Saturday, September 19, 2009
Monday, September 14, 2009
AVL, or Anstalt für Verbrennungskraftmaschinen List, may not be a name well known to people in general and so are the engines and automotive machinery that they manufacture. It is an Austrian-based automotive consulting firm as well as an independent research institute. It is also the largest privately owned company for the development of power train systems with internal combustion engines (ICEs) as well as instrumentation and test systems AVL are well known throughout the automotive world for their engineering prowess when it comes to engine design and manufacture. Chances are, you most probably have witnessed an AVL engine in action during recent times, prime examples being the engines of Mahindra Scorpio/Xylo, and more importantly, the Enfield Bullet. These were designed by AVL and as you may know they are examples or reliable, efficient and powerful engines.
Here, we talk about a new kind of engine, one that has the potential to revolutionize the biking world. Yamaha has already applied a patent for it and AVL has almost completed the design and engineering phases of the same. Its the diesel turbocharged engine for bikes! The simple reason it’s going to be different is because of the fact that its a diesel engine. Yes you heard it diesel. You might be wondering what is so great about this because you already may have seen Enfield’s on the road fitted with diesel power plants. But there is a whole world of difference between an old age diesel engine and a new generation one.
You see, like all things, engines have gotten better and better over time and its actually rare for one to see a new bike or car with engine problems of any sort, anyone would know how silly the noises are from an old diesel engine but the fact of the matter is Yamaha and AVL are in no mood for old stuff, they’re focusing on turbocharged, lightweight, fuel injected or common rail systems for their diesel engines. The diesel engine on a Suzuki Swift is among the most technically advanced diesel engines in mass production, its silence, refinement, power, efficiency and size stands testimony to the fact that diesel engines can actually be as good as their petrol counterparts. Gone are the days when you needed twice the Cubic Capacity of a petrol engine to produce the same power from a diesel, with modern technologies like turbo systems, more power can be made from a lot smaller package.
Let’s move on to the details. We are focussing on the AVL engine as its the only one we have more information on while the Yamaha’s version is right now kept confidential. AVL has designed a 3 cylinder, turbo charged, common rail fuel injected diesel engine. These kinds of engines are widely used in the Indian automobile market because of their efficiency and the lost cost of diesel fuel. Also such engines generally have power in the low to mid range of RPM’s which make it much easier to drive than its petrol counterpart. Using this sort of engine on a bike would make perfect sense because of all the factors mentioned above. But there are certain problems like turbo lag and diesel smoke that make it a slightly worrying prospect; the folks at AVL managed to get past these hurdles with the use of a VGT (Variable Geometry Turbine) that adjusts the turbo blade angles to provide power in a smooth and steady manner, examples of this technology can be found in the Porsche 911 Turbo and the Hyundai Verna.
The AVL diesel engine and vehicle concept was performed as an internal research and development project. It is the first high performance diesel engine to be specially designed for motorcycles in terms of packaging and styling. The packaging of the engine in the vehicle was shown using a rapid prototype model. The engine design is based on AVL know-how from development results and measurement data of state of the art HSDI (High Speed Direct Injection) diesel engines, Also besides the packaging and design work, a 1D thermodynamic engine simulation system with AVL’s software code ‘BOOST’ was carried out in order to optimise the gas exchange of the engine including the VGT (Variable Geometry Turbine) turbocharger to predict the engine performance. To optimise the engine in terms of cyclic speed irregularity a torsion vibration system was set up using AVL’s software code ‘BRICKS’. This simulation included the variation of the flywheel mass and the analysis of different cylinder pressure and associated characteristics. Additional simulations of the entire motorcycle in order to determine the driving performance were carried out using AVL’s Vehicle simulation software ‘CRUISE’. The engine specifications were fixed under consideration of the required performance, emission, styling and noise targets. The table below gives an overview of the main engine specifications for the engine.
The crankshaft of the diesel engine was designed in order to achieve the required torsional rigidity with a minimum weight. Overall this is a promising development in engine technology and is one that will surely change the world of biking for some time to come. Yamaha has already filed for a patent for an engine with almost the same characteristics and its just a matter of time to see who comes out with the finished version first.
Saturday, September 5, 2009
Tuning the Carburetor
Tuning your Harley Davidson carburetor is simpler than most think and can be performed with a few common tools. This simple procedure is a great Harley tech tip that applies to all Harley carbs from 1989 to present that use the CV style Harley Davidson carburetor. Earlier models equipped with the older butterfly style carbs (pre-89 Evo's, Shovelheads, Pans, and Ironheads) are excellent candidates for upgrading to a modern Harley carburetor. Preparing the carburetor for tuning will require removal from your Harley-Davidson's engine but this is easily accomplished. Begin by shutting off the petcock fuel valve and starting the engine to allow all fuel within the carburetor bowl to be emptied. Remove the aircleaner assembly including the backing plate which is attached to each head with a banjo bolt. This is a good time to inspect these bolts for obstructions in their passages. Remove the choke cable from it's mounting bracket on the opposite side of the bike.
