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BELL PERFORMANCE FUEL ISSUES SERIES: MOST COMMON DIESEL FUEL PROBLEMS EXECUTIVE SUMMARY Diesel fuel, the fuel of choice for most of this country’s transportation and boating industries, is more prone than gasoline to difficulties with not complete combustion, deposits and poor emissions. Deposits on injectors, valve and in combustion chambers may all have negative effects on vehicle/& boat performance. Diesel fuel of the ultra-low sulfur potpourri has far less natural lubricity than before, and all #2 diesel fuels have the potential for cold weather gelling problems. The tendency to store diesel fuel leads to potential for oxidative breakdown, build up of destructive water in the storage tank, and microbial infestation of the fuel supply, which necessitates use of a biocide to eliminate the infection. INTRODUCTION Diesel fuel powers most of this country’s over-the-road transportation, rail and big marine fleets (as well as galore pleasure boats). In Europe, diesel cars are more mutual than here in the States. To be sure, diesel does offer vantages over gasoline as a vehicle fuel. Diesel engines tend to be more efficient, relying on compression ignition than spark ignition. They last longer as well, which is share of the reason they are universally preferent for big industrial applications. As a diesel fuel user, whether truck or boat, you may conscious of sure troubles that come with the territory. The mutual issues fuel users experience with diesel are: COMBUSTION CHAMBER DEPOSITS Diesel fuel does not burn as cleanly as gasoline does. This is due in part to diesel being composed of larger, heavier hydrocarbon chain molecules. Larger molecules integrate more energy than shorter molecules (because they incorporate more carbon bonds to break and release heat energy) but they likewise have a dandier chance of not combusting completely. When they don’t combust completely, they may form deposits in the combustion chamber. When deposits build up in the combustion chamber, it changes the volume of the chamber and subsequently increments the minimum cetane rating of the fuel necessitated by the engine to maintain perfective top-dead-center combustion and greatest or most complete or best possible fuel burn at the proper time. The same effect also happens in gasoline engines, where combustion chamber deposits increase the minimum octane rating by various points early in the engine’s life. Combustion chamber deposits may also act as both insulators and fuel sponges. Excessive deposits will alter the rate at which heat may escape the cylinder, trapping the heat inside and raising temperatures. When this happens, nitrogen oxide emissions (NOx) increase, which are terrible for air quality. Excessive chamber deposits disrupt idealisti combustion and performance by absorbing fuel and by disrupting proper air flow within the cylinder. Typically these deposits may build up in the piston bowl area. This changes the air flow within the chamber away from the idealisti flow designed when the engine was engineered, and this leads the engine away from idea combustion. Absorbing fuel happens because chamber deposits are porous with a network of cracks and crevices that may act as sponges. This being said, combustion chambers deposits tend to have a dandier effect on engine performance and power than they do on mileage. Vehicular studies do not show combustion chamber deposits to significantly lower fuel economy; injector and valve deposits have a much dandier effect on fuel economy. INJECTOR DEPOSITS All diesel engines use some form of fuel injection. Most little diesel engines used to use a scheme called indirect injection (ID1) while larger engines use direct injection (DI). Today, most modern passenger car diesels have swopped to DI for fuel economy reasons. IDI have a tendancy to be smoother and quieter, while DI is more fuel efficient. The fuel injector sprays the diesel fuel into hot, compressed air, and the mixture auto-ignites. Efficient metering, atomization and fuel-air mixing are key requirements for good combustion and particularly crucial for low levels of exhaust emissions. Spray Patterns of Clogged vs Clear Injectors Modern diesel injectors are designed to exacting standards and form an integral part of the routine for optimizing fuel combustion. Their flow characteristics are set to grant a little pilot injection of fuel to initiate combustion, and then inject growingly more fuel into the burning mixture. Such an approach provides a low rate of pressure rise and smoother combustion. Mechanism of Formation of Injector Deposits in Diesel Engines Both gasoline and diesel fuels consist of elements that boil over a wide temperature range (the diesel range is higher than the gasoline range). When the engine is swapped off, fuel remaining in or near the pintle tips mixes together with any remnants of un-burnt engine oil and is subjected to high heat soak temperatures. Such high temperatures lead to the formation of free radical species, and then to a combining of auto-oxidation, chemical rearrangement and degradation of the remaining fuel – and deposits form within the injector. Diesel fuel does not have the same injector deposit control specifications that gasoline does. Therefore it may be utile for the buyer to use an aftermarket