dynamometers, some Myths and Facts.
02-22-2006, 04:05 PM
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dynamometers, some Myths and Facts.
<center><img src="http://pictureposter.audiworld.com/1185/dynox.jpg"></center><p>Well, dynos are probably one of the most misunderstood tools around in the automotive industry, and having been around quite a few of them, i even find people who actually own one dont know how to use it properly, and yes i really mean that statement about people dont know hoe to use them.
Having also recently taking on a large design and test project of a Full engine Data acquisition system and eventual Dyno controller i have spent countless hours of research and time on both chassis and engine dynos, also looked and many different brands of dynos and see what they do and dont do.
What is really sickening that this tool is also used to lie and mis-inform people and is often used in order to back up a false claim of vendor. Yes i do mean Lie and misguide people.
Just to illustrate this i had a car on a dyno last night, performed 2 power runs 30 seconds apart, what the cars was is irrelevant (but it was a mildy modded Chev 350 Ci NA), The First run produced 240KW(322HP) at rear wheels, second run produced on dyno chart 500KW(670HP) at rear wheels. NOTHING WAS DONE TO THE CAR OR ENGINE OR FINAL DRIVE SELECTION.
HOW CAN THIS BE???
In fact i can make the dyno show what ever power i want it to show! and this is not particualar to this dyno, each and every dyno i have seen and used this can be easily done.
The proceedure i used i deliberately made it show a big difference to illustrate the point how far you can go, but i can easily show even a bigger difference.
I am deliberately keeping brand names out of this post, and this post is meant for information only.
For example, i happen to be a "Guy called performance parts supplier", and say fabricate say a Cat back exhaust and in my own private testing find it really only gains 3-5HP, but **** who is going to buy this from me for $1000, not much gain for money, i know i will alter slightly the parameter on dyno test make it show 20hp gain. PRESTO! I have proof my exhaust gains 20HP, 15 more horsepower than anyone elses, advertise it as such, the average customer will read about a huge 20HP gain figure, its more than anyone elses exhaust I will buy it!!!
Well thats the sad truth on whats going on out there, believe it or not, and i welcome anyones critics on what i have stated.
I am almost at the stage i can write a book on this, but i will give a few short reasons how the above is achieved, its up to the interested individual to do research and you will find out what i am saying is correct.
Firstly, Dyno Correction Factor, there are a few different ways to calculate this.
But in its simplist form is a calculation that take into account Air Temp, Air Humidity, Barrometric pressure and Air Density.
You dont know how many dyno operators either simply use a figure correction of 1, because they never purchased a air anaylser. This correction factor is not a constant and should be checked every time before a dyno run occures, last night with 5 hours on dyno, 16 runs produced 14 different correction factors, the ambient condition are constantly changing.
Infact if you got one car on dyno, performed a power run, let the car sit there for 1 hour, performed another run and never checked correction factor, the dyno WILL SHOW different power level. If the correction Factor is checked and used, the car should show exactly the same power.
A intesive correction factor that is professionally used actually takes into more ambient conditions to what i mentioned like vapour pressure etc.
more explantion see http://wahiduddin.net/calc/calc_hp_dp.htm
If this is not done correctly before power run is made, what ever figures the dyno show as far as i am concerned you can use as toilet paper.
Another Factor that is often not checked is INERTIA.
This varies from car to another.
Inertia = the resistance an object has to a change in its state of motion.
Each car set on dyno, this inertia has to be calculated.
This taked into aggoing rotating weight of dyno rollers, tires, wheels, differential, gearbox and even the viscosity of oil in drivetrain.
If this is not done correctly before power run is made, what ever figures the dyno show as far as i am concerned you can use as toilet paper.
Infact on most dynos this process of setting up and calibration can take 10-30 minutes before a power run is performed.
So just think back when you have had your car on a dyno and just what did the operator do before he done a power run and what calibration equipement did he really have?
Some dyno manufacturers sell their dynos even without a ambient air temp sensor! As far has i am concered you might as well chained up your car to a heavy weight and measured har far you can drag it!
The Other great catch cry of some dyno suplliers, oh we have a fixed factor shoot out mode, what a joke this is, so what does that mean? what it actually measure the correct horsepower? what is will give the same reading of horsepower given the same car run at 2 different locations? or it will acurately show one car has more power than another if being run back to back?
Take 2 identical engine proven on engine dyno to produce exactly the same HP.
put it in two different drivetrain car, the shoost out mode will show what exactly? what one engine is more power than other?
or same build 2 identical cars, run it on same model dyno bot tin fixed correction mode, one 1000ft elevation above sea level, the other at 6000ft? is that supposed to show the same power?
