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EFI to carbureted

Rajobigguy

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My take on it is that a carb, no matter how good is nothing more than a controlled fuel leak. A well set up one can do a pretty fair job of leaking the right amount of fuel but can never mimic what a true mass air efi can accomplish.
Yes efi can be complicated in design but doesn't have to be for the end user. If you think of your engine as a large positive displacement air pump (which is precisely what it is) then the things that you need to know is how much air it will move at any given RPM, what the potential for air ingestion is at that RPM given the engine displacement vs the throttle opening (load) and a few other variables like IAT and engine temp. and from there the fuel map is pretty easy to draw up with only minor changes. Systems that use O2 sensors as a means of "auto-tuning" are way behind the curve. O2 sensors shouldn't be used to adjust fuel flow they are really only a report card for the computer to let it know that things are working the way they were set up to work.
 

DaveH

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the EPA and CARB is what ruined it. Carbureted motors only went away because the cores that they were built out of went away. Reduced availability of carburetor related parts due to the entire ICE industry being forced into fuel injection. It became more cost effective for the marinizers to keep the fuel injection that the engines were coming with from Ford/GM

Although I suspect today with glass cockpits on the rage that they actually would be going out the wayside.
there is no doubt emissions laws forced the move to EFI.

but that doesn't mean there isn't merit to what efi offers....... fewer emissions does equate to a better running more efficient engine. take a look at engines today that ARENT's emissions regulated.....say a high performance dirt bike or quad....and yet many are efi. they are designed with efi to squeak out every last bit of efficiency, economy, HP and longevity. that's why we don't run carbs anymore.
 

Shlbyntro

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there is no doubt emissions laws forced the move to EFI.

but that doesn't mean there isn't merit to what efi offers....... fewer emissions does equate to a better running more efficient engine. take a look at engines today that ARENT's emissions regulated.....say a high performance dirt bike or quad....and yet many are efi. they are designed with efi to squeak out every last bit of efficiency, economy, HP and longevity. that's why we don't run carbs anymore.
I totally and 100% agree with that. But if one were to look at that through a different lense. It means you're running your engine on the ragged edge which translates to a very small problem causing very big problems in a hurry. It takes a lot more to hurt an engine with a carburetor vs with FI. And when were talking about 1mpg vs 1.25mpg in a boat, fuel economy isn't one of my bigger concerns

Just my $0.02
 

rrrr

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Carbureted motors only went away because the cores that they were built out of went away. Reduced availability of carburetor related parts due to the entire ICE industry being forced into fuel injection. It became more cost effective for the marinizers to keep the fuel injection that the engines were coming with from Ford/GM
This is nonsense. Mercury and other companies have made life easier for a generation of boaters with EFI. It's dependable and requires little maintenance.

There's also the issue of emissions, and federal laws require new boats to have EFI and catalytic converters to meet standards.

My last boat had a 675 HP 540 CI EFI engine in it, and the MEFI 4 ECU performed flawlessly.
 

zx14

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So, what does it take to ditch the mefi box? Have to re wire the whole boat.
 

DaveH

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I totally and 100% agree with that. But if one were to look at that through a different lense. It means you're running your engine on the ragged edge which translates to a very small problem causing very big problems in a hurry. It takes a lot more to hurt an engine with a carburetor vs with FI. And when were talking about 1mpg vs 1.25mpg in a boat, fuel economy isn't one of my bigger concerns

Just my $0.02
when you pull up to the pump and save 25% every time you fuel up i suspect the attitude may be different. and yes, i have taken carb engines that were converted to efi and saw fuel economy gains greater the 25%.
 

Shlbyntro

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when you pull up to the pump and save 25% every time you fuel up i suspect the attitude may be different. and yes, i have taken carb engines that were converted to efi and saw fuel economy gains greater the 25%.
On a properly tuned carb vs its efi equivalent, i have never seen those kinds of gains unless there was something wrong with the carb that caused you to ditch it for efi in the first place. I own and have owned several of both. I like my carbed motors better.
This is nonsense. Mercury and other companies have made life easier for a generation of boaters with EFI. It's dependable and requires little maintenance.

There's also the issue of emissions, and federal laws require new boats to have EFI and catalytic converters to meet standards.

My last boat had a 675 HP 540 CI EFI engine in it, and the MEFI 4 ECU performed flawlessly.
And I have a mefi4 on the Ultra. Its a good motor, good setup, dont get me wrong. I ultimately kept the efi when I rebuilt the motor on that boat because it would have been more expensive to go carbed and I was already spending money like it was going out of style on it. I wouldnt have kept it if i legitimately had a fundamental problem with it.

The bottom line is: a boat is a boat. They like to, and need to be used on a regular basis regardless of carburetion or fuel injection. Sitting is what causes the most problems with both fuel systems.

