The scavenged oil exiting the dry sump pump should flow into a manifold from each pump sec
The job of an engine tuner is to continually discover new ways of gaining performance by making engines live longer and produce more useable horsepower. The tuners sometimes run across undesirable engine mechanics that end up robbing some of the available horsepower. Here are some valuable tips that the average short-track racer can use to help the car go faster. These are simple in concept, but very effective in reality.
Oil Pump Horsepower Drain The oil pump in your engine requires a certain amount of horsepower to pump the oil through the engine, filters, and to and from the sump tank. The amount of horsepower it takes is directly dependent upon the amount of pressure the oil is under at any one point along the route, and the efficiency of the plumbing that the oil has to flow through.
One restriction lies in how the oil is routed through the oil pump on a dry sump system. A more efficient plumbing of the oil flow can result in an increase of 5 to 10 hp, depending on the type of engine. A study of fluid dynamics teaches that a liquid will flow with less pressure through a larger opening and through bends in the plumbing that are designed with a larger and smoother radius.
Running and tuning a new engine on the dyno is just the first step in the process of prepa
If we are scavenging from three locations in the engine into the oil pump, but exiting from only one outlet, the oil from at least two of the pump sections must pass through the chambers of other pump sections in order to flow out to the reservoir can. The proper way to exit the oil is out of each individual pump section into a collector manifold where all of the scavenged oil will flow to the reservoir.
Most top engine builders will tell you to run a manifold, but most aren't willing to tell you how much horsepower gain comes from using one. It is substantial. Because this added pressure (which is actually felt as resistance that requires more horsepower from the engine) is inside the pump itself, it will never register on the oil pressure gauge and be detectible. It will, however, register on an engine dyno. The bottom line is that you need a manifold attached to the oil sump pump so that no oil from one pump section flows into or through another section.
Carburetor Jetting and Power Valve Adjusting Most engine tuning related to air density and humidity is done with the fuel jets, but a more efficient way to adjust the air/fuel mixture to react to small changes in atmospheric conditions is by changing the air bleed jets instead of the fuel jets. These units are easier to get to and are more appropriate for matching the changes in air density to air/fuel ratio.
A much easier way to adjust the air/fuel mixture in order to match current atmospheric con
The air bleeds assist the fuel jets in supplying fuel to the air. Most classes of circle track racing allow carburetors with changeable air bleeds. In the past, changes to the fuel jetting have not adequately modified the air/fuel ratio to affect a gain in horsepower. It was discovered that, in many cases, it is more appropriate to make adjustments to the air bleed to see a noticeable change in horsepower.
We all need to monitor the weather at the track on the day of the race. I have worked with many teams who take weather measurements at the track on race day. These are serious teams who have won big championships and left nothing to chance. They recorded the air temperature, the barometric pressure, and the relative humidity. The engine builder or dyno operator can supply the weather data recorded on the day the engine was on the dyno. That information is entered as the baseline into a small computer and compared to existing conditions. Most popular weather stations built for racing engine applications have provisions for changes to the air bleeds as well as the fuel jets to adjust the air/fuel mixture to current weather conditions.
The power valve is an overlooked performance variable. If not properly matched to the engi
The power valve (PV) is a fuel valve that provides additional fuel flow at higher rpm in a Holley-type carburetor. It operates on vacuum, and various power valves open at different levels of vacuum. Low-speed open throttle yields less pressure (meaning a more powerful suction inside the intake manifold) compared to atmospheric pressure than high rpm at open throttle. The vacuum in the intake manifold is reduced as the rpm increase and the power valve opens at a preset pressure level to provide added fuel for a more efficient air/fuel ratio.
If the PV opens too early, the air/fuel mixture will be too rich. If it opens too late, the engine will starve for fuel. Both results bring a loss of horsepower. Before trying to work with the PV, it is best to know the amount of manifold vacuum you have.
If the PV closes at 5 inches of Mercury, it will open when the engine accelerates and the pressure in the intake manifold reaches that level. The engine might start out drawing 10 inches of vacuum on corner exit, be down to around 5 inches at the flagstand when the PV opens, and be at 2 inches or less at the end of the straightaway at the engine's highest rpm.
