Why do people convert Injected 5.0s to carb?

The best system is one that works properly, that system will vary based on budget and individual requirements.

 A properly set up carb will do everything FI does with two exceptions

           A. It won’t adjust itself.

           B. Achieve the emission standards that modern fuel injection will.

I'm surprised at how man people on both sides buy into fueling folklore.

Some things to ponder.

A 1978 Civic gets slightly better gas mileage than a 2018 Civic. 

In some applications a carbed motor will make more power, has to do with fuel atomization,  the Keihin flat slide carbs on my Datsun motor will make more power than a fuel injection set up. Why because the slide valve configuration flows more than a butterfly throttle. The throttle shaft is an obstruction. The fuel injected version of my motor made 70 rear wheel horsepower vs 73 for the flat slide equipped motor.

I also seem to recall a Pro Stock cars where another application where this is the case.

Prior to 2002-2005 most liter sportbikes used carbs; the bikes ran flawlessly and had higher power per liter figures than fuel injected cars. 

The removed the smog stuff to make more power as well as carbed motors don't make as power or won't be streetable once modded are both bunk. It's the overall set up that controls these things.

Where FI does win out is the ability to make power AND return maximum fuel economy. That's hard to do with a carb, it can be done but it's going to be a compromise.  

With all that said like many others here I would stick with FI for day to day use because it does offer an advantage. Modern fuel injected cars are amazing but once you start modifying them they need to be set up as well. 

Constant velocity carbs do a pretty good job being a great all arounder fueling setup while having a bit of "self adjusting". Look at the millions of Japanese motorcycles equipped with then. SU carbs are also pretty good at it, especially considering they have one jet and one needle. You can't get much more simple than that.

In reply to Tom1200 :

A properly done EFI will always make more power than carbs.  There's no venturi to restrict the flow.  And fuel injection can better take advantage of evaporative cooling to make more power.

And carbs generally mean mechanical timing, where as EFI means digital control of spark- which is even more important that fuel prep.

Your comparisons are not exactly valid:

A 1978 Civic is smaller and lighter than the 2018 Civic, and it also has very different emissions rules to deal with- so it could run lean all the time.  They are far from an equal comparison.

Comparing a small very high revving engine to a larger low revving engine is not a fair comparison either for specific output, since power goes up with engine speed.   A 500cc bike motor spinning at 12000rpm can make 50.1% the specific torque of a 6000rpm 2000cc motor, but will have far better specific power output since it's doubled the engine speed.

And anymore, power isn't limited nearly that much by emissions control devices, especially compared to 20 years ago (let alone 40 years ago).

Carbs are just "simple" and cheap.

And if you look at the physics of a carb, they are not exactly that simple- it's just that it's been solved by someone smart a long time ago.  And you don't have to mess with it much.

alfadriver said:

And if you look at the physics of a carb, they are not exactly that simple- it's just that it's been solved by someone smart a long time ago.  And you don't have to mess with it much.

Unless you are trying to get a carb to maintain an accurate air/fuel ratio everywhere from light cruise to around 10 psi of boost and everywhere in between. Trying to figure THAT out drove me to converting the Dart to EFI. 

MadScientistMatt said:

alfadriver said:

And if you look at the physics of a carb, they are not exactly that simple- it's just that it's been solved by someone smart a long time ago.  And you don't have to mess with it much.

Unless you are trying to get a carb to maintain an accurate air/fuel ratio everywhere from light cruise to around 10 psi of boost and everywhere in between. Trying to figure THAT out drove me to converting the Dart to EFI. 

So the numbers match exactly? Yawn!!! Try taking a hand drill to the injector pill and getting the fuel mixture close enough to qualify for the race!  

Chuck a SU needle into a drill and with a piece of emery paper richen it up enough to get rid of that flat spot from 3500-4300 rpm. 

Solve a sinking float with a piece of chewing gum. 

Have a poorly assembled carb fall apart on a empty highway,  find all the pieces by the light of a Coleman lantern, and put it together properly.  

Ya can’t do any of those things with EFI.  In fact few can even fix EFI without a plug in to diagnose the problem. 

In reply to frenchyd :

I'm not sure how those kinds of failure fixes are features for carbs, as opposed to faults that need to be dealt with that carbs have....

alfadriver said:

In reply to frenchyd :

I'm not sure how those kinds of failure fixes are features for carbs, as opposed to faults that need to be dealt with that carbs have....

 

I think the point he's trying to make is that a car will run for a long time with an ill-tuned, or failing carb.   A car comes to a stop with a malfunctioning EFI system.   On one case, you can limp home, on the other, you are calling a tow truck.  

As proof that an engine will always run on a poorly tuned carburetor, I present every car that ever got a WEBER DCOE bolted to it.

