Dyno Dynamics
Sep 6, 2003, 06:51 PM
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Dyno Dynamics
Hi Guys,
It is very interesting reading the different posts on dynos. I distribute the Dyno Dynamics dynos in the USA. I am going o try to help people understand the differences.
Corrections:
SAE is a form of correction that takes in account temp, humidity, baro pressure. Keep in mind that it adds or subtracts a percentage from the Hp figure that the dyno calculates. It is NOT a method of calculating power. So if a if 2 dynos read 10% different they will still read 10% when corrected.
Dyno Dynamics uses an outboard weather station. It is not important(to us) what the temp close to the computer stack is, but the temp in front of the car is what is important. We want to know what the temp of the air is the car is using. We use the same calculations to compensate for weather as most dyno companies.
All dynos read different HP. This is more true when comparing numbers from different factories. Our numbers are lower than most. The next company is about 8% higher, and the highest difference is about 15%. There are dyno's made in the US that read the same as ours.
The biggest problem for most people to grasp is losses AREN'T linear!Take a car that makes 100 BHP, and dynos at 70 WHP. If you modified that car to make 1000 BHP that doesn't mean it will make 700 WHP. A 300hp loss would melt the tranny. So just to add 20-30% to get engine power is wrong. When a customer dynos his stock type r and get 125 HP from a engine that makes 190 BHP doesn't mean he will make 250 WHP when he doubles his engine HP.
Often, people use 1/4 mile calculators to measure HP. There are as many of those using different formulas as there are chassis dyno companies. www.smokemup.com gives HP numbers that are very close to ours. They use F=M*A to calculate an average HP. That is the same formula we use. Most formulas are taylored to equal higher chassis dyno numbers. Some are even data bases that use numbers from the inertia dynos. That is why they get close to equaling the inertia dyno.
A Dyno Dynamics dyno measures power by using f=M*A. Our retarder is connected to a load cell that measures Newtons(Force), and our wheel speed is also measured(acceleration). You can see why it is hard to make a mistake when measuring HP on our dynos.
The method used to calculate HP is not important. An inertia dyno can be calibrated and read exactly what ours does. You would then be stuck making full throttle runs. You don't stay at full throttle all of the time so it would be nice to tune for throttle positions below 100%.
Dyno Dynamics dynos can tune at any speed, and any load. They can be changed at any time and the tuner can see realtime HP, A/F, and boost numbers to tune from. All owners get 3 days of training and are aware of the fact that the dyno numbers are lower than some. They choose to buy it anyway because of the repeatability, and accuracy of our products.
I can understand why people want to believe the higher numbers. We could change the way we "correct" hp, but that is not how we operate. If you want to know what your car would make on an inertia dyno made in the States just ask the operator of the dyno. They all know how to do that.
Just a little more:
Dyno Dynamics makes a line of inertia dynos, and they read the exact same power as our eddy current dynos.
Moroso makes a hand held slide rule HP calculator that gives HP the same as our dynos. Grab one and give it a try. Also try the smokemup.com website.
This debate will never be settled in a day. Until someone regulates the power readings of dynos this problem will always exist. Regulation doesn't always work. Just look at car audio. Amps that are rated at 25wpc that are 3 feet long just so that the customer can be in a different class. That is cheating as well.
If you ever want to check the calibration of one of our products it is real easy. Take a 20 KG weight and put it one our load cell. Ask the operator to show you how much it weighs. Thats it!!! If it reads 20 KG, and the speed is correct then the power must be correct.
Thanks for reading,
Steve Nichols
E-mail me with ?'s about this post at :
stevenichols@aussieimportsllc.com
It is very interesting reading the different posts on dynos. I distribute the Dyno Dynamics dynos in the USA. I am going o try to help people understand the differences.
Corrections:
SAE is a form of correction that takes in account temp, humidity, baro pressure. Keep in mind that it adds or subtracts a percentage from the Hp figure that the dyno calculates. It is NOT a method of calculating power. So if a if 2 dynos read 10% different they will still read 10% when corrected.
Dyno Dynamics uses an outboard weather station. It is not important(to us) what the temp close to the computer stack is, but the temp in front of the car is what is important. We want to know what the temp of the air is the car is using. We use the same calculations to compensate for weather as most dyno companies.
All dynos read different HP. This is more true when comparing numbers from different factories. Our numbers are lower than most. The next company is about 8% higher, and the highest difference is about 15%. There are dyno's made in the US that read the same as ours.
