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What's New In High Performance
By Ken Weber
If the Greek philosopher Socrates didn’t say it, he probably would agree that the acquisition of knowledge is one of the most important pursuits of human existence. You could probably make a case that food and shelter come first, but without knowledge, how could you acquire them? Certainly, when building an engine, it helps to know what you’re doing and to be current on the latest technology. For sure, if you’re not up to speed, your competitor will be.
To that end, Superflow Corp., and the University of Colorado at Denver, hosted the annual Advanced Engine Technology Conference (ATEC) this past December. Presented at the Antlers Plaza Hotel in beautiful Colorado Springs, CO, the theme of the three-day conference was to offer people in the engine building industry the opportunity to share information about current developments.
The conference was emceed by Harold Bettes, vice president of Superflow Corp., and his humor and antics alone were worth the price of admission. Of course, if you won the drawing for a flow bench given away by Superflow, the price of admission became secondary.
A number of other prizes were given away to those guessing the horsepower of Floyd Kyle’s big block Chevy Malibu drag car, or the power of several bikes tested on the Autodyne and Cycledyn, both located at the Superflow facility just a short bus ride up the street from the conference’s hosting hotel.
The engine in Kyle’s Chevy was run on the engine dyno first on Monday night, during the tour of the Superflow facility, where it made 680 hp. On Tuesday the engine was installed in the car and run on the chassis dyno where it made 501 hp at the rear wheels. The game was to guess in advance the amount of horsepower lost between the engine dyno and the chassis dyno. If your guess wasn’t within one to two horsepower on either the Chevy or the bikes, you weren’t in the game.
While the conference is certainly slanted toward performance related topics, the 13 different speakers covered a wide range of useful and insightful information. Information glean-ed from the presentations on engine bearings by John Havel of Clevite Engine Parts, and on valve design and materials by Ted Tunnecliffe of Met Tech, for example, would be useful in even the most basic engine rebuilding business.
I counted 242 attendees and 13 speakers on the lists handed out during the conference. In addition to the USA contingent, there were attendees from Norway, Argentina, Columbia and Canada. It seemed that this number was almost matched by the number of Superflow and University of Colorado people making sure the proceedings went smoothly.
The best went first
The presentations were kicked off by, in my opinion, the most stunning presentation of advanced technology of the conference. Yehoram Uziel, of Soligen Technologies, Northridge, CA, detailed his Direct Shell Production Casting (DSPC) process of producing prototype castings without the need for conventional patterns, core boxes, or other tooling. The process goes directly from the customer’s CAD file to the mold, and then to the foundry to cast the part. In this technology, the prototype part can be produced, tested and revised as necessary without any investment in patterns or tooling.
The DSPC process produces ceramic casting molds directly from CAD files. The computer literally prints the mold, one layer at a time using a ceramic powder and a binder. If you have ever watched a dot matrix or ink jet printer at work, you have the idea of how the mold printer operates. Just imagine the print head going back over a previously printed layer to add a new layer time after time until a three dimensional mold is completed. Molds can be made for parts cast from any normally casted metal.
Uziel reported that in addition to a large segment of the world’s car makers, at least one well known racing team has used his company’s capabilities to produce intake manifolds that on the outside are identical to the one required by the rules, but somewhat different inside.
Intake valve seats
The renown writer and engine builder, David Vizard, of Vizard, Inc., Colton, CA, presented a compelling case for the use of 30-degree intake valve seats. The game plan he presented is to use a 30-degree seat to gain a large increment of flow in the .050" to .300" lift range where the valve spends most of its time. This comes at the expense of a smaller increment of high lift flow.
The key ingredient in the plan is the shape of the approach to the seat. When a 30-degree seat is used, for any given size valve, the throat below the valve will be smaller than those with a 45-degree seat. This hurts the high lift flow. However, this penalty in high lift flow can be minimized by using a slightly narrower seat, combined with the correct combination of approach angles.
The angles Vizard offered as a good starting point, are a 45 degree x .046" wide, a 60 degree x .035" wide, and a 75 degree x .075" wide angle(s). The other key ingredient is to cut a groove in the chamber side of the valve, .060" radius, .025" deep, and centered .055" to .062" from the edge of the valve. The purpose of the groove is to increase the conformability of the valve to the seat.
To maximize the potential of the better low lift flow, cam and port changes also need to be made. You can reduce cam duration four to six degrees, widen the lobe separation angle a couple of degrees, and use a slightly smaller port cross section.
Insights on intakes
Keith Wilson of Wilson Manifolds, Ft. Lauderdale, FL, presented a step-by-step video on the rigors of making an intake manifold. Essentially, they chopped an Edelbrock manifold all to pieces, welded it back together, ported it, shot peened it, milled it, drilled it and flow tested it. And when all is said and done it looks like it just came out of a brand new Edelbrock box.
The craftsmanship exhibited in the video and the products Wilson had on the display table were exceptional to say the least. If you didn’t know about all the welding, you would swear these pieces were just examples of meticulously ported, but otherwise untouched Edelbrock castings.