Pete

Joe Gearin said:

alfadriver said:

In reply to frenchyd :

I'm not sure how those kinds of failure fixes are features for carbs, as opposed to faults that need to be dealt with that carbs have....

 

I think the point he's trying to make is that a car will run for a long time with an ill-tuned, or failing carb.   A car comes to a stop with a malfunctioning EFI system.   On one case, you can limp home, on the other, you are calling a tow truck.  

With cars with carbs the biggest source of being stranded is usually a fuel pump failing 

Joe Gearin said:

alfadriver said:

In reply to frenchyd :

I'm not sure how those kinds of failure fixes are features for carbs, as opposed to faults that need to be dealt with that carbs have....

 

I think the point he's trying to make is that a car will run for a long time with an ill-tuned, or failing carb.   A car comes to a stop with a malfunctioning EFI system.   On one case, you can limp home, on the other, you are calling a tow truck.  

Exactly! Problems I pointed out were typical of cars of the era.  Electrical, mechanical etc. were all relatively easy to diagnose and repair.  

Today 99% of car problems result in a  tow truck  not a roadside repair. 

MotorsportsGordon said:

Joe Gearin said:

alfadriver said:

In reply to frenchyd :

I'm not sure how those kinds of failure fixes are features for carbs, as opposed to faults that need to be dealt with that carbs have....

 

I think the point he's trying to make is that a car will run for a long time with an ill-tuned, or failing carb.   A car comes to a stop with a malfunctioning EFI system.   On one case, you can limp home, on the other, you are calling a tow truck.  

With cars with carbs the biggest source of being stranded is usually a fuel pump failing 

Those with British cars and no knowledge or skill knew enough to wack the fuel pump a few times. The rest of us would take about the same time to clean the points  and fix it for good.  

frenchyd said:

Joe Gearin said:

alfadriver said:

In reply to frenchyd :

I'm not sure how those kinds of failure fixes are features for carbs, as opposed to faults that need to be dealt with that carbs have....

 

I think the point he's trying to make is that a car will run for a long time with an ill-tuned, or failing carb.   A car comes to a stop with a malfunctioning EFI system.   On one case, you can limp home, on the other, you are calling a tow truck.  

Exactly! Problems I pointed out were typical of cars of the era.  Electrical, mechanical etc. were all relatively easy to diagnose and repair.  

Today 99% of car problems result in a  tow truck  not a roadside repair. 

Well, they also fail a whole lost less often, thus requiring far less need for roadside hack repairs.  Which is why I don't think being ABLE to fix a carb on the side of the road is exactly a feature.  It's more a necessity.  Which isn't a good thing in my book.

NOHOME said:

As proof that an engine will always run on a poorly tuned carburetor, I present every car that ever got a WEBER DCOE bolted to it.

 

Pete

Honestly, tuning EFI to be as good as a DCOE is pretty easy.   Not sure why people think it's so hard.  Don't look at tuning an EECIV as an example- that was not easy in it's day- when computers were not what they are now.  

But, hey, I've only been doing it for my entire career, so I'm biased.

In reply to alfadriver :

Other way around. I don't think I have ever seen a DCOE  install that is well tuned.

NOHOME said:

In reply to alfadriver :

Other way around. I don't think I have ever seen a DCOE  install that is well tuned.

They take some dyno time and lots of fiddly bits to get right. 

alfadriver said:

NOHOME said:

As proof that an engine will always run on a poorly tuned carburetor, I present every car that ever got a WEBER DCOE bolted to it.

 

Pete

Honestly, tuning EFI to be as good as a DCOE is pretty easy.   Not sure why people think it's so hard.  Don't look at tuning an EECIV as an example- that was not easy in it's day- when computers were not what they are now.  

But, hey, I've only been doing it for my entire career, so I'm biased.

I have no doubt that you are as good at tuning EFI as I am at tuning carbs. 

The difference I suspect is knowledge. The training or education you received either by reading or by having someone show you the ropes.

That’s  how I learned,  reading or someone showing me. 

But I don’t need to do it in the shop.  Side of the road works just as well as the shop. A screwdriver and maybe a small crescent wrench.  

While I envy your knowledge it’s not enough motivation to spend the time.  I’ll continue to pick up what I can but due to the reliability of modern EFI systems it’s unlikely I’ll pick up too much.  

In reply to frenchyd :

You can learn EFI by training, education, and experience, too.  It just takes effort to learn it.  Just like tuning carbs.  Can do it at the side of the road, too- but instead of special screwdrivers and a set of jets, you need a computer of some type.  

Carbs and EFI do the exact same thing- deliver fuel. The target result is the same, the process can be the same, etc.  It's just a different set of tools.

I'm not trying to convince YOU to do EFI- that's entirely up to you.  If you want to tune a turbo V12 with carbs, go for it.  I'm 100% sure that a decently tuned EFI will be light years better, and take a lot less effort, let a lone simpler, than trying to boost with carbs.

