Let's discuss dyno calibration and consistancy
12-20-2007, 11:49 AM
#21
Another unappreciated factor to consider is I seriously doubt that many dyno's weather stations ever undergo any calibration, especially with atmospheric pressure and humidity.
Even the most expensive barometers are calibrated monthly. I've seen good ones be off .030 of an inch a year. Add that to being off 10-20% in humidity, and now your SAE readings are off as much as 5-10%.
While there could be numerous factors involved, that would be my hunch how the same dyno would begin to have erroneous readings over time.
I like the before/after concept of dyno testing. At least on that particular day you are pretty much assured of the gain/loss results.
No dyno expert, but testing a few dyno's up here at Mile High on hot summer days and bringing my own weather station along..a few times I saw variations in their weather data that made readings about 4-5% off.
In essence track testing encounters the same dilemma. That track time may simply just reflect how much air got into your engine on that particular day, which depends on air temperature, pressure, humidity, driver ability etc..
Something to consider..WeathermanShawn..
Even the most expensive barometers are calibrated monthly. I've seen good ones be off .030 of an inch a year. Add that to being off 10-20% in humidity, and now your SAE readings are off as much as 5-10%.
While there could be numerous factors involved, that would be my hunch how the same dyno would begin to have erroneous readings over time.
I like the before/after concept of dyno testing. At least on that particular day you are pretty much assured of the gain/loss results.
No dyno expert, but testing a few dyno's up here at Mile High on hot summer days and bringing my own weather station along..a few times I saw variations in their weather data that made readings about 4-5% off.
In essence track testing encounters the same dilemma. That track time may simply just reflect how much air got into your engine on that particular day, which depends on air temperature, pressure, humidity, driver ability etc..
Something to consider..WeathermanShawn..
12-20-2007, 12:36 PM
#22
I agree about the track numbers vs. the dyno numbers. But every one wants SAE Dyno numbers but no one wants Corrected track numbers. Here on the East Coast from SC to NJ we get great air and the tracks are mostly just above sea level. So our cars run great for the amount of power they are making. My car only makes 465/426rw SAE on a Mustang Dyno and ran 10.8's@130 on the first time out. It was actually making a little less then. Now take my car to LACR or Bandimere and see what happens. I would probably run 11.5's@125-7. I have seen the DA as low as -2,000 in the dead of winter here. Some tracks never see +2,000 on a good day. Why do you think all the best times for cars come from the East Coast in winter time. I think comparing track time is useless as well, unless you compare them Corrected. The day after I ran the 10.8s@130 I took the car to the dyno in the same weather and put down 465/430 Uncorrected and 460/424 Corrected. Last week in 20* cooler weather I went back to the same dyno and put down 486/445 Uncorrected 465/426 Corrected. So when I take my car to the track in like weather next time it will go at least 2 tenths and 2mph faster. The track shows your uncorrected hp/tq. My point is, like others have said, is to find a dyno and a track around where you live and do before and after testing on both. That is the only way you are going to be able to tell what is really going on. You will never race all the guys on the internet so don't worry about what they say. Just beat all the guys around you and you will know who is the fastest.
I think everyone wants to have the best ET as well for bragging rights, but no one cares to slow down their ET for comparison sake, like dyno figures. Then you have dyno validity as well, from different brands. Not to mention some shops alter the weather data to match other local dyno shop numbers. The correction factors and weather info should not be allow to be alter from the (dyno) manufacturer, I say.
12-20-2007, 01:59 PM
#23
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Hey Brianc:
Thanks.
If you have the date, time, place you tested and your SAE correction number, I could try to double-check the numbers. Especially if they list the pressure, temp, humidity on the bottom of the dyno run.
Or before you test again just get the nearest weather report. It only takes a few quick calculations to see if its a SAE correction problem.
Good luck...
Thanks.
If you have the date, time, place you tested and your SAE correction number, I could try to double-check the numbers. Especially if they list the pressure, temp, humidity on the bottom of the dyno run.
Or before you test again just get the nearest weather report. It only takes a few quick calculations to see if its a SAE correction problem.
Good luck...
12-20-2007, 02:31 PM
#24
The two shops that I have used to dyno do not alter weather data. Most of the time they pull out a little portable weather station and check the calibration. That may be why I always have low dyno numbers but my car runs great track numbers. Usually 2-3mph faster than it "should". I never really considered the weather data as a way to inflate numbers.
Hey Weatherman. Are you out of Carson?
