Kawasaki Ninja ZX Forum banner

1 - 2 of 2 Posts

·
Registered
Joined
·
1,623 Posts
Discussion Starter #1
Direct Injection Opens The Door For More Usable Turbocharged Motors
By Alex Edge

Regarding direct injection, you know that by allowing more precise control of fuel delivery, direct injection opens the door for engineers to design a bike with a higher compression ratio that will still run safely on pump gas. Direct injection doesn't just allow higher compression ratios, though - it allows higher cylinder pressures overall.

For this reason, direct injection is a perfect fit with turbocharging. The ability to design a motor to operate with higher overall cylinder pressures means that engineers can build an engine with a higher compression ratio (compared to the typical 8:1-9.5:1 ratio found on most turbocharged motors), which increases exhaust gas velocity and volume, thus 'spooling' the turbocharger at a lower rpm. At the sime time, they can still run the same boost pressure (in psi) used on a typical turbocharged production engine (5-11psi) - which results in the higher overall cylinder pressures I mentioned.

So what's the bottom line? A direct-injection turbo engine will spool the turbo sooner (at a lower rpm), as well as have a more linear powerband - a result of the higher compression ratio, which helps the motor make more power when 'off' boost (i.e. before the turbo has spooled).

Apparently the results are good enough for BMW, as the US Automotive press report that the German company plans to offer a twin-turbocharged, direct-injection inline six in it's forthcoming range of 3-Series coupes. BMW has traditionally eschewed turbochargers and the consequent laggard throttle response - linear and snappy engine response is a hallmark of the company's 'Ultimate Driving Machine' slogan. Apparently, BMW feels that technology has advanced far enough to make this paradigm obsolete - company spokesmen claim the new turbo six is just as responsive as their traditional naturally-aspirated motors have been, with turbo lag all but eliminated by the higher compression ratio allowed by direct injection.

Does this mean that turbocharged sportbikes are just over the horizon? Right now, we would say it's a distinct possibility that when the motorcycle manufacturers bring direct injection to the market, turbocharging won't be far behind, at least for some models. However, the real question is: how long will it take for the OEMs to begin producing direct injection bikes? We're not sure, but we expect it to happen quickly, probably with the next two to three years.

Source: Motorcycle Daily
 

·
Registered
Joined
·
1,623 Posts
Discussion Starter #2
The Sportbike Engine of the Future: Fuel Delivery

The Sportbike Engine of the Future: Fuel Delivery
By Alex Edge

In my two previous articles about the future of sportbike engine design, I discussed different valve control systems and their potential for making more horsepower on street-ridden sportbikes. This time, I'm going to talk about fuel injection, and how new advances in the way fuel is delivered could result in more powerful production sportbikes.

First of all, I thought I'd offer a quick explanation of how fuel injectors work, for those of you still stuck in the carburetor era. A fuel injector is basically just an electronically-controlled valve - a signal from the ECU opens the injector, and pressurized fuel sprays out through a nozzle which is designed to atomize the fuel (turn it into an extremely fine mist that can mix homogenously with the intake air). The fuel comes from the fuel rail, which is nothing more than a tube which gets pressurized fuel from the fuel pump and runs it into the back end of the injectors.

For optimum power production and efficiency, the goal is to get the fuel to atomize as finely as possible and for it to mix evenly throughout the intake charge, thus becoming distributed evenly throughout the cylinder before being ignited by the spark plug. Uneven distribution of fuel, or fuel that falls out of atomization and clusters into droplets on the inside of the combustion chamber will result in weak power and poor mileage, or even pre-ignition or detonation.

Advances are made every year in the design of the injector's atomizing nozzle, which usually results in small power increases. In recent years, many sportbike engines have picked up bigger gains by switching to a dual-injector setup, with the second set of injectors positioned above the throttle body (prior to the butterfly) pointing directly down towards the 'throat' of the intake tract (traditionally, injectors are placed in the sidewall of the intake port or manifold just after the throttle body butterfly). At high RPM, when the engine is producing a huge vaccum and sucking a massive volume of air into the throttle bodies, placing the injectors further back in this airstream aids atomization and helps distribute the fuel more evenly. This can provide horsepower increases in the 4-5% range - but only in the upper RPM.

So now you know what's being done right now, but the question is: what will happen next? Most experts believe that the next big step in fuel delivery will be the switch to direct injection, where special injectors spray the fuel directly into the combustion chamber rather than delivering it into the intake tract.

Several car companies have sold production automobiles with direct injection gasoline engines, with Audi being one of the biggest users of this new technology. Because direct injection provides the ECU with more precise control of fuel delivery, Audi has been able to run higher compression ratios in its direct injection engines than was previously possible when using traditional fuel injection. This can result in higher horsepower and torque outputs, in the range of 10% in some cases.

Another beneficiary of direct injection is fuel mileage. During light-load conditions (part-throttle cruising), the engine can be run in an extremely lean condition, again due to the more precise control of fuel delivery which is offered by direct injection. This opens the doors to mileage increases of as much as 50% when spending long periods of time cruising at part-throttle, as when traveling on the freeway.

Does direct injection have any drawbacks? Well, it does require more expensive hardware than traditional injection, as both the injectors and the ECU are more advanced than those found on current production bikes. However, this is a minor hurdle, and we expect to see direct injection appear on large volume production motorcycles within the next two years.

Source: Motorcycle Daily
 
1 - 2 of 2 Posts
Top