LaserBob
New member
- Joined
- Apr 17, 2007
- Messages
- 74
How do I make a Dyno Run?
Tom S. asked me what goes into a dyno run. The more that I thought about it, the more sense it made to give an explanation of what I do in the trucks when it is on the GAM Super Flow Lie Detector.
The obvious is just that: we need a good set of tie downs on all four corners to ensure no surprises. We use two straps in the front and four straps in the rear. That front wall is pretty close when the Speedo reads 60-80-120 mph. We use wheel chocks (2) on both front wheels. (Just a little clink of one strap will get your hair standing up when you are under power.) The guys at the rear of the truck get the smoke pipe hooked up.
The tach signal is, and has always been, a bugger. I have been at dyno events around the country and we are not alone in having problems in that department. The young man (young is better) that puts the pickup sensor on is the key to the run getting done rapidly. I have read the Super Flow manual about getting this signal several times. I have done the tach signal on three different dyno brands and I still learn something every time. It should not be rocket science. I guess it is not science, but an art.
The software in the computer has multiple types of tests available. We use one called Proaccel. I pick a start speed, then a finish speed, then how long to make the run last (usually 8 seconds like a pro bull rider). The computer then askes me to stabilize the speed at the start setting and apply full throttle. The software makes the run with the help of a dual eddy current brake control in the ground under the truck. Simplified a lot, an eddy current brake is an electric motor to stop something rather than make it go.(See link below from Super Flow’s website.) Tire size has a small effect as does gear ratio.
http://www.superflow.com/dynamometers/index_846.cfm
Having the truck all tied down and connected, now I get a feel for the truck. A manual trans is easier to pick a range to run the truck. The range is picked based on the rpm range that the engine will pull. The first thing that I do is run the truck in direct gear through its rpm range to see what speeds it will operate within. If you start the run too low, the engine lugs and smokes and makes mostly heat. If you start too high, you miss some of the power that we all like to see. The top end is limited by the rpm limit of the engine and a bit by the range that I picked. If I pick 82mph for a top range and the truck noses over (i.e. runs out of power or rpms just before it gets there) it will not record the run.
The run actually begins when I press the button labeled ACCEL. The dyno allows the truck to proceed through the range specified in the time allowed and records the information. If it gets a run within the parameters it is looking for, it records the run and the screen on the computer shows that the run has been recorded and saved. The instant that I see a good run on the handheld console, I can select NEW RUN and repeat the run at a different power level if the owner has changed power levels.
An automatic trans adds choices to the equation. If it can be held in direct gear and the converter can be locked, and it does not downshift, it works just like a manual transmission. Nothing to it! On the dyno a manual is great! On the street good autos rule!
Just an observation from where I sit on this dyno stuff: I have been around Dyno Jets, Mustangs, Dyno Dynamics, portable Dyno Jets, and GAM’s Super Flow. I have run my truck on PFI’s Dyno Jet and GAM’s Super Flow within 2 hours of each other and put down power and torque levels within 1% of each other. For me that is good enough. We use the STPPwr corrected numbers at GAM/PDT when we are talking about these runs.
The sheets that everyone should have gotten have the STPPwr #s and WhlPwr #s on them.
STPPwr is Super Flow’s accepted correction factors for horsepower that day.
STPTrq is Super Flow’s accepted correction factors for torque for that day.
WhlPwr is uncorrected horsepower numbers for that day.
WhlTrq is uncorrected torque numbers for that day.
If you come to a dyno event or just your own personal session, have an idea about holding your auto (if applicable) in direct, the converter locked and where your truck runs the best. The best run you get will likely be the first one, so crank it up (NASCAR Talk) as the heat soaking that occurs even when we run large fans right into the front of the truck will take some of the edge off your truck with repeated runs. The more you can tell the operator about how your truck performs, the better he can get results for you. Properly executed, a three-pull test (8 seconds each) can be made in less than one minute. All the rest is getting ready, hooking up and unhooking.
I hope that this helps you who are curious about the runs that are made on a dyno when you do a run.
Thanks for giving me the opportunity to try to explain things.
I am not nearly as knowledgeable or experienced as some are on this subject, and these are my ideas and opinions from my training and experience.
