited by Blusmbl; 12/07/19 06:51 PM.
'18 Ford Raptor, random motorcycles, 1968 Plymouth Fury III - 11.37 @ 118
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Re: Fuel atomization: Carb vs. EFI
[Re: Blusmbl]
#2724320
12/15/19 09:37 PM
12/15/19 09:37 PM
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Joined: Jan 2011
Posts: 4,785
Utah and Alaska
astjp2
master
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master
Joined: Jan 2011
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Utah and Alaska
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In the aviation world, a carburetor in an engine running at constant rpm and power level (above the transition circuit power level) will make as much or more power than FI. The FI will have an advantage in varying levels of power and lower power levels because it is more adaptable than the idle circuit and intermediate circuits of a carburetor. Airplane carbs have variable mixture via an adjustable port for the main jet in the carb. 1935 technology at its finest.
1941 Taylorcraft
1968 Charger
1994 Wrangler
1998 Wrangler
2008 Kia Rio
2017 Jetta
I didn't do 4 years and 9 months of Graduate School to be called Mister!
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Re: Fuel atomization: Carb vs. EFI
[Re: astjp2]
#2724743
12/17/19 11:00 AM
12/17/19 11:00 AM
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Joined: Jan 2003
Posts: 1,756
London, England
Gavin
top fuel
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top fuel
Joined: Jan 2003
Posts: 1,756
London, England
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There are a lot of different (good) questions and answers being discussed......but to simply answer the OP's short Q - My question is: Which system will atomize the fuel better (I suspect EFI) ? The simple answer is...EFI. It's down to fuel pressure, and any injection system has higher fuel pressure than a carb. Modern Direct injection systems run at crazy pressure. The reason - better atomisation. What you do with it after it gets atomised is part of the discussion here, but better atomisation - EFI every time.
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