Why convert EFI to Carbs!?

[previasc96]

Why do people convert EFI to carbs other than aesthetics? Explain how you can make a better race car with carburetors over Electronic Fuel injection.

[Bimmerman325i]

Because people are stupid, that's why.

[BlackbirdM3]

It depends on the car. If it happens to be an Alfa Romeo SPICA mechanical fuel injection system, and you want to run a set of big cams, you have two choices. Either send the motor to a guy in Seattle who can rebuild the FI pump for a large amount of time and money, or install a set of carbs. Also if the SPICA system is tired and unhappy, its a serious pain in the ass to keep running. Don't get me wrong, the system is a mechanical marvel, much like a fine mechanical watch, but if/when it wears out, its expensive to rebuild. I think a rebuilt pump is going for about $1300 these days. Like I said earlier, it also doesn't do cams larger than stock without being rebuilt to work with a specific set of cams. Its not flexible at all.

Its been proven that you can pull more power out of carbs, and carbs are more flexible. Besides, there are few things that sound as good as a big set of side drafts inhaling large amounts of air at WOT.

Will

[pureaudio]

Because an M20 with triple webers is a glorious thing.

[mikeedler]

because an Edelbrock carb. with manifold is like 400 dollars NEW!for a chevy v8. there is almost no tuning to do- 1 to 2 screws and it runs.
some people are just old school- why drive an e30 when you can drive an F30?

[Julien]

because RAUH WELT BEGRIFF

[tom d]

^ pretty sure that's fuel injected, right?

[Emre]

If you've built an engine with high lift/duration cams, high compression pistons, larger valves, and a port-and-polish, you quickly realize you'll need to flow far more air through the head than your OEM manifold will allow; and you'll need much more fuel than your stock FI system can provide. At that point, you need to upgrade.

Once you've decided to upgrade, you have to decide between upgrading your single throttle plus ancient Bosch (Motronic or K-Jet) system vs. ditching it in favor of: (a) ITBs plus EFI; or (b) carbs. There are pluses and minuses to each approach.

If you've built a dedicated racecar that will only be used for a few weeks out of the year in the middle of the summer at specific race tracks, then you can fairly accurately predict the range of temperatures and atmospheric pressure the engine will see. And you'll be at WOT most of the time, so tuning is pretty straightforward. In that context, swapping in some Weber DCOE carbs isn't as crazy as it might seem. Even though you probably won't save any money over ITB plus standalone EFI, it's a simpler system to install. And if you know a good Weber guru, setup isn't as big of a deal as people make it out to be.

Besides that, the sight, sound, and throttle response of Webers must be experienced to be believed.

[JasonC]

I have both, but rather have a carb. But no room under the hood of the Firehawk to do that. And i wasnt about to go cutting on it to fit one on.

[u3b3rg33k]

It depends on the car. If it happens to be an Alfa Romeo SPICA mechanical fuel injection system, and you want to run a set of big cams, you have two choices. Either send the motor to a guy in Seattle who can rebuild the FI pump for a large amount of time and money, or install a set of carbs. Also if the SPICA system is tired and unhappy, its a serious pain in the ass to keep running. Don't get me wrong, the system is a mechanical marvel, much like a fine mechanical watch, but if/when it wears out, its expensive to rebuild. I think a rebuilt pump is going for about $1300 these days. Like I said earlier, it also doesn't do cams larger than stock without being rebuilt to work with a specific set of cams. Its not flexible at all.

Its been proven that you can pull more power out of carbs, and carbs are more flexible. Besides, there are few things that sound as good as a big set of side drafts inhaling large amounts of air at WOT.

Will

LOL WUT?

In any given situation, EFI has an advantage. Cold starting, fuel economy, power, emmisions. If you can't get EFI to beat carbs, you're bad at setting up EFI.
If you want to compare good carbs to a tired out CIS system, sure, then the carbs will probably beat it, until you fill up somewhere with oxygenated gas and you run lean and lose power.

All hail the mighty O2 sensor and the long term trim variable.

If you're comparing a specific carburetor setup to a specific FI setup, then I can see your argument having a leg to stand on, but there's a reason EVERYTHING now has EFI, and it's not because it's cheaper.

