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A dynamometer is basically a device that measures the amount of power being developed by an engine. A good dyno can analyze the entire power band of any engine and present the user with the results in some type of readable format. In the past, if you wanted accurate information about the performance of your automobile engine, you had to take your car to a dyno facility and have it tested. A typical dyno test usually costs £50 - £75 and is only good for a single test.

The Road Dyno Kit allows anyone to get accurate dyno results any time they wish. All you'll need is a flat section of roadway, usually less than 1/4 mile in length. How does it work? Well, basically the Road Dyno is a precision timing system that looks at a record of ignition sparks or vehicle movement over time. Based on when a single spark plug fires, the program can compute acceleration, and therefore, power. The user must supply the car's weight, gear ratios, tyre sizes, and some other variables, but the rest is pure physics. This is not a power estimating program! The Road Dyno measures the power of your engine directly by making precise measurements. Many programs are available that allow the user to "estimate" power by supplying quarter mile speeds, 0-60 times, etc. Road Dyno v1.0 measures power by the same method as a chassis dyno. Instead of measuring the amount of power required to accelerate a drum, you are measuring the amount of power required to accelerate the car. This is really what you are interested in anyway isn't it? Some cars may even perform differently on a chassis (stationary) dynamometer because the car is not actually moving. Accelerating the car has an effect on fuel in the bowl of the carburettor (if you happen to have one of those), oil distribution through the engine, air resistance, turbo airflow etc, etc. The Road Dyno Kit will allow you to accurately measure the amount of power your car is putting to the ground, which is an invaluable tool when doing aftermarket modifications. The Road Dyno taught us a LOT about the performance of numerous cars. It identified a 5000 rpm stumble that was traced to an overly sensitive knock sensor. After fixing the sensor, the Road Dyno shows a smooth power curve.

The Road Dyno takes hundreds of power measurements through the entire power band of the engine being tested. This provides enough resolution to be able to analyze performance parameters like spark advance, knock retard, power drops as a result of fuel pressure, etc. For example, a power curve that is jagged with small spikes indicates that the engine management computer may be "hunting" for the proper timing. The results will still be accurate, but the shape of the curve tells a lot here. Also, a sudden dip in the curve can indicate that the computer has detected engine knock and backed off the timing. It is important to correct conditions like these to ensure that your engine is performing to potential and live a long life!

We have tested numerous automobiles, four of which were in stock condition. On each of the four stock vehicles, the Road Dyno produced numbers VERY close (within 5 hp) to stock specifications. On the one modified vehicle, the Road Dyno returned numbers exactly where expected (within 5 hp) when compared to other vehicles with the same modifications that had been dynoed at a dyno facility. In addition, several Road Dyno users have run their cars on chassis dynos to compare. Not only do the power curves match nicely, but the maximums recorded by Road Dyno were within 5 hp of the chassis dyno!  Please note that the Road Dyno measures the amount of power actually used to accelerate the vehicle.  For this reason, it may be necessary to add a small percentage (3-5% average) if you wish to exactly match a stationary (chassis) dyno.

Consistency is important when making aftermarket modifications. We performed 16 separate dyno runs on the same vehicle (95 Trans Am). Approximately six of these runs were done with the car in the same condition (same mods). All six runs were within 5 horsepower of each other. Although temperature, humidity, barometric pressure, fuel, and even your car's computer learning capability can affect power from one given day to the next, the Road Dyno's accuracy is believed to be plus or minus about 3 horsepower. On this vehicle, we have not only improved the consistency of power by removing the power fluctuation at 5,000 rpm, but also have added about 8 horsepower and trimmed 0-60 times from 5.55 to 5.45 just by using information provided by Road Dyno runs!

The picture shows the Road Dyno unit with serial cable, interface cable and inductive pickup.

Insert disk 1 and run "d:setup.exe" where d: is your floppy drive letter or CD ROM letter. Then follow any on screen instructions or requests.

Technical support will be provided via email.

