DYNOJET VS DYNODYNAMICS... Round XX
Apr 11, 2009, 08:45 PM
#106
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Ivan,
I know you understand dynos very well. I've read some of your 'war' discussions with other vendors on this site. BUT, I don't see anywhere in the quote I posted that says the 'load adding dyno ONLY' uses strain guages to measure power -- nor did I see it implied.
From what I read, the amount of 'force' is measured with the strain guage. The body of the paragraph 2nd up from your quote contains the formula...
Force = Mass * Acceleration
Force in this case is TORQUE not horsepower since it's derived from the strain guage's multiplier effect on the roller. Keep in mind it's the roller's inertia that begins the entire equation.
Perhaps if you read the entire essay, you would not have come to your conclusions as an arguement since one of the major points the author intended to make agreed with your statement....
I know you understand dynos very well. I've read some of your 'war' discussions with other vendors on this site. BUT, I don't see anywhere in the quote I posted that says the 'load adding dyno ONLY' uses strain guages to measure power -- nor did I see it implied.
From what I read, the amount of 'force' is measured with the strain guage. The body of the paragraph 2nd up from your quote contains the formula...
Force = Mass * Acceleration
Force in this case is TORQUE not horsepower since it's derived from the strain guage's multiplier effect on the roller. Keep in mind it's the roller's inertia that begins the entire equation.
Perhaps if you read the entire essay, you would not have come to your conclusions as an arguement since one of the major points the author intended to make agreed with your statement....
Superior in what regards? Weight? Price? Pimp factor?
Last edited by Ivan@AMS; Apr 11, 2009 at 09:02 PM.
Apr 12, 2009, 07:07 AM
#109
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Yes,,,, Pimp factor.
It's amusing that out of 8 pages, 1 sentence in a quote I posted is where you stand ground as being incorrect. I can stand for your opinions as being very valid, but I don't think you are looking at the big picture. Fact is, load bearing dynos use the extra 'mile' to isolate the vehicles output.
If higher dynojet figures give you a marketing edge, so be it-- but please do not ignore 8 pages of information and base your entire stance on what you interpreted from reading 1/4 of a very informational piece.
It's amusing that out of 8 pages, 1 sentence in a quote I posted is where you stand ground as being incorrect. I can stand for your opinions as being very valid, but I don't think you are looking at the big picture. Fact is, load bearing dynos use the extra 'mile' to isolate the vehicles output.
If higher dynojet figures give you a marketing edge, so be it-- but please do not ignore 8 pages of information and base your entire stance on what you interpreted from reading 1/4 of a very informational piece.
Now you are twisting the topic around to a numbers argument and I have said exactly ZERO about numbers on ANY dyno.
BTW, the length of a post (or quote) has no direct correlation to accuracy or credibility.
Apr 12, 2009, 08:07 AM
#110
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This is where the author of this should have just gotten to the point. Instead of giving the "first" example... we get this:
the engine produces horsepower at the flywheel (brake horsepower) that is reported by the automobile manufacturers. Engine power is coupled to the rear wheels by a transmission and a rearend. But this is no free ride - there are losses in both the trans and the rearend. Therefore, the power to the rear wheels is equal to the flywheel horsepower minus the drivetrain power loss.
The drivetrain losses are mainly composed of three loss areas: friction loss, inertia loss, and viscous loss. The friction loss is largely due to the surfaces of the gear teeth rubbing against each other. Gear friction is related to the torque being transmitted through the drivetrain. The gear power loss is related to the speed at which the torque is being transmitted. This is why it is recommended to have a transmission cooler for towing. The transmission must couple more torque to pull the boat resulting in more frictional power loss, which shows up as more heat in the transmission to be taken away by the transmission cooler.
Inertial loss is related to the rotational acceleration (i.e., angular acceleration) of the drivetrain components. The inertial loss does not result in a power loss (i.e., heat) but absorbs energy that can be coupled to the rear wheels. This energy actually gets stored in the drivetrain components. The stored inertial energy in the flywheel keeps the revs up while the clutch is pressed in during shifts. The inertia loss is more pronounced in lower gears (i.e., First or Second) when the acceleration is highest.
Therefore, to measure the actual rear-wheel horsepower, the drivetrain must be properly loaded to obtain the correct drivetrain loss. If the dyno provides a lower drivetrain load, then the drivetrain losses will be lower and the resulting rear-wheel horsepower will be higher.
The second reason why vehicle loading is important is that the newer computer-controlled vehicles use engine load as a control parameter. For example, ignition timing is a function of engine load. You will see higher timing advance when revving the engine in Neutral than you will when the vehicle is fully loaded at wide-open throttle in Third gear.
Who cares????? Which is more repeatable, easier to use, more widely accepted and can be compared from one end of the country to the other with a reasonable assurance of being able to be accurately compared?
