{"id":82547,"date":"2021-11-23T07:31:38","date_gmt":"2021-11-23T15:31:38","guid":{"rendered":"https:\/\/www.racingjunk.com\/news\/?p=82547"},"modified":"2021-11-23T07:45:07","modified_gmt":"2021-11-23T15:45:07","slug":"dyno-to-race-day-tuning-tweaks-to-transition-to-the-track","status":"publish","type":"post","link":"https:\/\/www.racingjunk.com\/news\/dyno-to-race-day-tuning-tweaks-to-transition-to-the-track\/","title":{"rendered":"Dyno to Race Day: Tuning tweaks to transition to the track"},"content":{"rendered":"

Running your engine on a dyno helps to zero in your engine\u2019s specific characteristics and tuning specifications. You will leave with a better understanding of your engine, however may only provide data specific only to that location, time of day, and season. Taking your vehicle out to the track with a different air density and running with your new engine specs is sometimes a disappointing experience.<\/p>\n

The weakest link between the dyno and the track is often the fuel system. Some fuel systems can maintain a standard when running in differing air densities. Examples are common circle racing 305, 360, and 410 MFI engines. Other engines need regular tweaking. A custom setup with a unique engine size or application can be more difficult to transition between the dyno and the racetrack or course.<\/p>\n

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This mechanical fuel injection setup on an outlaw sprint car depends on jetting changes to maintain the best fuel mixture for air density changes. Air density changes occur from the dyno-to-track and from track-to-track. This popular FI setup is made by Engler Machine & Tool Company who also provides dyno setup services with experience in the transition from dyno-to-track.<\/strong><\/em><\/figcaption><\/figure>\n

Problems transitioning to the track<\/strong><\/p>\n

So where is the problem?\u00a0 The dyno is in a controlled environment with a specific temperature, atmospheric pressure, and atmospheric moisture content.\u00a0 In addition, air quality that is characteristic of an indoor environment at an industrial location is also a factor.\u00a0 The dyno test takes place at a particular altitude and season of the year.\u00a0 The results of the dyno test are dependent on these factors.\u00a0 When you go out to the track, the atmosphere can be very different from the altitude of the location and the season.<\/p>\n

The following is a mechanical fuel injection setup for a 305 cubic inch methanol V-8 racing engine with a 3.5 GPM fuel pump.\u00a0 It is from an indoors dyno at a location near sea level and then outside during the summer, at a high-altitude racetrack:<\/p>\n

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Weather combinations are shown for both locations.\u00a0 A density altitude of 1,620 feet occurred for low altitude dyno location on the day and time of dyno testing in-doors.\u00a0 A density altitude of 7,270 feet occurred for the high-altitude track location on the outside day and time of racing.<\/p>\n

*Barometer values provided by the local weather report are corrected to provide a standard reading at sea level across all altitudes.\u00a0 Uncorrected values are more accurate values when it comes to engine tuning.\u00a0 These uncorrected values tend to decrease as altitude increases.<\/p>\n

Mechanical fuel injection setups<\/strong><\/p>\n

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ref. High HP Tuning for MFI for Norm. Asp. Racing Engines<\/a>, fuel injection tune-up analysis from Air Density Online<\/a><\/strong><\/p>\n

Two jetting setups were determined for the mechanical fuel injection.\u00a0 Both had the same, optimum air\/fuel ratios.\u00a0 These two setups were determined from the resulting jetting combinations and air density.\u00a0 Both are nearest an optimum target of 5 to 1 air\/fuel ratio.\u00a0 That AFR produced the best power and punch on the dyno and on the track out of the turn.<\/p>\n

Both had the same fuel pressure at 5,000 RPM that was just over 50 psi.\u00a0 That was considered the minimum pressure for the best punch coming out of a circle race turn \u2013 a standard from experienced mechanical fuel injection suppliers.\u00a0 Both nozzle and main bypass jetting changes were necessary to hold those optimum values for the two different locations and density altitudes. \u00a0The fuel to the engine differed quite a bit.\u00a0 The dyno test would not reveal the optimum jetting for the high-altitude track.<\/p>\n

