I haven't seen many apples to apples comparisons of different Dyno pulls with the same exact car and tune. All dyno's were run with the exact same set-up and tune: Maddad exhaust; v2 headers, v2 downpipe [catted], and whisperback exhaust [resonated] and colder 1 step plugs.

Automasters Dynodynamic dyno. Stock pull and Tune. Tune is same on all following graphs.

http://img294.imageshack.us/img294/8027/dynoni1.jpg


Agile's dynapac dyno:

http://img132.imageshack.us/img132/3197/kinghptqep1.gif


And finally Veracious Tuning (formerly Xotic motorsports) Dynojet dyno
http://img119.imageshack.us/img119/6347/veracious1strunfi8.png

Wow, I didn't realize how low a dynodynamics reads comapred to dynojet/dynopack!! Good comparison for everyone.

in terms of precision, maha > everything else

The intereesting thing is how closely the dynapack and dynojet read both the wtq and whp. Hill from Agile stated that stock 07 STI's dyno around 240 for both wtq and whp. Andy from Veracious tuning said stock STI's dyno around 250 wtq and whp.

Increase in wtq and whp over stock:
Automaster dynodynamic= 110 wtq and 60 whp
Agile dynopack = 110 wtq and 60 whp
Veracious dynojet = 110 wtq and 60 whp

The gains were basically the same on all three dynos.

Now here is the rub. On automasters dynodynamic has a very low initial reading followed by the same increase in hp and tq makes the increases look statistically more inpressive. It looks like Automasters increase are more dramtic because his baseline is way low. For example and increase of 110 wtq over a baseline of 200 wtq looks huge compared to the same increase over higher stock baselines.

I think the take home message is no matter how low a dyno baselines, the increases in wtq and whp are exactly the same on these three radically different dynos. To put it another way, the dynodynamic dyno does not read the increases low like it does the baselines so the increases are artifically high compared to stock.

Were these runs done on the same day?

If not, (actually even if the answer is yes) you need to include the atmospheric conditions (air temp, humidity, and absolute barometric pressure) for each test or the comparison is of very limited value.

Larry

Were these runs done on the same day?

If not, (actually even if the answer is yes) you need to include the atmospheric conditions (air temp, humidity, and absolute barometric pressure) for each test or the comparison is of very limited value.

Larry


theres always a complainer

Were these runs done on the same day?

If not, (actually even if the answer is yes) you need to include the atmospheric conditions (air temp, humidity, and absolute barometric pressure) for each test or the comparison is of very limited value.

Larry

Right, 3 seperate tuning facilities in the same garage dyno'd with 3 different dynos with-in 15 minutes of each other...sure they were.

The dyno's were run with-in 2 weeks of each other in fairly simular cold weather while inside garages. Its not a triple blind study but its as close to 3 dyno readings on the same tune/mods as I have found recently.

Here's a very rough excel chart of the three runs. It took a bit of interpolating to get the numbers and I only did it by 500 rpm increments, but it's still interesting nonetheless:

http://share.3wheel.net/incoming/john_caldwell_at_kyliptix.com/dynos.PNG

I'll try to get the resolution down to 250rpm with a bit more effort.

need to add a mustang dyno to that list.

need to add a mustang dyno to that list.
That would be nice but It has been retuned since these three dynos were run.

Very interesting....Thankyou! Great comparison

Anyone notice that peak torque on the Dyno Dynamics and the Dynapack are at about 3800 where as the dynojet is at about 3300?

Another funny thing is how peaky the dynapack looks, yet at 4500rpm, the dynapack is on par with the dynojet.

Amazing how low the dyno dynamics reads, I wonder how that compares to a mustang....probably pretty similar?

Here's a very rough excel chart of the three runs. It took a bit of interpolating to get the numbers and I only did it by 500 rpm increments, but it's still interesting nonetheless:

http://share.3wheel.net/incoming/john_caldwell_at_kyliptix.com/dynos.PNG



I was wondering when someone was going to take the time to do this...

Very interesting results...

Just goes to show that a dyno is only a tool to measure with...

I have seen similar results with engine dyno's as well... Even at the same acceleration rates...

I am not sure how each of these dyno's loads the car when it is on it, but all 3 obviously load it a little differently...

Where would a mustang dynometer fall in the output of dynos?

OK, I am VERY confused.