Particularly interesting was his discussion of some of the problems associated with NASCAR restricter plate manifolds. The problems of fuel distribution and fuel puddling, how the fuel tends to bounce off the floor of the manifold and go right back up through the restricter plate, and the role of the pipe organ in the plenum.
His solution to the wet flow problem is to shot peen the floor of the plenum to help break up the fuel particles. Because the restricter plate shears the fuel out of suspension in the air, the use of the tubes under each hole in the plate helps suck the fuel back into the stream. Wilson also lowers the roof of the runners, so they are lower than the ends of the tubes, reducing the volume in the manifold and improving flow between the tubes and runners.
John Havel, director of aftermarket engineering, Clevite Engine Parts, Ann Arbor, MI, discussed bearing performance and construction. Starting with an overview of bearing properties and lubrication requirements, he pointed out that because the loaded shaft runs off center in the bearing bore, it is common for the oil film to be only .0001" to .0002" thick. For this reason, the surface condition of the shaft and bearing housing bore are very important to maintain a consistent oil film across the face of the bearing.
Part of the presentation was on the relative fatigue strengths of the different types of bearing materials. The "flaking" seen on the surface of some bearings is, in reality, fatigue failure of the babbitt overlay. The fatigue strength of the babbitt overlay is inversely proportional to its thickness (thinner is stronger). Havel pointed out that Clevite replacement bearings have a .001" babbitt over-plate, and the performance bearing has a .0006" over-plate. The thinner overlay has a higher fatigue life by a factor of 10 or more.
If you’re not already aware of it, you should know that most OEM cam bearings are bored to size in the block. This is why cams won’t always go into newly installed cam bearings.
Tractor pull technology
Tuesday’s session was kicked off with Dave Bamber of Bamber Racing Engines, Bolivar, MO. Bamber Engines is heavily involved in tractor pull technology, and he had a single cylinder head he manufactures on his CNC equipment on display that had a 3" intake valve. His description of an inline six cylinder diesel with 17 lbs. pistons, four turbochargers, turning upwards of 7500 rpm, and making more than 3000 hp with 240 lbs. of boost amazed the audience. They wrap two-inch cables around the engine to keep the heads on in the event of an explosion.
In the remainder of his presentation, Bamber covered some of the considerations in cylinder head development to "optimize the compromise." One area he talked about is the condition of the charge air in the combustion chamber, and the necessity to make sure the spark plug is in the area most favorable to ignition, avoiding areas of wet flow. Either change the flow away from the plug or change the plug location were Bamber’s recommendations.
Racing valve springs
Steve Bown, president of Performance Springs, Inc., Brighton, MI, and former senior valve spring design engineer for Peterson Spring, discussed some of the design parameters and application considerations for racing valve springs.
One area of interest to every engine builder is spring life. Good service life starts with the proper spring selection in the first place. Different applications such as drag racing and endurance racing (circle track or road racing), require a different approach to spring selection and installation.
Drag springs should be installed to maximize the distance-to-coil-bind and still provide enough pressure to control the valve. The retainers should be a line fit to slightly loose in the spring, and the diameter should be at least the size of the spring OD, minus one times the wire diameter of the outer spring.
Endurance springs should be installed to minimize oscillating stress. Springs with higher spring rates are lighter and perform better, but have higher operating stress so the key is to maximize spring rate without putting the spring into a danger zone on stress. The retainer should be a line fit to a snap fit, but not so tight as to spread the top coil. Cooling the spring with spray bars and the placement of the spray bars is critical to spring life.
The modern technology in two-stroke engines is reducing emissions levels and fuel consumption through electronic controls. The potential of these lightweight engines for future automotive applications is high. In the afternoon session, Eyvind Boyesen, founder and president of Boyesen Engineering, Lenhartsville, PA, presented an overview of the various designs of two cycle engines, and the advantages of each type.
Boyesen pointed out that the Achilles heal of the two-stroke engine is keeping the intake charge from short circuiting and blowing out the exhaust port causing high emissions levels. Current trends to address this problem such as Orbital, Lotus, Ficht and Honda technologies hold promise for the future by keeping the fuel out of the cylinder until the exhaust port is closed.
Tim Wusz, performance products engineer for 76 Performance Products, Yorba Linda, CA, presented an in-depth look at racing gasoline and its applications. His topics included octane numbers, leaded versus unleaded, too much octane, volatility and distillation, slow burn versus fast burn, detonation and gasoline storage.
One of the most misunderstood items in the performance industry is gasoline. Foremost is the misconception that racing engines need a slow burning fuel to make horsepower. This notion probably came from the fact that alcohol burns slower than gasoline. However, it completely ignores the different thermal properties of the two fuels.
Alcohol’s big contributor to power is its latent heat of evaporation that cools the intake charge and thereby increases volumetric efficiency. In simple terms, fuel burns at the same rate all the time. Why else would we need ignition advance mechanisms? The higher the rpm you turn the engine, the faster the fuel needs to burn. Diesel engines turn slow because diesel fuel burns slow. Aircraft engines turn slow because aircraft fuel burns slow. Makes sense, right? Not that aviation gas won’t run, it just won’t be optimum in a high rpm racing engine.
