Abacus Racing in Virginia Beach has both a chassis dyno and an engine dyno on premises to facilitate the engine tuning needs of our clients. Read below to learn more about each.
Our chassis dyno is based on the DynoJet Model 248 single drum dyno. This dyno features a 48-inch diameter drum and 1200 whp capability. DynoJet’s are known for their durability and repeatability. The repeatability is due to the simple fact there is only one moving part- the drum. Wheel horsepower is determined by how quickly your vehicle can accelerate the drum. By sampling the rotational speed of the drum the acceleration rate is determined. Once the acceleration rate known, wheel horsepower is calculated. No special absorbers or brakes are attached to your vehicle and you don’t need to know the weight or gear ratios of your car. The vehicle is strapped into position on the dyno, an ignition lead is connected to your vehicle and you’re ready for testing. For advanced engine tuning, additional engine parameters can be monitored and logged. We can provide Wideband 02, fuel pressure and manifold vacuum or boost.
If you would like to test your car at our shop, please contact us to set an appointment. Baseline testing (for three test runs) is $75.00 (no air/fuel) $100 (with air/fuel). Three test runs are accomplished to ensure the vehicle has stabilized. Vehicles that are not run at WOT often see an increase in power from the first to second run and the third run will usually overlay the second confirming the power has stabilized.
If you’re interested in extended tuning and testing, the Dyno may be rented for longer blocks of time.
Please contact us for details.
More Chassis Dyno Information
Can horsepower at the flywheel be determined solely from wheel horsepower (whp) readings? The short answer is no. Wheel horsepower is equal to engine horsepower minus the horsepower it takes to rotate the driveline components. The horsepower absorbed by the driveline due to friction, windage, inertia, rolling resistance etc., results in wheel horsepower readings lower than the actual flywheel hp. Unfortunately, there is no quick or convenient way to accurately measure overall driveline losses on a vehicle.
Driveline losses noted above can be lumped together and expressed in terms of efficiency. Typical driveline efficiencies are quoted between 80 and 85% for the average vehicle. By guessing at the driveline efficiency of your car, estimated flywheel horsepower can be determined. For example, if your car produced 300 whp and you estimate the driveline is 80% efficient, the engine would be producing 375 hp (300/0.8 = 375) at the flywheel. The problem is we really don’t know exactly how efficient (or inefficient) a particular driveline may be. If you instead assumed it was 85% efficient the same 300 whp would be equivalent to 353 hp (300/0.85 = 353) at the flywheel. That’s a 22-hp difference for the same 300 whp. To make things worse a very efficient or inefficient driveline will break out of the 80 to 85% rule of thumb. Flywheel hp derived from whp should be used with caution.
Keep in mind that whp readings obtained on the chassis dyno reflect the total power available to propel the vehicle down the road. Wheel horsepower is an excellent indication of the performance potential of your vehicle. Be sure to clarify whether it’s wheel horsepower, estimated flywheel hp or brake horsepower you’re talking about when comparing numbers. It is also beneficial to note what brand dyno was used to obtain the power readings. Aside from the usual testing variances, results obtained on different dyno’s of the same manufacturer are generally very close. A comparison of results between different manufacturer’s dyno’s e.g., Dynojet and Mustang will show some variation possibly up to 5% of the whp reading.
Can steady-state testing be performed on the DynoJet? DynoJet’s are equipped with the Dyno-Trac system that allows the operator to maintain a steady load on the test vehicle. Dyno-Trac is designed to maintain either a wheel speed or engine rpm regardless of the throttle opening. The load setpoints are adjustable on from the operator’s pendant.
Dyno-Trac does not provide power or torque readings. Absorption type chassis dyno’s do have the capability to provide steady-state torque and power readings. The maximum power that can be continuously sustained is a function of the absorber (brake) capacity, the cooling system (car and dyno) and the duration of the test.
We mainly use Dyno-Trac for part-throttle mapping of EFI systems. The dyno is programmed to maintain an rpm setpoint and the throttle angle or MAP pressure is varied to permit tuning of numerous load points at that rpm. This is repeated for several rpm steps until the fuel and ignition maps are almost filled in. This method is used in conjunction with a wideband O2 so part-throttle maps can be developed quickly and efficiently.
Engine dynamometer testing is an important and integral part of an engine development program. The ability to accurately and repeatedly measure, control, and monitor the engine is the hallmark of the engine dyno. No other piece of shop equipment can match the overall test capabilities of the engine dyno.