Note: Before proceeding to rejet your carburetor it is recommended that you perform the following tuning procedure. Once the the mixture has been properly tuned there is often no need to rejet the carb.
The choke cable will stay attached to the carburetor during this procedure. Disconnect the fuel line from the fuel inlet on the carburetor or the opposite end connected to the fuel petcock, whichever is simpler to access. The hose is likely fastened using a special crimped clamp. This may be cut or pried off to remove since you won't be using it again. Be sure to have a new hose clamp available. Next loosen both throttle cables from their adjusters located just beyond where they exit the throttle grip. A couple turns is usually all it takes to give you enough slack. If you count how many turns each adjuster is loosened then you can return them to the exact adjustment when reinstalling your carb. This is a good time to label each cable to avoid any confusion when reconnecting them to the carb's throttle cam. A simple "Top" and "Bottom" should suffice when tagging each cable. Now that you have enough slack in the cables you can pull the carburetor away from the manifold. A Harley carb is only held to the manifold with a slip fit rubber boot. Gently rock or twist the carb back and forth as you pull it away from the engine. Remove the cables that you tagged and remove any vacuum hoses. If your model has multiple vacuum hoses it would be a good idea to label these as well. With the carb removed, place upside down on a sturdy work surface. Do not remove the bowl at this point to prevent debris from entering the carburetor. The CV style Harley carburetor has a small cylindrical tower protruding from the bottom rear of the spigot (behind the bowl). The tower is plugged with a soft metal insert covering the mixture screw. Gaining access to this screw is key to fine tuning and must be remove. The metal plug is very soft and only requires a household drill and 7/64" to 1/8" bit. Secure the carb in either a vise or by other means that will allow the carburetor to remain steady. Drill a hole into the plug making sure not to "punch" through too fast. You don't want to damaged the mixture screw just below the plug. Allow the drill to slowly cut into the plug rather than push.
Tip: To keep from drilling too far into the plug, it has been suggested to wind electrical tape around your drill bit quite a few times about 3/16" from the tip. This will create a stop to keep the bit from drilling too deep. Pry the plug out using a pick or awl. You can also thread a sheet metal screw into the drilled hole and use this to pull the plug out. Now that the plug is removed clean the area around the mixture screw so no metal fragments remain. At this point there are two methods for adjusting the mixture.
Adjustment Method: Using a small flat head screwdriver turn the screw clockwise until it gently seats. DO NOT OVER TIGHTEN AS THIS WILL DAMAGE THE NEEDLE SCREW. Count how many turns it takes to reach the closed position. Mark the screwdriver if needed to properly count each turn. Now turn the screw out counter clockwise stopping at a 1/4 turn beyond that which you originally counted. For example, it you turned the screw in 1-1/2 turns then unscrew it 1-3/4 turns. This is your base starting point and alone will allow your idle mixture to be slightly richer than the factory's EPA setting. In many cases this will be the ideal setting. As an alternative to adjusting the mixture screw with a screwdriver, many prefer using an EZ-Just mixture screw to ease adjustments and fine tuning. If the mixture screw has been reset by the dealer or previous owner (evident by the plug already being removed), turn the screw clockwise until it seats. Now turn the screw outward 2 turns to establish a starting point. The same procedure applies if using an EZ-Just screw. Reinstall the carburetor back on your bike by reversing the steps taken during removal. Be sure to replace the fuel hose clamp and vacuum lines. It may be a matter of dexterity but I prefer to install the cables before pushing the carb back onto the manifold. Make certain the carb firmly seats back onto the manifold boot. Test the throttle for binding and smooth operation. Double check each hose and connection.
The air cleaner assembly MUST be installed prior to starting the engine, not only to hold the carburetor in place but to prevent having the carb backfire in your face while tuning. Start the engine as normal and bring up to operating temperature prior to fine tuning. Let the bike idle for no more than 5 minutes. The modified carburetor should allow your bike to run well enough for a mild test run around the block to speed up the warm-up process. With the engine warmed up and at idle you may now fine tune the idle mixture screw for optimal performance. Acquainting yourself with the adjustment screw location at the bottom rear of the carburetor prior to running the engine is advised, which also prevents burning your hands. You will need a small screw driver for adjusting the screw unless an EZ-Just has been installed. With the engine idling slow (no more than 900 rpm), turn the screw inward (clockwise) SLOWLY until the engine starts to stumble. You are working with the screw upside down so check to make sure you are turning the screw clockwise or inward.
Note: Be careful not to allow the screw to fall out as there is a very small spring, washer, and o-ring that will fall out as well. These items known as the mixture screw packing kit are not available from the dealer or manufacturer, however if you should lose these parts there is an aftermarket replacement kit available here.