fuel treatment to remove these deposits and prevent their formation. Effect of Deposits on Diesel Injectors Clean fuel injectors are critical for effective diesel engine operation. A well dispersed spray pattern maximizes fuel-air mixing, while good atomization ensures rapid, effective combustion. All diesel fuels, but particularly those containing merchandise from refinery conversion processes, have a tendency form a little amount of coke in the annulus of the injector. This coke is believed to be caused by the thermal decomposition of unstable compounds in the fuel. It is such a mutual problem that injectors are designed to tolerate a sure level of coke. However, a good deal of of today’s diesel fuels give exuberant levels of injector coking, disrupting the fuel spray pattern and degrading atomization. Higher emissions, noisier engines and a decrease in fuel economy are the result, as shown by controlled vehicle studies. These studies show up to a 15% decrease in city economy and 5% decrease in highway (according to EPA test protocols). For the FTP driving protocol, the results are a 2-11% reduction in fuel economy over the FTP driving protocol, depending on the level of plugging (8-30%). Another definitive study employed fouled injectors assembled from two dissimilar types of vehicles in the field to show the changes in performance based on sets of injectors with varied intermediate levels of fouling and ranges of fouling. Under the worst conditions of 30% intermediate flow restriction, with a corresponding range of 30% amidst the best and worst injectors, the author showed: a 700% increase in hydrocarbon (HC) emissions In high-fouling injectors, exploration shows the engine compensates and may cause a great deal of cylinders to receive too much fuel and a lot of to receive too little (rich and lean). Once cleaned, a 10.5% betterment results in 40-100 kph acceleration times and a 15.8% betterment in 80-100 kph times. This is confirmed in other parallel vehicle studies, where clogged injectors show a reduction in engine power up to 22% and a 1.3 – 2.8 second penalty in acceleration tests. INTAKE AND PORT VALVE DEPOSITS Example showing the effect of detergent additives on inlet valve deposits equated to unadditized fuel. Poor fuel combustion and stratified diesel fuel which has broken down in storage (because of water buildup, age or microbial contamination) may lead to the deposit particular spatial arrangements building up on the valves in the engine. Problems with power loss, decreased fuel economy, startability, driveability demerits, decreased power (increased acceleration times) and increased emissions may all result from this. Valve deposits may also be a result from a mixture of environmental contaminants and likewise from mechanical issues in older engines, where engine blow-by (from a worn PCV valve), cylinder blowback (from insufficient ring seal and wear), exhaust gas recirculation (in big transportation truck engines) and lubricating oil, all of those may combine to build up on the valve stems and undersurface of the valve, forming deposits. Typically the greatest effect from these deposits comes when they get huge sufficient to physically block the manifold passage and restrict air and fuel flow into the cylinder. This employed to be rather mutual when carburetors were widespread, and would result in poor acceleration, power, fuel economy and raised emissions. But even low levels of deposit accumulation may affect mileage and emissions, since the deposit may act as a sponge, absorbing fuel into the pores of the deposit, then freeing the fuel through evaporation or desorbtion (release of absorbed fuel). This disrupts the flow of fuel at the proper timing interval into the cylinder and reduces droplet evaporation efficiency, therefore creating an imbalance in the fuel/air mixture into the cylinder. And this means the engine isn’t functioning or combusting fuel optimally. So the typical issues in modern, port fuel-injected engines that have valve deposits are poor driveability (particularly upon cold start-up and for the duration of warm-up conditions) and poor emissions performance. Vehicular studies using frequent driving procedures like the CRC show a linear correlation amidst the level of valve deposits and “driveability demerits”, which are an index related to how well or poorly the vehicles performance on “driveability”. It may be without doubt or question show that valve deposit buildup affects the vehicle’s driving performance and it gets worse the more deposits that build up. LUBRICITY The term “lubricity” means the lubricating power of the fuel as it flows through the engine. Most buyers only think of engine oil (their typical 10W30 blend) when taking into account engine lubrication. But diesel engine technologies have long relied on the lubricity of the diesel fuel to keep galore types of engine parts from wearing out too quickly. Fuel pumps and injectors both rely on the lubricating compounds naturally found in diesel fuel after distillation at the refinery. In recent times, the federal government has employed amendments to the Clean Air Act to strength reductions in the greatest or most complete or best possible level of sulfur to be found in on-road diesel fuel. Reducing sulfur in the fuel is good for the surroundings because it means less sulfur