Ensure your Road Dyno unit has a fresh PP3 / 1604 battery. The first step is to connect the recorder to a suitable spark or timing source. This can be a spark output from the ECU, the coil, or using the inductive pickup to a spark plug wire (see below). If connecting to an ECU output, use the crocodile (alligator if you're in the USA!) clip connections and leave the clamp connector unconnected (See important note below). Connect the black clip to a good ground - usually an ECU fixing bolt - and the red clip to one of the spark control outputs. One way to do this is to carefully push a dressmaker's glass topped pin through the wire, then clip to that. Either way, ensure the connections are stable and won't short or fall off under test. A little insulating tape can be helpful here!

To connect to the coil, clip the red lead to the coil "-" terminal, and the black lead to a good ground. (See important note below). If the tacho LED doesn't seem to work, you may need to move the black lead to coil "+". In this case, connect the red clip to coil "-", and the black clip to coil "+". The Road Dyno can to be configured to coil mode, by connecting the Dyno to a PC and using the Road Dyno Processor software (rdp.exe) to set the higher number of pulses per rev. This is done by establishing a link to the Dyno (see instructions below) and selecting Config under the Edit menu. Follow the instructions there. This will re-program the Dyno to "coil" mode. Note that you will need to re-program the unit to go back to clamp or ECU mode. You don't have to do this step; if the Dyno isn't programmed to coil mode you can correct the excess count using the "Sparks/Rev" setting in Road Dyno. The difference is that the Dyno unit's memory will fill quicker if you don't tell it to count less pulses! As the memory lasts about 4 minutes this may not be a problem! IMPORTANT NOTE: It is ESSENTIAL to connect the clips to the coil or ECU and plug the cable into the Dyno BEFORE starting the engine!!!
This photo shows the coil connection - red to "-", you can see the black clip earthed on the coil clamp in the background.

The picture below shows the inductive pickup.

Refer to the vehicle's workshop manuals to find a suitable pickup point (see picture below), or open the bonnet, and clamp the pickup to any spark plug wire. The following illustration shows the pickup being connected to the number 1 plug wire on an LT1 engine. This is the front, driver's side of the engine. Just make sure that the exhaust manifold isn't too hot!

Next we need to make sure that the cable and pickup if used doesn't drop down any while we're driving. To do this, just tape the pickup wire in place. (See lower right side of the above picture). Then, just run the wire to the driver's side corner of the bonnet and into the car as illustrated in the next photograph.

When routing the wire into the car, just make sure that the bonnet doesn't shut and crimp the wire. Also, make sure that the driver's door won't cut into the wire with any sharp edges. You can also route it through a partially open driver's window if you like. We find that it is easiest to route the wire into the car and over the steering column, then in front of the gear lever, to the passenger seat, where the Road Dyno sit. It's best to clip the two crocodile clips together to prevent any noise if you're using the clamp.
With the engine running and the Dyno turned on, the tacho led should flash approx. 1 flash per second per 1000 rpm. If it doesn't, check all the connections. Make sure the pickup is connected to the Road Dyno cable, and the jack is correctly inserted into the Road Dyno. Make sure the clamp is fully around the plug lead, and fully shut. You may need to reverse the clamp to get the best results:

Now you're ready for a run! Make a note of the time, date and temperature, pressure and humidity before setting out. Note down any other pertinent information - you won't remember it later! Go to a flat section of road, preferably one that has a pull-off on the side. Pull over, stop but don't start recording yet. There are two different methods for making a run based on whether you have an automatic transmission or a manual transmission.

Now note down any other relevant information about the run, such as maximum turbo boost, etc. If you're going to make multiple runs, keep the Dyno on for now (If you turn off the unit, it keeps the data but will record over it on the next run. If the unit is kept turned on, successive recordings will follow in memory like tracks on a tape). You may wish to do a run the other way along the same road, to cancel wind or slight gradient effects. If the memory gets full, the red record light will flash continuously - time to go and process data!

Now that you have made a run and recorded it, it's time to get the data into your PC. Start by connecting the recorder to a comms port on your PC with the supplied cable.

You can get help for operating the software by pausing the mouse over active (not greyed out) controls. First select the comms port which you connected the Dyno to on your PC, with the pull down menu. (Showing comms port 3 in the illustration). Then click on Link to establish communication. Next, press Play to download data from the recorder to the PC. The program will prompt you when it needs to save the data. You can use the default promoted filename (derived from the date) or enter your own. Finally you can clear the recorder's memory if you want. It may be better to process the data first, in case of any problems.

