Thanks from LPS + an explanation
Discussion
Dear All
Many thanks to those that attended the Rolling Road day at LPS on Saturday the 29th. It was a pleasure to meet you all and we hope you enjoyed the day as much as we did. Any feedback on how the day went would be greatly appreciated and we hope you all thought it was a worthwhile trip.
Renowned as we are for long posts on this forum, we thought we would continue the tradition, in order to explain how the rolling road works and how the figures are calculated. We are sure that many of you know how it is done, but we hope the information here will be useful to others, and will hopefully clear up any confusion. There seems to be some confusion amongst some of the S2000 owners with regards to the figures they achieved!
The dyno takes measurments in the following way:
1. Horsepower at the flywheel
The dyno measures horsepower at the wheels and then the software calculates horsepower at the flywheel by measuring drag (transmission loss) during the initial "coastdown" period. This is calculated by speed loss over a fixed period of time with no power loaded. The drag figure is then added to the horsepower readings at the wheels to obtain horsepower at the flywheel. This drag measurement is measured logarithmically (sp?) with absolutley no input from the operator. This is software calculated and is basic physics principles (more drag = faster slow down).
2. Torque (lb ft) at the flywheel
This measurement works in exactly the same way as above using the initial "coastdown" period to calculate with no manual input.
3. Transmission/drivetrain losses
As explained above, these figures are calculated through the software. Those that attended the day will remember that the first run was not a power run. This was a gearing calculation run, which allows us to match RPM readings on the system to that of the car. We did this for every vehicle, even if it was the same vehicle one after another, to allow for possible tyre size/pressure variation. This is our safeguard against any inconsistency. This is the easiest and most accurate way to get an accurate RPM reading in the system for the power runs.
4. Air/Fuel Ratio
This measured "live" by placing a wide band, heated lambda sensor into the exhaust. This reads exactly as the ECU on the vehicle would, and allows us to accurately check the ratio while on the run to isolate any problems that maybe occuring and would require further attention.
In addition to these system measurements, before every run the operator enters climate information from the weather station inside the booth. Measurements for ambient air temperature, humidity and atmospheric pressure are entered. The software will then compensate for these factors (known as "Ambient Correction" on your power graphs) to ensure that measurements are constant whether it be the middle of summer or the middle of winter.
Other readings can be measured (boost, temperature, etc) through the system but these tend to be impractical to test on a rolling road day - these are usually used for diagnostic work.
The operators of the Dyno have no way of manually changing the figures achieved from the Dyno. What a Power Run does is tell you exactly what the car is doing there and then. We have no interest in changing the figures as there is no reason to do so.
We saw a number of mixed responses yesterday to the figures achieved, many being very happy and many not so happy (usually those that have spent a lot of money on modifications and have been promised much which had not done the job!).
Hopefully those that did not get what they expected had the chance to discuss with us the reason why and know the way forward to improve performance.
Just as an addition, when testing REAR engined vehicles, it is a common estimation that anything between 10 to 20hp maybe lost through heatsoak in the engine bay due to cooling restrictions on the booth. However hard we try to pump air in it can never accurately duplicate road conditions. Tom's Boxster is the one reading yesterday we feel is actually a little lower than it is in reality. This estimation DOES NOT apply to front engined vehicles.
Sorry for the long and boring post but we hope it is of value to some.
Thank you all again for your time and patience yesterday and we very much look forward to seeing some if not all again in the near future. Hope you enjoyed the barbeque also.
Also. many thanks again to Doug for organising this for us.
Regards
Neil & Steve @ LPS
Many thanks to those that attended the Rolling Road day at LPS on Saturday the 29th. It was a pleasure to meet you all and we hope you enjoyed the day as much as we did. Any feedback on how the day went would be greatly appreciated and we hope you all thought it was a worthwhile trip.
Renowned as we are for long posts on this forum, we thought we would continue the tradition, in order to explain how the rolling road works and how the figures are calculated. We are sure that many of you know how it is done, but we hope the information here will be useful to others, and will hopefully clear up any confusion. There seems to be some confusion amongst some of the S2000 owners with regards to the figures they achieved!
The dyno takes measurments in the following way:
1. Horsepower at the flywheel
The dyno measures horsepower at the wheels and then the software calculates horsepower at the flywheel by measuring drag (transmission loss) during the initial "coastdown" period. This is calculated by speed loss over a fixed period of time with no power loaded. The drag figure is then added to the horsepower readings at the wheels to obtain horsepower at the flywheel. This drag measurement is measured logarithmically (sp?) with absolutley no input from the operator. This is software calculated and is basic physics principles (more drag = faster slow down).
2. Torque (lb ft) at the flywheel
This measurement works in exactly the same way as above using the initial "coastdown" period to calculate with no manual input.
3. Transmission/drivetrain losses
As explained above, these figures are calculated through the software. Those that attended the day will remember that the first run was not a power run. This was a gearing calculation run, which allows us to match RPM readings on the system to that of the car. We did this for every vehicle, even if it was the same vehicle one after another, to allow for possible tyre size/pressure variation. This is our safeguard against any inconsistency. This is the easiest and most accurate way to get an accurate RPM reading in the system for the power runs.
4. Air/Fuel Ratio
This measured "live" by placing a wide band, heated lambda sensor into the exhaust. This reads exactly as the ECU on the vehicle would, and allows us to accurately check the ratio while on the run to isolate any problems that maybe occuring and would require further attention.
In addition to these system measurements, before every run the operator enters climate information from the weather station inside the booth. Measurements for ambient air temperature, humidity and atmospheric pressure are entered. The software will then compensate for these factors (known as "Ambient Correction" on your power graphs) to ensure that measurements are constant whether it be the middle of summer or the middle of winter.
Other readings can be measured (boost, temperature, etc) through the system but these tend to be impractical to test on a rolling road day - these are usually used for diagnostic work.
The operators of the Dyno have no way of manually changing the figures achieved from the Dyno. What a Power Run does is tell you exactly what the car is doing there and then. We have no interest in changing the figures as there is no reason to do so.
We saw a number of mixed responses yesterday to the figures achieved, many being very happy and many not so happy (usually those that have spent a lot of money on modifications and have been promised much which had not done the job!).
Hopefully those that did not get what they expected had the chance to discuss with us the reason why and know the way forward to improve performance.
Just as an addition, when testing REAR engined vehicles, it is a common estimation that anything between 10 to 20hp maybe lost through heatsoak in the engine bay due to cooling restrictions on the booth. However hard we try to pump air in it can never accurately duplicate road conditions. Tom's Boxster is the one reading yesterday we feel is actually a little lower than it is in reality. This estimation DOES NOT apply to front engined vehicles.
Sorry for the long and boring post but we hope it is of value to some.
Thank you all again for your time and patience yesterday and we very much look forward to seeing some if not all again in the near future. Hope you enjoyed the barbeque also.
Also. many thanks again to Doug for organising this for us.
Regards
Neil & Steve @ LPS
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