Facts/./
1. Dyno's are a tool.
2. Bad operator the tool is useless and unreliable.
3. Dyno's in the right hands are invaluable
4. Dyno's are often used to justify a false claim.
5. Dyno days and shootouts should be treated as social events and the power figure you are given you might as well consider that as a lottery number.
6. Many Guys out their selling products and claim all sorts of things, in reality few products on the market actually provide what was promised.
Project I am working on.
Minimum 64 Ch Engine data acquasition system
12 O2 probes
12 EGT probes
8 MAP sensors
3 barro sensors
2 RPM sensors
Fuel Flow
Fuel pressure
12 Injector pulse width
12 Spark analysis
plus more i wont go into
Want to make a resonable priced system that is equal or better than whats available.
Much of the topics above are mensioned in short form only, indepth explanations are very very involved.
Having also recently taking on a large design and test project of a Full engine Data acquisition system and eventual Dyno controller i have spent countless hours of research and time on both chassis and engine dynos, also looked and many different brands of dynos and see what they do and dont do.
What is really sickening that this tool is also used to lie and mis-inform people and is often used in order to back up a false claim of vendor. Yes i do mean Lie and misguide people.
Just to illustrate this i had a car on a dyno last night, performed 2 power runs 30 seconds apart, what the cars was is irrelevant (but it was a mildy modded Chev 350 Ci NA), The First run produced 240KW(322HP) at rear wheels, second run produced on dyno chart 500KW(670HP) at rear wheels. NOTHING WAS DONE TO THE CAR OR ENGINE OR FINAL DRIVE SELECTION.
HOW CAN THIS BE???
In fact i can make the dyno show what ever power i want it to show! and this is not particualar to this dyno, each and every dyno i have seen and used this can be easily done.
The proceedure i used i deliberately made it show a big difference to illustrate the point how far you can go, but i can easily show even a bigger difference.
I am deliberately keeping brand names out of this post, and this post is meant for information only.
For example, i happen to be a "Guy called performance parts supplier", and say fabricate say a Cat back exhaust and in my own private testing find it really only gains 3-5HP, but **** who is going to buy this from me for $1000, not much gain for money, i know i will alter slightly the parameter on dyno test make it show 20hp gain. PRESTO! I have proof my exhaust gains 20HP, 15 more horsepower than anyone elses, advertise it as such, the average customer will read about a huge 20HP gain figure, its more than anyone elses exhaust I will buy it!!!
Well thats the sad truth on whats going on out there, believe it or not, and i welcome anyones critics on what i have stated.
I am almost at the stage i can write a book on this, but i will give a few short reasons how the above is achieved, its up to the interested individual to do research and you will find out what i am saying is correct.
Firstly, Dyno Correction Factor, there are a few different ways to calculate this.
But in its simplist form is a calculation that take into account Air Temp, Air Humidity, Barrometric pressure and Air Density.
You dont know how many dyno operators either simply use a figure correction of 1, because they never purchased a air anaylser. This correction factor is not a constant and should be checked every time before a dyno run occures, last night with 5 hours on dyno, 16 runs produced 14 different correction factors, the ambient condition are constantly changing.
Infact if you got one car on dyno, performed a power run, let the car sit there for 1 hour, performed another run and never checked correction factor, the dyno WILL SHOW different power level. If the correction Factor is checked and used, the car should show exactly the same power.
A intesive correction factor that is professionally used actually takes into more ambient conditions to what i mentioned like vapour pressure etc.
more explantion see http://wahiduddin.net/calc/calc_hp_dp.htm
If this is not done correctly before power run is made, what ever figures the dyno show as far as i am concerned you can use as toilet paper.
Another Factor that is often not checked is INERTIA.
This varies from car to another.
Inertia = the resistance an object has to a change in its state of motion.
Each car set on dyno, this inertia has to be calculated.
This taked into aggoing rotating weight of dyno rollers, tires, wheels, differential, gearbox and even the viscosity of oil in drivetrain.
If this is not done correctly before power run is made, what ever figures the dyno show as far as i am concerned you can use as toilet paper.
Infact on most dynos this process of setting up and calibration can take 10-30 minutes before a power run is performed.
So just think back when you have had your car on a dyno and just what did the operator do before he done a power run and what calibration equipement did he really have?
Some dyno manufacturers sell their dynos even without a ambient air temp sensor! As far has i am concered you might as well chained up your car to a heavy weight and measured har far you can drag it!
The Other great catch cry of some dyno suplliers, oh we have a fixed factor shoot out mode, what a joke this is, so what does that mean? what it actually measure the correct horsepower? what is will give the same reading of horsepower given the same car run at 2 different locations? or it will acurately show one car has more power than another if being run back to back?