The biggest problem for most people to grasp is losses AREN'T linear!Take a car that makes 100 BHP, and dynos at 70 WHP. If you modified that car to make 1000 BHP that doesn't mean it will make 700 WHP. A 300hp loss would melt the tranny. So just to add 20-30% to get engine power is wrong. When a customer dynos his stock type r and get 125 HP from a engine that makes 190 BHP doesn't mean he will make 250 WHP when he doubles his engine HP.
Often, people use 1/4 mile calculators to measure HP. There are as many of those using different formulas as there are chassis dyno companies. www.smokemup.com gives HP numbers that are very close to ours. They use F=M*A to calculate an average HP. That is the same formula we use. Most formulas are taylored to equal higher chassis dyno numbers. Some are even data bases that use numbers from the inertia dynos. That is why they get close to equaling the inertia dyno.
A Dyno Dynamics dyno measures power by using f=M*A. Our retarder is connected to a load cell that measures Newtons(Force), and our wheel speed is also measured(acceleration). You can see why it is hard to make a mistake when measuring HP on our dynos.
The method used to calculate HP is not important. An inertia dyno can be calibrated and read exactly what ours does. You would then be stuck making full throttle runs. You don't stay at full throttle all of the time so it would be nice to tune for throttle positions below 100%.
Dyno Dynamics dynos can tune at any speed, and any load. They can be changed at any time and the tuner can see realtime HP, A/F, and boost numbers to tune from. All owners get 3 days of training and are aware of the fact that the dyno numbers are lower than some. They choose to buy it anyway because of the repeatability, and accuracy of our products.
I can understand why people want to believe the higher numbers. We could change the way we "correct" hp, but that is not how we operate. If you want to know what your car would make on an inertia dyno made in the States just ask the operator of the dyno. They all know how to do that.
Just a little more:
Dyno Dynamics makes a line of inertia dynos, and they read the exact same power as our eddy current dynos.
Moroso makes a hand held slide rule HP calculator that gives HP the same as our dynos. Grab one and give it a try. Also try the smokemup.com website.
This debate will never be settled in a day. Until someone regulates the power readings of dynos this problem will always exist. Regulation doesn't always work. Just look at car audio. Amps that are rated at 25wpc that are 3 feet long just so that the customer can be in a different class. That is cheating as well.
If you ever want to check the calibration of one of our products it is real easy. Take a 20 KG weight and put it one our load cell. Ask the operator to show you how much it weighs. Thats it!!! If it reads 20 KG, and the speed is correct then the power must be correct.
Thanks for reading,
Steve Nichols
E-mail me with ?'s about this post at :
stevenichols@aussieimportsllc.com
I have always dreamed of opening some Dyno shops, And here you deal them?How did you come about that job?
Sep 8, 2003, 08:20 AM
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Nice info Steve, thanks! The more accurate info we can get that helps educate all of us regarding dyno differences and characteristics the better off we are!
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Sep 8, 2003, 09:25 AM
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I understand that your latest dynos have an accurate way of measuring drivetrain loss and correct the dyno graph using this. Could you go into some details?
A local company (in Ayer, MA) recently took delivery of one and mentioned the feature.
A local company (in Ayer, MA) recently took delivery of one and mentioned the feature.
Sep 8, 2003, 04:13 PM
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Hi Steve,
Thanks for trying to provide more insight regarding your dyno, unfortunately for me it just raises more questions. No one is arguing that that your dyno can be a useful tuning tool, but I still do not see any evidence to indicate that this dyno has a higher accuracy for WOT max HP when compared to an inertia dyno.
Despite the marketing hype insinuating that we (in the US) are a bunch of ignorant NASCAR red necks that just want to see big numbers, we actually are very interested in truth and accuracy.
We do not have a lot of data from the DD system yet, but some that I have seen so far appears to be inconsistent with real world performance.
Your saying that driveline losses are not linear, I agree. looking at the results from KTR (attached image below) they are linear and average around 22%! Looking at EVO curves from the DD system, it appears that the torque peaks at >4K. Anyone who has driven an EVO can tell you, 3rd/4th gear the torques peaks much sooner than 4K more like 3-3.5K. This is consistent with what is seen on the Dyno Jet, among others.
Can you start to see why I have a hard time believing the accuracy of this system?
As far as calibration, putting a 20kg weight on the load cell tells me that the strain gauge can accurately measure 20 KG. It doesn't tell me how accurate and reliable the load cell is at loading the rollers. If the loading is off, so are the measurements from the strain gauge, isn't that right? Any good bathroom scale can accurately measure 20KG, it doesn't mean I have an accurate chassis dyno in my bathroom does it?
