How Accurate is a Dyno Jet?
12-21-2004, 06:25 PM
#1
How Accurate is a Dyno Jet?
How Accurate is a Dyno Jet?
Or more precisely, "How Precise" or repeatable are runs on a Dynojet.
Using basic statistical sampling and assuming that peak power or peak torque numbers are normally distributed we can estimate the 95% confidence interval for Dynojet runs with a motor.
Anybody want to flog their motor 30 times (30 samples). Tbone is willing.
. I've talked to him about this.
What does this mean? In simple terms we can scientifically estimate that "a Dynojet is X% accurate"
The result may be shocking but for sure will be educational.
Modified by Rocket at 7:13 AM 12/22/2004
Or more precisely, "How Precise" or repeatable are runs on a Dynojet.
Using basic statistical sampling and assuming that peak power or peak torque numbers are normally distributed we can estimate the 95% confidence interval for Dynojet runs with a motor.
Anybody want to flog their motor 30 times (30 samples). Tbone is willing.
. I've talked to him about this.What does this mean? In simple terms we can scientifically estimate that "a Dynojet is X% accurate"
The result may be shocking but for sure will be educational.
Modified by Rocket at 7:13 AM 12/22/2004
12-21-2004, 09:18 PM
#5
Honda-Tech Member
Re: How Accurate is a Dyno Jet? (Rocket)
I am going to get my car dyno tuned in January. I would be down to let my car be a guiena pig if I were able to get the cost cut in half.
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12-22-2004, 12:11 AM
#9
Re: (Rocket)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Rocket »</TD></TR><TR><TD CLASS="quote">I hope you realize that 10+ dyno runs is pretty tough on the motor.
Not trying to scare you but just letting you know.</TD></TR></TABLE>
haha, actually i am about to rebuild my motor, so i really dont care too much
but how is 10+ dyno runs tough on the motor?
Not trying to scare you but just letting you know.</TD></TR></TABLE>
haha, actually i am about to rebuild my motor, so i really dont care too much
but how is 10+ dyno runs tough on the motor?
12-22-2004, 04:35 AM
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Re: How Accurate is a Dyno Jet? (Rocket)
What has brought this "concern" up?
I think we've seen that dyno numbers from different dynojets on comparable engines are relatively close. If you want som eeye popping data you guys should be doing this with different Mustang dynos with different operators.
I think we've seen that dyno numbers from different dynojets on comparable engines are relatively close. If you want som eeye popping data you guys should be doing this with different Mustang dynos with different operators.
12-22-2004, 06:28 AM
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Re: How Accurate is a Dyno Jet? (SMSP)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SMSP »</TD></TR><TR><TD CLASS="quote"> If you want som eeye popping data you guys should be doing this with different Mustang dynos with different operators.</TD></TR></TABLE>
I bet you could get as much as 60 whp difference on the same motor.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Rocket »</TD></TR><TR><TD CLASS="quote">One key point is a reliable motor.</TD></TR></TABLE>
Got that one covered.
I bet you could get as much as 60 whp difference on the same motor.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Rocket »</TD></TR><TR><TD CLASS="quote">One key point is a reliable motor.</TD></TR></TABLE>
Got that one covered.
12-22-2004, 07:10 AM
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Re: How Accurate is a Dyno Jet? (b19coupe)
want to see the out come.
my friend owns a dyno and i will see if can it on his ? (dyno jet)
i do not think the numders will be off at all!
my friend owns a dyno and i will see if can it on his ? (dyno jet)
i do not think the numders will be off at all!
12-22-2004, 07:20 AM
#13
Re: How Accurate is a Dyno Jet? (SMSP)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SMSP »</TD></TR><TR><TD CLASS="quote">What has brought this "concern" up?
I think we've seen that dyno numbers from different dynojets on comparable engines are relatively close. If you want som eeye popping data you guys should be doing this with different Mustang dynos with different operators.</TD></TR></TABLE>
Not really a concern. I just had to revisit some basic statistic principles and saw that it could be applied to looking at sample runs on a dyno meter. I chose dyno jet because it is the most common for us. You are 100% correct that the operator is a great varying factor.
My point is that I've seen back to back runs on a dynojet vary by 7-10whp so I want to see if this is relatively rare or common. If you see a 5whp difference is that just random variation or a true gain. Now if you saw a 20whp gain you're pretty sure you gained hp but really how much since some the 20whp could be random variation.
I think we've seen that dyno numbers from different dynojets on comparable engines are relatively close. If you want som eeye popping data you guys should be doing this with different Mustang dynos with different operators.</TD></TR></TABLE>
Not really a concern. I just had to revisit some basic statistic principles and saw that it could be applied to looking at sample runs on a dyno meter. I chose dyno jet because it is the most common for us. You are 100% correct that the operator is a great varying factor.