Sure, a carburetor problem can ruin your weekend, but a fuel injection problem can ruin your motor. It is for that reason alone that i advocate for carburetors. They are not any more or less problematic than fuel injection and they are safer for your engine.
 

DRYHEAT

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Thanks for all the input gentleman I like to cover all my bases. In the long run I'm going with whatever Barry suggest for my application .

Ill update my rebuild thread and keep you guys in the loop thanks again!

Andy
I was going to suggest you go with what the engine builder/tuner suggests, but I was having too much fun enjoying the back-and-forth. 😂
 

Rajobigguy

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Sure, a carburetor problem can ruin your weekend, but a fuel injection problem can ruin your motor. It is for that reason alone that i advocate for carburetors. They are not any more or less problematic than fuel injection and they are safer for your engine.
I'm not so sure that I would agree with that. A good EFI will detect a problem and go into a safe limp home mode while a plugged jet in the carb can cause a lean condition and burn valves or melt pistons. Every system has their advantages and their drawbacks. In the end it's really just what someone is more comfortable with.
 

Shlbyntro

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I'm not so sure that I would agree with that. A good EFI will detect a problem and go into a safe limp home mode while a plugged jet in the carb can cause a lean condition and burn valves or melt pistons. Every system has their advantages and their drawbacks. In the end it's really just what someone is more comfortable with.
That is far more likely with fuel injectors getting clogged and not keeping up with the rest of the injectors than it is with a carburetor having that kind of issue. Usually with a carb issue the engine just won't run. Individual lean/rich cylinder conditions will not be detected by nearly all fuel injection ecms. And the ecm will literally let you burn that one cylinder down without you ever realizing there was an issue until its too late.

I was going to suggest you go with what the engine builder/tuner suggests, but I was having too much fun enjoying the back-and-forth. 😂
Me too 😜
 

Rajobigguy

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That is far more likely with fuel injectors getting clogged and not keeping up with the rest of the injectors than it is with a carburetor having that kind of issue. Usually with a carb issue the engine just won't run. Individual lean/rich cylinder conditions will not be detected by nearly all fuel injection ecms. And the ecm will literally let you burn that one cylinder down without you ever realizing there was an issue until its too late.



Me too 😜
Like I said " A good system " will detect a problem. For instance, my system will detect a lean or unbalanced condition from one cylinder bank to the other and will give an alert, it can also be programed to go into a safe mode for limp home or shutdown entirely until the problem is corrected.
 

Shlbyntro

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Like I said " A good system " will detect a problem. For instance, my system will detect a lean or unbalanced condition from one cylinder bank to the other and will give an alert, it can also be programed to go into a safe mode for limp home or shutdown entirely until the problem is corrected.
What system?? I'm legitimately curious
 

DaveH

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What system?? I'm legitimately curious
a GOOD system will have wideband 02 sensors and is capable of detecting a cylinder being lean or a misfire condition. this also requires logging and alarming capabilities. I've seen plenty of carb systems with damaged cylinders.....broken ring lands, burned valves etc from lean conditions.

GREAT systems have wideband and EGT's.........now you have a high visibility of what each cylinder is doing and if there is a single cylinder problem.

back to my original assertion that most wont spend the $$ for a GOOD system.
 

zx14

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a GOOD system will have wideband 02 sensors and is capable of detecting a cylinder being lean or a misfire condition. this also requires logging and alarming capabilities. I've seen plenty of carb systems with damaged cylinders.....broken ring lands, burned valves etc from lean conditions.

GREAT systems have wideband and EGT's.........now you have a high visibility of what each cylinder is doing and if there is a single cylinder problem.

back to my original assertion that most wont spend the $$ for a GOOD system.
I was told you can’t leave afr sensors in the headers they stop reading correctly due to the water stream
 

zx14

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What are the pros and cons its an 99 502 mpi? I mainly boat at mead with an occasional trip to Havasu.
Do you know what ecu you have? Who is going to re-wire it?
 

rivermobster

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Pro-M Racing Mass air system. It isn't cheap but it lives up to the hype.
Interesting concept...

Using a modified factory ECU and supplying a wire harness and air mass meter.

2k is a Bit expensive for just those 3 components, bit really not crazy out of line considering all the options they have added in

I don't see that they offer any marine applications though? Are you using this system on a car or a boat?

 

DaveH

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I was told you can’t leave afr sensors in the headers they stop reading correctly due to the water stream
moisture will almost INSTANTLY kill an 02 sensor. to combat moisture, good efi systems delay the heating of the element to allow the exhaust system to heat up first and rid any condensation.

wild cams will pull water back into the motor and careful exhaust system design needs to factor this in and correct location of an 02 sensor.
 

DaveH

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Interesting concept...