Here are some additional thoughts from a gentleman who designed and built his own inertia dyno. What he says makes a lot of sense to me, what do you think?
Advantages and disadvantages of each type.
A steady state dyno has the advantage that an engine can be loaded up and held at a constant speed. This can be used to find a miss at a certain speed or tune the engine for maximum power at a certain speed etc. The disadvantage of these types of dynos is that they are expensive (compared to inertial type) and they are more complex. These dynos also need regular calibration of a load cell if they actually use one. If calibration checks aren’t performed regularly then the results can be wrong. The braking mechanism of the dyno will generate a lot of heat that has to be dealt with as well. If it is an electrical brake it has to be cooled, water and hydraulic brake will need radiators and may even need cooling towers.
Each type of dyno has its own advantages and disadvantages. Traditional dynamometers are typically known as "pump" or "brake" type dynos, whether they use a hydraulic pump or a water pump they all work on the same principle. The engine being tested is run at a steady speed, load is applied via the pump until the engine can no longer maintain this speed at Wide Open Throttle (WOT), at this point the rotational force or "torque" being applied to the pump housing is measured and converted to "standard" engine output readings. The results are calculated by the values obtained from a load cell or simply converting pump pressure. This method, known as "steady state testing" is normally performed at 200-500 rpm increments across the "power band" of the engine. This type of dyno testing has been used for many years on all types of engines, however for racing applications it has a few inherent problems.
"Pump" type dynos must use some form of fluid to pump, be it water or oil. Everyone knows what happens to oil as it is pumped, it gets hot very quickly and the viscosity or "thickness" of the oil goes down. As this happens the power required to pump it changes dramatically, this will in turn change the power output readings on the dyno. Water has this same tendency, although to a lesser extent. Water and oil pumps also tend to mix air with the fluids, causing them to become aerated, or "foamy", changing it's "thickness" and again changing output readings.
"Steady State" testing is fine for equipment such as water pumps, generators tractors etc, equipment that operates at a steady load and rpm for long periods of time. How often does your racing engine operate at a steady speed? Almost never, from the start of a race to the finish the engine operates in an almost constant state of acceleration or deceleration. The thermal dynamics of intake and exhaust flow, combustion and mechanical components are much different under these conditions than at a steady state.
"Steady State" testing also requires that an engine be held at WOT at each test increment for a period of time while test readings are taken. The advent of computerized data acquisition systems has helped this considerably, but the engine still spends a relatively long period of time under load at high rpm and WOT.
Over time the internal workings of a pump type dyno wear causing it's power absorption characteristics to change. Unless these changes are carefully monitored and compensated for, the dyno can become very inconsistent and inaccurate.
Inertial dynos are the simplest and cheapest of all types. An Inertia Dyno operates much differently than a "pump type" dyno. Inertia Dynos consists of one major component, a large flywheel, mounted on an axle and connected to the engine via the wheels. The disadvantage of these over brake dynos is that they can only be used for wide-open throttle tests (WOT).
Back to top
Results from each type.
Typically a steady state dyno will give results of up to about 20% less than inertia types. Here is an example of how different results occur. You have a bike that shows a maximum of 100HP on an inertia dyno and xxHP on a steady state dyno. Now we lighten the crankshaft and flywheel, fit a lighter rear wheel, fit a lightweight chain and some alloy sprockets. We run the bike on the steady state dyno and it still shows a maximum of xxHP. We run the bike on the inertia dyno and find it is now producing 105HP. These modifications didn’t actually make the engine produce more horsepower just as the brake dyno shows. So why does the inertia dyno now say it is producing more horsepower? This is because the inertia dyno gives a true representation of what the “road” sees. Of course the engine isn’t producing more horsepower, but there is more horsepower available to accelerate the bike because less power is needed to accelerate the crankshaft, chain and sprockets and finally the wheel. Because less power is need to accelerate these things more is available to accelerate the bike, and it will accelerate faster on the road. The inertia dynamometer calculates horsepower from how fast its drum is accelerated, therefore in this example the bike engine was able to accelerate the drum more quickly after the modifications so more horse power is available at the rear wheel to accelerate the bike on the road. In my opinion steady state dynos are good for tuning tractors that are going to run at 1500-rpm day in day out. To tune an engine for the type of riding I do, or bush riding or racetrack riding I think an inertial dyno is more than sufficient. How often do you care how much power you’re making at a steady throttle? When I’m out having fun, the engine is rarely at a constant speed, it is either constantly accelerating or decelerating.