The following is a short description of each entry and its importance:

• Quit when RPM decreases: Normally, you want to enter Y to let the program figure out where you changed to the next gear, or let off the accelerator. Through the entire run, RPM should increase with time, until the run is over. You can do some pretty nice things with this variable set to N. For example, if you have either an automatic or manual, and you want to do some zero-to-speed or speed-to-speed runs, you can record your run starting in first gear and accelerate as fast as possible, using as many gears as you want. With this variable set to N, the program will give you numbers for the entire run. You will have to run Road Dyno once for each gear, but you will be able to pick out where gears were changed by looking at each time the RPM decreases. For example, run the program once with first gear ratio entered. All values are valid until the first drop in RPM (first gear change). Now run the program again and enter the second gear ratio. Now you have to pick up where you left off (at the first RPM drop) because numbers prior to this are for the wrong (first) gear. After the first RPM drop, however, up to the second RPM drop, the numbers will all be valid. Get the idea?
• Engine type: Select 4 stroke for all cars and 2 stroke for some motorcycles and other off-road vehicles. The program must know whether the engine fires once every other revolution (4 stroke) or once per revolution (2 stroke).
• Test weight: The test weight is very important for getting an accurate analysis. You should be able to get close enough by doing the following. Look up your gross vehicle weight restriction (GVWR) on your driver’s doorjamb, or vehicle manual. Next subtract the vehicle capacity, and you get your car's weight. Now add in the driver's weight, as well as any passengers, equipment, etc in the car. Finally, estimate the number of gallons of fuel left in your tank, and multiply gallons by 6.1 to get pounds. Add this to the total. This is your total test weight.
• User comment: This will become a very useful tool as it serves to help you remember what you did to the car for the run in question, the weather conditions, etc.
• Transmission: Enter A for automatic, M for manual. The program must know this to get an accurate reading on the vehicle's speed since automatics are not direct drive. The program was modeled using 4th generation F-body vehicles with stock (~1650) stall converters. If you have an automatic transmission and you have a torque converter with a stall speed other than 1650 RPM, see the next parameter.
• TC stall RPM: For automatic transmissions, this is the torque converter stall speed. Stock torque converters on most performance cars are around 1650 (default). If your car has an aftermartket high stall speed converter, change this value as appropriate. Values range from 1200 rpm to 3000 rpm. If you don't know your stall speed, leave this value at the default 1650 rpm. If you are off by only a hundred rpm or so, there will be little affect on your dyno results, especially at midrange to high rpm.
• Drive axle ratio: Enter the rear axle (differential) ratio. Typical values are 2.73:1, 3.23:1, 3.42:1, etc. If you don't know it, you'll have to find it somewhere, because it directly affects power analysis. Oh, and don't worry if you have front wheel drive. You still have a differential, it's just in the front of the car, not the rear!
• Test gear ratio: Enter the gear ratio of the gear used in the test. Similar to the rear axle ratio, the program needs this to calculate power properly. As mentioned above, try to use second gear if you have a manual transmission.
• Wheel/Tyre info: The wheel diameter, tyre width, and tyre aspect ratio are also needed for proper calculation of power.
• Drag coefficient: Enter the vehicle's drag coefficient. This is needed to accurately measure acceleration (and hence power), especially if you need to run the test in a higher gear due to wheelspin. If you don't know your drag coefficient, just enter 0.32. That should be close enough unless you plan to break the sound barrier!
• Frontal area: Enter the vehicles frontal area. The default is based on 4th generation f-body vehicles, but should be pretty close for most muscle cars. If you are running a smaller or larger car, you should look up the frontal area for your vehicle.
• Drivetrain loss factor: If you want the "compensated" numbers to indicate engine power rather than drive wheel power, you need to enter the approximate drivetrain frictional loss factor. This number is generally 0.15-0.20 depending on vehicle/drivetrain. We have also found that at least for the Camaro/Firebird, drivetrain losses are not increased by having an automatic transmission, so don't enter the typical 0.20 value for automatics. Just stick with the 0.17 as a good median if you are trying to obtain engine horsepower. Note that if you want all numbers in the graph and OUT file to indicate drive wheel power, you can enter 0.00 here! 4WD drive vehicles have typically around 25% loss.
• Temperature: Enter the air temperature during the dyno run. Approximate numbers are ok, but try to get within 2-4 degrees C.
• Relative humidity: Enter the relative humidity during the dyno run.
• Barometric pressure: Enter the barometer reading during the dyno run. This value should be the barometer reading corrected to sea level. All weather reports refer to this number already corrected to sea level, so just call the weather or get it from the most recent weather report.
• Altitude: Enter the altitude of the test site. The number should be feet (or meters) above sea level.
• Std: Press the "Std" button to revert to "standard atmospheric conditions". You would do this if you didn't want any correction for weather conditions for example.