West Automotive Performance Engineering has developed a proprietary device that independently measures a vehicle's actual speed and acceleration. This device is similar in operation to a fifth wheel but doesn't use accelerometers that can be influenced by the vehicle's body tilt. Using the vehicle's speed, acceleration, and weight (mass) and the application of simple physics equations, the exact horsepower and torque can be calculated. The horsepower and torque measured by West Automotive Performance Engineering's dyno is actually the horsepower made-good, or the horsepower left over to accelerate the vehicle after all the aerodynamic and rolling-friction losses have been overcome. These losses were accounted for and included West Automotive Performance Engineering's dyno so that a comparison with a chassis dynamometer can be made. The Mustang dyno includes the aerodynamic load that it places on the drivetrain as part of its reported rear-wheel horsepower and torque. Stated another way, the Mustang dyno does not measure the horsepower made-good.
Graphs 7 and 10 show the horsepower and torque versus rpm in Second and Third gear, respectively, for the Dynojet dyno, the Mustang dyno, and from road testing with the dyno from West Automotive Performance Engineering. You can see that the horsepower and the torque, as measured on the road, are closer to the Mustang dyno measurements. Also from the acceleration tests you can see how the Mustang dyno loads the vehicle very closely to how it will be actually loaded on the road. Based on our test data, the Mustang dyno loaded our test vehicle and measured the rearwheel horsepower closer to what the vehicle experiences on the road.
Graphs 7 and 10 show the horsepower and torque versus rpm in Second and Third gear, respectively, for the Dynojet dyno, the Mustang dyno, and from road testing with the dyno from West Automotive Performance Engineering. You can see that the horsepower and the torque, as measured on the road, are closer to the Mustang dyno measurements. Also from the acceleration tests you can see how the Mustang dyno loads the vehicle very closely to how it will be actually loaded on the road. Based on our test data, the Mustang dyno loaded our test vehicle and measured the rearwheel horsepower closer to what the vehicle experiences on the road.
Conclusions
The Test Results table summarizes the testing that we performed. Keep in mind that the peak numbers are influenced by the amount of smoothing or averaging done to the final data. For comparing dyno plots to determine losses or gains, don't focus on the peak values but take a visual average by comparing the before and after curves on the same graph. If you can't see a marked improvement on the dyno, you probably won't see a performance improvement on the street. Also, realize that both the Dynojet and Mustang chassis dynamometers are useful tools that have excellent repeatability. Both dynos measure the correct horsepower and torque for the load that they apply. Both dynos will show losses or gains from modifications. It is recommended that you pick a dyno for your baseline testing and stick with that dyno type and dyno location (and dyno operator) for subsequent testing.,,, "
The Test Results table summarizes the testing that we performed. Keep in mind that the peak numbers are influenced by the amount of smoothing or averaging done to the final data. For comparing dyno plots to determine losses or gains, don't focus on the peak values but take a visual average by comparing the before and after curves on the same graph. If you can't see a marked improvement on the dyno, you probably won't see a performance improvement on the street. Also, realize that both the Dynojet and Mustang chassis dynamometers are useful tools that have excellent repeatability. Both dynos measure the correct horsepower and torque for the load that they apply. Both dynos will show losses or gains from modifications. It is recommended that you pick a dyno for your baseline testing and stick with that dyno type and dyno location (and dyno operator) for subsequent testing.,,, "
In actuality, NEITHER is probably all that accurate.
Apr 12, 2009, 10:53 AM
#114
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4K,
The "twisting" comment came from the fact that what I had posted had nothing to do with numbers or accuracy. I just stated facts about how each dyno has the exact same inertia basis of operation.... which seemed to be omitted from your quoted article. Your eventual response to that "flipped the script" and landed us on an "accuracy / numbers" discussion. From my prospective, I was still on the original discussion... ergo the confusion.
Yes, there is probably a competitive edge when higher gains are shown for a part. This is most likely to affect the under-educated consumer though. The same person who is likely to buy a part because it is claimed to make an extra 5 HP over another part is also likely to add 25% to a MD dyno chart to "simulate" what it might make on a DJ. I guess it would all depend on what they last read on the internet.
As far as numbers and accuracy.... here are the facts as I see them:
DynoJet dyno numbers can not be messed with. You can make small changes in the chart using different correction factors and smoothing and that is it. Correction factors and smoothing is shown right on the dyno graph.
Mustang Dyno numbers can be changed at will. I can put down just about any number I want on a MD just by changing roller weight. Roller weight is not shown on the dyno chart. I can post up a 300 RWHP MD Dyno chart for bone stock 240sx if you like.
A DynoJet is simple. It is basically rollers. Maintenance is simply ensuring the bearings are properly serviced.