I was tuned at Automaster, on their DynoDynamics. I baselined at what looks like 177 or so whp (see graph). So if I had baselined on one of these other dyno's it would have read something completely different, much higher.

YET, AFTER the tune I made ~250whp. So if i then put it on another dyno AFTER the tune (250whp on DynoDynamics) it would tell me something very very close to 250whp.

I DONT GET IT.

It's like AMR's dyno "knows" when its doing a baseline run, and spits out incredibly low numbers.:confused: :confused:

ROB???


http://img.photobucket.com/albums/v237/Redline927/IMG_1351.jpg

It's like AMR's dyno "knows" when its doing a baseline run, and spits out incredibly low numbers.:confused: :confused:



I will throw you on the dyno for a pull or 2 if you would like. You can have a good comparison.. DynoJet

LOL... .

FYI the dynojet is Uncorrected so it is high. If this was corrected power then it would be much lower. Some people leave the dyno as Uncorrected to show higher results. Go back and ask for the Corrected values.

I will throw you on the dyno for a pull or 2 if you would like. You can have a good comparison.. DynoJet

LOL... .

am I making sense?

OK, thank you, I will take you up on that... I will PM you shortly.

theres always a complainer
Not complaining just stating an obvious fact --- bad data is worse than no data.
Dyno readings can change by 10% -15% due to weather changes --- sometimes in a matter of a couple hours.



FYI the dynojet is Uncorrected so it is high. If this was corrected power then it would be much lower. Some people leave the dyno as Uncorrected to show higher results. Go back and ask for the Corrected values.

Uncorrected means it is the raw power at the wheels with no correction for altitude, barometer, temperature or humidity. Since very few if anyone does dyno runs at 0 ft altitude, 29.23 in hg barometer, 45 degrees F and 0 percent humidity, the corrected numbers are always going to be higher than uncorrected numbers (with the exception of dyno runs made in death valley in the winter time during high barometer conditions ) ;)

Larry

Junior, PM'd, sorry for sending two, my PM thing is messed up.

Uncorrected means it is the raw power at the wheels with no correction for altitude, barometer, temperature or humidity. Since very few if anyone does dyno runs at 0 ft altitude, 29.23 in hg barometer, 45 degrees F and 0 percent humidity, the corrected numbers are always going to be higher than uncorrected numbers (with the exception of dyno runs made in death valley in the winter time during high barometer conditions ) ;)

Larry

I was always told it was the opposite. Infact the Corrected data for my runs was more then 20hp lower then the Uncorrected.

I was tuned by Ron at poweraxis in St. Louis MO. He said that his dyno dynamics dyno reads 17% less than most other dynos. He said that when he first got it they called it "The Heartbreaker" because that's exactly what it does to people who are wanting certain numbers. Those dyno's are not much more than a tuning tool.

FYI the dynojet is Uncorrected so it is high. If this was corrected power then it would be much lower. Some people leave the dyno as Uncorrected to show higher results. Go back and ask for the Corrected values.

Hotrod already hit it on the head. If you read the SAE paper that explains the formula etc for horsepower correction it states right in there that SAE correction is BS for forced induction vehicles.

Good information to know.

now run on a dyno dynamics with the "new version of calibration".... you should get peak results that are similar to the jet and pack.

;)

Wow, this is a pretty funny thread with a lot of misinformation.

Dynojet – it’s an inertia dyno (yea, they have Eddy Current loading dynos too….but they don’t work!!). So the only load being applied to the vehicle is the weight of the rollers. Xotic Motorsports has a hodge-podge AWD system…it’s a 248c in the back and a 224xl in the front. So there is probably 4500lbs of load being applied to the vehicle. Want to know why the turbo spooled up quicker on the Dynojet…..TO MUCH LOAD!!!!

Dynapack – This dyno is a loading dyno. It uses some sort of hydraulic magic to provide the load. This dyno can be made to read whatever you want it to read based on what gear you test the vehicle in, run time and hold time. Changing the gear you test in can affect HP numbers 30 to 50 HP – I have verbal proof from a very prominent shop that is a vendor on this board.

Dyno Dynamics – This dyno is a loading dyno. It uses Eddy Currents to provide the load on the vehicle. I don’t know a whole lot about this dyno except I laughed in one of their rep’s face when he told me it doesn’t matter if the front and rear wheels speeds are different. Tell that to some poor sap’s center diff when it gets nuked! When you do a power pull on this dyno, you also set the run time, so I’m assuming that is going to affect the HP output just like it does on the Dynapak.


