Techa Tipz: Motorcycle EFI vs Carbs

1] Differentiation between EFI and Carburator type,

Carburetor system:

Principles: The carburetor works on Bernoulli's principle: the faster air moves, the lower its static pressure, and the higher its dynamic pressure. The throttle (accelerator) linkage does not directly control the flow of liquid fuel. Instead, it actuates carburetor mechanisms which meter the flow of air being pulled into the engine. The speed of this flow, and therefore its pressure, determines the amount of fuel drawn into the airstream.

A carburetor basically consists of an open pipe through which the air passes into the inlet manifold of the engine. The pipe is in the form of a Venturi: it narrows in section and then widens again, causing the airflow to increase in speed in the narrowest part. Below the Venturi is a butterfly valve called the throttle valve — a rotating disc that can be turned end-on to the airflow, so as to hardly restrict the flow at all, or can be rotated so that it (almost) completely blocks the flow of air. This valve controls the flow of air through the carburetor throat and thus the quantity of air/fuel mixture the system will deliver, thereby regulating engine power and speed. The throttle is connected, usually through a cable or a mechanical linkage of rods and joints or rarely by pneumatic link, to the accelerator pedal on a car or the equivalent control on other vehicles or equipment.

Fuel is introduced into the air stream through small holes at the narrowest part of the Venturi and at other places where pressure will be lowered when not running on full throttle. Fuel flow is adjusted by means of precisely calibrated orifices, referred to as jets, in the fuel path.

Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive engines, having replaced carburetors during the 1980s and 1990s. A variety of injection systems have existed since the earliest usage of the internal combustion engine.

The primary difference between carburetors and fuel injection is that fuel injection atomizes the fuel by forcibly pumping it through a small nozzle under high pressure, while a carburetor relies on suction created by intake air accelerated through a Venturi tube to draw the fuel into the airstream.

Modern fuel injection systems are designed specifically for the type of fuel being used. Some systems are designed for multiple grades of fuel (using sensors to adapt the tuning for the fuel currently used). Most fuel injection systems are for gasoline or diesel applications.

The functional objectives for fuel injection systems can vary. All share the central task of supplying fuel to the combustion process, but it is a design decision how a particular system is optimized. There are several competing objectives such as:

• Power output

• Fuel efficiency

• Emissions performance

• Ability to accommodate alternative fuels

• Reliability

• Drivability and smooth operation

• Initial cost

• Maintenance cost

• Diagnostic capability

• Range of environmental operation

• Engine tuning

The modern digital electronic fuel injection system is more capable at optimizing these competing objectives consistently than earlier fuel delivery systems (such as carburetors). Carburetors have the potential to at

Driver benefits

Operational benefits to the driver of a fuel-injected car include smoother and more dependable engine response during quick throttle transitions, easier and more dependable engine starting, better operation at extremely high or low ambient temperatures, smoother engine idle and running, increased maintenance intervals, and increased fuel efficiency. On a more basic level, fuel injection does away with the choke, which on carburetor-equipped vehicles must be operated when starting the engine from cold and then adjusted as the engine warms up.

Environmental benefits

Fuel injection generally increases engine fuel efficiency. With the improved cylinder-to-cylinder fuel distribution of multi-point fuel injection, less fuel is needed for the same power output (when cylinder-to-cylinder distribution varies significantly, some cylinders receive excess fuel as a side effect of ensuring that all cylinders receive sufficient fuel).

Exhaust emissions are cleaner because the more precise and accurate fuel metering reduces the concentration of toxic combustion byproducts leaving the engine, and because exhaust cleanup devices such as the catalytic converter can be optimized to operate more efficiently since the exhaust is of consistent and predictable composition atomize fuel better. More efficient because, this fuel injection system operates

such that excess fuel from the injectors is redirected back to the fuel main filter or tank for recirculation unlike carburetor type where fuel are totally introduced into the combustion chamber and reliant on the manual settings done on the unit.

