should i change over to fuel injection?

[thumpar]

I like my EFI. It is a super simple TB injection. Troubleshooting is easy on these systems. It is really just an electric carb. When you get to the newer systems they can get pretty complicated. Mine starts just a tiny bit faster than the carbed boat I had but not a big thing. I do like the not having to set the choke. I would not pay to switch if it didn't come with it.

 

[scoflaw]

Carbs don't like to get too hot, and they really suck when it's cold enough where they ice up, and they certainly don't like a change in barometric pressure. Other than that, if you can operate them when the conditions are "just right" they do fine.

 

[Leardriver]

Where I live at high altitude, EFI is way better at fuel metering than carb. But, as everyone says, sell your boat and buy an injected one before you try to re-engineer everything.
I don't understand why claims are made about no additional power. The carbed 5.0 GL is 220 HP, the EFI is 260. Is there tuning to do to bring the carbed version up to 260?

 

[Scott06]

Four bbl carb would get you part of the way there. I believe the rest of hp difference is more ignition advance that can be utilized with more precise fuel mapping of mpi. I believe the camshaft is he same part number between 2 bbl and mpi engines

The 5.0 4 bbl partial engine I got from Michigan motorz is rated at 260 hp.

at altitude I can see where mpi with an o2 sensor for feedback would be a huge advantage vs re jetting... especially if you use your boat at multiple altitudes

 

[Scott Danforth]

Where I live at high altitude, EFI is way better at fuel metering than carb. But, as everyone says, sell your boat and buy an injected one before you try to re-engineer everything.
I don't understand why claims are made about no additional power. The carbed 5.0 GL is 220 HP, the EFI is 260. Is there tuning to do to bring the carbed version up to 260?

if you dont understand wrenching on motors, then you wouldnt understand the explanations. a 4-barrel carb and high-rise intake will get a 5.0 up to about 270hp as well. you can get about 330hp out of a 5.7 and over 500hp on a 7.4 big block. what EFI gets you is closer to the edge of the envelope on spark and fuel management, however it doesnt get you more power. the power comes from intake plenum volume, cylinder head geometry, piston geometry and cam timing profile.

 

[Leardriver]

Don't understand wrenching on motors? I work for a Nascar team and raced motocross for 25 years. I get motors. I was just curious about the claims that EFI doesn't make any more HP. Certainly you can change the carbed motor to make it a more efficient air pump, but it does seem that as delivered, out of the box, EFI has higher HP ratings than carbed

 

[Scott Danforth]

If you work on a NASCAR team than you fully understand cam profiles, metering signals, plenum volume, runner geometry, dynamic compression ratios, overlap, and lobe center as well as knock threshold and wave front propagation. that is what determines HP more so than the fuel dispensing system

you would also know that if you have one widget that you have for sale that produces 260hp, you cant quite have a similar widget using 50 year old technology for sale at the same output. that would not make good marketing and would not make as much profit because you couldnt sell the higher priced widget. you have to justify the higher priced widget. so as a company you put a poorly designed low profile carb manifold with each cylinder getting a different runner geomery on the 5.0 carb motor and a large plenum with equal length runners on the EFI motor

assuming the cam profile, spark timing profile, combustion chambers and pistons were identical, the motor with the larger plenum and equal length runners would product higher torque (therefore higher hp numbers) than the one with the poorly designed plenum and runners

 

[netting one]

It does have a weber carb. It was 42 degress out yesterday and water temp at 51 and did seem to restart in about 2-3 seconds. The warmer it get it seems to take 5-7 seconds. Ive you give it and throttle it really takes a long time wich tells me it doesnt need more fuel. maybe time for a carb rebuild? thanks all

 

[Scott Danforth]

could be choke needs to be adjusted.

 

[H20Rat]

Liquid gasoline doesn't burn, it must be a vapor. Fuel injection is inherently better at atomizing fuel than a carb will ever be, no matter how much you tune it. A fuel injection system will always be capable of slightly more horsepower and efficiency just for that fact alone. Now if you thrown in other variables such as changing engine parameters based on sensors, you gain even more power.


And I don't think DFI exists in the marine world, but that is where you can pick up some serious horsepower compared to a carb. An identical displacement engine can be +100hp or more and way better mileage if you compare it to a similar displacement carb engine. The DFI system in my car runs a mechanical fuel pump at 3000 PSI, with 300+hp and 300 ft/lb of torque at relatively low rpm on a 2.0L. There is zero chance a carb could ever do that, it simply isn't possible, because of how DFI operates.

 

[Scott06]

Volvo has direct injection on their new v6 & v8s

 

[scoflaw]

Liquid gasoline doesn't burn, it must be a vapor. Fuel injection is inherently better at atomizing fuel than a carb will ever be, no matter how much you tune it. A fuel injection system will always be capable of slightly more horsepower and efficiency just for that fact alone. Now if you thrown in other variables such as changing engine parameters based on sensors, you gain even more power.


And I don't think DFI exists in the marine world, but that is where you can pick up some serious horsepower compared to a carb. An identical displacement engine can be +100hp or more and way better mileage if you compare it to a similar displacement carb engine. The DFI system in my car runs a mechanical fuel pump at 3000 PSI, with 300+hp and 300 ft/lb of torque at relatively low rpm on a 2.0L. There is zero chance a carb could ever do that, it simply isn't possible, because of how DFI operates.