In regards to the weather correction factor….here is the real answer. A long time ago, June 1990 to be exact, SAE (Society of Automotive Engineers) came up with J1349 Certified Power. This is what we use….I don’t know what the other dyno manufacturers use. According to this, the perfect weather you compare to is 77*F, 29.235InHg baro pressure and 0% humidity. Comparing current weather to these numbers comes up with a weather correction factor. Multiply your HP and TQ numbers by this correction factor and you get corrected numbers. Corrected numbers can be either higher or lower than uncorrected numbers. After some quick searching on the internet, I see quite a few HP numbers from turbocharged vehicles with J1349 Standards. So I highly doubt the auto manufacturers would use it if it was BS for turbo vehicles.

In regards to the weather correction factor….here is the real answer. A long time ago, June 1990 to be exact, SAE (Society of Automotive Engineers) came up with J1349 Certified Power. This is what we use….I don’t know what the other dyno manufacturers use. According to this, the perfect weather you compare to is 77*F, 29.235InHg baro pressure and 0% humidity. Comparing current weather to these numbers comes up with a weather correction factor. Multiply your HP and TQ numbers by this correction factor and you get corrected numbers. Corrected numbers can be either higher or lower than uncorrected numbers. After some quick searching on the internet, I see quite a few HP numbers from turbocharged vehicles with J1349 Standards. So I highly doubt the auto manufacturers would use it if it was BS for turbo vehicles.
Do some more in depth searching and actually read the J1349 Standard.
"Look closely at SAE document J1349. If you really want to compare sea level standard day conditions on a turbo car to a dyno pull done at altitude, you must measure the inlet air temp and absolute pressure entering the cylinder (at the throttle body would be a likely place). Use these values to correct horsepower numbers."

The key problem with SAE and turbo cars is with barometric pressure compensation. For a turbo car, it may run the same manifold absolute pressure even with changes in barometric pressure. Thus the power loss due to altitude is not equivalent for a turbo car vs. a naturally aspirated car.

Specifically, Subarus do not cut the desired manifold absolute pressure as fast as altitude lowers barometric pressure. It does cut as barometric pressure falls, but it lags well behind how fast barometric pressure is dropping. That is, your gauge pressure should actually go up as you go up in altitude.

For example, let's look at the stock 2002 WRX tune.
http://freon.shackspace.com/car/ecu%20and%20tuning/boost_barocomp.png
(keep in mind this is raw ECU data, I know some tuning tools convert units so it may look different. I'm show native units in the ECU--mmHG and a factor which is directly multiplied to the desired boost value, which also in mmHG absolute in raw format, to avoid any of the possible fudge factor involved in conversion of units)

At 664 mmHG (~3600 ft), the car only cuts total manifold absolute pressure desired boost by 3.9%, rather than the 12.6% difference in barometric pressure compared to sea level (664mmHG / 760mmHG). I don't know the specifics of SAE J1349 (and I'm not paying $59 to download it), but I imagine the barometric pressure portion of the correction factor is very close to the barometric pressure difference. That's how I imagine you would compensate a naturally aspirated car.

Also note until below 728 mmHG (a little over 1000ft) atmospheres there is NO cut in desired boost at all. The car should run the same manifold absolute pressure at sea level all the way up to a little over 1000ft in altitude.

If J1349 somehow covers the above problem and differences in how turbo and NA cars, I'd love to hear how, especially considering different manufacturers may choose to tune boost in varying ways.

edit:
Do some more in depth searching and actually read the J1349 Standard.
"Look closely at SAE document J1349. If you really want to compare sea level standard day conditions on a turbo car to a dyno pull done at altitude, you must measure the inlet air temp and absolute pressure entering the cylinder (at the throttle body would be a likely place). Use these values to correct horsepower numbers."This makes sense. If you want a dyno number at altitude to be equivalent to what the same car would do at sea level, or SAE's STP, you would have to know what boost it would run at sea level and correct for it yourself, or at least feed that into the correction factor. It couldn't possibly be automatic.

Here at high altitude, we clearly see the errors in the SAE standard. At 5800 ft altitude the SAE correction is typically 1.22 - 1.25 (occasionally they are as high as 1.27), With those corrections a stock car makes more power up here than it does at sea level. The correct correction factor for turbcharged cars at high (any) altitude is approximately 1/2 the SAE correction. One of our local shops uses a flat 1.15 correction and his dyno numbers compare very favorably to dyno tunes done at sea level.

