Fuel Injection vs Carburation

[DonSor]

With the latest technology used in some carburated systems, is there still a notable performance between a carburated as opposed to a fuel injected engine?

[wtousand]

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Yes, there is a difference in performance(s). Economy and power.

Modern OEM FI (Original Equipment Manufacturer Fuel Injection) is often set up with long tuned runners that produce impressive mid range torque which is difficult to do with carbed intakes. Carbed intakes tend to have problems with maintaining a balanced fuel mix in long runners. FI is often port injected so fuel can't miss its intended cylinder nor fall out of suspension.

On the other hand, simple carbed intakes often have shorter runners which promote top end horsepower (with a sacrifice in midrange). Still, the total HP added up across the rpm range will often add up higher with common OEM FI ...and special FI intakes can be built with short runners to enhance high rpm if a wider power-band than carbed is not critical.

In addition, carbed intakes usually need a grossly richer idle mixture just to get enough suspended fuel into the cylinders to maintain idle. Excess unburned fuel, in large droplets, is then expelled out the tailpipe or worse, past the rings into the crankcase. Port injected FI engines, with dry runners, are cleaner engines, both from the aspect of emissions and oil durability. And ...it's hard to beat both FI fuel economy and reliability. FI has become more reliable than Carburation, sometimes running in excess of 100,000 miles trouble-free.

There is sometimes a fear of understanding modern FI, promoted by garages implying it is akin to voodoo. This book is one of the best in making it comprehensible: http://www.amazon.com/Ford-Racing-M1.../dp/0837603013 . You'll discover that OEM FI systems throughout the world are pretty much the same design, quite simple and definately not as difficult to troubleshoot as carbs with their mysterious finicky passages. The book is used to teach mechanics in dealerships. Same guy did one for GM.

Wes


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[DonSor]

Very informative however, in terms of application, why do dragsters use multiple carburators instead of fuel injection? Are NASCARS FI or carburated?

[wtousand]

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Originally Posted by DonSor

Very informative however, in terms of application, why do dragsters use multiple carburators instead of fuel injection? Are NASCARS FI or carburated?

Some dragsters use FI. A popular example is the Hilborn system which has been around for many years. Here is a general link( http://www.hilborninjection.com/ ). I don't really see the point in using FI in most WFO naturally aspirated drag racing. The idea is to simply pour as much air and fuel in as possible and many efficiency benefits of FI are lost anyway. Close counts.

When I was a kid, one of my co-workers drove the wrecker truck in a service bay for the night. The throttle was stuck WFO so he modulated it by turning the key on and off. When he finished parking it inside, he opened the hood to check it out. Unbeknownst to him, the carb was off for service and it ran by pumping gas directly from the disconnected gas-line into the open manifold. Luckily no fire ensued.

Check out the $6800+ price of this naturally aspirated Hilborn setup: ( http://www.hilborninjection.com/prod...Id=52&CatId=37 )... .

On the other hand, most modern blown engines need FI to assure a correct mix. This has long been a problem with blown gassers. Simple centrifugal blowers (and even nitrous) were difficult to adapt to wet carbed setups but they are easy to adapt to FI. FI is why cheap easy to maintain blowers have suddenly gotten popular.

NASCAR is a different cat. They use carbs only because it is a strictly enforced rule. NASCAR is a holdout for the "old way" of doing things. They banned Chevy Corvette type Rochester FI in 1957 along with Fords McCullough Super chargers. The '57 Fords kicked butt by the way ...but the Chevy FI is more well known. So in 1958, Ford came out with their early "big-block" FE motors, the 332 and 352ci., smaller versions of their eventual 427FE. Chevy came out with the 348, a precurser to their 409 and eventually 427. Chrysler came out with the big Hemi. Then NASCAR limited all motors to the pushrod 355ci we have today. They are now as sophisticated as any carbed motor anywhere, amazing HP.

Indy and F1 cars are injected. In a long race, fuel efficiency wins. NASCAR would if they could, but hey, it's supposed to be a bit primitive. Heck, we still race flesh-and-blood horses. So good for NASCAR.

Wes


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[wafrederick]

ASA which is not around anymore did run electronic fuel injected engines,out of the Corvettes.Race officials did have GM's factory scan tool,Tech 2 so noboby would not cheat.Electronic fuel injection is a lot more reliable than the carburator.Most rock crawlers use electronic fuel injection over a carburator,no fuel starvation issues.