[LJ851]

Its been proven that you can pull more power out of carbs, and carbs are more flexible. Besides, there are few things that sound as good as a big set of side drafts inhaling large amounts of air at WOT.

Will

Sorry, this is utter bullshit. And i love carbs and am building a carbed bmw.

A carb (especially a single throat per cylinder setup) is always a compromise between low speed drivability (good vacuum signal) and max power. You cant have both. ITB's will win every time and sound exactly the same at WOT.

That being said, a properly sized (compromise) sidedraft carb setup does offer an organic feel and connection to the driving experience that can't really be duplicated by fuel injection and at lower throttle openings and RPM offer a slightly different sound than ITB's.

[BlackbirdM3]

LOL WUT?

In any given situation, EFI has an advantage. Cold starting, fuel economy, power, emmisions. If you can't get EFI to beat carbs, you're bad at setting up EFI.
If you want to compare good carbs to a tired out CIS system, sure, then the carbs will probably beat it, until you fill up somewhere with oxygenated gas and you run lean and lose power.

All hail the mighty O2 sensor and the long term trim variable.

If you're comparing a specific carburetor setup to a specific FI setup, then I can see your argument having a leg to stand on, but there's a reason EVERYTHING now has EFI, and it's not because it's cheaper.

I'm going to call BS on some of that. Perhaps if you have an aftermarket, tuneable EFI system, where you can tweak things, but OEM off the shelf, not a chance. I know for a fact that I can't tune EFI. I also know that I can set up a set of carbs pretty well (as long as they aren't some 4 barrel for a V8, I don't have the slightest clue how to work on those.) I will say that my 43 year old Datsun will start faster cold than my M3 any day of the week, and that's with no choke hooked up. Heck, hot it will out start the M3 as well. Is a wide band o2 sensor a useful too to set carbs up? Yes, you bet. It saves lots of time.

My statement about the Alfa SPICA system couldn't be any more true. Most people who have pre 1975 cars have pulled the SPICA off and replaced it with Webers (that were sock in Europe) if they wanted to add bigger cams, and or, didn't have the $$$$ to fix the SPICA system. When it works, it works great for a stock motor, but it really can't handle the needs of anything more than stock. Heck, it has trouble feeding stock cams on a stock motor. It was designed to meet emissions, not for performance, as were many of the FI systems of the '70s and '80s on cars exported to the US from Europe or really anywhere else.

More modern EFI setups are likely better than Bosch D-Jet or things like that, but they still are a preset item. Unless you happen to have something like Megasquirt or the Miller WAR chip, odds are that your car isn't totally right. Every car is different and any broad based chip isn't going to be 100% right. I've read that quite a few of the chips out there for the S14 are a death sentence for it if you happen to be in California where 91 octane fuel is the best you can widely get. The aftermarket chips are designed for 93 or higher and have too much spark advance causing them to ping and have other problems. Eventually the motor is a boat anchor. Granted, you can very easily do this with carbs, but its a simple jet change to fix as well.

This is an interesting read. Its not very informative, but still interesting to hear the thoughts of some pretty well placed people in the industry.

http://www.carcraft.com/techarticles/carburetor_vs_injection/index.html

What can I say? I'm a carb guy in a fuel injected world. I'd love to stick a set of carbs on my S14 just to see what it could do.

Will

[LJ851]

What can I say? I'm a carb guy in a fuel injected world. I'd love to stick a set of carbs on my S14 just to see what it could do.

Will

It would lose substantial power on one end of powerband, take your pick.

The Alfa example you mention is true, but ITB's would beat the webers in power and drivability hands down, every day.

The main reason your (or my) carbed cars start quicker is because there is nothing telling the car not to start until it "sees" a certain # of the required signals like most OEM injection systems do.


There are some carb setups can produce similar power levels across the RPM band compared to injection but it (unfortunately) will never be a sidedraft weber carb.

I sincerely wish this wasn't true because i love them and am using them on my M30.

[nbio]

A carb (especially a single throat per cylinder setup) is always a compromise between low speed drivability (good vacuum signal) and max power. You cant have both. ITB's will win every time and sound exactly the same at WOT.

they make carbs with multiple barrels.

[M-technik-3]

Tell GA pilots carbs are better than a good FI setup.