If the engine will not idle on its own during this procedure, adjust the idle set screw on the throttle side of the carburetor until it idles correctly. Now turn the mixture screw outwards (counter-clockwise) until the engine begins to run smoothly, then add 1/8 of a turn. Maintain proper idle speed and repeat the adjustment each time you adjust the idle speed. Blip the throttle a couple of times and observe the results. If the engine responds quickly with a smooth blast and no backfiring through the carburetor, you have your idle mixture right. If backfiring occurs through the carburetor then adjust the idle mixture screw out another 1/8 turn. Normally, the mixture screw should only require 2 to 3 turns. Anything above 4 turns indicates the pilot jet is too small.
Twin Cam Harley engines have a mixture screw sweet spot approximately 2 to 2-1/8 turns out from seat, whereas Big Twin Evo and Sportsters can require up to 3 turns. Adjusting the mixture screw out to far will result in an overly rich fuel mixture in the low RPM range. Avoid tuning too rich, thus leading to poor gas mileage and fouled plugs. Optimal setting on most Harley's is approximately 1/4 turn clockwise when backed out from the point of backfiring (coughing). Take your newly tuned bike for a ride and note how it idles and responds off idle. If you experience any coughing through the carburetor, adjust the mixture out another 1/8 of a turn.
Black smoke seen from the exhaust at idle or a feeling of sluggishness off idle indicates you may have set the mixture too rich. If your bike is now idling steady and responds well from a start then you are all set. If your engine still runs lean you should move on to rejetting your carburetor. The same stock Harley Davidson carburetor has been used on all production bikes from 1989 to 2006 due to it's reliability and ability to adapt to different conditions. With just the right amount of tuning there's no reason why you can't have some of the same performance gains advertised by the major racing carb manufacturers.
Stage 1 tuner kits are available for those who wish to take their carb to the next level of performance.
Courtesy :- harley-performance.com
Wednesday, September 2, 2009
Tuning the Carburetor
Harley carburetor jetting should only be performed after completing the fine tuning procedure described under Performance Tuning and your Harley is still running too lean.
A good rule of thumb is to replace the Pilot Jet first and only replace the Main Jet once the engine's idle and midrange are satisfactorily tuned. The Main Jet is only used at 3/4 to full throttle and has no effect on the idle or midrange mixture.
Main jet replacement should be reserved until after the slow idle jet is replaced and mixture is tuned unless a lean condition is apparent during full throttle. Harley carburetor jetting can be accomplished with minimal mechanical knowledge.
Tools to perform this task include just a simple set of screwdrivers. You will also need an assortment of jets or a Stage 1 kit. Remove the 4 screws securing the bowl to the base of the carburetor and remove the bowl. Using a narrow 1/8" flat head screwdriver unscrew the Pilot Jet from within the orifice pictured. The jet size is stamped into the top of the jet (i.e. 42). Be careful not to strip the head of the jet.
Pilot Jet location
With a flat head screwdriver unscrew the Main Jet from the brass needle jet holder (aka Emulsion Tube).
Note the jet size stamped into the top of the jet (i.e. 165). There is no need to remove the emulsion tube unless required for cleaning. I don't recommend "Power Tubes" as they change the mixture and ability to tune with stock jets.
Replace the Pilot Jet with one size larger. This of course assumes that you are starting out with the stock jet size. Harley Davidson Pilot Jets for CV Carburetors are normally sold in sizes 40, 42, 45, 48, 50, and higher. A Stage 1 Carb Kit will normally offer you a proper range of jets for your particular model. If your stock jet was a #42 the next size larger will be #44 or #45. Only increase the jet sizing one size at a time to avoid an overly rich idle. An EZ-Just mixture screw will also assist in fine tuning once you have the correct jetting.
Pilot and Main Jets
Only replace the Main Jet with one size larger after properly tuning your slow/idle jet settings. Main Jets are sized incrementally by 5, so if your stock jet was a #175 the next size larger will be #180. you should only increase the jet sizing one size at a time. Avoid installing jets that are too rich as this will create a sluggish feeling at full throttle as well as contribute to plug fouling.
Many Twin Cam models (except California) are already appropriately jetted with a main jet that will allow for a good starting point for tuning. As mentioned, proper mixture adjustment is key to proper jetting and should be performed first.
Reinstall the bowl making sure to align the accelerator pump shaft and rubber boot. Install the carburetor back onto the bike and perform the tuning procedure as described under Carburetor Tuning.
As you can see, Harley carburetor jetting is a fairly simple procedure that under most conditions will yield greater performance when requiring a richer fuel mixture.
The same procedure can be applied on any other motorcycles or scooters for performance purpose. But jet sizes are different for all the vehicles. The given jet size data in the article is related to HD's not Indian vehicles. So please do not get confuse.