Injection vs. carbs

Is there any big HP gains from using one or the other? i assume carbs are easier to work on then MPI or DI fuel rails. How would if effect forced induction as well? Supercharges seem to benefit due to the straight downwards flow from the intake to the centrifuge straight to the carburetor.

Properly tuned port injection will always make more power with better economy and better emissions than carbs.

Properly tuned DI will do those 3 things better than port injection.


I personally prefer port injection as the simplest to work on and service.

intake manifold design makes more difference than carb or injection.

they all behave very differently. an engine with webers like this, has no plenum. it means that UNLIKE a 4bbl each cyl sees only one venturi.

so it can get away with a bigger cam and so on, and act "tamer"

a 4bbl intake, single plane, means each cyl can suck from all 4 venturi at the same time, giving it a good breathing.

Thank you for your post, In your opinion what would be the most powerful of the tree options? Im not worried about emissions or economy due to the laws in my area involving older cars.

really depends on money and goals. i personally like a flat plane v8 with webers
for that sound, who cares about speed when it can sing?

I can agree with you on that

Taking what you said would a supercharger (take a roots for example) overcome the more restricted intake manifold? Or would it be better to leave the throttle response at a good rate with NA?

Port injection will make more power than the carb, DI more than port - ALL ELSE EQUAL.

Take a car with a stock ecu map and a shitty intake, put a ram style manifold on it with a free flowing carb and it might make more power. Give the port injection a similar manifold and ECU tuning, it will beat the carb every single time. DI wins over port via, directly injecting the fuel. This cools the combustion charge, and very evenly distributes fuel. DI tuning is much different, since you can run more timing and (if applicable) more boost, due to the cylinder cooling effect.
Carburetors are "simple" to the average joe. To properly tune a carb, you need an AFR gauge. Tuning it to run fine, start decent, and get acceptable economy can be tuned by the seat of the pants, MAYBE a vacuum gauge if you want the best you can get. Nothing beats knowing the true AFR though.

Yup I like carbs for the sound and ease of backyard tune.

How do carbs sound different? Say you have a fuel injected engine and carb swap it, how will it sound different?

Depends on your goal
pure horsepower? DI. moderm horsepower with modern MPG? MPI. Old school horsepower? Carbs.
Thing is you have to play by the port-per-cylinder rule. You'll get way more power from an engine with 1 carb per cylinder than single point injection.
If you supercharge?turbo your engine go injection tho, its way simpler.
However i know i love carbs and they're far from being as unreliable as anyone memes.They're also literally tunable and fixable with a simple tolbox unlike injection.
DI is abolute shit in reliability.
just look it up on youtube, but carbed engines sound absolutely beautiful everytime.

Carbs are easier to work on if you know what you're doing - and very few people truely do. Apart from that, using and modifying MPI is a lot easier. DI is definitely the worst.

Carbs do have the best atomisation, do they can make a fraction of a fraction more HP. They're also better for convetional superchargers (not centrifugals) since their vaporisation can cool the intake air. You can't use carbs before a centrifugal compressor, since it'll erode the compressor blades over time - and carbs after compressor is a recipe for extremely hard tuning.

Properly tuned DI does better emissions and MPG than both - but carbs are better at the extreme high end competition if you want pure horsepower.

>but carbs are better at the extreme high end competition if you want pure horsepower
That must be the reason they use either port or direct injection in higher racing classes like F1 or LeMans...

Direct injection gives you the highest power since it has:
>least intake restriction
>no fuel in intake displacing the air
>always the desired A/F ratio
>charge cooling effect during compression

The only issue with direct injection are emissions since it does emit a bit of fine dust.

Carb sound 10,000% better than Injected 200% of the time desu

ITBs always sound great, no matter if carb or EFI...

DI is also massively unreliable.

Ah yes series that are entirely power centric like top fuel

If it is made shitty, like in VAG engines, indeed.
>top fuel
They have rules mandating stuff like that, they could make a bit more power with direct injection.

If they could run DOHC and injection they would.

DI i shit in general, wether VAG or not tho.

No, VAG just veaps out on engines and therefore they constantly fail.

The main reliablity issue on DI engines are carbon deposits on the intake valves since they are not cleaned by fuel beeing sprayed on them.
If you get these valves up to a decent temperature (mazda) or have port/singlepoint (Toyota) as well to switch they clean themselfes.

This is also the reason for the torque dip of the GT-86, it is the switching point between the different injection systems if I remember correctly.

Uh maybe if it's shitty DI lmao

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