TBI not carb?

hostage

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May 4, 2010
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I have a basic understanding of motors and I assumed my 2000 Maxum 1900 SC had a carborated 4.3L v6 merc @ 190hp. My mechanic told me today it is actually Throttle Body Injection. What and how does it compare to carborated motors? Is it better etc, how is it for boating, etc?

Thanks,

Hostage
 

Boomyal

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Aug 16, 2003
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Re: TBI not carb?

TBI is a step up from a carburetor, IMHO. It is controlled by a computer and is therefore more precise than a carburetor. TBI was really a precursor to the sequential multiport fuel injection.

Not a total expert on marine versions but I believe the computer uses a mapped function as you cannot run an oxygen sensor in an exhaust/water stream.

It should give you better starts, quicker warm up and better fuel efficiency.
 

bruceb58

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Mar 5, 2006
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30,454
Re: TBI not carb?

One of the main benefits is probably in starting from cold and acceleration. When you really move the throttle fast on a carb, you can create a lean condition because you have a low vacuum condition and there isn't a large enough air flow through the carb venturi to compensate. That is why carbs have accelerator pumps to compensate for this condition. Not needed on an injection system.

When the engine is cold, a fuel injection sytem is more precise in richening up the mixture when cold and can control the amount of fuel deliverd directly in proportion to the engine temp as it warms up.

Fuel injection systems tend to be a little more efficient because of the way the fuel is atomized. A TBI system is not nearly as good as a multiport system though because it still suffers the drawback of a carb where the TBI body is still different lengths away from the cylinders just like a carb.
 
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