Hey Weatherman. Are you out of Carson?
12-20-2007, 03:02 PM
#25
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Pray:
Probably 95% of the time no one is purposely manipulating the weather data. Just the nature of calibration and time. If you are at sea level and testing under fairly weather conditions, most of the time the numbers are dead on.
Add altitude, heat, humidity etc..
No not out of Ft. Carson, but did do military weather previously. Now doing aviation meteorology for an airline.
Had to learn a few of these things to get some HP up here in Mountain country.
..WeathermanShawn..
Probably 95% of the time no one is purposely manipulating the weather data. Just the nature of calibration and time. If you are at sea level and testing under fairly weather conditions, most of the time the numbers are dead on.
Add altitude, heat, humidity etc..
No not out of Ft. Carson, but did do military weather previously. Now doing aviation meteorology for an airline.
Had to learn a few of these things to get some HP up here in Mountain country.
..WeathermanShawn..
12-20-2007, 06:22 PM
#26
Hey Brianc:
Thanks.
If you have the date, time, place you tested and your SAE correction number, I could try to double-check the numbers. Especially if they list the pressure, temp, humidity on the bottom of the dyno run.
Or before you test again just get the nearest weather report. It only takes a few quick calculations to see if its a SAE correction problem.
Good luck...
Thanks.
If you have the date, time, place you tested and your SAE correction number, I could try to double-check the numbers. Especially if they list the pressure, temp, humidity on the bottom of the dyno run.
Or before you test again just get the nearest weather report. It only takes a few quick calculations to see if its a SAE correction problem.
Good luck...
12-20-2007, 07:13 PM
#27
I've tuned on a Mustang, a Dyno Dynamics, a Bosch dyno (in Germany) and my own DJ 248.
Let me start by saying people that say you cant properly load an inertia dyno havent spent any significant time on a DJ with proportional air control. In addition to using that, and just the weight of the drum to lug down a motor in the lower rpms, you can hit most of the cells in the VE table, and end up with a VE table thats very, very close on the street.
All that being said, the DD and mustang dynos, with all of their operator entered correction factors, never have seemed to be consistent from car to car, and run to run. They may be great for loading, and steady state tuning, but for repeatable numbers, whether favorable or not, not exactly what I want to run a car on over and over and over.
We ran 3 cars that had been run on my DJ, on a Dyno Dynamics dyno, on the same day. One car was right on, within a couple HP. One car was high, and one car was low. Both of them by a significant amount. One by 30 HP plus (low). We in turn ran them again on my dyno to check the accuracy of them. They were all with 1 or 2 HP of their previous numbers on the same dyno (mine).
I've had numerous cars on my dyno that have previously been on a local Dyno Dynamics, and have had mixed results from them as well. One was 60 HP LESS on mine, than on the local D.D. So much for DJs reading high, eh?
We dont fudge or weather station. We print the weather specs on the printout. Our dyno computer in online and I check the local weather daily to make sure we're close. The only thing thats of by more that a couple % is the humidity, and thats usually within 10%.
I'd also like to note, that consistency and repeatability of a car on a dyno has as much to do with the accuracy of the tune as it does the dyno. I've tuned cars that come back 6 months later (after a tune) for a dyno day, and make within 1 hp of what they did when I tuned them. And thats on cars well over 500 hp.
In closing, I'd like to say, I like the steady state tuning capability with an eddy current dyno. But I wouldnt trade my DJ for one. EVER.
Let me start by saying people that say you cant properly load an inertia dyno havent spent any significant time on a DJ with proportional air control. In addition to using that, and just the weight of the drum to lug down a motor in the lower rpms, you can hit most of the cells in the VE table, and end up with a VE table thats very, very close on the street.
All that being said, the DD and mustang dynos, with all of their operator entered correction factors, never have seemed to be consistent from car to car, and run to run. They may be great for loading, and steady state tuning, but for repeatable numbers, whether favorable or not, not exactly what I want to run a car on over and over and over.
We ran 3 cars that had been run on my DJ, on a Dyno Dynamics dyno, on the same day. One car was right on, within a couple HP. One car was high, and one car was low. Both of them by a significant amount. One by 30 HP plus (low). We in turn ran them again on my dyno to check the accuracy of them. They were all with 1 or 2 HP of their previous numbers on the same dyno (mine).
I've had numerous cars on my dyno that have previously been on a local Dyno Dynamics, and have had mixed results from them as well. One was 60 HP LESS on mine, than on the local D.D. So much for DJs reading high, eh?