leaving the vehicle as SO2 or SO3 emissions (which may lead to acid rain). But the chemical processes applied to strip the sulfur from the fuel – hydro-treating – drasti reduce the low-sulfur fuel’s capacity to lubricate the engine parts that applied to depend on such lubrication (because it chemically destroys the complex organic corpuscles that carry out the function). And with that comes injectors and fuel pumps that wear out faster, leading to higher maintenance costs. This issue is most pronounced in the long-haul trucking industry where vehicles log a great deal of hundreds of thousands of miles per year. COLD WEATHER PERFORMANCE Cold weather performance is a big issue for diesel truckers who live and work in cold northern climates. Diesel fuel, being a mixture of carbon-based molecules, comprise complex “paraffin wax” molecules as portion of it is composition. These waxes serve to bestow to the energy value of the fuel. But when the fuel gets cold, these waxes will come out of solution, making the fuel cloudy. Once out of solution, they stick together to form more prominent and more prominent crystals of wax. This effect increments the colder the weather. Eventually sufficient wax floats around in the fuel that the fuel gels up and the wax plugs the fuel filter, shutting off fuel flow and sidelining the vehicle. This is why diesel operators in cold weather will use a “cold flow improver” product. These kind of productions keep the fuel from gelling by keeping the wax crystals in suspension from sticking together. They stay little sufficient that they may pass through the fuel filter without a problem, where they get burned off in the combustion chamber with the rest of the fuel. If you live up in cold northern weather, it would be wise to consider this kind of treatment if you have not already. Cold weather may likewise make more prominent diesel engines hard to start. Diesel engines rely on compression to heat the air in the cylinder (compressed gas, all other things being equal, gets hotter than the same amount of gas in a larger volume of space). Gasoline engines don’t have the same cold starting issues because they have the aid of a spark plug to strength the fuel to combust. But in a diesel engine there is no spark, and the engine will have to turn over some times in order for sufficient heat to build up and permeate the walls of the cylinder such that auto-ignition of the fuel will happen. This is why huge trucks are hard to get started in the winter. Diesel fuels with higher cetane ratings are posing no difficulty to commence in cold weather because more of the different-size molecule combust at the proper time. Some drivers may have a cetane-raising fuel treatment in order to gain these effects without the extra expense of higher-cetane diesel fuel. DIESEL FUEL STABILIZATION AND BREAK DOWN OVER TIME Any petroleum product – gasoline, diesel, fuel oil, natural gas – will react with things in the surroundings they are exposed to, like water, metals and light. Light genuinely just acts as a catalyst to accelerate oxidation reactions – where oxygen reacts with the fuel corpuscles and causes them to react with other molecules – fuel or not – leading to the formation of polymers that react with other polymers in chain reactions. Over time, the fuel starts to distinguished and break apart, with these “heavy end” atoms agglomerating together and sinking to the bottom of the mixture (because they are the heavier molecules). Fuel which has oxidized and stratified like this loses some or most of it is capacity to combust at an optimal level. And this means poor fuel combustion in the engine, not complete combustion, formation of deposits, more unburned or partially burned fuel leaving the combustion chamber (poor emissions), and less-than-optimal fuel economy (because stratified fuel doesn’t give the greatest or most complete or best possible energy value upon combustion that fresh fuel does). All in all, this is not the best circumstance for the vehicle or boat operator that is stuck with this kind of fuel problem. What most commonly causes or contributes to fuel instability and breakdown? As cited before, exposure to water or air may begin or speed up fuel oxidation. Both water and air are splendid oxygen donators, and oxygen is the important culprit in oxidation. Exposure to sure kind of metals (like copper) as the fuel passes through a fuel storage and deliverance scheme – this may also get started and speed up oxidation, though these kind of metals merely act like catalysts and oxygen would still need to come from another source (not normally an issue in the typical fuel storage scheme or tank). Exposure to light, like exposure to metals, is a catalytic contributor, because sunlight (and likewise heat contributes energy necessitated to jumpstart the oxidation chain reactions. This is why diesel fuel poured into a glass jar and left exposed to sunlight will still darken over time – the oxidation reactions cause the color change. Lastly, if the tank has a microbial contamination (more on that later), these acids given off by the microbial biological processes attack fuel and hasten it is breakdown. The whole issue of stabilization and storage is a more spectacular issue for diesel than for gasoline because it is much more mutual to store diesel fuel for longer periods