More than mere muscle: Kohler's new Command Pro engines deliver bigger power, but also put a premium on serviceability.
The Engine Division of Kohler Co. has developed the largest and most powerful air-cooled gasoline engines in the company's history, with the new Command Pro 34, 36 and 38 hp V-twin engines. The new engines, available in horizontal and vertical shaft configurations, will be officially unveiled at the International Lawn, Garden & Power Equipment Expo 2006 in Louisville, Ky.
Yet while the new engines represent a significant leap in terms of horsepower and torque over Kohler's existing Command Pro models and even outpace the premium liquid-cooled Aegis engines, what's as noteworthy as the raw muscle is the company's focus on making them the most service-friendly engines in the industry.
"It started out in '04 and it's been a clean sheet of paper from a design standpoint," said Cam Litt, senior product manager at Kohler's Engine Division. "We based a lot of it on our well-proven Command engines, but made some significant enhancements, especially in terms of engine service.
"We aimed to improve access to the maintenance areas--the oil filters, the cleanout areas to the cylinder heads. A number of enhancements have optimized some features on our other Command engines and made this next generation of Command engines more user friendly."
The new engines target a range of commercial and industrial applications, including turf mowers, generators and pumps, etc., and meet EPA and CARB emissions standards, the company said. The basic configuration of the engine is the tried-and-true 90[degrees] twin-cylinder, overhead valve design with an electronic ignition system, two-barrel carburetor and mechanical governor. The engine incorporates an aluminum block with cast-iron cylinder liners, a common feature on such engines intended to promote longer service life and durability. Where the new engine starts to shows its difference is in displacement, a healthy 999 cc on a bore and stroke of 83 mm x 69 mm and a dry weight of 130 lb.
"The engine maintains the traditional Kohler design and quality of our Command family," noted Jason Kreulen, program engineer for the new engine development. "We made it larger and spent time on optimization with various different analytical tools."
These tools included GT Power Model and Computational Fluid Dynamics (CFD) programs to optimize combustion. Kohler also utilized a former Ford Powertrain engineer to help optimize the cylinder head design, resulting in a more efficient design with lower cylinder head temperatures.
"Kohler is becoming more sophisticated in product development by utilizing more finite element analysis (FEA), GT Power Models, and computer-aided manufacturing (CAM) design programs," Kreulen added. "The airflow into and through the head was optimized, which makes for a more efficient engine."
Where the differences between the new engines and existing Command models--and other gasoline engines in the industry--are most evident are right in front, in the form of specially designed oil and air filter systems.
The top access oil filter is a Kohler patented design in which the spin-on oil filter canister is mounted in an inverted position between the cylinders. "Some people are going to question why we put it where we put it," said Jeff Wilke, product analyst at Kohler. "But when they actually spin the oil filter off and find they don't have a mess, that's where the benefits are going to be the most obvious."
The filter system is designed to ensure that oil in the filter is allowed to drain out as completely as possible before the filter is actually separated from the filter base. To ensure that, the filter base incorporates a spring-loaded cup that maintains contact with the filter seal.
During initial turns of the filter when it is being removed, the cup springs upward, which also opens an integral drain valve that allows oil to flow down and out if the filter housing into the crankcase without contact being broken between the filter housing and the seal. As the filter is turned further, the seal is broken, but a slightly longer than usual spud on the filter base allows whatever small amount of oil is remaining in the filter to drain out before the filter is completely removed.
"It came down to taking the initial objectives in the product spec of focusing on the end user and increasing serviceability, looking at all of the current service features and brainstorming in design sessions what could be improved," said Kreulen. "At that point, the design simply spawned from our engineering creativity and experience.
"We've received very positive responses from our OEM customers when they review the engine. They really light up when we show the oil filter mechanism. Since it's a fairly easy mechanism to understand, most customers quickly see the advantages of the no-spill design. They also understand that there's nothing the customer needs to do differently with this design. Turn the filter off just as done on the previous engines."
"The big issue was making key maintenance points more accessible," Litt added. "These things get shoehorned in some applications and if you can see the filter, maybe you're going to change it. But if you can't see it, well, maybe you'll worry about it later.