Thanks,
LaserBob
PDT
rlberends@aol.com
Tom S. asked me what goes into a dyno run. The more that I thought about it, the more sense it made to give an explanation of what I do in the trucks when it is on the GAM Super Flow Lie Detector.
The obvious is just that: we need a good set of tie downs on all four corners to ensure no surprises. We use two straps in the front and four straps in the rear. That front wall is pretty close when the Speedo reads 60-80-120 mph. We use wheel chocks (2) on both front wheels. (Just a little clink of one strap will get your hair standing up when you are under power.) The guys at the rear of the truck get the smoke pipe hooked up.
The tach signal is, and has always been, a bugger. I have been at dyno events around the country and we are not alone in having problems in that department. The young man (young is better) that puts the pickup sensor on is the key to the run getting done rapidly. I have read the Super Flow manual about getting this signal several times. I have done the tach signal on three different dyno brands and I still learn something every time. It should not be rocket science. I guess it is not science, but an art.
The software in the computer has multiple types of tests available. We use one called Proaccel. I pick a start speed, then a finish speed, then how long to make the run last (usually 8 seconds like a pro bull rider). The computer then askes me to stabilize the speed at the start setting and apply full throttle. The software makes the run with the help of a dual eddy current brake control in the ground under the truck. Simplified a lot, an eddy current brake is an electric motor to stop something rather than make it go.(See link below from Super Flow’s website.) Tire size has a small effect as does gear ratio.
http://www.superflow.com/dynamometers/index_846.cfm
Having the truck all tied down and connected, now I get a feel for the truck. A manual trans is easier to pick a range to run the truck. The range is picked based on the rpm range that the engine will pull. The first thing that I do is run the truck in direct gear through its rpm range to see what speeds it will operate within. If you start the run too low, the engine lugs and smokes and makes mostly heat. If you start too high, you miss some of the power that we all like to see. The top end is limited by the rpm limit of the engine and a bit by the range that I picked. If I pick 82mph for a top range and the truck noses over (i.e. runs out of power or rpms just before it gets there) it will not record the run.
The run actually begins when I press the button labeled ACCEL. The dyno allows the truck to proceed through the range specified in the time allowed and records the information. If it gets a run within the parameters it is looking for, it records the run and the screen on the computer shows that the run has been recorded and saved. The instant that I see a good run on the handheld console, I can select NEW RUN and repeat the run at a different power level if the owner has changed power levels.
An automatic trans adds choices to the equation. If it can be held in direct gear and the converter can be locked, and it does not downshift, it works just like a manual transmission. Nothing to it! On the dyno a manual is great! On the street good autos rule!
Just an observation from where I sit on this dyno stuff: I have been around Dyno Jets, Mustangs, Dyno Dynamics, portable Dyno Jets, and GAM’s Super Flow. I have run my truck on PFI’s Dyno Jet and GAM’s Super Flow within 2 hours of each other and put down power and torque levels within 1% of each other. For me that is good enough. We use the STPPwr corrected numbers at GAM/PDT when we are talking about these runs.
The sheets that everyone should have gotten have the STPPwr #s and WhlPwr #s on them.
STPPwr is Super Flow’s accepted correction factors for horsepower that day.
STPTrq is Super Flow’s accepted correction factors for torque for that day.
WhlPwr is uncorrected horsepower numbers for that day.
WhlTrq is uncorrected torque numbers for that day.
If you come to a dyno event or just your own personal session, have an idea about holding your auto (if applicable) in direct, the converter locked and where your truck runs the best. The best run you get will likely be the first one, so crank it up (NASCAR Talk) as the heat soaking that occurs even when we run large fans right into the front of the truck will take some of the edge off your truck with repeated runs. The more you can tell the operator about how your truck performs, the better he can get results for you. Properly executed, a three-pull test (8 seconds each) can be made in less than one minute. All the rest is getting ready, hooking up and unhooking.
I hope that this helps you who are curious about the runs that are made on a dyno when you do a run.
Thanks for giving me the opportunity to try to explain things.
I am not nearly as knowledgeable or experienced as some are on this subject, and these are my ideas and opinions from my training and experience.
Thanks,
LaserBob
PDT
rlberends@aol.com