of time. Fuel suppliers and industrial clients who store fuel and need to keep it fresh will use an oxidation inhibitor – a fuel stabilizer – to interfere with these destructive reactions and keep the fuel fresh. Consumers who store fuel (such as the boat proprietor who leaves fuel in his tank over the boat’s winterization period) are advised to do the same. WATER BUILD-UP Water build-up in diesel fuel tanks is a universal problem all over the nation. Almost any stored diesel fuel left for any amount of time will end up with water in the bottom of the tank; it’s an even larger issue for boats and marine storage tanks. Water sinks to the bottom of the tank because water is heavier than diesel fuel is. What’s more, you don’t even have to have a storage tank for this to occur – water even builds up in the fuel tanks of long haul trucks. The culprit in all of these situations is the venting of the tank to the outside air. Outside air packed with water vapor travels in and out of the tank. In storage tanks, the water from the air condenses and rolls down the side of the tank when the air cools down in the evening. In diesel vehicles, the temperature alter comes from hot diesel fuel returning to the tank after being applied to cool the injectors. Injectors get hot due to their vast pressures. The engine uses diesel fuel propagated from the tank to dissipate a heap of of this heat. The now-hot fuel is then disseminated back to the fuel tank. This temperature divergence causes water condensation in this environment, even when the fuel isn’t technically being “stored” for a long time. So what’s the problem with water build-up? Why does it matter? It matters, for the following reasons: • As brought up below, water permitted to pile up in a tank increments the chance of a microbial infestation – bacteria and fungi which may play mayhem with the fuel system. All of these are good sufficient reasons to control the build-up of water in the tank; this is specifically done by using a good deal of kind of concentrated fuel treatment. MICROBIAL CONTAMINATION Storage of diesel fuel for long periods of time likewise makes them more susceptible to contamination by microorganisms like bacteria and fungus. This happens when the stored fuel becomes contaminated with water; this happens in storage tanks that are vented to the outside. Humid air flows in and out of the storage tank, and when the air cools at night, the temperature alter causes the moisture in the air to condense into the tank. Since water is heavier than diesel, the water collects at the bottom of the tank. This provides the necessary surroundings for microbes to grow and flourish in fuel – they lived at the interface with the water and fuel, and draw their necessary constituents and nutrients from both the fuel and water phases. Pretty soon you’ve got a microbial infestation that develops slimy “mats” which float on top of the fuel. The microbes multiply, excreting acids from their biological processes which both corrode the fuel tank and accelerate the breakdown of the diesel fuel, leaving you with a tank of nasty, poor quality fuel. As you may guess, microbial contamination’s are most mutual in situations where the fuel is stored for long periods of time, and likewise more mutual in marine situations where the fuel tank is around water. How do you recognise if you’ve got an infested tank? You’ll in all probability observe rough running and poor performance with your vehicle or boat. Fuel filters will clog more oftentimes and (if you have a storage tank you may see the fuel in), you must be capable to see slime drifting on top of the fuel (along with foul sulfurous odors). All of these are strong indicators that the diesel fuel tank has a microbial problem. There are a number of diesel fuel additive productions that will assert to eliminate microbial infestations from fuel merely by controlling water. This is where the devil is in the details. Once a tank has an active infestation, plainly removing the water alone will not disinfect the tank. You could put fresh fuel in the tank, and over time the microbes would come back in full force. To kill an active infestation, you need to use a Biocide product, which acts such like a pesticide or disinfectant to actively kill and destruct the bacteria and fungi. However, this is not to say that productions which control water build-up are useless in this context. Controlling the water buildup is a preventative measure; by keeping water from building up in the tank, you make it much less likely that you will have an infestation. So using an additive which controls water is a good idea when applied as share of a preventative maintenance regiment for the fuel. But removing water along will not kill an infestation if it does take root in your fuel. CONCLUSION Rudolph Diesel’s conception of an engine which combusted fuel based on compression (instead of a spark ignition) is the dominant engine applied in heavy industry, long-haul transportation and boating. Consumers who own diesel cars love the outstanding fuel economy. Using a little care and good housekeeping (and a good diesel fuel additive ) in taking care of your diesel fuel will not leave you disappointed with the results. |
Small Automotive Problems That Can Lead To Huge Repair Bills
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