We dont fudge or weather station. We print the weather specs on the printout. Our dyno computer in online and I check the local weather daily to make sure we're close. The only thing thats of by more that a couple % is the humidity, and thats usually within 10%.
I'd also like to note, that consistency and repeatability of a car on a dyno has as much to do with the accuracy of the tune as it does the dyno. I've tuned cars that come back 6 months later (after a tune) for a dyno day, and make within 1 hp of what they did when I tuned them. And thats on cars well over 500 hp.
In closing, I'd like to say, I like the steady state tuning capability with an eddy current dyno. But I wouldnt trade my DJ for one. EVER.
12-20-2007, 08:09 PM
#28
Well, the real best thing to do is sit down with your tuner/dyno guy and have them explain everything they are doing, so you know what is going on.
We run a Dyno Dynamics dyno and will gladly go thru the process of setting it up with our customers.
The first thing to know is that the load cell is constantly re-calibrating...it is doing it right now and all night and all day tomorrow... The mustang dynos have crude re-calibration technique, so thats one factor to consider. The dynojets I am not sure about (maybe someone can shed some light on that for me)
The second step is westher factors - Temp, Humidity and DA are entered. Those are saved on EVERY single run, so we can access them at any time forever. This eliminates any future questions.
The third step is communication. It is important that the customer and shop are on the same page. ..this is the biggest factor IMO.
We run a Dyno Dynamics dyno and will gladly go thru the process of setting it up with our customers.
The first thing to know is that the load cell is constantly re-calibrating...it is doing it right now and all night and all day tomorrow... The mustang dynos have crude re-calibration technique, so thats one factor to consider. The dynojets I am not sure about (maybe someone can shed some light on that for me)
The second step is westher factors - Temp, Humidity and DA are entered. Those are saved on EVERY single run, so we can access them at any time forever. This eliminates any future questions.
The third step is communication. It is important that the customer and shop are on the same page. ..this is the biggest factor IMO.
12-20-2007, 08:13 PM
#29
I've tuned on a Mustang, a Dyno Dynamics, a Bosch dyno (in Germany) and my own DJ 248.
Let me start by saying people that say you cant properly load an inertia dyno havent spent any significant time on a DJ with proportional air control. In addition to using that, and just the weight of the drum to lug down a motor in the lower rpms, you can hit most of the cells in the VE table, and end up with a VE table thats very, very close on the street.
All that being said, the DD and mustang dynos, with all of their operator entered correction factors, never have seemed to be consistent from car to car, and run to run. They may be great for loading, and steady state tuning, but for repeatable numbers, whether favorable or not, not exactly what I want to run a car on over and over and over.
We ran 3 cars that had been run on my DJ, on a Dyno Dynamics dyno, on the same day. One car was right on, within a couple HP. One car was high, and one car was low. Both of them by a significant amount. One by 30 HP plus (low). We in turn ran them again on my dyno to check the accuracy of them. They were all with 1 or 2 HP of their previous numbers on the same dyno (mine).
I've had numerous cars on my dyno that have previously been on a local Dyno Dynamics, and have had mixed results from them as well. One was 60 HP LESS on mine, than on the local D.D. So much for DJs reading high, eh?
We dont fudge or weather station. We print the weather specs on the printout. Our dyno computer in online and I check the local weather daily to make sure we're close. The only thing thats of by more that a couple % is the humidity, and thats usually within 10%.
I'd also like to note, that consistency and repeatability of a car on a dyno has as much to do with the accuracy of the tune as it does the dyno. I've tuned cars that come back 6 months later (after a tune) for a dyno day, and make within 1 hp of what they did when I tuned them. And thats on cars well over 500 hp.
In closing, I'd like to say, I like the steady state tuning capability with an eddy current dyno. But I wouldnt trade my DJ for one. EVER.
Let me start by saying people that say you cant properly load an inertia dyno havent spent any significant time on a DJ with proportional air control. In addition to using that, and just the weight of the drum to lug down a motor in the lower rpms, you can hit most of the cells in the VE table, and end up with a VE table thats very, very close on the street.
All that being said, the DD and mustang dynos, with all of their operator entered correction factors, never have seemed to be consistent from car to car, and run to run. They may be great for loading, and steady state tuning, but for repeatable numbers, whether favorable or not, not exactly what I want to run a car on over and over and over.