It is best to try different PVs, especially while the engine is on the dyno, to find the maximum efficiency and horsepower. Monitoring the exhaust gas temperature (EGT) would be a great way to judge the fuel burn efficiency at various rpm. Is this done on a regular basis? In reality, no.
Make sure the fuel bowl vent (the angle cut tube that is sticking up at the left side of t
Air Filter Tech
Most of us don't think much about the air filter as it relates to horsepower, but there are some tuning tips that can help produce added horsepower. We need to think about how the air is routed to the carburetor and how we can improve the flow.
Four-barrel carburetors were designed originally to draw air from the sides. If we direct air from the base of the windshield through a tunnel to the carb, or from any one direction, we could be disturbing the function of the carburetor and not getting an even distribution of air/fuel mixture to each cylinder.
The entire surface of the air filter should be pressurized by the incoming air-not just the side facing the air inlet. Many engine tuners tape off a portion of the air filter or build a wall in front of it to force the carb to draw its supply of air from all around the air filter in equal amounts.
Improved air flow is critical to the carburetor. That is why racers are particular about the design of air filter housing. Care should be taken to make sure that the air coming into the carb is flowing in from all sides.
Adequate air flow is equally important for the fuel bowl vent atop the carburetor. A minimum of 31/44 to 1 inch of space must remain above this vent so that the fuel bowl will be properly ventilated. These vent tubes can be cut shorter to provide more space between the top and the air filter box.
Spark Plug Tech
The heat experienced by your plugs can dictate how efficiently your engine is burning the air/fuel mixture. One easy way to tell if your plugs are getting hot enough is to observe how far the heat has penetrated the threaded portion of the plug. We need to make sure that we are using the correct length for the spark plug's threaded portion. The threads cannot extend into the combustion chamber or end up short of the chamber.
Many top engine tuners have made a science of inspecting the tip and insulator of the plug. Most short-track racers don't have the time or the patience to get that technical. If you remove the plug and visually observe how many rings of the threaded portion of the plug are discolored, you can tell if the plug is hot enough for your application. Usually, if two to three threads from the end of the spark plug are discolored, it means that there is sufficient heat to provide complete combustion.
We can easily read the threaded end of the spark plug to see how much heat is being genera
The level of voltage being supplied from the battery helps determine the degree of heat of the spark plug. Teams that run without alternators run the risk of having low voltage in the system, resulting in a cooler spark. A minimum of 11.5 volts should be maintained to the coil so that the spark will generate sufficient heat needed to completely ignite the mixture. The engine will run at a lower voltage than that, but a number of negative issues may arise that decrease your engine's horsepower.
Plug and Coil Wire Efficiency
There are a couple of tricks that involve the spark plug wires that supply the energy to ignite the air/fuel mixture in the engine. The first important issue is the quality and size of the wire. It goes without saying that the better wire you run, the better ignition you will have.
It's important to keep the length of the ignition wire from the coil to the distributor as short as possible-under 18 inches, preferably at or around 12 inches. It is the same with the plug wires, i.e., the shorter the better. Line loss, which is a loss of energy when electricity flows through a wire, decreases the heat generated by the spark and results in a less efficient burn of the air/fuel mixture.
The plug wires that are routed to cylinders beside each other in the firing order should be crossed to eliminate interference. High-energy wires that run close together and parallel will pick up the energy from each other unless the field is broken by crossing the wires to form an "X." In a GM V-8, the fifth cylinder fires just before the seventh cylinder, and they are next to each other. Those two plug wires need to be crossed.
Oil Temperature Generates Horsepower In any internal combustion engine, heat is horsepower. All of the elements of the engine must contribute to the overall operating temperature of the engine. The oil that flows through the engine is a source of retained heat and must be maintained at an optimum temperature.
As the oil becomes hotter, the engine will actually generate more horsepower. For circle track racing applications, the oil temperature should run 220 to 230 degrees. Modern synthetic oils will stand temperatures upwards of 300 degrees, and most high-quality "standard" engine oils will sustain comfortably in the 230-degree range. To a point, the hotter the oil, the better the engine will run. With modern components, and the way race engines are assembled, there should be no problems with the higher oil temperatures listed.
Proper Oil Filtering
An item unrelated to horsepower and more appropriately related to the survival of the engine is the filtering of the oil. The placement of the oil filter and accessory filters such as an Oberg filter is important for longevity. Having a ton of horsepower is of no use if the engine does not live long.