Back to top
Just how accurate is this dyno?
"Accuracy", for many reasons, is a very relative term as far as dyno's go. Just how accurate is anyone's dyno? Take 2 motors, test them on 2 different dynos, one comes out at 100hp, the other comes out at 110hp, but they run the same lap times. Which dyno is "accurate"? Which one is giving you the correct numbers? Horsepower is simply a calculated number. Dyno 10 engines on the same dyno at 100HP, put them all in the same bike one at a time, and they all run the exact same lap times. Is the dyno accurate? No, the dyno is however "repeatable". "Repeatability" is what you want in a dyno, test the same engine time after time and get the same results. Take one of the 10 engines from above, change a pipe or a cam so you get 5% more power, run it against all the others again. It runs 5% faster, you re-dyno it and it still says 5% better, now you have an "accurate" and more importantly, a "repeatable" dyno. A couple hints: Always start your tests at the same engine temps and settings. Pay close attention to weather conditions. Get yourself a good barometer, thermometer, and humidity gauge, and enter the conditions into the program each time you make a run.
Back to top
The testing procedure
The test procedure is simple:
Start the engine
Warm to operating temperature
Accelerate from near idle through the power band to max rpm
Close the throttle, and apply the brake to slow the flywheel
During the acceleration of the engine, a computerized data acquisition system is monitoring the speed of the dyno flywheel. After shutting off the engine the data collected by the computer is analysed and processed to produce the appropriate information. The computer "knows" the weight of the flywheel and calculates horsepower and torque values based on the amount of time it took to accelerate the flywheel from start to finish and moment to moment.
Notice that nothing was mentioned about: hot or cold fluids, load control valves, throttle actuators, load sensors, component wear, Etc....
These items do not exist on an Inertia Dyno, the flywheel is always the same size, nothing changes over time and temperature except the engine. The dyno's output is consistent run to run, day to day, and year to year. Output readings are very consistent and reliable. This entire process takes a relatively short amount of time, after set-up, warming the engine etc, typical full throttle run times take from 10 - 20 sec depending on the power produced by the bike. The engine is placed under no more stress than a run up the block or a lap around the track for each "run". HUGE amounts of testing can be performed with less "wear and tear" than a night at the races.
Thanks for trying to provide more insight regarding your dyno, unfortunately for me it just raises more questions. No one is arguing that that your dyno can be a useful tuning tool, but I still do not see any evidence to indicate that this dyno has a higher accuracy for WOT max HP when compared to an inertia dyno.
Despite the marketing hype insinuating that we (in the US) are a bunch of ignorant NASCAR red necks that just want to see big numbers, we actually are very interested in truth and accuracy.
We do not have a lot of data from the DD system yet, but some that I have seen so far appears to be inconsistent with real world performance.
Your saying that driveline losses are not linear, I agree. looking at the results from KTR (attached image below) they are linear and average around 22%! Looking at EVO curves from the DD system, it appears that the torque peaks at >4K. Anyone who has driven an EVO can tell you, 3rd/4th gear the torques peaks much sooner than 4K more like 3-3.5K. This is consistent with what is seen on the Dyno Jet, among others.
Can you start to see why I have a hard time believing the accuracy of this system?
As far as calibration, putting a 20kg weight on the load cell tells me that the strain gauge can accurately measure 20 KG. It doesn't tell me how accurate and reliable the load cell is at loading the rollers. If the loading is off, so are the measurements from the strain gauge, isn't that right? Any good bathroom scale can accurately measure 20KG, it doesn't mean I have an accurate chassis dyno in my bathroom does it?
Here are some additional thoughts from a gentleman who designed and built his own inertia dyno. What he says makes a lot of sense to me, what do you think?
Advantages and disadvantages of each type.
A steady state dyno has the advantage that an engine can be loaded up and held at a constant speed. This can be used to find a miss at a certain speed or tune the engine for maximum power at a certain speed etc. The disadvantage of these types of dynos is that they are expensive (compared to inertial type) and they are more complex. These dynos also need regular calibration of a load cell if they actually use one. If calibration checks aren’t performed regularly then the results can be wrong. The braking mechanism of the dyno will generate a lot of heat that has to be dealt with as well. If it is an electrical brake it has to be cooled, water and hydraulic brake will need radiators and may even need cooling towers.