Our facility is equipped with a Stuska Model 800 water brake dynamometer. Data acquisition and processing is handled by a Depac data logger. Recorded data is stored and displayed on a PC running Depac software. The Stuska Model 800 water brake is capable of absorbing 800 hp at 8,000 rpm.
With the rise in popularity of the chassis dyno, many people consider engine dyno testing expensive, unnecessary or redundant. A comparison of engine and chassis dyno capabilities can help determine which dyno will meet your objectives. Our engine dyno test package includes free chassis dyno testing to verify “installed” engine performance expectations.
More Engine Dyno Information
What is an engine dynamometer? The engine dynamometer is a device used to measure engine power developed at the flywheel. A typical dynamometer consists of a chassis or stand to hold the engine, a brake to load the engine and a strain gauge or load cell to measure the torque applied to the brake. A cooling system maintains engine temperatures and a data acquisition system monitors and records various sensor outputs such as rpm, torque, water and oil temp, oil pressure and so on. Recorded data is stored for output in graphical and numerical formats. The dyno is installed in a purpose built test cell with considerations for noise, air intake, exhaust and cooling. The control room is at the forward end of the test cell where the remote throttle, load control, instrumentation and computers are located. The test cell is visible from the control room through a viewing window.
The term brake horsepower (bhp) refers to the horsepower measured at the dyno brake. It is generally assumed the dyno brake is directly coupled to the flywheel or crankshaft. Therefore, bhp usually represents power measured at the flywheel although this is not always the case. For example, motorcycle engines may have the dyno brake coupled to the transmission output shaft or outboard marine engines may have the dyno brake coupled to the prop shaft on the lower unit. In the preceding examples, the measured bhp would not be representative of flywheel or crankshaft horsepower due to transmission or driveline losses.
Technically speaking a dyno does not directly measure horsepower. The dyno measures engine rpm and brake torque. Brake horsepower is then calculated using the formula bhp = (rpm*torque)/5252. Dyno’s equipped with electronic data gathering and processing make this calculation transparent to the operator.
How is the dyno used for engine development? The engine dynamometer is a device designed to measure engine power output. The basic premise in engine development work is a comparison of engine output in different configurations. An engine is tested in configuration X, changed to configuration Y and tested again. The recorded power and torque of the engine in both configurations is compared. A judgment is then made as to the efficacy of the configuration changes as it relates to the performance objectives. Configuration changes can be as simple as ignition timing or as complex as cylinder head and manifold changes. Often the same tests are run several times to ensure repeatability. In general, the idea is to minimize the number of variables between tests so the effects of a change are readily apparent. This methodology is the basis for the dyno-testing portion of an engine development program.
In addition to changing engine configurations, different test methods may be used. An engine may be tested steady-state (holding set rpm’s) or accelerated through a range of rpm’s. Prior to the use of electronic data gathering, step testing was necessary to allow time for the operator to record torque and rpm readings. The brake load would be adjusted to hold the engine at specific rpm points. When the readings stabilized they were manually recorded. Brake horsepower at each step was then calculated from the recorded torque and rpm. Current dyno’s record test data as the engine speed is changing. This method can approximate an engine accelerating in a vehicle. More sophisticated dyno’s can be programmed to simulate road loads as though the engine were installed in a vehicle.
The engine dyno also serves as a quality control tool. Program or “spec” engines are tested to verify power output. For example, rebuilt engines are tested prior to shipping to confirm expected performance.
Advantages of the engine dyno over other methods of measuring engine output e.g., chassis dyno, g-meter (accelerometer), time/distance are:
- The ability to maintain a continuous load on the engine for endurance testing.
- Control over engine water and oil temperature set points.
- Monitor numerous operating parameters e.g., air-fuel ratio, manifold vacuum, EGT’s, fuel flow.
- No wear and tear on the vehicle driveline.
- Complete access to the engine for changing out or modifying components.
Can any engine be tested? Virtually any type of piston or rotary engine can be tested on our engine dyno. The engine should be greater than 30 bhp and less than 800 bhp with a maximum speed less than 8,000 rpm. Unusual engines may need special driveshaft adapters and mounts.
Is engine testing expensive? The engine dyno is operated on a per hour basis that includes engine installation, testing and removal. Additional expenses include consumables and materials e.g., fuel, oil, spark plugs. Total test time is dependent on the test plan. Minimum test time is 8 hours. This generally allows for break-in and basic fuel and spark calibration. Call 757-363-8878 or e-mail for additional information.
If you plan to use your engine for competing in a sanctioned performance series where significant modifications are permitted, an engine development program including dyno testing should be considered.