Take 2 identical engine proven on engine dyno to produce exactly the same HP.
put it in two different drivetrain car, the shoost out mode will show what exactly? what one engine is more power than other?
or same build 2 identical cars, run it on same model dyno bot tin fixed correction mode, one 1000ft elevation above sea level, the other at 6000ft? is that supposed to show the same power?
Facts/./
1. Dyno's are a tool.
2. Bad operator the tool is useless and unreliable.
3. Dyno's in the right hands are invaluable
4. Dyno's are often used to justify a false claim.
5. Dyno days and shootouts should be treated as social events and the power figure you are given you might as well consider that as a lottery number.
6. Many Guys out their selling products and claim all sorts of things, in reality few products on the market actually provide what was promised.
Project I am working on.
Minimum 64 Ch Engine data acquasition system
12 O2 probes
12 EGT probes
8 MAP sensors
3 barro sensors
2 RPM sensors
Fuel Flow
Fuel pressure
12 Injector pulse width
12 Spark analysis
plus more i wont go into
Want to make a resonable priced system that is equal or better than whats available.
Much of the topics above are mensioned in short form only, indepth explanations are very very involved.
02-22-2006, 05:32 PM
#2
your inertia comment ties in what I was explaining on the A4 forum yesterday...
therefore, butt dyno works decently 
<ul><li><a href="https://forums.audiworld.com/a4/msgs/2499094.phtml">CAPs time discussion</a></li></ul>
<ul><li><a href="https://forums.audiworld.com/a4/msgs/2499094.phtml">CAPs time discussion</a></li></ul>
03-05-2006, 05:27 PM
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Questions?
I have always used the dyno to test the state of tune, i.e. measure A/F, EGT's, O2 adj., IAT's etc. and to have a controlled means of seeing if everything is working well together and not going bad. I have also assumed if you make a correction (say timing across a 500rpm range)and do the run and see an improvement that you are truly seeing an improvement (say dialing 2 degrees of timing and seeing a 6 hp jump in the same range).Calibration would not have a material effect in this instance would it? would the gain be legitimate (not the 6hp being correct, but the assumption that there was an actual improvement).
The reason I ask is that I do not hold out much hope for these calibrations to be done in the manner you say they should be done, and not if they need to be made for every run. I wish they would be, and wish I knew of one that did calibrate, but I dont. I want to have some idea however that when we make a change (assuming these dynos are out of calibration) and show a drop or gain in power we can be relatively sure that we are going in the right direction - we are not that concerned that it was worth 6hp exactly, just that we are going in the right direction. Pulls are usually within 5 minutes. Are you saying that atmospheric and other conditions can change so rapidly and to an extent where we cant count on the results we get after just taking 5 minutes to change the value in a table and upload the file? If you are saying that you cant count on the numbers being accurate (say an actual 6 hp gain being manipulated to show a 15hp gain) I am OK but if you are saying you cant depend on comparisons showing gains or losses with a 5 to 20 minute shutdown then I will have to wonder why I am tuning on a dyno. Can you clarify this for me? If we showed 400whp yesterday and start today with 380 it doesnt worry me, but if I shut the car down making 300hp at 5000rpm then advance timing 3 degrees between 4500 and 5000rpm and it shows a 15hp gain when I have really lost power (and my piston is starting to get hot)because the conditions have changed then I have some big concerns.
Rod
The reason I ask is that I do not hold out much hope for these calibrations to be done in the manner you say they should be done, and not if they need to be made for every run. I wish they would be, and wish I knew of one that did calibrate, but I dont. I want to have some idea however that when we make a change (assuming these dynos are out of calibration) and show a drop or gain in power we can be relatively sure that we are going in the right direction - we are not that concerned that it was worth 6hp exactly, just that we are going in the right direction. Pulls are usually within 5 minutes. Are you saying that atmospheric and other conditions can change so rapidly and to an extent where we cant count on the results we get after just taking 5 minutes to change the value in a table and upload the file? If you are saying that you cant count on the numbers being accurate (say an actual 6 hp gain being manipulated to show a 15hp gain) I am OK but if you are saying you cant depend on comparisons showing gains or losses with a 5 to 20 minute shutdown then I will have to wonder why I am tuning on a dyno. Can you clarify this for me? If we showed 400whp yesterday and start today with 380 it doesnt worry me, but if I shut the car down making 300hp at 5000rpm then advance timing 3 degrees between 4500 and 5000rpm and it shows a 15hp gain when I have really lost power (and my piston is starting to get hot)because the conditions have changed then I have some big concerns.
Rod
04-01-2006, 05:41 AM
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Thanks
I've been thinking about buying a dyno for awhile now. There's another local shop who's done quite well with their 2wd dyno. The closest AWD dyno is more than 75 miles away.
Recommendations?
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