The Mustang Dyno is complicated with many things that can be out of adjustment or repair. In addition to rollers, you have belts linking rollers and linking PAUs, chains, fulcrums and pivots for the strain gauges, strain gauge calibration, etc etc.
A DynoJet calibration is set by the factory and does not get messed with. The end user has NO control over any of the math that is used to calculate HP and TQ. All DynoJet dynos read the same way and use the exact same math. Numbers from a DJ on the east coast can be accurately compared to a DJ on the west coast.
A Mustang Dyno calibration is done by the end user and can be improperly altered at any time. The end user can alter numbers that are actually used in the calculation of HP and TQ which leads to inaccurate numbers and differences between other MD dynos. Two MD dynos in the same city will not even read the same.
The best reason to own a DynoJet is so you never have to say "Well... on a DynoJet I would make XXX HP" Every time you hear this, it lends credibility that the DynoJet is the STANDARD.
A Mustang Dyno is claimed to normally read low. People who arbitrarily add percentages and then post up those numbers further confuse the issue. Especially when a MD dyno reading can be either high or low depending on how it is maintained and set up.
Bottom line... I personally prefer numbers that come from a DynoJet dyno that can not be messed with, are repeatable on any other DynoJet and are the STANDARD by which all others are judged by.
The "twisting" comment came from the fact that what I had posted had nothing to do with numbers or accuracy. I just stated facts about how each dyno has the exact same inertia basis of operation.... which seemed to be omitted from your quoted article. Your eventual response to that "flipped the script" and landed us on an "accuracy / numbers" discussion. From my prospective, I was still on the original discussion... ergo the confusion.
Yes, there is probably a competitive edge when higher gains are shown for a part. This is most likely to affect the under-educated consumer though. The same person who is likely to buy a part because it is claimed to make an extra 5 HP over another part is also likely to add 25% to a MD dyno chart to "simulate" what it might make on a DJ. I guess it would all depend on what they last read on the internet.
As far as numbers and accuracy.... here are the facts as I see them:
DynoJet dyno numbers can not be messed with. You can make small changes in the chart using different correction factors and smoothing and that is it. Correction factors and smoothing is shown right on the dyno graph.
Mustang Dyno numbers can be changed at will. I can put down just about any number I want on a MD just by changing roller weight. Roller weight is not shown on the dyno chart. I can post up a 300 RWHP MD Dyno chart for bone stock 240sx if you like.
A DynoJet is simple. It is basically rollers. Maintenance is simply ensuring the bearings are properly serviced.
The Mustang Dyno is complicated with many things that can be out of adjustment or repair. In addition to rollers, you have belts linking rollers and linking PAUs, chains, fulcrums and pivots for the strain gauges, strain gauge calibration, etc etc.
A DynoJet calibration is set by the factory and does not get messed with. The end user has NO control over any of the math that is used to calculate HP and TQ. All DynoJet dynos read the same way and use the exact same math. Numbers from a DJ on the east coast can be accurately compared to a DJ on the west coast.
A Mustang Dyno calibration is done by the end user and can be improperly altered at any time. The end user can alter numbers that are actually used in the calculation of HP and TQ which leads to inaccurate numbers and differences between other MD dynos. Two MD dynos in the same city will not even read the same.
The best reason to own a DynoJet is so you never have to say "Well... on a DynoJet I would make XXX HP" Every time you hear this, it lends credibility that the DynoJet is the STANDARD.
A Mustang Dyno is claimed to normally read low. People who arbitrarily add percentages and then post up those numbers further confuse the issue. Especially when a MD dyno reading can be either high or low depending on how it is maintained and set up.
Bottom line... I personally prefer numbers that come from a DynoJet dyno that can not be messed with, are repeatable on any other DynoJet and are the STANDARD by which all others are judged by.
Apr 12, 2009, 01:48 PM
#115
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4K,
The "twisting" comment came from the fact that what I had posted had nothing to do with numbers or accuracy. I just stated facts about how each dyno has the exact same inertia basis of operation.... which seemed to be omitted from your quoted article. Your eventual response to that "flipped the script" and landed us on an "accuracy / numbers" discussion. From my prospective, I was still on the original discussion... ergo the confusion.
Yes, there is probably a competitive edge when higher gains are shown for a part. This is most likely to affect the under-educated consumer though. The same person who is likely to buy a part because it is claimed to make an extra 5 HP over another part is also likely to add 25% to a MD dyno chart to "simulate" what it might make on a DJ. I guess it would all depend on what they last read on the internet.
As far as numbers and accuracy.... here are the facts as I see them:
DynoJet dyno numbers can not be messed with. You can make small changes in the chart using different correction factors and smoothing and that is it. Correction factors and smoothing is shown right on the dyno graph.
Mustang Dyno numbers can be changed at will. I can put down just about any number I want on a MD just by changing roller weight. Roller weight is not shown on the dyno chart. I can post up a 300 RWHP MD Dyno chart for bone stock 240sx if you like.