Each type of dyno has its own advantages and disadvantages. Traditional dynamometers are typically known as "pump" or "brake" type dynos, whether they use a hydraulic pump or a water pump they all work on the same principle. The engine being tested is run at a steady speed, load is applied via the pump until the engine can no longer maintain this speed at Wide Open Throttle (WOT), at this point the rotational force or "torque" being applied to the pump housing is measured and converted to "standard" engine output readings. The results are calculated by the values obtained from a load cell or simply converting pump pressure. This method, known as "steady state testing" is normally performed at 200-500 rpm increments across the "power band" of the engine. This type of dyno testing has been used for many years on all types of engines, however for racing applications it has a few inherent problems.
"Pump" type dynos must use some form of fluid to pump, be it water or oil. Everyone knows what happens to oil as it is pumped, it gets hot very quickly and the viscosity or "thickness" of the oil goes down. As this happens the power required to pump it changes dramatically, this will in turn change the power output readings on the dyno. Water has this same tendency, although to a lesser extent. Water and oil pumps also tend to mix air with the fluids, causing them to become aerated, or "foamy", changing it's "thickness" and again changing output readings.
"Steady State" testing is fine for equipment such as water pumps, generators tractors etc, equipment that operates at a steady load and rpm for long periods of time. How often does your racing engine operate at a steady speed? Almost never, from the start of a race to the finish the engine operates in an almost constant state of acceleration or deceleration. The thermal dynamics of intake and exhaust flow, combustion and mechanical components are much different under these conditions than at a steady state.
"Steady State" testing also requires that an engine be held at WOT at each test increment for a period of time while test readings are taken. The advent of computerized data acquisition systems has helped this considerably, but the engine still spends a relatively long period of time under load at high rpm and WOT.
Over time the internal workings of a pump type dyno wear causing it's power absorption characteristics to change. Unless these changes are carefully monitored and compensated for, the dyno can become very inconsistent and inaccurate.
Inertial dynos are the simplest and cheapest of all types. An Inertia Dyno operates much differently than a "pump type" dyno. Inertia Dynos consists of one major component, a large flywheel, mounted on an axle and connected to the engine via the wheels. The disadvantage of these over brake dynos is that they can only be used for wide-open throttle tests (WOT).
Back to top
Results from each type.
Typically a steady state dyno will give results of up to about 20% less than inertia types. Here is an example of how different results occur. You have a bike that shows a maximum of 100HP on an inertia dyno and xxHP on a steady state dyno. Now we lighten the crankshaft and flywheel, fit a lighter rear wheel, fit a lightweight chain and some alloy sprockets. We run the bike on the steady state dyno and it still shows a maximum of xxHP. We run the bike on the inertia dyno and find it is now producing 105HP. These modifications didn’t actually make the engine produce more horsepower just as the brake dyno shows. So why does the inertia dyno now say it is producing more horsepower? This is because the inertia dyno gives a true representation of what the “road” sees. Of course the engine isn’t producing more horsepower, but there is more horsepower available to accelerate the bike because less power is needed to accelerate the crankshaft, chain and sprockets and finally the wheel. Because less power is need to accelerate these things more is available to accelerate the bike, and it will accelerate faster on the road. The inertia dynamometer calculates horsepower from how fast its drum is accelerated, therefore in this example the bike engine was able to accelerate the drum more quickly after the modifications so more horse power is available at the rear wheel to accelerate the bike on the road. In my opinion steady state dynos are good for tuning tractors that are going to run at 1500-rpm day in day out. To tune an engine for the type of riding I do, or bush riding or racetrack riding I think an inertial dyno is more than sufficient. How often do you care how much power you’re making at a steady throttle? When I’m out having fun, the engine is rarely at a constant speed, it is either constantly accelerating or decelerating.
Back to top
Just how accurate is this dyno?
"Accuracy", for many reasons, is a very relative term as far as dyno's go. Just how accurate is anyone's dyno? Take 2 motors, test them on 2 different dynos, one comes out at 100hp, the other comes out at 110hp, but they run the same lap times. Which dyno is "accurate"? Which one is giving you the correct numbers? Horsepower is simply a calculated number. Dyno 10 engines on the same dyno at 100HP, put them all in the same bike one at a time, and they all run the exact same lap times. Is the dyno accurate? No, the dyno is however "repeatable". "Repeatability" is what you want in a dyno, test the same engine time after time and get the same results. Take one of the 10 engines from above, change a pipe or a cam so you get 5% more power, run it against all the others again. It runs 5% faster, you re-dyno it and it still says 5% better, now you have an "accurate" and more importantly, a "repeatable" dyno. A couple hints: Always start your tests at the same engine temps and settings. Pay close attention to weather conditions. Get yourself a good barometer, thermometer, and humidity gauge, and enter the conditions into the program each time you make a run.
