2009 Honda CRF450R Engine
Naturally, the big buzz about the 2009 CRF450R tends to focus on its all-new battery-less Programmed Fuel Injection (PGM-FI) system. And garner attention it should, although EFI is only one part of the greater overall whole in a completely redesigned CRF450R. Specifically, this EFI system utilizes a 50mm throttle body design with a 12-hole injection nozzle fed by a lightweight plastic 50-psi pump to ensure optimum fuel atomization and a precisely targeted fuel charge.
Bringing the full benefits of EFI to bear proved to be an arduous task. Since its introduction, the CRF450R has enjoyed a well-deserved reputation as being the easiest starting bike in its class, as well as having the best throttle response. So even though it was no small task to improve on the best carburetion system around, thanks to countless hours of testing and perfecting this system the new CRF450R meters fuel even more precisely now. Credit also the intrinsic precision provided by the minute tolerances inherent in a fuel injection design, which allowed Honda engineers to take tuning to a higher level. So the 2009 CRF450R now delivers amazing drive right off the bottom, super-strong midrange punch and a stronger rush of top-end power.
Next, factor in another remarkable benefit that comes as a direct result of this more accurate and efficient fuel metering: this EFI system also achieves a significant improvement in fuel consumption. Therefore, the fuel load can be smaller and lighter yet the CRF450R can still handle the longest motos. In addition, the fuel tank itself can now be shorter, smaller and slimmer and that means the seat could be made flatter all the way up to the gas cap to allow the rider a greater range of unimpeded movement on the bike. Reaping handling and rider ergonomic benefits from a fuel injection system? This is typical of the synergistic forward-thinking that created the new CRF450R design.
The PGM-FI system monitors throttle position, intake air and coolant temperatures, air pressure and gear position to accurately map fuel charge and ignition spark, significantly improving partial-throttle response and helping assure excellent rideability. An enlarged AC generator delivers the needed power to the PGM-FI system without a battery, and two crankshaft position sensors (instead of the solo sensor used previously) determine crank position more quickly to provide speedy starts, whether the engine is hot or cold. The engine stop switch also features an integrated LED pre-ride check indicator. This confirms the EFI system is operating normally. In addition, Honda also has available an HRC PGM-FI Setting Tool, which allows CRF450R owners to alter EFI fuel delivery as well as ignition timing over a wide range of settings to alter engine power characteristics.
Thanks to a wealth of improvements, the new engine spins faster— 11,450 rpm—and harder, churning out 56.3 bhp at 8500 rpm and 37.5 lb./ft. of torque at 7000 rpm. This liquid-cooled four-valve Unicam® 449cc engine now utilizes a four-lobe camshaft and individual rocker arms for each exhaust valve to reduce weight and contribute to its higher rpm ceiling. The net advantage is not only more power, but also a broader powerband for better drive out of corners.
Thanks to its complete redesign, the CRF450R’s smaller, lighter engine contributes significantly to improvements in the chassis, ultimately adding to new class-leading handling traits. Perhaps most significantly, the 2009 CRF450R engine features a lower overall height and it has been positioned closer to the front wheel, resulting in a lower overall Cg and more optimum weight distribution for better handling. This lower Cg also means the engine’s rotating mass rides lower in the chassis, producing less gyroscopic effect for more neutral handling.
This reduction in engine height was achieved in part via a shorter cylinder head that now positions the camshaft directly in the cylinder head; previous 450s featured a bolt-on cam mount. More engine height was shaved off by shortening the connecting rod 3.5mm (102.1mm from 105.6mm), which allowed a correspondingly shorter cylinder. In addition, the crankshaft main journal cradles were relocated to the inside of the flywheels to allow a reduction in connecting-rod pin diameter from 34mm to 33mm, which further reduced weight while maintaining overall strength. Shaving a small flat into the bottom of the crankshaft flywheels allowed for a bit more con-rod shrinkage by providing a pinch of added clearance for the piston skirt, while also reducing weight—an insightful bit of efficiency contributing to the shorter engine.
Other changes to the CRF450R powerplant include a reshaped combustion chamber that’s a touch shallower to further reduce cylinder head height but features a larger-volume squish area for efficient flame propagation. The lightweight titanium intake valves now have shorter stems, and redesigned valve springs also help reduce overall engine height and permit higher rpm. Slimmer intake valve stems shrink in diameter from 5.5mm to 5.0mm to reduce reciprocating weight, and the cam sprocket is now press-fitted to the camshaft, reducing weight by 20 grams compared to the previous bolted-on design. The use of a new, tougher material in the forged slipper piston permits a thinner crown along with a relocated piston pin, contributing to shorter cylinder height and less reciprocating weight. A low-friction surface treatment on the piston assures high-rev potential.
Lightweight Ni-SiC cylinder lining provides cooler and quieter operation for extended engine life, and for easier servicing the cylinder attaches to the engines cases with through-bolts instead of studs, allowing in-frame cylinder removal.
The CRF450R incorporates the use of a new, lighter automatic decompression system, so the hot restart procedure is simplified. This cam-integrated plunger and shaft-integrated decompression weight allow for easy starting in both hot and cold conditions.
2009 Honda CRF450R
This new-generation CRF450R features a redesigned five-speed gearbox that incorporates numerous modifications—often measured by a mere millimeter or two—to narrow transmission width and reduce weight without sacrificing durability. Transmission ratios remain the same as last year, and the transmission still incorporates a gear-position sensor, which now also works in conjunction with the EFI system. This sensor signals a new, sophisticated electronic control module (ECM), which uses a multi-map system to alter ignition plus EFI mapping for optimum power in varying riding situations. Specific maps control the EFI and ignition settings so power application in first and second gears provide maximum acceleration with minimum wheel spin, and third through fifth gears utilize maximum-power mapping.
Eight clutch plates handle the engine’s massive torque, and the new CRF450R incorporates only four clutch springs rather than the previous six springs to reduce centrifugal weight, thereby allowing the engine to rev quicker. Kashima coating is applied to the clutch basket and clutch center to improve clutch life and clutch feel.
In keeping with previous practice, a twin-sump lubrication system separates the oil supply for the crankshaft, piston and valve train from the clutch and transmission. This ensures a cool supply of oil to the clutch, eliminates clutch and transmission material contamination of the engine oil and reduces the amount of circulating oil, which allows the oil pump size to be reduced. A gear-driven balancer serves double duty, reducing vibration while also driving the water pump. A new mechanical water pump seal improves durability, and coolant flow is now rerouted outside the engine cases via a bolt-on flange/jacket, allowing reduction of crankcase and cylinder width as well as overall engine weight. Also, an oil pump strainer is now built into the engine case to reduce the number of parts and shave additional grams.
Sharp eyes will note that exhaust gasses now exit from the left side of the cylinder head. This change shifts an increased length of the head pipe closer to the engine as it wraps around to the right side and culminates with a new muffler that’s positioned dramatically farther forward and closer to the CRF450R’s center of mass. A large lightweight titanium section in front of the aluminum-body muffler contributes significantly to improved weight distribution and the handling benefits of this radical new exhaust system.
Posted on
02.4.2009 @ 11:03