SCHEMATICS – ELECTRONIC CONTROLS

To highlight more on FI tech bits and pieces; There are two types of FI - open loop and closed loop systems. Open loop systems have pre-programmed parameters and targets for optimization. If you target more than 14:1 AFR [Air Fuel Ratio] during WOL (wide open throttle),the air and fuel will be metered and adjusted to achieve this accordingly regardless of any engine rpm or fuel changes. Closed loop systems relies on an O2 sensor (wideband or single-band) monitoring the exhaust for real time feedback to the ECU giving it the capability to range AFR on the fly or in real time. Even if you have a pre-programmed fuel map, it’s compensating because of the self-adjusting feature. Unless you have your Oxygen sensor welded on your exhaust pipe, then you have an Open Loop FI, if not then Closed loop is the Motorcycle set up. Either of these set up makes it more fuel efficient than the carburetor type. There is another variation of the FI but requires more investment, but you attain a more stable, smooth, friendly ride. This features has the IAC (idle air controller), added sensors, better fuel feed ranges or maps, etc.

Note the difference. Most of the FI for MC nowadays uses open loop systems (big bikes equipped with FI usually use closed looped FI designs). Of course, cheaper, less parts, less maintenance activities, as they say in its barest form FI. The heart of the FI system is the ECU[Engine Control Unit-the computer box, in layman’s term] and most, if not all aftermarket ECU's are fully programmable, while most factory ECU's are not (unless it's been already hacked by users).

FI some DOs and DON’Ts: Very typical of us to tinker on our priced possessions. More often than not, it wouldn’t last a week or two that we would alter it to our taste like engine upgrades, exhaust systems, racing kits like CDIs. Note that FI [open looped systems], our engine will stay fuel efficient as long as the engine and peripherals is unaltered. The FI’s ECU are pre-programmed parameters are tuned only to stock parts, and changing even the exhaust system definitely would affect your overall fuel economy and power. Even just changing fuel types/octane rating will have a direct effect on fuel economy (for better or for worse). Same goes with electrical upgrades. It would be interesting to note that FI systems are very sensitive to its input voltage that accessorizing it with any power hungry item[s] in an FI Motorcycle will have a direct effect on its performance. Again, since you’re into dressing it up like installing HIDs, power horns, MP3 boosters and what have you, then you need to invest on upgrades on your charging system to compensate for these increase electrical power requirement. Not doing so, will also result to early damage to your ECU and its related sensors. Worse, if any OEM would check on your unit, such defect on your FI system’s Factory warranty maybe void.

Your choice, if you got an FI unit to serve its rightful purpose of fuel economy and efficiency then enjoy it to the fullest. Otherwise, an upgrade lingers in your vein-you want more power and speed, be prepared for the added investment that comes with it; look for closed loop systems to have the best of both worlds (check if the exhaust have an O2 sensor), upgrade your electrical charging system, source hack able ECUs or stick with the Carburetor type system. Excerpts taken fr: FB@Sixace.

2] Why manufacturers are slowing turning to EFIs MCs,

With the worldwide clamor for cleaner air emissions as enforced, we’re moving up from UN-ECER 40 Exhaust Emission (Euro 2) in 2012 to the current UN-ECER 40 Exhaust Emission (Euro-3) by 2015 where World-wide registration started since 2007.

Supersession of carburetors

In the 1970s and 1980s in the US and Japan, the respective federal governments imposed increasingly strict exhaust emission regulations. During that time period, the vast majority of gasoline-fueled automobile and light truck engines did not use fuel injection. To comply with the new regulations, automobile manufacturers

often made extensive and complex modifications to the engine carburetor(s). While a simple carburetor system is cheaper to manufacture than a fuel injection system, the more complex carburetor systems installed on many engines in the 1970s were much more costly than the earlier simple carburetors. To more easily comply with emissions regulations, automobile manufacturers began installing fuel injection systems in more gasoline engines during the late 1970s.