Back to top
The testing procedure
The test procedure is simple:
Start the engine
Warm to operating temperature
Accelerate from near idle through the power band to max rpm
Close the throttle, and apply the brake to slow the flywheel
During the acceleration of the engine, a computerized data acquisition system is monitoring the speed of the dyno flywheel. After shutting off the engine the data collected by the computer is analysed and processed to produce the appropriate information. The computer "knows" the weight of the flywheel and calculates horsepower and torque values based on the amount of time it took to accelerate the flywheel from start to finish and moment to moment.
Notice that nothing was mentioned about: hot or cold fluids, load control valves, throttle actuators, load sensors, component wear, Etc....
These items do not exist on an Inertia Dyno, the flywheel is always the same size, nothing changes over time and temperature except the engine. The dyno's output is consistent run to run, day to day, and year to year. Output readings are very consistent and reliable. This entire process takes a relatively short amount of time, after set-up, warming the engine etc, typical full throttle run times take from 10 - 20 sec depending on the power produced by the bike. The engine is placed under no more stress than a run up the block or a lap around the track for each "run". HUGE amounts of testing can be performed with less "wear and tear" than a night at the races.
Sep 22, 2003, 09:36 AM
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Dyno Dynamics
Great Post!!!
Some food for thought. When I said that losse aren't linear I meant from power measurements of the same car. You compared losses of several different cars. I meant that a 100hp engine that dynoed at 70whp will NOT dyno at 700whp when modified to 1000 Engine HP. The tranny would melt if it had to soak up 300hp .The numbers from KTR where generated by special software on the dyno called "shootout" It eleminates the Cheating factor that all dyno's have. The software locks out all controls so that nobody can mess with settings. The software also estimate engine power.
Torque number can be changed by all dyno's. If the car is turbo charged. If you have a honda that weighs 2300lbs and makes 500hp, and you have a Chevy the weighs 3500lbs and makes 500hp the inertia dyno will make the load exactly the same on each car. The honda will NEVER accelerate that slowly, and it will hit site in its fuel map that it will never see on the road. The inertia dyno will also make the turbo spool at a different rate than it will see on the road. These problems will change the torque of the motor. I am trying to addres the issue of the EVO8 here. Knowing that the "RamP' rate of the dyno changes the spool time of a turbo you can then see why the torque numbers would be different even on the same dyno. If I make 20psi boost at 3000rpm my torque will normally be higher than if I make 20 psi at 4000rpm. That is assuming the engine can use the boost that soon.
I think an inertia dyno would be great for full throttle testing if you could change the weight of the roller to suit the weight of the car. That is why a properly trained person using an eddy current style dyno can more completely tune a car for all instances.
Subjecting a ligt weight drag car to a 3500-5000lb roller just doesn't make sense. You can also see that a roller of that size could also "dampen" small power losses in the graph.
One last thing. Dyno Dynamics dyno's graphs at 50 times per second. We don't use any "Smoothing" to make our graphs pretty. A 1msec missed injector pulse show up on our dyno. We also graph live. You can actually see the boost increase an the A/F get richer Live. We don't plot graphs after the run. This is valauble info when tuning.
I really enjoy the feedback. Keep it coming.
Some food for thought. When I said that losse aren't linear I meant from power measurements of the same car. You compared losses of several different cars. I meant that a 100hp engine that dynoed at 70whp will NOT dyno at 700whp when modified to 1000 Engine HP. The tranny would melt if it had to soak up 300hp .The numbers from KTR where generated by special software on the dyno called "shootout" It eleminates the Cheating factor that all dyno's have. The software locks out all controls so that nobody can mess with settings. The software also estimate engine power.
Torque number can be changed by all dyno's. If the car is turbo charged. If you have a honda that weighs 2300lbs and makes 500hp, and you have a Chevy the weighs 3500lbs and makes 500hp the inertia dyno will make the load exactly the same on each car. The honda will NEVER accelerate that slowly, and it will hit site in its fuel map that it will never see on the road. The inertia dyno will also make the turbo spool at a different rate than it will see on the road. These problems will change the torque of the motor. I am trying to addres the issue of the EVO8 here. Knowing that the "RamP' rate of the dyno changes the spool time of a turbo you can then see why the torque numbers would be different even on the same dyno. If I make 20psi boost at 3000rpm my torque will normally be higher than if I make 20 psi at 4000rpm. That is assuming the engine can use the boost that soon.