We ran 3 cars that had been run on my DJ, on a Dyno Dynamics dyno, on the same day. One car was right on, within a couple HP. One car was high, and one car was low. Both of them by a significant amount. One by 30 HP plus (low). We in turn ran them again on my dyno to check the accuracy of them. They were all with 1 or 2 HP of their previous numbers on the same dyno (mine).
I've had numerous cars on my dyno that have previously been on a local Dyno Dynamics, and have had mixed results from them as well. One was 60 HP LESS on mine, than on the local D.D. So much for DJs reading high, eh?
We dont fudge or weather station. We print the weather specs on the printout. Our dyno computer in online and I check the local weather daily to make sure we're close. The only thing thats of by more that a couple % is the humidity, and thats usually within 10%.
I'd also like to note, that consistency and repeatability of a car on a dyno has as much to do with the accuracy of the tune as it does the dyno. I've tuned cars that come back 6 months later (after a tune) for a dyno day, and make within 1 hp of what they did when I tuned them. And thats on cars well over 500 hp.
In closing, I'd like to say, I like the steady state tuning capability with an eddy current dyno. But I wouldnt trade my DJ for one. EVER.
Well said Ed, It seems that the "all over the place" Mustang and Dyno dynamics results are over looked for some reason. A strain gauge which is used in most/all loading dynos are extremely sensitive to temperature and drift. I just redynoed a car that I did 3 weeks ago. It was less than 1 hp difference.. That is very good repeatablity if you ask me.
Ed, If you ever in my area your welcome to try out my loading 224xlc dynojet. Its the best of both worlds.. ultra consistant inertia numbers and steady state load testing.
12-21-2007, 06:48 AM
#31
Well said Ed, It seems that the "all over the place" Mustang and Dyno dynamics results are over looked for some reason. A strain gauge which is used in most/all loading dynos are extremely sensitive to temperature and drift. I just redynoed a car that I did 3 weeks ago. It was less than 1 hp difference.. That is very good repeatablity if you ask me.
Ed, If you ever in my area your welcome to try out my loading 224xlc dynojet. Its the best of both worlds.. ultra consistant inertia numbers and steady state load testing.
Ed, If you ever in my area your welcome to try out my loading 224xlc dynojet. Its the best of both worlds.. ultra consistant inertia numbers and steady state load testing.
12-21-2007, 08:52 AM
#32
A dyno dynamics dyno is in a CONSTANT recalibration loop...it is ALWAYS adjusting for temp and metal growth, everything. On a DD you can pull up the load cell and look at it re-calibrating for 0.
I think anyone saying that about a DD dyno is either biased or unfamiliar with the hardware involved.
12-21-2007, 10:17 AM
#33
I dont know why, or how, but I know what I saw.
For load tuning, they work great.
12-21-2007, 01:40 PM
#35
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I swear sometimes I hate the freedom to compete laws. Why don't everybody use a GD Dynojet like 90% of the people on this site use. All these BS numbers that are way off just stir **** up and it's mainly people who fudge their dynos to try to bring business. Dynojet ought to lock their software so tuners cant **** with the calibration.
But then again if there was only one type of dyno 25% of the posts on this site wouldn't exist. LOL
But then again if there was only one type of dyno 25% of the posts on this site wouldn't exist. LOL
12-21-2007, 02:02 PM
#36
There may be some back door way to hack into their software, but not that I'm aware of. Thats going to the extreme just for higher numbers.
12-21-2007, 03:05 PM
#39
I swear sometimes I hate the freedom to compete laws. Why don't everybody use a GD Dynojet like 90% of the people on this site use. All these BS numbers that are way off just stir **** up and it's mainly people who fudge their dynos to try to bring business. Dynojet ought to lock their software so tuners cant **** with the calibration.
But then again if there was only one type of dyno 25% of the posts on this site wouldn't exist. LOL
But then again if there was only one type of dyno 25% of the posts on this site wouldn't exist. LOL
Well, the reason is certain dynos are much better in design then the current and older dynojets. One of the major DJ flaws is the size of the roller. At 2000lbs a piece it is very hard for a tuner to see a small gain of 1-5ft/lbs or what 1 degree of timing does. The mass of the roller makes it impossible to be extremely accurate. Also, the faster you spin a heavy mass, the easier it becomes. This is the reason dynojet tq curves always fall slowly, while an engine dyno will drop right after peak tq. Of course, you have drivetrain inertia but look at a dynopack vs. a dynojet graph and you will see the difference.