502MagMPI conversion to Carb
#21
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Pat,
I am very interested in this project, as I'd love to go the other direction on my engine. After years of working with EFI both at GM as well as on my own, I'm completely in awe at just how HORRIBLE a job a carb does even when it's tuned "perfectly". Cyl-cyl fuel balance is horrible, resulting in having to run the entire engine way richer than it should need. If you keep the manifold cool for max power, it kills idle and fuel economy. If you size the carb right for part throttle, you lose 20hp on top....etc, etc. All compromises I NEVER had to deal with on EFI.
I wish I was near you. I'd love to be able to help you out. I want to get some experience with MEFI. One possible solution is to keep the complete fuel system, but change to an aftermarket ECU.
If you do go with the carb, I'll be interested in how much driveability you think you lose.
I am very interested in this project, as I'd love to go the other direction on my engine. After years of working with EFI both at GM as well as on my own, I'm completely in awe at just how HORRIBLE a job a carb does even when it's tuned "perfectly". Cyl-cyl fuel balance is horrible, resulting in having to run the entire engine way richer than it should need. If you keep the manifold cool for max power, it kills idle and fuel economy. If you size the carb right for part throttle, you lose 20hp on top....etc, etc. All compromises I NEVER had to deal with on EFI.
I wish I was near you. I'd love to be able to help you out. I want to get some experience with MEFI. One possible solution is to keep the complete fuel system, but change to an aftermarket ECU.
If you do go with the carb, I'll be interested in how much driveability you think you lose.
Overall, I think you can get EFI closer to dead on, but you have to have the right manifold setup, and you have to have it in the dyno making run after run to get it just right. That can turn into a pretty big financial investment for a 500 hp engine.
#22
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Guys I would rather run the EFI for sure.
I am just done putting money into this old MEFI-1 system.
If/when I go back to EFI, I'll use my newer MEFI-3 computer and harness.
I'll also have an O2 sensor bung added to the risers to double check the mixture.
I am just done putting money into this old MEFI-1 system.
If/when I go back to EFI, I'll use my newer MEFI-3 computer and harness.
I'll also have an O2 sensor bung added to the risers to double check the mixture.
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#23
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I can't even imagine trying to calibrate any efi system by mail!!! Seems a lot of people around here try, and almost all turn into a nightmare. If you're going to try to modify an EFI engine, you HAVE to have the ability to monitor and change the calibration at the boat. Imagine trying to tune a carb through the mail everytime you needed to change a jet????
I've been hearing good things about this new MEFI TUNE system. I'm anxious to try it out. Some systems are easy to tune and some are clumsy, but ALL are easier to tune than a carb. The only reason people have trouble tuning an EFI is because they try to play around with too many variables at once or they just don't understand how an IC engine works. Of course this assumes the system is functioning correctly, and that's a BIG if when we're talking about electrons
You also have to have the right manifold to start with. Trying to make over 500hp with a manifold and throttle that are only made for 450hp max is always going to be an exercise in frustration.
I've been hearing good things about this new MEFI TUNE system. I'm anxious to try it out. Some systems are easy to tune and some are clumsy, but ALL are easier to tune than a carb. The only reason people have trouble tuning an EFI is because they try to play around with too many variables at once or they just don't understand how an IC engine works. Of course this assumes the system is functioning correctly, and that's a BIG if when we're talking about electrons
You also have to have the right manifold to start with. Trying to make over 500hp with a manifold and throttle that are only made for 450hp max is always going to be an exercise in frustration.
#24
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I have in my stockpile of parts an AZ Speed intake, throttle body, camshaft, and other parts from a 500EFI. It has been my plan for a while to rebuild my 502MagMPI into a 500EFI clone. Getting the proper calibration for that combo should not be a problem. We’ll see if I have the time and $$ this winter. Right now, I’d like to just get the thing running OK to finish out the last 6 weeks or so.
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I don't know iif it is to any help but how can a MEFI-1 get stuck in knock retard mode? If I recall correctly knock retard is controlled by the knockmodule which in a knock event delays the ignition trigger signal from the distributor IC to the ECU.
The ECU doesn't have a clue if there is knocking going on or not. That is how simple this generation of MEFI ecu's are.
The ECU doesn't have a clue if there is knocking going on or not. That is how simple this generation of MEFI ecu's are.
#26
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I don't know iif it is to any help but how can a MEFI-1 get stuck in knock retard mode? If I recall correctly knock retard is controlled by the knockmodule which in a knock event delays the ignition trigger signal from the distributor IC to the ECU.
The ECU doesn't have a clue if there is knocking going on or not. That is how simple this generation of MEFI ecu's are.
The ECU doesn't have a clue if there is knocking going on or not. That is how simple this generation of MEFI ecu's are.
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I can't even imagine trying to calibrate any efi system by mail!!! Seems a lot of people around here try, and almost all turn into a nightmare. If you're going to try to modify an EFI engine, you HAVE to have the ability to monitor and change the calibration at the boat. Imagine trying to tune a carb through the mail everytime you needed to change a jet????
I've been hearing good things about this new MEFI TUNE system. I'm anxious to try it out. Some systems are easy to tune and some are clumsy, but ALL are easier to tune than a carb. The only reason people have trouble tuning an EFI is because they try to play around with too many variables at once or they just don't understand how an IC engine works. Of course this assumes the system is functioning correctly, and that's a BIG if when we're talking about electrons
You also have to have the right manifold to start with. Trying to make over 500hp with a manifold and throttle that are only made for 450hp max is always going to be an exercise in frustration.
I've been hearing good things about this new MEFI TUNE system. I'm anxious to try it out. Some systems are easy to tune and some are clumsy, but ALL are easier to tune than a carb. The only reason people have trouble tuning an EFI is because they try to play around with too many variables at once or they just don't understand how an IC engine works. Of course this assumes the system is functioning correctly, and that's a BIG if when we're talking about electrons
You also have to have the right manifold to start with. Trying to make over 500hp with a manifold and throttle that are only made for 450hp max is always going to be an exercise in frustration.
#28
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efi vs carb
i have been also thinking about a change from efi to carb.what i want to know is how much fuel comsumption do you give up w/the carb?
#29
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Any chance you would let me test your MEFI1 ECM (no charge)? I have a test bench for MEFI 1 and 2 controllers, with knock module and everything. I am very curious about how/why yours failed.
Dave
#30
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PM me your address, and I'll send it to ya.
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