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In defense of carburetors

Posted By Lord Gaga 5 Months Ago
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Lord Gaga
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Interesting article;
https://www.enginebuildermag.com/2020/02/are-carburetors-dead/?oly_enc_id=7809B4488578E6R


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Ted
Posted 5 Months Ago
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It’s been a known fact now for several years now that engine performance with electronic fuel injection lags behind carburetor performance.  For a number of years, engine dyno contests handicapped the carbureted engines to make for a more level playing field when the carbureted and fuel injected engines ran together in a single competition class.  Once it was figured out that carburetors were superior when all aspects of the engines were equal, those competitions are now almost all carbureted.  There are still engine classes that require fuel injection only but most of those are for the late model engines for which carburetion and their subsequent intake manifolds are not readily available.
 
When it comes to cold start and overall drivability aspects, electronic fuel injection wins that part of the contest easily.  Service life is also much better with modern fuel injection than with carburetors.  Hence the reasoning why all new vehicles are supplied with electronic fuel injection rather than carburetors.  A normal life expectancy for the electronic fuel injection would be 10+ years while carburetors are in the 3 year range before requiring some kind of service.
 
When it comes to peak performance, carburetors are still superior in that department.  In the racing environments, carburetors reign supreme.  A good example is NHRA Pro Stock.  Several years ago NHRA mandated the move to electronic fuel injection and outlawed carburetors in that class.  Those competition cars are just now getting back to the performance levels they enjoyed with carburetors when the switch was made to electronic fuel injection.  The old carburetor technology went to Europe where they still use carburetors in those similar classes.  Whereas the European Pro Stock cars use to be roughly two tenths of a second slower than the U.S. cars, that all changed when the U.S. went fuel injection.  The European Pro Stock cars are now running on the order of two tenths of a second quicker than their U.S. counterparts.

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Lord Gaga
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Thanks for expounding on the subject Ted. Great information. 
Does this mean that modern carburetors can also produce more power than mechanical fuel injection? I'm thinking of old school Hilborn port injection and even the more complex GM scrubette type?






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Ted
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Carburetors do a great job in emulsifying the fuel before it enters the engine.  The older fuel injection setups did not do well in mixing air with the fuel prior to that mixture entering the engine.  By adding air to the fuel mixture prior to the fuel getting to the discharge nozzles, fuel droplet sizes are greatly reduced thus increasing the overall exposed surface area of the fuel mixture.  It’s that additional surface area on the droplets that makes for both increased fuel efficiency and power numbers.  Said another way, if you can break up the fuel into smaller droplets, the power potential increases accordingly.

Modern fuel injection does a good job of controlling the ideal air/fuel ratios which the earlier mechanical fuel injections could not do.  While modern carburetor design does a fair job of controlling the air/fuel ratio, the electronic fuel injection does a superior job in that department and especially throughout a given rpm range.  While a carburetor can be tuned for a specific rpm, it's a challenge to get that fuel curve ideal from idle to the top end of the rpm range.  Where a carburetor has the advantage over modern fuel injection is in the physics end where the carburetor can sense what the engine needs whereas the F.I. units are strictly controlled by the map or program running the unit.  If it’s a daily driver, modern fuel injection does everything it’s designed to do while also having a good service life.


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Ted
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Here’s an excerpt from the link above which gives a reasonably good explanation why carburetors give the performance levels that they do over the fuel injection units.
 
Secondly, carburetors make more power. I know, some of you don’t like hearing that, but the science backs it up. While EFI has the important advantage of cylinder distribution tuning, the systems are not designed to atomize fuel. By design, a carburetor’s primary job is to atomize the fuel before it even exits the booster. Emulsion bleeds in the metering blocks inject air into the liquid fuel that is in the main well causing it to turn into a light, homogenous mixture that can be more easily lifted to the booster. Once this mixture exits the booster it is blown apart by air that is being accelerated to a high velocity through the venturi of the booster and spread into a nice cone-shaped column of air/fuel fog that is perfect for the engine to consume and burn. A fuel injector does not have this advantage, as its only capability is to spray a high-pressure quantity of fuel across an orifice to turn it into droplets. These droplets must see copious amounts of swirl and tumble of the airflow to help them mix with the air.



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charliemccraney
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In racing, the power advantage of a carburetor cannot be denied.  However, I think for street use and considering the average persons willingness or understanding required in order to tune their engine and that many newer injection systems are self tuning, fuel injection will produce better all around results for the average person who is going to buy a carburetor, bolt it on and do nothing more.

One part I don't agree on, "To make calibration changes, simple hand tools like a 5/16ths nut driver, flat blade screw driver, and a 5/8ths wrench are all you need to change jets, air bleeds and float level. It doesn’t get any easier than that!"

There are injection systems that allow you to tune the engine manually, while cruising down the road and the only tool needed is a laptop.  For most the vehicle does need to be stationary.  As easy as carbs are to work with, they are not easier than pressing a few buttons on a laptop.


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Florida_Phil
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As a certified "old timer", I am always astounded at posts demonizing the carburetor.  When there's a problem, it's the first thing that is blamed.  Truth is, most engine problems are not the carburetor and it should be the last thing that is suspect.  If you mess around with old carburetors, you are asking for trouble.  There are modern replacements that will make your life much easier.  If you buy a new carburetor, get one that fits your application.  I have spent many many hours trying to tune an over carbureted engine when I could have bought the right carburetor to begin with.  My Holley 465 came out of the box working perfectly.  It's a direct replacement for a 1957 Holley "D" code carburetor and the perfect carburetor for a street driven 292 like mine.  It's performance is instantaneous.  There are no flat spots, the secondaries open when they should and WOT street performance is great.  I have tried both trips and dual quads on my motor and they don't perform as well as that 4V.   Fuel injection might make my car start easier, I may get better fuel mileage and my emissions may be less.  I don't need a laptop or a degree in computer science to fix my Holley.  The screw driver on my front seat works just fine.   Hehe

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