My point is that I've seen back to back runs on a dynojet vary by 7-10whp so I want to see if this is relatively rare or common. If you see a 5whp difference is that just random variation or a true gain. Now if you saw a 20whp gain you're pretty sure you gained hp but really how much since some the 20whp could be random variation.
12-22-2004, 07:21 AM
#14
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Re: How Accurate is a Dyno Jet? (Rocket)
This is a great project!
You need to keep absolute barometric data for each run, not series of runs, each pull. Atmospheric pressure with a real mercury barometer, humidity, and test cell temperature. It would be nice to have key engine parameters also, like coolant temp, IAT, etc.... but ... the atmospheric parameters are more important. Also all the dyno dither factors.
It may be an eyeopener to do 10 runs on a dynojet, 10 on a Mustang, and 10 on a dyno pak... etc. Does not have to be the same car, but the same "class" car on each. 10 runs start to get the statistics defined.
On second thought, it may actually be better to not run a "hot" engine combo for this test. A stock say type R may be a better choice to determine the dyno's characteristics.
Now if its a mustang with a static calibration of the load cell, you should calibrate the dyno before the 10 runs and after the 10 runs. Show how the calibration did/did not drift.
This has the making of a good performance magazine article, maybe someone would be willing to underwrite the costs?
You need to keep absolute barometric data for each run, not series of runs, each pull. Atmospheric pressure with a real mercury barometer, humidity, and test cell temperature. It would be nice to have key engine parameters also, like coolant temp, IAT, etc.... but ... the atmospheric parameters are more important. Also all the dyno dither factors.
It may be an eyeopener to do 10 runs on a dynojet, 10 on a Mustang, and 10 on a dyno pak... etc. Does not have to be the same car, but the same "class" car on each. 10 runs start to get the statistics defined.
On second thought, it may actually be better to not run a "hot" engine combo for this test. A stock say type R may be a better choice to determine the dyno's characteristics.
Now if its a mustang with a static calibration of the load cell, you should calibrate the dyno before the 10 runs and after the 10 runs. Show how the calibration did/did not drift.
This has the making of a good performance magazine article, maybe someone would be willing to underwrite the costs?
12-22-2004, 07:22 AM
#15
Re: How Accurate is a Dyno Jet? (b19coupe)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b19coupe »</TD></TR><TR><TD CLASS="quote"> Got that one covered.</TD></TR></TABLE>
I'll see if we can do a West Coast and East Coast "Statiscal Dyno Test"
I'll see if we can do a West Coast and East Coast "Statiscal Dyno Test"
12-22-2004, 07:53 AM
#16
MEAT PATTY
Re: How Accurate is a Dyno Jet? (Rocket)
I know everyone is talking about dyno jets. The shop I used to work at had a dynapack and the consistency and repeatable of the dynapack was always accurate. Even though sometimes it was difficult because the temperature would change by only 3 degrees and you would see a difference but it wasn't anything substanial. Have fun with your field experiment. 
12-22-2004, 07:55 AM
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Re: How Accurate is a Dyno Jet? (Rocket)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Rocket »</TD></TR><TR><TD CLASS="quote">My point is that I've seen back to back runs on a dynojet vary by 7-10whp so I want to see if this is relatively rare or common. If you see a 5whp difference is that just random variation or a true gain. Now if you saw a 20whp gain you're pretty sure you gained hp but really how much since some the 20whp could be random variation.</TD></TR></TABLE>
I have a few questions for you about this topic. I I have been doing this with hondas on my dynojet 248c for almost 2 years now and have never seen issues where hp jumps that much. It has the most to do with the dyno operator and how constant the runs are.
Are you going to be Data logging all of the vehicle information as far as temps and ignition so you don't actually get horsepower spikes from the car? Because the hondas have an ideal temp where it runs constant the entire time. If you go outside that temp, you are going to have power loss and gains that should not be calculated.
What are you going to do if the vehicle you choose for running, has an ignition that may spike at high rpm? That is another way to see spikes in hp and tq. It all depends on what you set the smoothing to? I would suggest messing around with it quite a bit before hand just you get the right setting where runs are the most consistant, that way you can smooth out those hp and tq ingnition spikes.
What are you going to do about keeping constants on the vehicle as far as fuel, oil, and ignition? Running a vehicle 30 times depending on the richness of the setup, will probably wear on the spark plugs, ignition wires, cap and coil. Especially if the Plug wires aren't kept at the same temp to keep the same resistance.
My point is, I can stand by a dynojet being 100% accurate as far as the calculations it does goes. As far as a car being 100% consistant, very hard to prove and test. I would love to help you out with this process if you would like some good tips and pointers. If you get enough people interested in it, i think I might just have to conduct a test myself.