The Oberg filter is a screen and/or paper filter that is designed to catch larger-diameter particles after they leave the engine and before they are pumped back into the system. The filter should be placed just behind the scavenging pumps and in front of the reservoir can. It should be checked often for the existence of small particles that can mean a bearing is going bad or any other part is failing. In the event of catastrophic engine failure, the Oberg type of filter will catch large metal pieces.
The oil filter should be the last thing the oil passes through before entering the engine. The filter will prevent contamination from getting into the engine. The contamination could come from welding slag in aluminum oil coolers. Using old oil lines is another source of potential contamination. Never reuse old oil lines from blown engines because they may have pieces lodged in the lines. The lines are much cheaper to replace than a complete motor.
Setting Timing and Advance
Setting the timing in your race engine can affect the efficiency of your ignition system. There is a way to set the timing, perhaps different from the method your team uses, that will assure the proper timing advance at top engine rpm.
Many teams will set the low-speed timing and then perhaps check the high-speed timing with any advance timing the distributor provides by revving up the motor to a high rpm. If at some point in the future the advance timing changes, and it can with mechanical systems, then we won't necessarily have the proper high-rpm timing we need.
We need to run the engine up to an rpm that is just above the point where the maximum high-speed advance is activated, and set the total timing we will need before top dead center (BTDC). Then, at the lower rpm ranges, the timing advance will be deactivated and the engine timing will be retarded by some number of degrees. This low-speed timing is not as important as the high-speed timing. The only reason we need less low-speed timing is so the engine will start easily.
Many distributors have a mechanical advance mechanism that may not be totally reliable for the advance curve. Therefore, we cannot count on the distributor adding a constant number of degrees of advanced timing to the low-rpm timing. When we set timing with full advance, whatever that may be at any given time, we are assured of the correct high-speed timing when the engine is at race-speed rpm.
Cooling Fan Techniques
Many racing engines do not need a cooling fan. Some need the fans only at lower rpm and need for them to be less efficient at higher rpm. Running a fan uses up some of the available engine horsepower. The idea is to run the fan only enough to cool the engine.
Some believe that having a high water temperature creates the need for a bigger and more efficient fan, when the real culprit is that the flow of water through the radiator is too fast to enable proper cooling. The radiator needs time to draw off the heat from the coolant. If we do not restrict the flow of coolant by use of a restrictor inserted into the system, we may never be able to lower the water temperature to an acceptable level.
A stock water pump is designed to run at 3,000 to 4,000 rpm-not at or above 6,500 rpm, as in racing applications. When we spin the water pump that high, we are forcing even more water through the system at a higher velocity, draining even more horsepower. There are several things we can do to help this situation.
By installing a larger pulley behind the fan, we can alleviate the drain on horsepower while slowing the flow of water through the engine. This slows down the rotation of the fan and the water pump, which both drain horsepower. Less drag from the fan and a slower flow of water helps the radiator do its job and can mean an additional 10-20 hp going to the rear wheels.
Exhaust Header Design for More Horsepower
The diameter of the header tubing must be correct for the size and design of the engine in order to produce maximum torque and horsepower. Installing the largest header tubing will not necessarily yield the best power numbers. Consult your engine builder for information on the best header design to use. Better yet, send your headers to be used when the engine is on the dyno.
Always tie together the two sides of the engine with a crossover tube. This connection should be located within 30 inches of the collectors that are located at the ends of the headers for improved scavenging effect.
Coating the headers actually gets rid of the heat of combustion faster and moves it out of the pipe to help cool the engine as well as the engine compartment. Upon cool-down, the mechanic will notice that working around the coated headers is much easier because they cool much faster.
The average racer can benefit from the hard work and innovation of top engine tuners. You do not need an education in electrical or mechanical engineering to understand and apply the suggestions. If you are able to utilize even a few of these simple, yet effective tips to your racing effort, you will enjoy a more powerful engine that just might live a bit longer.
Editor's Note: Crandall Sizemore has worked with just about every type of racing engine, from the Cup teams to Late Model short-track engines. He has worked with some of the top engine builders and race teams in many divisions as well as the best damn mechanic we've known-Smokey Yunick. His expertise comes in tuning engines to a particular application and having a knack for discovering how all of the components work together in a racing engine.