Using a modified factory ECU and supplying a wire harness and air mass meter.

2k is a Bit expensive for just those 3 components, bit really not crazy out of line considering all the options they have added in

I don't see that they offer any marine applications though? Are you using this system on a car or a boat?

wouldn't be my first choice. i have yet to see a factory system that offers many of the deireable features aftermarket has, including logging, real time tuning, etc. furthermore i wouldn't want a one size fits all harness and most of these systems use cheap automotive grade wiring and the cheapest connectors they can source.
 

Blackmagic94

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moisture will almost INSTANTLY kill an 02 sensor. to combat moisture, good efi systems delay the heating of the element to allow the exhaust system to heat up first and rid any condensation.

wild cams will pull water back into the motor and careful exhaust system design needs to factor this in and correct location of an 02 sensor.

a wideband will not work in a wet system at all. End of story.

That’s why I converted my botë to a complete dry system and I’m still running into false signals from to short of tail pipes in the system.

My cigarette has dry pipes so the o2 bung is welded in a circle to prevent the jacketed tail pipe from contacting the sensor and the water injection is like 40” behind the sensor.
 

Rajobigguy

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Interesting concept...

Using a modified factory ECU and supplying a wire harness and air mass meter.

2k is a Bit expensive for just those 3 components, bit really not crazy out of line considering all the options they have added in

I don't see that they offer any marine applications though? Are you using this system on a car or a boat?

Originally they used factory ford ECUs that were modified with a quarter horse piggy back but the new ECUs were designed by the guys that built the Ford racing team electronics package and although factory quality they are infinitely more programable.
Like I said they are not cheap but they actually live up to the hype.
For marine apps you need to discuss your needs with Chris (the owner) and he can program a few variables that make it suitable for boats
Have done two cars with outstanding success and I'm building a new engine for my boat that incorporates one now.

wouldn't be my first choice. i have yet to see a factory system that offers many of the deireable features aftermarket has, including logging, real time tuning, etc. furthermore i wouldn't want a one size fits all harness and most of these systems use cheap automotive grade wiring and the cheapest connectors they can source.
This isn't just a modified factory unit and is capable of data logging and real time, on the fly tuning. It also has several outputs that can be used to turn things on or off in sequence or by condition. You would be surprised at how programable the unit is. I'm pretty impressed with the harness that they supply it's not a one size fits all.

You guys should visit the site and watch some of the videos. It's easier to deal with than some of the other units I've played with.
 

Blackmagic94

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The very best efi is Motec. AEM and a few others are decent as well. But motec is what real cars run
 

rivermobster

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Originally they used factory ford ECUs that were modified with a quarter horse piggy back but the new ECUs were designed by the guys that built the Ford racing team electronics package and although factory quality they are infinitely more programable.
Like I said they are not cheap but they actually live up to the hype.
For marine apps you need to discuss your needs with Chris (the owner) and he can program a few variables that make it suitable for boats
Have done two cars with outstanding success and I'm building a new engine for my boat that incorporates one now.


This isn't just a modified factory unit and is capable of data logging and real time, on the fly tuning. It also has several outputs that can be used to turn things on or off in sequence or by condition. You would be surprised at how programable the unit is. I'm pretty impressed with the harness that they supply it's not a one size fits all.

You guys should visit the site and watch some of the videos. It's easier to deal with than some of the other units I've played with.
You didn't notice the link to the website in my post? Lol

I read up on how it all works. Like I said, interesting concept.

It's basically designed for narrow segment of the market, where no other options exists when you want to retain a factory Look system.

Since you have to use all the factory components, it's not exactly a stand alone system like FAST or Holly have created, or that DaveH could build. They have no marine applications. Yet.

What ECU are they going to use on your boat?
 

farmo83

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My vote would be EFI.

Yes carberators are simple,however if you can't work on them the fact they are simple is irrelevant

My personal opinion is if building new then don't go with antiquated technology.

I say this having a well tuned holly 800 in my boat
 

Rajobigguy

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You didn't notice the link to the website in my post? Lol

I read up on how it all works. Like I said, interesting concept.

It's basically designed for narrow segment of the market, where no other options exists when you want to retain a factory Look system.

Since you have to use all the factory components, it's not exactly a stand alone system like FAST or Holly have created, or that DaveH could build. They have no marine applications. Yet.

What ECU are they going to use on your boat?
It's the same ECU it just has the programing tweaked to be suitable for my app.
Mine is set up for coil on plug ignition with a boost referenced timing curve and a lower temp. transition point from open to closed loop.
I've got everything that I need to put the new engine together, well everything except time that is but retirement is right around the corner and this is going to be my first project that I'm tackling. I will be posting the build, I think you'll find it interesting, I'm doing a lot of unusual things.
 

rivermobster

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It's the same ECU it just has the programing tweaked to be suitable for my app.
Mine is set up for coil on plug ignition with a boost referenced timing curve and a lower temp. transition point from open to closed loop.
I've got everything that I need to put the new engine together, well everything except time that is but retirement is right around the corner and this is going to be my first project that I'm tackling. I will be posting the build, I think you'll find it interesting, I'm doing a lot of unusual things.
Sounds interesting! I have many questions. I'll be looking forward to the build!