I think an inertia dyno would be great for full throttle testing if you could change the weight of the roller to suit the weight of the car. That is why a properly trained person using an eddy current style dyno can more completely tune a car for all instances.
Subjecting a ligt weight drag car to a 3500-5000lb roller just doesn't make sense. You can also see that a roller of that size could also "dampen" small power losses in the graph.
One last thing. Dyno Dynamics dyno's graphs at 50 times per second. We don't use any "Smoothing" to make our graphs pretty. A 1msec missed injector pulse show up on our dyno. We also graph live. You can actually see the boost increase an the A/F get richer Live. We don't plot graphs after the run. This is valauble info when tuning.
I really enjoy the feedback. Keep it coming.
Last edited by Stevenich; Sep 22, 2003 at 09:46 AM.
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Sep 22, 2003, 03:09 PM
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Dyno Locations
I am sorry I have missed you e-mails. Try stevenich@insightbb.com
Are you interested in 2wd or 4wd dyno?
Are you interested in 2wd or 4wd dyno?
Sep 23, 2003, 08:33 PM
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May i point you learned gentlemen to the issue of variance? I understand (correct me if Iam wrong) that roller based dynos generally have a larger variance in between runs. Thus setting a proper baseline to work with is difficult. In the end, some sort of estimation or getting a mean, average figure is what you end up with. Whereas I have heard that those hub dynos like dynopac where they take out your wheels and affix the dyno to your wheel hub are generally more accurate with much lesser variance as they discount tire pressure issues etc. (forgive the layman description, i dont know the technical lingo.)
Sep 24, 2003, 05:16 AM
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What are the opinions on yet another type of dyno, the Road Dyno (http://www.microsmith.co.uk/rd/dyno.htm)- what's bad/good about it?
It uses real world conditions, it has the real air flow though the intercooler (no simulated fans) and turbo hits its peaks in the real places (you accelerate the car not a drum). The biggest advantage is that it is super cheap and most hobbyists can affort one. I found this dyno provides quite repeatable numbers but people still think its some kind of Gtech hack and don't tend to believe the numbers it produces.
The downsides is that you need a good flat road, may have to deal with traffic, may risk getting a ticket, and you can't exactly mess around tuning while you are making runs. It also takes time to get out, make the runs and go back. Definitely not an effective tuner business tool... but we are talking about the different types of dunos and how they work, their advantages and disadvantages.
You can find sample Road Dyno data graphs in these threads:
https://www.evolutionm.net/forums/sh...dent+road+dyno
https://www.evolutionm.net/forums/sh...dent+road+dyno
It uses real world conditions, it has the real air flow though the intercooler (no simulated fans) and turbo hits its peaks in the real places (you accelerate the car not a drum). The biggest advantage is that it is super cheap and most hobbyists can affort one. I found this dyno provides quite repeatable numbers but people still think its some kind of Gtech hack and don't tend to believe the numbers it produces.
The downsides is that you need a good flat road, may have to deal with traffic, may risk getting a ticket, and you can't exactly mess around tuning while you are making runs. It also takes time to get out, make the runs and go back. Definitely not an effective tuner business tool... but we are talking about the different types of dunos and how they work, their advantages and disadvantages.
You can find sample Road Dyno data graphs in these threads:
https://www.evolutionm.net/forums/sh...dent+road+dyno
https://www.evolutionm.net/forums/sh...dent+road+dyno
Sep 26, 2003, 12:57 PM
#13
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Hi Steve,
Thanks for getting back on this, I am traveling right now so... Anyway regarding your response:
I understand what your trying to get at, but for most street cars the drive train load to engine power measurment variation does not appear to change signifigantly in the higher gears 3,4,5. Accept in the most extreme situations such as trying to compare a 1000 LB/HP hi power drag car to a regular 4000 LB 200HP street car. I agree that the drum inertial load dynos are designed to work best for the average street car (weight/power), since the EVO fits well into that category it is not an issue here.
The loading is obviously going to be different with every car for any given gear. By using a fixed load and similar gearing we are actually able to get a better comparison of what a given engine and drivetrain are capable of producing under the same conditions. IMO this is better for comparisons, since it can remove the load effect variable. Looking at the plots from these dynos and factoring in the weight and gearing, you can get a very good idea of the acceleration potential for each car.
From what I can tell, the loading on the DD system seems to have a large influence on the measurement values, this is simply not an issue on a inertia drum system.
I can easily see how your dyno would be far more flexible, it is also far more complex compared to an inertia drum dyno. I have already mentioned several times that I think active load dyno's like the DD have several advantages for tuning/detecting minor power fluctuations. So no argument there!