Any SAE dyno correction over 7% is not considered acceptable for direct comparison according to SAE.

Here is the basic correction formula in the SAE standard: (how the dyno actually computes it and impliments it in hardware and code is unknown and the dyno companies have not given meaningful explainations on that regard)


The SAE J1349 (Jun 90) power correction formula is:

Metric units millibar / deg C
CF = 1.180 [ ( 990/Pd) x (( Tc + 273)/(298)) ^ 0.5 ] - 0.18

in hg / deg F units
CF = 1.180 [ ( 29.23/Pd) x (( Tc + 460)/(505)) ^ 0.5 ] - 0.18


Pd = dry air pressure ( ie absolute air pressure minus the contribution of the partial pressure of the water vapor in the air)

Tc = Ambient air temp ( ie temp outside the car, not the intake air temp)

The formula is supposed to give you the hp the car would make if it was at an absolute air pressure of 990 mb (29.92 in hg) 0% humidity and 25 deg Centigrade (77 deg F) outside air temp.


If you do a bit of reverse engineering, you will see that the SAE standard conditions match up very well with typical temperture/pressure conditions in the Detroit area (probably matches well with the major european manufactures as well as that pressure is equivilant to an altitude of about 800 ft ) ---- Hmmmm don't suppose the standard was set up to be a convenient tool for the major auto manufactures do you?

To do it properly (as mentioned earlier) the dyno correction would need to know the peak boost the car is running, because the base air pressure + boost pressure is the true manifold pressure. The power correction for the 3 psi in base air pressure we lose at altitude is relatively a smaller fraction of total manifold pressure if you are running 30 psi boost than it is if you're only making 13 psi boost.

Since altitude also effects turbo spool the dyno correction would be different for different rpm segments of the pull due to the lower boost pressures attainable early during spoolup, and late in the run near red line when you frequently push the turbo out of its normal operating range and effeciency drops like a rock.

The SAE standard does include complex adjustments for turbocharged diesel engines, which include things like intercooler effeciency etc.

Several of us up here in Colorado have asked the dyno manufactures about this issue and we have simply been blown off.

With the 1/2 correction factor or a flat 15% correction factor a stock STi or WRX dynos with about the same wheel hp as you see from sea level dyno runs. To back that up the NHRA correction factors for altitude specify a 1/2 correction for super charged/turbo charged vehicles vs NA vehicles and these correction factors give very good correspondence to real world strip times and trap speeds. The NHRA 1/2 trap speed correction factor here at 5800 ft is 3%. Since trap speed varies at the cube root of the power, this corresponds to a power correction of 9% here at this altitude for a turbocharged car where a NA car would be a 6% NHRA trap speed correction factor or 19% change in power.

Larry

[QUOTE=hotrod;17428188]Not complaining just stating an obvious fact --- bad data is worse than no data.

I know, i just thought it was funny....but yea...correction makes a huge difference

Good info on this page!!! Just goes to show that it turly is nearly impossible to compare one dyno to another, even with the same car/altitude/correction factor, etc.

A dyno is a TUNING TOOL ONLY, to help the tuner tune a car for the best performance possible at a safe level.

Alright, I went through and revised the chart, now with 250 rpm datapoints:

http://share.3wheel.net/incoming/john_caldwell_at_kyliptix.com/dynos2.PNG

I also calculated the average of the difference between the graphs. It's not exactly useful in the case of the dynojet since the initial high torque reading skews things a bit, but it roughly works out to 12% higher for the dynapack, and 20% higher for the dynojet.

Wow nice posts in this thread guys. I'm glad I started this thread as I have learned alot.

Alright, I went through and revised the chart, now with 250 rpm datapoints:

http://share.3wheel.net/incoming/john_caldwell_at_kyliptix.com/dynos2.PNG

I also calculated the average of the difference between the graphs. It's not exactly useful in the case of the dynojet since the initial high torque reading skews things a bit, but it roughly works out to 12% higher for the dynapack, and 20% higher for the dynojet.

Excellent chart. I always wondered how to put together a charge like that. Yea I see the percentages. They look exactly to what they claim. Great job on that chart. +1

now run on a dyno dynamics with the "new version of calibration".... you should get peak results that are similar to the jet and pack.

;)

Totally untrue- I have proven that the shop claiming this made their own "calibration" by adding an extra CF.