Density altitude and air density percentages were provided instead of actual altitude.\u00a0 Both of these values include effects from the weather and altitude differences.\u00a0 Density altitude and air density are more valid indicator of the effect on power and the tuning needs than altitude alone.\u00a0 Spark plug readings, engine temperature, the feeling of punch out of a turn, and lap times are common tuning indicators in circle racing.\u00a0 They are used to make jetting adjustments for the best outcome.\u00a0 Tuning at this track weather would be difficult to sort out for an engine right out of the dyno shop under different conditions and circumstances.<\/p>\n

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High output racing EFI, like on this 2500+ HP ProMod drag racing car, most often run fuel rich for good response, engine cooling, and a safety factor to minimize engine damage from preignition. Often, they run open loop since closed loop tuning values from onboard sensors may not be accurate for rich mixtures. As a result, fuel maps set up on a dyno usually need to be adjusted for air densities on the track that differ from the dyno test air density. If the EFI is run in closed loop, enrichment AFRs should be maintained for cooling and engine response. Prior dyno testing and optimization would be at one air density. If the overall setup is robust, a closed loop control should compensate for air density changes. That is, there is adequate range for enrichment or leaning for air density variations from the EFI controller. If nozzles are marginal or the fuel map is overly rich, proper EFI control may be more difficult in the transition.<\/strong><\/em><\/figcaption><\/figure>\n

Jetting changes for different racing locations around the country are a challenge for crew chiefs and tuners once the engine leaves the dyno. Air density at different locations varies from altitude, temperature, humidity, and air pressure. Altogether, that determines a fuel flow target specific to the current conditions. The selection of a dyno service for the dyno-to-track transition could be dependent on added fuel system tuning, either from the dyno shop with experience or a tuner with experience. If not, trial-and-error adjustments can be costly and time consuming.<\/p>\n

Additional factors should be considered when transitioning to the track after a dyno test that are discussed next.<\/p>\n

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Boating engines, such as this stunning fuel injection engine on a show quality racing boat, can present challenges when transitioning from a dyno to a race. The air in a dyno facility is often drier than the air on the water, affecting the air density. In addition, the dyno may be located in-land at a different altitude while boats running in the ocean are at a sea level. Tuning is necessary on the water for mechanical fuel injection and many other fuel systems.<\/strong><\/em><\/figcaption><\/figure>\n

Environmental factors at a dyno facility<\/strong><\/p>\n

In addition to atmospheric and altitude differences between the dyno and the track, other factors influence how the engine performs in the different environments.\u00a0 The dyno is stationary, so there are no effects from ram air or from wind resistance at high speed.\u00a0 In addition, the engine is stationary with no effects on the fuel system from acceleration, turning, or deceleration.\u00a0 These changes may alter fuel flow into the engine when at the track.\u00a0 The original fuel tank in the racer also may experience fuel sloshing or circulating bubbles from return fuel entries that may not be demonstrated in a dyno test with a different fuel tank source.\u00a0 These changes can affect the tune-up needs at the track or course.<\/p>\n

Dyno calibration can also be an issue.\u00a0 These factors may affect dyno calibration.<\/p>\n

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  1. Calibration of the load measuring instrument on the dyno. One of our local dyno service providers consistently reads horsepower and torque values 10% higher than expected values from similar engine builds.\u00a0 It was reported that the dyno operator has not calibrated anything in the test station since installation many years ago.\u00a0 The dyno operator is also the engine builder, so their motivation is to get good power numbers.\u00a0 Most racer customers are not aware of the absence of calibration and the exaggeration of the power values that may occur.<\/li>\n
  2. Calibration of other instruments such as measuring sensors: fuel flow & fuel pressure, air flow, and temperature measures (fuel temp, air temp, oil temp, exhaust temp). Most dyno service providers do not maintain international calibration standards often required in commercial manufacturing or service.<\/li>\n
  3. Dyno setups and procedures may involve different techniques to collect date. Here are some factors to consider:<\/li>\n<\/ol>\n