You forgot to mention the turbo

 

[Scott Danforth]

Liquid gasoline doesn't burn, it must be a vapor. Fuel injection is inherently better at atomizing fuel than a carb will ever be, no matter how much you tune it. A fuel injection system will always be capable of slightly more horsepower and efficiency just for that fact alone. Now if you thrown in other variables such as changing engine parameters based on sensors, you gain even more power.


And I don't think DFI exists in the marine world, but that is where you can pick up some serious horsepower compared to a carb. An identical displacement engine can be +100hp or more and way better mileage if you compare it to a similar displacement carb engine. The DFI system in my car runs a mechanical fuel pump at 3000 PSI, with 300+hp and 300 ft/lb of torque at relatively low rpm on a 2.0L. There is zero chance a carb could ever do that, it simply isn't possible, because of how DFI operates.

Pull the turbo and your LNF based motor falls on its face. My daily driver ia a 2liter LNF on its 2nd turbo.

Same 2 liter motor without the turbo is only 170hp, and the low to midrange is gone when you are naturally aspirated

2 liter cosworth from the 70's were about 190hp with a pair of webbers

 

[QBhoy]

Love the extra power and efficiency of my MPI. But hated it for a while when I had to sort out the usual niggles with it.
Also love the carbs I’ve previously had.
The fuel efficiency is almost unreal on my MPI. Honestly. It will use certainly less fuel than if it was a carb. There is no doubt. Part of the reason they produce more power (out the factory) compared to the carb equivalent is likely the way the fuel burns...but more than likely it’s because they rev higher than the carb with a different power curve. Their power band is usually at least 200 rpm up on the carb version.

To the chap earlier who said his takes a long time to start when cranking. Get it checked out or make sure the diz cap is good.

I always say it...and most know...but mpi and gxi not to be confused with efi and gli. Different animals and way of injecting.

Down side...the cost of the bloody spark plugs !!

 

[Scott Danforth]

QBhoy , my BBC spins to 7000 rpm if I wanted, and I can hold it there all day.

 

[QBhoy]

QBhoy , my BBC spins to 7000 rpm if I wanted, and I can hold it there all day.

Haha Scott. I’m certain that you know exactly what I mean. More rpm means more power...as long as the torque and essentials needed to provide it are present. A man a clever as yourself knows what I’m getting at. I also know what you mean by a well set up carb. Was actually trying to back you up a little with the main reason the mpi makes more power in general terms. The rpm range is higher than the carb.

Simple terms. This is why F1 cars and serious engines have crazy rpm figures. The serious engines in power boats with the big hp all see much higher rpm than your average everyday machine.

 

[QBhoy]

QBhoy , my BBC spins to 7000 rpm if I wanted, and I can hold it there all day.

Also. Totally with you on the idea of a well set up carb being probably just as capable in producing power bit in general terms the standard version variant between the carb and mpi sees the mpi with more power.
Your amazing engine turning at 7000 rpm is a different animal. Just the sort of engine I refer to above. To see 7000rpm on yours will involve and be the result of lots of things to make it do that and maintain the rpm. Imagine your carb will be set up perfectly and you’ll likely have fancy heads, ported, rods, cam, crank shaft and intakes etc ?

 

[QBhoy]

Common rail and individual injection will always make power easier than a carb we all know. Not to say a well set up carb won’t make power, but not as efficiently for sure.

 

[achris]

It does have a weber carb. .

About the best carb you can put on an engine. BUT, they have a problem with 'dribbling'... The passage sizes are very small, and petrol will continue to run through them after the engine is shutdown due, I believe, to 'capillary action'...

Very common problem on the V6s with the Weber in the 90's. Years ago I had a Weber 9600 carb apart and sitting on the bench, blew air through the one of the primary barrels, and that was enough to generate a fuel/air mixture. When I stopped the air flow, that barrel continued to 'leak' fuel until the float chamber was empty. I watched it happen! When I talked to a few carburetor 'experts', they told me that couldn't happen, yet I watched.

Apart from the long cranking restarts, that engine was absolutely flawless, and had it not been for that carb problem, I may still have it today. That said, I replaced it with the MPI version of the same engine, and I like this engine a lot more. Much easier starts, slightly more power and way, way less maintenance.

But the most important benefit is that it consumes about 25% less fuel. And in an era when the price of fuel is rising and our collective emissions are causing environmental problems, that fuel saving alone makes an MPI engine far better value than 100year old technology.

Chris........

 

[havoc_squad]

Haha Scott. I’m certain that you know exactly what I mean. More rpm means more power...as long as the torque and essentials needed to provide it are present. A man a clever as yourself knows what I’m getting at. I also know what you mean by a well set up carb. Was actually trying to back you up a little with the main reason the mpi makes more power in general terms. The rpm range is higher than the carb.

Simple terms. This is why F1 cars and serious engines have crazy rpm figures. The serious engines in power boats with the big hp all see much higher rpm than your average everyday machine.

Just for clarification, F1 race cars out-do most other engines in torque and horsepower of the same displacement is because of the crazy high compression ratio in those engines.

Because of the very tight cylinder tolerances, the engines have to be pre-warmed to operating temp before starting them.