GM’s SB2.2 engine
Ron Sperry of GM Motorsports, Warren, MI, presented a look at the design process involved in creation of GM’s SB2.2 package for NASCAR. The design program consisted largely of taking the canted-valve Trans-Am head, in which all of the ports angle in the same direction, as a starting point. Then, using two ports on one end of the head and mirror imaging them on the other end, the result is a set of ports that continue the curvature of the intake runners from the manifold, on down to the valve with no reversal of direction. The concept is simple, but the packaging problems were considerable.
Just the effort that went into the design of the upper head bolt (nearest the lifter valley) that’s in the floor of the intake port was a story in itself. The lifter bore spacing was also changed to accommodate the necessary pushrod locations. Sperry’s presentation was a great insight into the challenges design engineers wrestle with when creating a new product.
Next on the podium was Jim McKenzie from Hendrick Motorsports, Harrisburg, NC. Jim is a former customer service engineer for Superflow who migrated to Hendrick via the Roush Racing engine shops. He currently is a dyno operator at Hendrick and he related some of the details of dyno cell configuration, testing and calibration. Harold Bettes begged the representatives of the media in attendance not to say that the biggest revelation of the conference was that Hendrick Motorsports uses a 5 hp Briggs & Stratton engine to calibrate the oxygen sensors on its dynos. Remember, you didn’t hear it here.
McKenzie made a strong point of emphasizing the need to calibrate, calibrate and recalibrate, to keep the margin of error in the dyno results to an absolute minimum.
Diving into valves
Ted Tunnecliffe, retired chief aftermarket engineer for Eaton Engine Components, North America, presented an in-depth exploration of valve technology. His discussion of valve design was condensed from a training seminar given to Eaton technical personnel. Opening with the basic manufacturing processes, Tunnecliffe progressed to metallurgy, heat treatment, testing, corrosion, wear resistance, microstructures, and finally ended with advanced designs.
His discussion of manufacturing processes put to bed the misconception that a two-piece valve is a stem with the head welded on. In fact, the welding is done mid-stem with either a friction weld or a resistance weld. So, if you’ve had the head break off of a valve, don’t blame the weld because it’s not the problem. The reason for two-piece valves is to use a high temperature alloy for the head and lower stem, and a good wearing alloy for the upper stem.
Winding up with advanced designs such as internally cooled (sodium) valves, and the beer can valve, so called because of its thin-walled, lightweight construction, Tunnecliffe mentioned another advanced design under development by Harley Davidson that significantly improves air flow. Very simply, it’s an intake valve with holes in the fillet, covered by a smaller valve which opens during the intake stroke. It has demonstrated marked improvements in power, fuel consumption and emissions.
Thomas Griffin, of Competition Cams, Memphis, TN, concluded the conference presentations with his look into the life and times of the valvetrain. In their presentations at the 7th and 8th Superflow AETC conferences, valvetrain dynamics and the causes of valve bounce were discussed. This year, as a follow-up to those presentations, the material presented focused on the entire valvetrain system and the effect that changing a single item has on the whole system.
After a lesson in vibration, harmonics and natural frequencies, Griffin illustrated the effect reduced component mass, different cam profiles, and different spring combinations can have on valve bounce at closing. He also compared the difference in valve motion traces at low rpm versus high rpm.
Of particular interest was the comparison of pushrod forces at low and high rpm. At low (below 5000) rpm the pushrod forces are mostly a reaction to valve spring pressure. As the rpm increases, the inertial effects of accelerating the valve up to maximum velocity and then slowing it down again changes the entire force picture. The inertial effects become the dominant force, particularly at the initial opening and final closing points of the valve events. At high rpm, valvetrain inertia over the nose of the lobe reduces loading, like driving over the crest of a hill fast enough to get light in the seat.
We were treated to an interesting ultra slow motion video of a rocker arm and valve spring in action at various speeds into the 9000 rpm range. The dynamics of the valve spring at work are an amazing thing to see. Once the valve has opened and returned to the seat, the middle coils of the spring continue to cycle up and down between the spring seat and the retainer. It makes me think of a fat man jumping up, and when he comes back to the floor and stops, his spare tire continues to cycle up and down.
The video showed the different oscillation characteristics of different springs at different rpms. From this example, I could visualize the possibility of spring harmonics so intense that they would cause the valve to open again on its own.
The closing banquet was equally as much fun as the rest of the conference. The prizes were awarded, and the keynote address by Paul "Scooter" Brothers, head of research and development at Competition Cams, was good food for thought. Of special mention is the lifetime achievement award presented to Dr. Dean Hill of New Mexico State University. A long time gearhead, his love of nitro is well known, as is his dedication to teaching chemistry to college students.
Throughout the conference, participants were encouraged to sit with different people at meals and talk to different people at breaks to develop new contacts and share ideas. These networking opportunities are invaluable in developing business contacts. Where else can you have breakfast with Allan Lockheed, author of the Engine Expert computer program, lunch with a Ford Formula One engineer, and have dinner with Joe Mondello of Mondello Technical School, renown performance head builder? If you go to this year’s conference, be sure to take a lot of business cards.