Feel free to call or email me Curt @ 608-268-0270 cmiller@dynotuned.com
I have a few questions for you about this topic. I I have been doing this with hondas on my dynojet 248c for almost 2 years now and have never seen issues where hp jumps that much. It has the most to do with the dyno operator and how constant the runs are.
Are you going to be Data logging all of the vehicle information as far as temps and ignition so you don't actually get horsepower spikes from the car? Because the hondas have an ideal temp where it runs constant the entire time. If you go outside that temp, you are going to have power loss and gains that should not be calculated.
What are you going to do if the vehicle you choose for running, has an ignition that may spike at high rpm? That is another way to see spikes in hp and tq. It all depends on what you set the smoothing to? I would suggest messing around with it quite a bit before hand just you get the right setting where runs are the most consistant, that way you can smooth out those hp and tq ingnition spikes.
What are you going to do about keeping constants on the vehicle as far as fuel, oil, and ignition? Running a vehicle 30 times depending on the richness of the setup, will probably wear on the spark plugs, ignition wires, cap and coil. Especially if the Plug wires aren't kept at the same temp to keep the same resistance.
My point is, I can stand by a dynojet being 100% accurate as far as the calculations it does goes. As far as a car being 100% consistant, very hard to prove and test. I would love to help you out with this process if you would like some good tips and pointers. If you get enough people interested in it, i think I might just have to conduct a test myself.
Feel free to call or email me Curt @ 608-268-0270 cmiller@dynotuned.com
12-22-2004, 08:51 AM
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Re: How Accurate is a Dyno Jet? (Rocket)
The thing I've noticed on our dyno (DYNOJET 248C), is that most all-motor cars stay at pretty consistent hp levels no matter how many runs are made. But yea that would be cool to see, maybe everyone that has a dyno could locate the same car with identical characteristic
and make 30 passes and see how consistent their dynos are? Just a thought, would be cool to see how other dynos like Dynopak, Mustang, Bosch, etc. perfrom.
and make 30 passes and see how consistent their dynos are? Just a thought, would be cool to see how other dynos like Dynopak, Mustang, Bosch, etc. perfrom.
12-22-2004, 10:08 AM
#19
Re: How Accurate is a Dyno Jet? (dynotuned)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dynotuned »</TD></TR><TR><TD CLASS="quote">
I have a few questions for you about this topic. I I have been doing this with hondas on my dynojet 248c for almost 2 years now and have never seen issues where hp jumps that much. It has the most to do with the dyno operator and how constant the runs are.
Are you going to be Data logging all of the vehicle information as far as temps and ignition so you don't actually get horsepower spikes from the car? Because the hondas have an ideal temp where it runs constant the entire time. If you go outside that temp, you are going to have power loss and gains that should not be calculated.
What are you going to do if the vehicle you choose for running, has an ignition that may spike at high rpm? That is another way to see spikes in hp and tq. It all depends on what you set the smoothing to? I would suggest messing around with it quite a bit before hand just you get the right setting where runs are the most consistant, that way you can smooth out those hp and tq ingnition spikes.
What are you going to do about keeping constants on the vehicle as far as fuel, oil, and ignition? Running a vehicle 30 times depending on the richness of the setup, will probably wear on the spark plugs, ignition wires, cap and coil. Especially if the Plug wires aren't kept at the same temp to keep the same resistance.
My point is, I can stand by a dynojet being 100% accurate as far as the calculations it does goes. As far as a car being 100% consistant, very hard to prove and test. I would love to help you out with this process if you would like some good tips and pointers. If you get enough people interested in it, i think I might just have to conduct a test myself.
Feel free to call or email me Curt @ 608-268-0270 cmiller@dynotuned.com</TD></TR></TABLE>
Agreed 100%. There are things you can't keep constant. Sampling will show us that they exist and affect the runs.
I have a few questions for you about this topic. I I have been doing this with hondas on my dynojet 248c for almost 2 years now and have never seen issues where hp jumps that much. It has the most to do with the dyno operator and how constant the runs are.
Are you going to be Data logging all of the vehicle information as far as temps and ignition so you don't actually get horsepower spikes from the car? Because the hondas have an ideal temp where it runs constant the entire time. If you go outside that temp, you are going to have power loss and gains that should not be calculated.
What are you going to do if the vehicle you choose for running, has an ignition that may spike at high rpm? That is another way to see spikes in hp and tq. It all depends on what you set the smoothing to? I would suggest messing around with it quite a bit before hand just you get the right setting where runs are the most consistant, that way you can smooth out those hp and tq ingnition spikes.
What are you going to do about keeping constants on the vehicle as far as fuel, oil, and ignition? Running a vehicle 30 times depending on the richness of the setup, will probably wear on the spark plugs, ignition wires, cap and coil. Especially if the Plug wires aren't kept at the same temp to keep the same resistance.
