Comparison of carburetor injection

Posted on by admin

Table of contents

motorcycles

Comparison carburetor / injection

Comparison carburetor / injection
(Ge) mixed calculation

The days when the good old carburettors were responsible for the mixture preparation seem to be over. Or? A generation comparison of the BMW F 650 and Honda CBR 600 F.

Stefan Kaschel, Waldemar Schwarz

08/13/2001

“The Times they are a changin?” Sang Bob Dylan, and the bard was right. Nothing remains as it is. If final proof was required, it will manifest itself at the latest at the showdown of the current BMW F 650 and CBR 600 F with their predecessors, who were only one year old. Modern injection technology on the one hand, the carburetor as the last polished bastion of traditional mixture preparation on the other. Comparative trips don’t necessarily mutate into a condolence walk, in which the merits of the past are praised in order to make the last rest of the jets and needles more bearable?
Not necessarily. Because nowhere else do some Japanese manufacturers in particular rely so tenaciously on tradition as in front of the intake ducts of motorized two-wheelers. The carburettors, which have been tried and tested a million times, are inexpensive and meet most requirements quite well. But new pollutant limit values ​​relentlessly reveal the limits of traditional technology. Reactions to exhaust gas composition by means of lambda probes and corresponding regulation of the mixture for the optimal function of a catalytic converter pose real problems for conventional gas factories.
Even the most stubborn proponents of the pure carburetor theory admit that stricter exhaust gas limits for motorcycles (see also page …) without fuel injection and a regulated catalytic converter are not? or only in a few exceptional cases ?? are to be created. There is no doubt that injection systems have a head start on technology. You can record constantly changing parameters of the environment such as air pressure and temperature and adapt the mixture to them in milliseconds. Nevertheless, the question arises: What does modern mixture preparation actually do? MOTORRAD went to the compulsory (exhaust test bench) in the freestyle, compared the consumption on the autobahn and country road, examined responsiveness and power delivery in the flat country and at around 2500 meters above sea level (Timmelsjoch), in short, checked the state of affairs both with the large individual cubic capacity of the BMW F 650 as well as the Honda CBR 600 with four small displacements.
But one after the other. On-site meeting at the type test center of TuV Automotive in xxxxxxxxxx. In addition to the not very practice-relevant motorcycle cycle, the car cycle with cold start and cross-country travel is measured on the exhaust test bench in order to discover what the different systems can achieve in areas outside of the legal requirements and how they behave in comparison to the car. The BMW F 650 with carburettor and unregulated catalytic converter, which emits more carbon monoxide (CO) than is currently permitted, is striking. The carburettor Honda manages the limit values, but also has high concentrations of CO (see page ..). Exemplary are the counterparts with injection and regulated catalytic converters, which undercut their predecessors by up to 21 times in terms of the individual pollutant components. The F 650 in particular shows the potential of the latest technology. In the car cycle, it almost achieves the Euro 3 limit values ​​for cars, with the exception of nitrogen oxide emissions that are a little too high.
And put one more on top as the icing on the cake. With a consumption of 2.7 liters per hundred kilometers according to the DIN standard of the passenger car, it clearly undercuts the three-liter Lupo from VW, which has a fuel-efficient direct-injection diesel engine, and thus becomes a 2.5-liter motorcycle. At least in theory. Or rather cyclically. Because on the road, things look different with cars too. Worse. Still good for the new BMW F 650. Because of all four motorcycles it is the most reluctant to use expensive fuel. For example, 3.6 liters are sensationally low on the country road, even among fuel-saving masters, as is the 4.5 liters at 140 km / h. The old F 650 also has nothing to oppose when it comes to consumption: the higher the speed, the greater the disadvantage. At 160 km / h it is a whopping 1.9 liters per 100 kilometers. So the advantage of injection across the board.
At least at BMW. The top class CBR 600 F shows that the brave new world of maps and parameters can also have its downsides. Its motto: The faster, the thirstier. If the injection Honda is at 80 km / h and on the country road still on a par with the carburettor model and has a slight advantage at 100 km / h, the gap between 120 km / h and higher and culminates at a constant 200 km / h in an additional consumption of over two liters to the detriment of the new CBR.
How can that be, given the many electronic helpers (see diagram) that provide all the necessary information for the optimal amount of fuel to be injected at all times? The answer is buried deep in the vastness of the map, that three-dimensional structure in which a certain injection time is assigned to every conceivable operating state. And precisely at this point there are still development deficits. Optimized for certain areas, the Honda technicians have not yet done their homework in many areas of the company. The decades of experience of our car colleagues in the development of characteristic maps cannot simply be transferred to the completely different conditions of comparatively small-volume motorcycle engines; glaring experience deficits are noticeable here, as with other manufacturers. This can only be determined to a certain extent when driving, but it can be determined at the petrol station. See Injection CBR.
In this case, the system-related advantages of injection can only really be enjoyed under extreme conditions. At high altitudes, for example, on the Timmelsjoch, where the air is getting thinner. Here the carburetor has only limited chances to react, continues its usual program. The result: The mixture is over-rich, the power falls into the cellar, the injection model pulls up and away in all speed ranges (with the exception of a trailer at a good 2000 rpm), while in the lowlands the carburettor-equipped CBR 600 up to its torque drop between 5000 and 6000 / min can even record advantages.
The two BMWs offer a different picture. The new F 650 is always ahead of the game. At sea level ?? and especially in the high mountains. If her predecessor drives up and away on the approach to Timmelsjoch, it is not impressed by 2500 meters of altitude either. In view of the low consumption, a mature achievement. Advantage through technology. Honda, on the other hand, should reconsider the mixture calculation for the CBR 600 F..