I'd say that if you put in a little bit up front to get the right equipment for data logging, EFI is almost easier to tune than a carb.  It might not be quite as simple, but you get more insight into "what is the engine doing?" in ways that point right to what needs changing and how far off it is. 

I am efi all day long.

Carbs suck.  

Every track and weather needs a different tune.

I just wanna drive.  Let the computer figure it out.

alfadriver said:

In reply to frenchyd :

You can learn EFI by training, education, and experience, too.  It just takes effort to learn it.  Just like tuning carbs.  Can do it at the side of the road, too- but instead of special screwdrivers and a set of jets, you need a computer of some type.  

Carbs and EFI do the exact same thing- deliver fuel. The target result is the same, the process can be the same, etc.  It's just a different set of tools.

I'm not trying to convince YOU to do EFI- that's entirely up to you.  If you want to tune a turbo V12 with carbs, go for it.  I'm 100% sure that a decently tuned EFI will be light years better, and take a lot less effort, let a lone simpler, than trying to boost with carbs.

I’m slowly learning EFI because I have to. I want to race and Turbo’s seem to be an affordable way but require EFI. So I’ll learn ( grumble grumble grumble) 

But nobody can tell me it’s simpler.  I can look at a carb and tell if fuel is getting to it. Not so with Injectors.  

Loose connectors or corroded wiring add another dimension that EFI is different,   loose fuel line will dribble or leak.  A crack in a fuel line to a carb is easy to detect.  A crack in the high pressure fuel line on an injector may only be detected when the fuel spray ignites the engine. 

alfadriver said:

In reply to frenchyd :

You can learn EFI by training, education, and experience, too.  It just takes effort to learn it.  Just like tuning carbs.  Can do it at the side of the road, too- but instead of special screwdrivers and a set of jets, you need a computer of some type.  

Carbs and EFI do the exact same thing- deliver fuel. The target result is the same, the process can be the same, etc.  It's just a different set of tools.

I'm not trying to convince YOU to do EFI- that's entirely up to you.  If you want to tune a turbo V12 with carbs, go for it.  I'm 100% sure that a decently tuned EFI will be light years better, and take a lot less effort, let a lone simpler, than trying to boost with carbs.

You are right about. Turbo needing EFI  but I don’t have to be happy about it.  ( grumble grumble grumble) 

Alfadriver, I most definitely have some apples to donuts comparisons, this why I said things to ponder.

Perhaps I should have said devils advocate.

What I really expected someone to call me out on is that if you put the 2018 Civic engine in the 1978 chassis is the fuel mileage would even better still.

One thing you brought up that I do think is a large portion of why FI is now better is the digital ignition but I will expand on that further. Modern injection is one component of an engine management system.

Modern FI / engine management is light years ahead of the stuff from the 80’s but I wouldn’t replace 80’s fuel injection on a street car.

wvumtnbkr not all carbs are created equal. Both my Datsun and my 2010 Beta 520RS use Keihin FCR flat slide carbs and at the risk of sounding like a fan boy, they are absolute works of art.

I ride the Beta in temps that range from 30-107F and altitudes ranging from 2000 to 7800. I’ve never had to change the jetting. Yes I’m giving up a tiny bit of power but the bike runs flawlessly.

I jet the Datsun for my home track but it is close enough in altitude to other west coast tracks not be an issue. The actual races I attend are in the cooler months so I jet for that. The track days are during the warmer months but I don’t bother rejetting because the difference is all of 2-3hp and well who cares it’s a track day.

My F500 uses Mikuni Super BN38s (pumper style carb used on watercraft) they have a high speed and low speed adjuster that you can turn by hand to adjust the jetting. The high speed adjuster works from 3/4 to WOT. I actually make adjustments to these from winter to summer because it takes all of 15 seconds.

I like many other people am not enamored with DCOE carbs because they are simply not of the same build quality of Keihin. Note I got a smoking deal on the Keihins for the Datsun, they are pricey, you could probably purchase a FI set up for less money than new Keihins.

I’ve never had either a carb or FI strand me on the side of the road, I’ve had them act up but never left me stranded. Modern FI is clearly an improvement but that doesn’t mean carbs are junk.

wvumtnbkr said:

I am efi all day long.

 

Carbs suck.  

 

Every track and weather needs a different tune.

 

I just wanna drive.  Let the computer figure it out.

See that right there is the main reason I hate EFI.  I spent a great deal of time learning how to tune based on air density temperature and other factors. 

That knowledge gave me something for my efforts. I could change the carb accordingly.  A little more power for my knowledge.  

Let the computer figure it out?  Talk about lazy, something for nothing!!  

But OK.  I guess I’ll have to find another way to beat you.