My point is, I can stand by a dynojet being 100% accurate as far as the calculations it does goes. As far as a car being 100% consistant, very hard to prove and test. I would love to help you out with this process if you would like some good tips and pointers. If you get enough people interested in it, i think I might just have to conduct a test myself.
Feel free to call or email me Curt @ 608-268-0270 cmiller@dynotuned.com</TD></TR></TABLE>
Agreed 100%. There are things you can't keep constant. Sampling will show us that they exist and affect the runs.
12-22-2004, 10:13 AM
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Re: How Accurate is a Dyno Jet? (Rocket)
i think the biggest varying factor is the cooling efficiency of the motor in the car being tested. not sure how you'd compensate for that on each pass ... I generally see 1-2hp variance and figure it to be heatsoak, not usually to the dyno accuracy/inaccuracy.
Then there is the dyno's software computation using the varying temp and humidity inputs ...
Greg
Then there is the dyno's software computation using the varying temp and humidity inputs ...
Greg
12-22-2004, 10:18 AM
#21
Re: How Accurate is a Dyno Jet? (BigMoose)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BigMoose »</TD></TR><TR><TD CLASS="quote">This has the making of a good performance magazine article, maybe someone would be willing to underwrite the costs?</TD></TR></TABLE>
The out of pocket cost won't be very high.
The out of pocket cost won't be very high.
12-22-2004, 11:04 AM
#22
Re: How Accurate is a Dyno Jet? (BigMoose)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BigMoose »</TD></TR><TR><TD CLASS="quote">On second thought, it may actually be better to not run a "hot" engine combo for this test. A stock say type R may be a better choice to determine the dyno's characteristics.</TD></TR></TABLE>
that was the first thing I thought of as well. Your test vehicle should be a relatively, if not completely, stock car.
that was the first thing I thought of as well. Your test vehicle should be a relatively, if not completely, stock car.
12-22-2004, 11:38 AM
#23
Re: How Accurate is a Dyno Jet? (jweller)
Here's the thing.
1. Just do 15 - 30 runs (the closer to 30 the better for statistical analysis).
2. Try to keep every thing as consistent as possible such as time between runs, when you start sampling, when you stop sampling during a run, motor needs to be at operating temperature for all runs ect. Very basic stuff here.
3. send me the dyno jet runs.
I'll
1. Statistically analyze the data for peak hp, peak tq, rpm at which peak hp and tq occur. (We'll calculate the mean and std deviation of the sample and runs use a normal/guassian distribution curve to come up with our confidence intervals).
2. I'll make histograms for the above listed data and show you guys how much variation there is in the sample and calculate the 95% confidence for doing runs on the Dynojet. We'll be able to test if peak hp, peak torque, peak hp rpm, and peak tq rpm vary more than one another.
This might tell us how to read dyno's better.
1. Just do 15 - 30 runs (the closer to 30 the better for statistical analysis).
2. Try to keep every thing as consistent as possible such as time between runs, when you start sampling, when you stop sampling during a run, motor needs to be at operating temperature for all runs ect. Very basic stuff here.
3. send me the dyno jet runs.
I'll
1. Statistically analyze the data for peak hp, peak tq, rpm at which peak hp and tq occur. (We'll calculate the mean and std deviation of the sample and runs use a normal/guassian distribution curve to come up with our confidence intervals).
2. I'll make histograms for the above listed data and show you guys how much variation there is in the sample and calculate the 95% confidence for doing runs on the Dynojet. We'll be able to test if peak hp, peak torque, peak hp rpm, and peak tq rpm vary more than one another.
This might tell us how to read dyno's better.
12-22-2004, 12:25 PM
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Re: How Accurate is a Dyno Jet? (Rocket)
DAMNIT! considering i did 14 pulls on our local dynojet last night i should have done a couple more. My numbers varied towards the end by 3-5 whp when we didnt TOUCH ANYTHING.
ROCKET you have your EAST COAST representative, let me know, you know i have access to a dyno 24/7
ROCKET you have your EAST COAST representative, let me know, you know i have access to a dyno 24/7
12-22-2004, 01:52 PM
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Re: How Accurate is a Dyno Jet? (Rocket)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Rocket »</TD></TR><TR><TD CLASS="quote">
..................
2. Try to keep every thing as consistent as possible such as time between runs, when you start sampling, when you stop sampling during a run, motor needs to be at operating temperature for all runs ect. Very basic stuff here.
......................................
</TD></TR></TABLE>
This won't work with a word/idea/mentality of "try". If you can't control that then there's no reason for the test.
..................
2. Try to keep every thing as consistent as possible such as time between runs, when you start sampling, when you stop sampling during a run, motor needs to be at operating temperature for all runs ect. Very basic stuff here.
......................................
</TD></TR></TABLE>
This won't work with a word/idea/mentality of "try". If you can't control that then there's no reason for the test.