👍
 

namba860

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I believe he was joking. Sarcastic humor....... Like saying using a hammer to drive a common nail will never work....
Ok wasn’t sure if he caught something on the set up I didn’t see.
 

SBMech

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moisture will almost INSTANTLY kill an 02 sensor. to combat moisture, good efi systems delay the heating of the element to allow the exhaust system to heat up first and rid any condensation.

wild cams will pull water back into the motor and careful exhaust system design needs to factor this in and correct location of an 02 sensor.
Uhh no. You know those pesky drain holes you have in EVERY vehicle's muffler? Yep, needed to drain the steam/condensation caused by temperature changes in the exhaust.

Heated O2 sensors turn the heater on immediately (it's the first test done by OBD2 monitors after the ignition event), so the sensor can start to work independently of the temperature of the exhaust or cat.

True if you get the sensor wet with a reversion pulse while it's at temperature it will most likely destroy it, but my point is that they can handle some moisture because they are designed to.

Getting back to the OP, you would have to be crazy to go back to carbs if you have EFI already. Yes the early systems are pretty crude, but they do work well. A proper modern injection system is far far superior to any carb'd system in terms of economy/power/drivability. Even the early stuff is certainly worth running vs a carb, you just need to know how to work on it.
 

MonkeyButt70

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EFI is the equivalent of a man wearing a dress. Carb it and bring back when men were men!
If the carb is setup correctly, they work much better than EFI in my humble opinion.
 

Blackmagic94

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Uhh no. You know those pesky drain holes you have in EVERY vehicle's muffler? Yep, needed to drain the steam/condensation caused by temperature changes in the exhaust.

Heated O2 sensors turn the heater on immediately (it's the first test done by OBD2 monitors after the ignition event), so the sensor can start to work independently of the temperature of the exhaust or cat.

True if you get the sensor wet with a reversion pulse while it's at temperature it will most likely destroy it, but my point is that they can handle some moisture because they are designed to.

Getting back to the OP, you would have to be crazy to go back to carbs if you have EFI already. Yes the early systems are pretty crude, but they do work well. A proper modern injection system is far far superior to any carb'd system in terms of economy/power/drivability. Even the early stuff is certainly worth running vs a carb, you just need to know how to work on it.
It takes up to 30 seconds for a wideband to reach temp. So no the pcm doesn’t not check the temp sensor before start lol
 

SBMech

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It takes up to 30 seconds for a wideband to reach temp. So no the pcm doesn’t not check the temp sensor before start lol
Can you translate this? O2 sensors including "wideband" sensors are heated to enable them to reach the proper temp before they are accurate.....

Did you read my post as saying something different?
 

Blackmagic94

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Can you translate this? O2 sensors including "wideband" sensors are heated to enable them to reach the proper temp before they are accurate.....

Did you read my post as saying something different?
Yes. Your claim the pcm is using wideband info on startup or first running is wrong. In fact most standalone efi ignore the wideband data until a pre-determined coolant temperature has been reached as a threshold and then it goes into open loop. So no the pcm ain’t looking at shit from the wideband at that point or if the sensor has reached preheated temps


and again. Wet exhaust with water traveling down the inside of pipes mixed with exhaust gas will destroy a wideband and more importantly give a incorrect signal which is even worse.
 

SBMech

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Yes. Your claim the pcm is using wideband info on startup or first running is wrong. In fact most standalone efi ignore the wideband data until a pre-determined coolant temperature has been reached as a threshold and then it goes into open loop. So no the pcm ain’t looking at shit from the wideband at that point or if the sensor has reached preheated temps


and again. Wet exhaust with water traveling down the inside of pipes mixed with exhaust gas will destroy a wideband and more importantly give a incorrect signal which is even worse.
Never claimed anything you said right there dude. Open loop is when the system is in warm up mode using the coolant temp and outside air temp sensors to make fuel system adjustments along with the A/F meter, closed loop is when the PCM starts using the O2 sensors to trim fuel pulse width.

Day Drinkin?
 
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DRYHEAT

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Instigator

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On a side note this is the longest thread for me that I started! 😁
Is this going to be on a Ford or Chevy?
Stern drive, v drive or jet?
Ask those questions next and your thread will last all winter.

And when it slows down, ask how fast the current in the river will need to be to get on plane 🙃.
Lol
 
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