I also believe that the added complexity of design and operation can make comparing the absolute output values from various similiar cars far less accurate with this type of dyno.
There are a few observations that lead me to this conclusion:
1. The absolute values from a DD system seem to suggest that most 300-400 HP cars loose 80-90HP in the drive train. This seems like a ridiculously high value to me. Other than measurements from your dyno, is there any evidence to suggest that these loses are accurate?
2. For a system that is supposed to accurately simulate real world load conditions, the torque curve does not seem to match real world performance. Even accelerometer type devices that actually measure acceleration on the road seem to agree more with the inertia drum systems.
3. According to one of your customers, this dyno shows significantly more power in a lower gear? This goes against what I have seen on every other dyno, including an active load system with similar type rollers to the DD.
4. I have seen two facilities using your system showing vastly different test results for the same type of car.
How do you accurately calibrate and monitor the "retarder" load device? Can we see some constant load and acceleration measurements for an EVO or some other similiar well known vehicle?
In more than one gear would also be very informative.
Thanks,
Eric
Thanks for getting back on this, I am traveling right now so... Anyway regarding your response:
Torque number can be changed by all dyno's. If the car is turbo charged. If you have a honda that weighs 2300lbs and makes 500hp, and you have a Chevy the weighs 3500lbs and makes 500hp the inertia dyno will make the load exactly the same on each car. The honda will NEVER accelerate that slowly, and it will hit site in its fuel map that it will never see on the road. The inertia dyno will also make the turbo spool at a different rate than it will see on the road. These problems will change the torque of the motor
The loading is obviously going to be different with every car for any given gear. By using a fixed load and similar gearing we are actually able to get a better comparison of what a given engine and drivetrain are capable of producing under the same conditions. IMO this is better for comparisons, since it can remove the load effect variable. Looking at the plots from these dynos and factoring in the weight and gearing, you can get a very good idea of the acceleration potential for each car.
From what I can tell, the loading on the DD system seems to have a large influence on the measurement values, this is simply not an issue on a inertia drum system.
I can easily see how your dyno would be far more flexible, it is also far more complex compared to an inertia drum dyno. I have already mentioned several times that I think active load dyno's like the DD have several advantages for tuning/detecting minor power fluctuations. So no argument there!
I also believe that the added complexity of design and operation can make comparing the absolute output values from various similiar cars far less accurate with this type of dyno.
There are a few observations that lead me to this conclusion:
1. The absolute values from a DD system seem to suggest that most 300-400 HP cars loose 80-90HP in the drive train. This seems like a ridiculously high value to me. Other than measurements from your dyno, is there any evidence to suggest that these loses are accurate?
2. For a system that is supposed to accurately simulate real world load conditions, the torque curve does not seem to match real world performance. Even accelerometer type devices that actually measure acceleration on the road seem to agree more with the inertia drum systems.
3. According to one of your customers, this dyno shows significantly more power in a lower gear? This goes against what I have seen on every other dyno, including an active load system with similar type rollers to the DD.
4. I have seen two facilities using your system showing vastly different test results for the same type of car.
How do you accurately calibrate and monitor the "retarder" load device? Can we see some constant load and acceleration measurements for an EVO or some other similiar well known vehicle?
In more than one gear would also be very informative.
Thanks,
Eric
Sep 26, 2003, 01:55 PM
#14
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May i point you learned gentlemen to the issue of variance? I understand (correct me if Iam wrong) that roller based dynos generally have a larger variance in between runs. Thus setting a proper baseline to work with is difficult. In the end, some sort of estimation or getting a mean, average figure is what you end up with. Whereas I have heard that those hub dynos like dynopac where they take out your wheels and affix the dyno to your wheel hub are generally more accurate with much lesser variance as they discount tire pressure issues etc. (forgive the layman description, i dont know the technical lingo.)
Unless tire pressures are significantly under or over inflated, the power measurment differences are minimal.
The problems with the Dynopac system is that:
1, They do not show actual power differences to the road that can occur from a car that may use unusually heavy or light wheel/tire combos. Most people chassis dynoing a car want to know the actual usable power to the road.
2, It uses a hydraluic system for loading which is also subject to fluctuaction as the fluid temperature changes.
3, Setup is cumbersome.
While finding a suitable test location could be difficult the Road Dyno seems like it could produce some of the most accurate data regarding actual power on the street. Interesting that it seems to agree with the test data produced from the Dyno Jet.
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