The open loop fuel injection systems had already improved cylinder-to-cylinder fuel distribution and engine operation over a wide temperature range, but did not offer further scope to sufficient control fuel/air mixtures, in order to further reduce exhaust emissions. Later Closed loop fuel injection systems improved the air/fuel mixture control with an exhaust gas oxygen sensor and began incorporating a catalytic converter to further reduce exhaust emissions.

Fuel injection was phased in through the latter 1970s and 80s at an accelerating rate, with the German, French, and U.S. markets leading and the UK and Commonwealth markets lagging somewhat. Since the early 1990s, almost all gasoline passenger cars sold in first world markets are equipped with electronic fuel injection (EFI). The carburetor remains in use in developing countries where vehicle emissions are unregulated and diagnostic and repair infrastructure is sparse. Fuel injection is gradually replacing carburetors in these nations too as they adopt emission regulations conceptually similar to those in force in Europe, Japan, Australia, and North America.

Many motorcycles still utilize carbureted engines, though all current high-performance designs have switched to EFI. With abovementioned economics and performance, this is paving the way for the shift to Fuel Injection systems not only in the big bike categories but now on the small to medium sized engine motorcycles.

3] Is the Aftermarket sales ready for EFI MCs?

Leading Japanese, other foreign branded motorcycle are currently introducing FI in their small to medium size engine models. European and US branded big bikes are now mostly equipped with FI. Backed by technology from their mother companies, they use state of the art components that would last them years [under normal use, unaltered] before major parts replacements are needed. In the meantime, as widely practiced by these OEMs, their market expansion development strategies comprises of continued monitoring of sales/area, training of these latest innovations to all major dealers, sub-dealers and major service centers. By way of this, they establish MADs [Monthly Average Demands] for parts and consumables that must be on hand to all these areas. Feedback systems are in place to monitor, control parts demand, quality performance, innovation needs. These OEMs have their own respective Aftersales of Standard parts or Access business activities; these Accessories meet their product standards, and duly certified. A regular clause in their Warranty policy of their products that only accredited Parts, Service repair and accessories are to be performed and used.

Aftermarket products; abundance is starting now, especially with the influx of importations from different entities who cater to replacement, to some extent genuine parts from all over the world, even China. The only hitch is that, with the advent of FI technology now being introduced by leading manufacturers, the use of these aftermarket parts is an avenue that your unit warranty will be void. Any alteration, installation of these A/M parts must bear approval of the Accredited Service Center/Dealer, much worse, approval from the Factory itself as this pose warranty issue.

4] Are there training centers for individual mechanics so that they will be equipped for FI MCs?

Leading brands thrust to penetrate market starts first with the 3S – Sales, Spare-Parts and Service. Service activities form a major role in promoting products. Some leading brands have set up Driving, Service training facilities to enhance these product innovations / introduction. Honda has Riding Academy and some other independent riding schools that include training on FIs. They ensure that these products, before any major sales are done, Networks such as Dealers, Service Centers are equipped with the know-how on the products. Even independent parts and service dealers have their own in-house training activities. Leading Technical Schools such as Don Bosco, Samson Tech to name a few have been including this in their curriculum. TESDA and other trade schools have short courses on FIs to train our youth on this new technology on top of the standard automotive technology course on hand.

5] Is it possible for Carb MC to convert to EFIs?

Possible, remember, prior to 1950s, gas engine vehicles were run by carburetor type. A matter of removing all the installed FI unit and its peripherals-injectors, sensors, ECU, plugging all ports where the sensors were installed, removal of the high pressure pump, replacing it with the right sized carburetor. Calibrate or fine tune the carburetor accordingly should do the trick, but this entails tedious activity such as removal of sensors installed internally the engine [such as temperature, rpm sensor, unless this has a feature that it can be left there and doesn’t affect engine performance; or maybe in the future you would want to return to FI system], rewiring and some body aesthetic works.

@#nandycerdeniaaturserviz