sv-wolf wrote:You may be right that carbs are cheaper, but I would have thought the opposite was true. Carbs are mechanically complex bits of fine engineering. Microchips can be turned out for a pittance these days.
I was wondering why it took manufacturers so long to start using FI in bikes. Could it just be that unlike in a car, carbs were part of the architecture and the 'look' of the bike. Anyone know?
Well, first off, fuel injection involves a lot more than just a chip. The injector mechanism itself is far and away a more complex bit of mechanism than any carburetor. And then you have to run pressurized fuel which involves a pump. And then there's the electronic architecture that involves a bunch of sensors and actuators to determine the right amount of fuel and precisely deliver it consistently across the rpm range.
A carburetor is fairly simple conceptually. When the throttle plate opens, the additional air flow uses Bernoulli's principle to suck fuel into the airstream. The trick is getting the jet sizes and positions right so the mixture is reasonable through the operating range. The more load and speed on an engine, the more air is pulled and fuel compensates to match.
Fuel injection must calculate the proper amount of fuel for each combustion event based on engine speed and load, operating conditions, ambient conditions as well as target emission levels, etc, throughout the operating map. For a 4 cylinder sport bike at a relatively moderate 6000 rpm, that's 200 calculations per second, or 1 precisely metered fuel event every 5 milliseconds or thereabouts.
I design engines for heavy trucks, so I don't know motorcycles that well, but I can think of a couple reasons why bikes have been slow to adopt fuel injection. First, bikes run at higher rpms than cars meaning there needs to be substantially faster processor speeds and that translates to $$$. Second, fuel injection requires the incorporation of an entire electronic and fuel pumping architecture which takes space, something bikes are not blessed with oodles of. Third, fuel injection is a whole different way of doing engine development. It requires more substantial engine mapping and testing to be able to cover the engine operating range. And finally, bike's are already fuel efficient and I don't believe they are under as much pressure from emissions regulations as other vehicles, so the technical pressure to move into more expensive technology just hasn't been there (YET).
Eventually, I'm sure all bikes will be fuel injected. For now, it's moving into high end bikes, where the cost can be recouped. It's optional or not offered where price points are still sensitive enough.
Mike 