The following screen is displayed immediately after processing the data.

Notice that after loading a file and/or processing it, the View Data and Print options are enabled. Click on View Data to use the Windows Notepad to view all calculated data in numerical/tabular format. Click Print to print either the dyno graph, or the numerical/tabular data to your Windows Printer. A Printer Setup option is also available to assist you in selecting the proper print quality, etc.

In addition to screen and printer output, the following files are saved in the current directory:

• *.ini.. this is the initialization file where all parameters were stored.
• *.out.. this is the file containing text output on all data points (see below).
• *.bmp.. this is the graph you just saw on your screen (from above).

The Road Dyno graphs contain a wealth of information about your car's performance. The following illustrations should help in the analysis of your car's performance, as well as help identify proper use of the Road Dyno.

Wheelspin
A peak followed by a short valley (usually in the beginning of the RPM range) likely indicates that wheelspin has occurred. Remember that the Road Dyno is measuring engine output, and can only give an accurate representation of power if that power is being applied to acceleration. When wheelspin occurs, a lot of the energy that could potentially be used to accelerate the car is being used to heat the tyres. Since heating the tyres often takes less energy than accelerating the car, the graph will show too much power while wheelspin is occurring.

Power Loss
This power loss occurred in the higher rpm range. It was later traced to an over-sensitive knock sensor that was sending a knock signal to the car's computer. The computer cut back (retarded) timing for an instant, and then ramped timing back up (advanced) when the false knock signal subsided. The rest of the curve in this example was relatively smooth.

Signal Noise
A power curve that fluctuates for most of the rpm range might indicate that there is noise in the signal. Noise can cause the Road Dyno software to misinterpret noise as pulses, or can cause a false pulse-start location. When noise is interpreted as a spark or timing reference, the software will interpret rpm in a high/low fashion. For example, if noise was picked up before the actual pulse, this rpm reading would be too high, resulting in a power reading that is too high. The next reading, however, would have too much time between pulses, resulting in too little rpm/power. This is the reason that noise can cause the "wavy" curve. If noise levels are low, fluctuations like this might indicate that your car is hunting for a variable such as timing, fuel mixture, etc. On some cars, power curves may smooth out after a few runs as the car's computer learns the proper parameters. This would only apply if the battery has been recently disconnected before the dyno run.

Too Much/Too Little Power?
Let's say you expect your engine to be putting out about 275 hp peak, but the Road Dyno is returning 350 horsepower. The most likely explanation for this discrepancy is an incorrect parameter entered into the program. Make sure that you know your axle ratio, and have entered the proper gear ratio. We have found that these parameters are the one's most commonly entered incorrectly. If you bought your car used, remember that changing the rear axle ratio is a very common performance mod, and the previous owner may have changed it. Other than a parameter error, the only other possibility for a curve that is too high is a slipping clutch. If you have a manual transmission, make sure your clutch is in good shape, because if it is slipping during a run, you will get false high power readings. If the curve is too low and you have checked all parameters, the problem is most likely a poorly performing engine.

Dropouts?
Severe power curve dropouts are almost always caused by loss of signal or signal strength fluctuations. It doesn't mean that your car was making near zero power in this range; it just means that the program lost the signal. It might be losing the signal due to improper connection to the plug wire, or a pickup that needs reversing (se above), or just a poor recording. But... the problem might be the car. We tested one car with coil problems that exhibited this problem. The spark was actually very weak at certain rpm ranges, but not others. To try the easiest thing first, just try a different plug wire in a different location.

Also included are two other software programs which will appear in your Road Dyno group from the start menu.

Memory: 64k non volatile (flash) memory. Typically 4 minutes record time.
Power: PP3 / 1604 Battery, preferably alkaline.

© GAA 2000 -