"Now it's right out in front on both the horizontal or vertical engines, and features easy access. The end user no longer needs to crawl on his back to access it."
The combination of the top access filter and larger oil drain ports allows oil changes to be done more quickly, Wilke said. "The larger drain holes speed up the oil draining out the engine and speed up the service to help that guy who's changing the oil in the field," he said. Another change, only slightly less obvious than the oil filter, concerns the two-stage, heavy-duty air cleaner system, which is also top mounted. While heavy-duty filters are a staple of engines operating in the industrial world, Kohler went to the trouble of designing its own air cleaner.
The filter system is joined directly to the intake manifold with just one gasketed joint as the interface between the filter and engine. This eliminates the hose connections commonly seen on many engine designs. "One of the key considerations was again, serviceability," said Kreulen. "The engine is very easy to access. Take the end cap off to access the filter and the safety filter. This design also optimizes the airflow to achieve higher horsepower. Air filters rob the engine of power and this design provides more control in managing the horsepower than if we used an off-the-shelf filter."
Litt added that the design also "gave us more control over calibration issues," and added, "we eliminated some leak points by going with the elbow right on the canister with the one gasket area where it mounts to the engine."
Other service-related features include a removable blower housing and a simplified valve cover fastening system. Removal of the blower housing involves removing a single screw to allow the shrouds to be snapped off of the main blower housing. This allows easier access to the cooling fins for cleaning, along with more open access to the ignition module.
The valve covers have just a single fastener rather than multiple screws more commonly seen. "There is equal pressure on the gasket during assembly," said Litt. "It's always a question when you're putting in four screws--which one do you torque down first and what happens to the gasket? The one-fastener design eliminates that concern."
The engines incorporate a number of other features that give them the potential for wide application in a number of markets. A 12% torque rise provides faster travel or cutting speed in mowers, along with better lugging performance. Full power is also available off either the front drive or the PTO side, with larger sleeve bearings able to handle the heavier side loads seen in many industrial drive applications. It also significantly increases the charging system capacity, from 20 on previous engines to 25 amps now, and the new engines are also EMC/RFI compliant, the company said.
Another measure of the flexibility of the basic design will allow the company to easily modify the engine to operate on liquid propane or natural gas and plans to offer gasified versions in 2007.
The new Command Pro engines are also designed to be quieter than their predecessors, which Kohler said can result in less operator fatigue. "We did a lot of work to reduce the noise," said Wilke. "We balanced all the rotating components to avoid any primary forces on the engine. We also included items like a nylon cam gear, hydraulic valve lifters that reduce the clanging of valves. A vented lube system reduces lifter clatter and an optimized fan and blower housing system all result in less noise coming out of there as well."
The hydraulic valve lifters, which have been used on Kohler engines since the late 1980s, are also a key service feature, as they eliminate the need for valve adjustments over the life of the engine.
"The hydraulic valve lifters are something carried over from earlier engines because our customers found it a great benefit," said Litt. "The hydraulic valve lifters reduce maintenance because there's no need for valve adjustments. Once the customer has them, he just forgets that he hasn't done valve adjustments, and it's money in the pocket."
It is an irony that, given the fact that there was such an emphasis placed on making the engines more serviceable, the new Command Pro 34, 36 and 38 engines have longer service intervals than many other engines. Oil change intervals are 150 hours. Air filters require changes every 300 hours and, as mentioned, there is no valve adjustment needed for the life of the engine.
The new Command Pro engines have been in test for most of 2006, and field test versions of the both the horizontal shaft and vertical shaft engines have been operating in customers' machines for months. "It's a bigger engine, but one of our major customers was able to put it into his machine with no modifications," Litt noted. "Our experience and feedback from the customers who have it has been pretty positive."
Following the conclusion of reliability testing at the end of the year, Kohler will go into regular production of the new Command Pro engines in the first quarter of 2007.
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|Title Annotation:||INDUSTRY NEWS|
|Publication:||Diesel Progress North American Edition|
|Date:||Oct 1, 2006|
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