A DynoJet is simple. It is basically rollers. Maintenance is simply ensuring the bearings are properly serviced.
The Mustang Dyno is complicated with many things that can be out of adjustment or repair. In addition to rollers, you have belts linking rollers and linking PAUs, chains, fulcrums and pivots for the strain gauges, strain gauge calibration, etc etc.
A DynoJet calibration is set by the factory and does not get messed with. The end user has NO control over any of the math that is used to calculate HP and TQ. All DynoJet dynos read the same way and use the exact same math. Numbers from a DJ on the east coast can be accurately compared to a DJ on the west coast.
A Mustang Dyno calibration is done by the end user and can be improperly altered at any time. The end user can alter numbers that are actually used in the calculation of HP and TQ which leads to inaccurate numbers and differences between other MD dynos. Two MD dynos in the same city will not even read the same.
The best reason to own a DynoJet is so you never have to say "Well... on a DynoJet I would make XXX HP" Every time you hear this, it lends credibility that the DynoJet is the STANDARD.
A Mustang Dyno is claimed to normally read low. People who arbitrarily add percentages and then post up those numbers further confuse the issue. Especially when a MD dyno reading can be either high or low depending on how it is maintained and set up.
Bottom line... I personally prefer numbers that come from a DynoJet dyno that can not be messed with, are repeatable on any other DynoJet and are the STANDARD by which all others are judged by.
The "twisting" comment came from the fact that what I had posted had nothing to do with numbers or accuracy. I just stated facts about how each dyno has the exact same inertia basis of operation.... which seemed to be omitted from your quoted article. Your eventual response to that "flipped the script" and landed us on an "accuracy / numbers" discussion. From my prospective, I was still on the original discussion... ergo the confusion.
Yes, there is probably a competitive edge when higher gains are shown for a part. This is most likely to affect the under-educated consumer though. The same person who is likely to buy a part because it is claimed to make an extra 5 HP over another part is also likely to add 25% to a MD dyno chart to "simulate" what it might make on a DJ. I guess it would all depend on what they last read on the internet.
As far as numbers and accuracy.... here are the facts as I see them:
DynoJet dyno numbers can not be messed with. You can make small changes in the chart using different correction factors and smoothing and that is it. Correction factors and smoothing is shown right on the dyno graph.
Mustang Dyno numbers can be changed at will. I can put down just about any number I want on a MD just by changing roller weight. Roller weight is not shown on the dyno chart. I can post up a 300 RWHP MD Dyno chart for bone stock 240sx if you like.
A DynoJet is simple. It is basically rollers. Maintenance is simply ensuring the bearings are properly serviced.
The Mustang Dyno is complicated with many things that can be out of adjustment or repair. In addition to rollers, you have belts linking rollers and linking PAUs, chains, fulcrums and pivots for the strain gauges, strain gauge calibration, etc etc.
A DynoJet calibration is set by the factory and does not get messed with. The end user has NO control over any of the math that is used to calculate HP and TQ. All DynoJet dynos read the same way and use the exact same math. Numbers from a DJ on the east coast can be accurately compared to a DJ on the west coast.
A Mustang Dyno calibration is done by the end user and can be improperly altered at any time. The end user can alter numbers that are actually used in the calculation of HP and TQ which leads to inaccurate numbers and differences between other MD dynos. Two MD dynos in the same city will not even read the same.
The best reason to own a DynoJet is so you never have to say "Well... on a DynoJet I would make XXX HP" Every time you hear this, it lends credibility that the DynoJet is the STANDARD.
A Mustang Dyno is claimed to normally read low. People who arbitrarily add percentages and then post up those numbers further confuse the issue. Especially when a MD dyno reading can be either high or low depending on how it is maintained and set up.
Bottom line... I personally prefer numbers that come from a DynoJet dyno that can not be messed with, are repeatable on any other DynoJet and are the STANDARD by which all others are judged by.
Apr 16, 2009, 08:32 AM
#116
Evolving Member
After plowing through all these DJ bashing posts, I really appreciate #114. I've read about how DJ's work in the past, and it seems pretty simple and straight-forward. So the only difference between a DJ and "real life" is the inertial loading on the drivetrain and wind resistance. Can't do much about wind resistance, since the car is sitting on a a dyno, but does anyone know the weight of the rollers in a DJ? There also needs to be a correction factor for the fact that the rollers have rotational inertia vs a car's linear inertia. I did some simple calculations a while ago and for a circumferencial mass on the rim of a wheel, the penalty is 45%. That means a 10lb weight on the wheel rim would feel like a 14.5 lb weight to the drivetrain. I guess a roller's mass is distributed and not a circumferencial mass, but this could be used as a rough guideline.
Jan 7, 2010, 12:51 PM
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