Comparison of pollutants

On the exhaust test bench, two Honda CBR 600s, one with a carburetor, the other with injection and a regulated catalytic converter and a BMW F 650 with a carburetor and an unregulated catalytic converter and one with an injection and regulated catalytic converter, had to prove their environmental compatibility. The pollutants were determined in the passenger car cycle, which also includes the motorcycle cycle ECE 40, but the exhaust system also records the cold start with warm-up phase and the extra-urban cycle. With a regulated catalytic converter, Honda’s injection engine emits slightly lower amounts of pollutants than its carburetor counterpart during a cold start. When warm, the 2000 model reduces pollutants by around 16 to 22 percent. This is not the case with the injection variant, whose catalytic converter reduces pollutant emissions by a whopping 42 to 86 percent in the warm cycle after the operating temperature has been reached. In the extra-urban cycle, the injection Honda then increases proportionally more pollutants than the carburettor variant, which is also reflected in consumption. The unregulated catalytic converter in the BMW F 650 is obviously not working properly. Even when it is warm, the CO values ​​hardly drop. Despite the U-Kats, the F 650 clearly falls short of the current limit values ​​for carbon monoxide. Convincing, however, is the variant with G-Kat and injection: After the catalytic converter has started, pollutant emissions drop dramatically by 72 to 79 percent. The HC and CO pollutant components also decrease in the extra-urban cycle, which is reflected in fuel consumption and the excellent overall result.

Interview with Honda

? Why does the Honda CBR 600 with injection have significantly higher consumption than the previous model with carburettor, especially at speeds above 120 km / h? In fact, we have also found that the consumption of the CBR 600 from model year 2001 is higher than the previous model in certain areas. Petrol consumption increased, especially at low temperatures, due to the automatic cold start enrichment. We attribute the consumption disadvantage at higher speeds on the one hand to the shorter overall gear ratio of the new CBR in fifth and sixth gear, on the other hand, the top priority during development was drivability and exhaust emissions. ? Is the carburetor superior to the injection in some criteria, such as fuel consumption? Today the carburetor is at an extremely high level of development. Injection technology is only just beginning for a motorcycle. Because of the completely different requirements, we were only able to make limited use of the experience from the car sector. We have to start on a blank sheet of paper for each displacement. The carburetor model was developed mainly towards performance. The CBR 600 with injection, on the other hand, not only had to meet the requirements for performance, but also with regard to low pollutant emissions. This corresponds to the objective of Honda to equip all two-wheelers over 50 cm3 with low-emission technology with four-stroke and injection by 2005. In the future, more attention will be paid to consumption. Is an injection system more expensive than a carburetor? At the moment the costs for the injection are significantly higher. Depending on the number of units, however, they will drop drastically and can easily level off at the level of the carburetor.

Bescher, Klaus: Interview

? Where do you see the advantages and disadvantages of injection compared to the carburettor? The advantage is that more engine and environmental conditions are recorded and thus a more favorable mixture adjustment is made possible. Individual functions such as height adjustment can be pre-assigned at the green table. The disadvantages are less due to the principle, rather they lie in the high development costs and the availability of suitable components such as the injection valves. In contrast to the carburetor, which can be adjusted relatively quickly, many more parameters have to be processed during injection. After the sometimes high pollutant emissions of the first F 650 GS models, our latest measurements show that the values ​​have improved dramatically. We’ve been working a lot on the GS lately, drastically reducing the “characteristics” areas where “rich” engine operation was required. The range in which Lambda 1 is used has increased significantly as a result. Why does the injection engine suffer from constant speed jolts while the carburettor version doesn’t? The partial load range between 3000 and 3500 rpm is extremely critical. With Lambda 1, the problem arises of ensuring even and clean combustion. Carburettor engines run richer at these speeds, and therefore more stable. In addition to the injection, the construction of the cylinder head in the F 650 GS in particular has changed significantly compared to the previous model. How many percent of the reduction in fuel consumption do you attribute to the design measures, how much to the injection? The completely new gas exchange and the increase in compression from 9.7 to 11.5 should account for around 50 percent, as well as the injection.

consumption

MOTORRAD checked a whole spectrum of consumption in addition to the values ​​determined by TuV Automotive analogous to the DIN measurement of the car. The result of the BMW F 650 with injection is astonishing, which with 2.7 liters undercuts the three-liter Lupo from VW, while the remaining three motorcycles achieved consumption of 4.4 to 5.5 liters. On the MOTORRAD consumption route, the F 650 GS with 3.6 liters set the standard again on country roads ahead of the carburettor BMW with 4.7 and the two Honda with 5.4 liters each. At constant speeds, MOTORRAD then determined the consumption curves. The injection BMW consumed between 80 and 160 km / h 0.6 to 1.9 liters less than the carburetor counterpart. The comparison of the two Honda is frightening: from 80 to 120 km / h the injection model is still on par with the carburettor CBR, above that it was very thirsty and swallowed 2.2 liters more at 200 km / h.

Carburetor

With the constant pressure carburetor, the driver operates the throttle valve located between the inlet valve and the throttle slide using the throttle grip. If this is opened, a negative pressure is created in the intake manifold, which continues through a hole in the gas valve into the space above the membrane attached to the gas valve. The negative pressure lifts the membrane and the gas slide, the conical nozzle needle continuously opens the hole for the fuel inlet in the nozzle assembly and sucks in the fuel.

Mixture preparation – injection

A large number of sensors feed the engine management system with information. The basic map is composed of the speed signal taken from the crankshaft and the load signal supplied by the throttle valve potentiometer. In wide load ranges it is corrected by the information from the lambda probe. The temperature of the air sucked in and the cooling water as well as the air pressure and other parameters enable exact adaptation to all operating conditions.

Leave a Reply

Your email address will not be published. Required fields are marked *