My understanding is that 'normal aspiration' is just a (hopefully advanced) form of traditional carburetter (i.e. fuel is drawn into cylinders from tank by a mixture of gravity and suction) whereas 'fuel injection' is where fuel is pumped into the cylinders.
What I find surprising is that some F1 cars and many other high performance cars and motorbikes have 'normal aspiration'. I can remember people like Jaguar and Kawasaki boasting about 'normal aspiration' when they previously boasted about 'digital fuel injection'.
Surely electronic engine fuel flow control & measurement systems, and engine management systems are able to out-perform 'gravity & suction' these days?
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'normal aspiration'
Air is sucked into the engine by the vaccum created when the piston moves down.
'"not" normal aspiration'
Air is forced (blown) into the cylinders by a turbo-charger.
Carburettors and Fuel-injection systems are very similar, just that carburettors use a venturi which creates a pressure-difference, which sucks fuel in, and Fuel-injection injects the fuel without relying on that pressure difference.
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I was always under the impressiont that "normally aspirated" meant an engine nof fitted with a turbo or supercharger ("forced induction"?)
Andy
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Andy is correct and I think Lizard is confusing his terms. A normally aspirated engine can have a carb OR be fuel injected. , in other words 'aspiration' does not dictate what the method of fuel delivery is. A normally aspirated engine draws air into the cylinders solely due to the vacuum created by descendng pistons. An aspirated engine can also have either a carb or be fuel injected but in this case the air delivery is enhanced by being blown into the cylinders, either by a turbo charger or by a supercharger. (Turbo charger is driven by exhaust gas supercharger is normally driven off the fan belt). You cannot answer the question 'What is better' without stipulating what you want to achieve. For example: more power, or better fuel consumption, or longer service intervals, or long life or ease of maintenance, or cheaper production costs etc etc. Any one of those objectives will be at the expense of one of the others to a greater or lesser extent.
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Part one has been answered (NA / FI - maybe it was the dual FI that added to the confusion Fuel Injection / Forced Induction!).
Performance bikes are now fuel injected not so much for performance as to keep within ever more strict emission regulations. A common complaint on injected bikes is hesitation/stumbling going from a lightly trailing throttle to a slightly open throttle. Carbs seem to be immune to this.
Martin
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Some performance bikes actually use a form of forced induction - hoses are connected to vents on the frontal face of the bike that use the forward motion of the bike to force air into the intakes. This differs from traditional forced induction, such as turbocharging or supercharging, that require a pump of some description to forcibly induct air. This is also different to the simplr act of locating the air inlet at a convenient site, as part of the principle (as for turbo- and superchagers) is to compress the air, in order to acheive a higher mass flow rate through into the cylinder. The limiting factor, in terms of performance, on most engines is the amount of air that can be inducted into the cylinder.
This principle, sometimes called ram induction, has received much attention in the military and aviation fields, where certain rocket turbines do not require compressors as the forward motion of the rocket provides sufficient induction and compression for combustion - the now defunct 'Bloodhound' anti-aircraft missile is a good example.
Matt
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Sorry, had to post this bit sperately, must be limit on post lengths.
A significant problem with some fuel injected engines (normally aspirated or otherwise) is the lack of mixing of fuel and air, as the fuel is injected immediately prior to the cylinder and doesn't always get evenly dispersed within the 'packet' of air for each cylinder. Multi-injector setups offer better control, as there is an injector for each cylinder, but there remains the problem of ensuring good mixing. Poor ixing results in a variable air/fuel ratio within the cylinder, with some areas rich and others lean, degrading combustion and reducing performance. This also happens with carbed engines, but as the fuel takeup is more 'continuous' (there isn't one discrete injection of fuel) there is generally a better and more consistent air-fuel ratio, although unlike injection it can't be altered for various operating conditions.
More modern injected engines may have addressed this (I know that tumbling is deliberately encouraged by profiling the cylinder head and ports), but I haven't looked at it for a while. This might explain why some bikes hesitate at low throttle, as there isn't enough mixing of the air to promote good combustion?
Matt
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Normal aspirated engine is what is known as a scavenger.even turbos are the same.supercharger forces air into cylinder as air is forced into combustion chamber.carb or injection both work in the same way.only difference is injection is more controlled ie single point has to supply all cylinders.multi point only supply one at a time.various probs occur with this method which would take a while to explain but I think covered by above post.your point as to gravity and suction.suction only applies to air intake.not fuel.fuel needs to be pumped from tank to engine.cant see where gravity comes in??
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Was mech1
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If you think you have fuel-injection problems, think of what pilots go through:
www.lycoming.textron.com/main.jsp?bodyPage=/suppor...l
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