Dyno test info

[mag2555]

Does anyone here here on the board have a dyno where your at high elevations ( 3000 ft ) 90 degree temps and humid conditions?

I would like to know if you have ever seen correction factors above 20% take place.

Thanks in advance!

[racear2865]

Easy for me to answer, I want test if conditions are bad. Data sucks and nothing to learn.
reed

[F-BIRD'88]

The SAE papers on engine dyno correction factors say basicly that extreme parameter test conditions correction should be taken with a grain of salt.
Your mileage may vary. as they say.

VortecPro used to test way up in the sky at his former shop location.
You should be using your dyno to test for engine performance improvements thru developments (as VortecPro does) not to compete with someone elses dyno.
Althou you want to measure daily weather test parameters for your engine tests don't get all wrapped up in
wether it corrects exactly to actual sea level tested . levels.

As long as you can test for improvments progressive +/-
, it does not really matter. If its burning more air and fuel it will make more power (relative) no matter where the testing is done.

[In-Tech]

As long as you can test for improvments progressive +/-
, it does not really matter. If its burning more air and fuel it will make more power (relative) no matter where the testing is done.

I couldn't agree more. Make the best with what measuring equipment you have and just tune. Use the dyno to show you what improvements or losses and learn.

I took a 430" ls3 ctsv that I was finished with the "tune" and drove it across town to another dyno and picked up 75hp

[Dave Koehler]

Too many get caught out by that correction factor.
I have a hell of a time explaining why I baseline an MFI for the client's altitude, etc. and not by their 1000 hp corrected dyno sheet from a former carbed version 3 years ago.
Example: I say sooo, it's probably about 800 HP at home. NO, they insist it can do 1000 hp. sigh
It would be nice to see the actual weather and resulting raw data.
I have gotten to the point of refusing to look at dyno sheets that don't have the uncorrected data.
Worse is the "it should make" crowd.
If one guy in a particular racing group claims 1500 HP they all assume their own similar looking stuff makes 1500 HP. sigh

[RCJ]

I'm at 600ft altitude and I've seen 4000ft on the density altitude. The jetting and timing are very different from say the best day of 400ft to the worst at 4000ft. Don't have any hard data to prove it but if you dyno a motor at those 2 altitudes , the high altitude would be down 1 or 2 % after changes IMP.

[novafornow]

I think that it would be down 10%. JMHO

[vortecpro]

The SAE papers on engine dyno correction factors say basicly that extreme parameter test conditions correction should be taken with a grain of salt.
Your mileage may vary. as they say.

VortecPro used to test way up in the sky at his former shop location.
You should be using your dyno to test for engine performance improvements thru developments (as VortecPro does) not to compete with someone elses dyno.
Althou you want to measure daily weather test parameters for your engine tests don't get all wrapped up in
wether it corrects exactly to actual sea level tested . levels.

As long as you can test for improvments progressive +/-
, it does not really matter. If its burning more air and fuel it will make more power (relative) no matter where the testing is done.

For the record: You might not know but I've moved to Texas a year ago, my testing at high elevation (Colorado 6400 feet) delivered basically the same results as on two different dyno's in Texas @ 800 feet elevation. In Colorado I had 1.24-1.30 correction factors, 7000-11,000 DA 23.30 baro to a 24.00 baro. In TX in the summer I see a 1.08 correction 28.80-29.20 baro, 3500 DA 98-100 degrees. We've run extremely quick at Little River drag strip, as good as a 30.0 baro there.

One other thing, 3500 feet DA with a 28.00 baro will not be as quick as 3500 feet DA in 28.90 baro, the higher baro will be quicker even though the DA is the same.


Heres an example of the same engines:

SF 901 corrected HP tested @ 6400 feet elevation: 821 HP
SF 901 observed or measured HP @ 6400 feet elevation 570 HP
Drag strip performance @ 600 DA 147.2 MPH @ 3440 pounds

SF 901 corrected HP @ 6400 feet elevation: 773.9 HP
SF 901 observed or measured HP @ 6400 feet 560 HP
Drag strip performance @ 600 feet DA 142.24 MPH @ 3580-3600 pounds

[RCJ]

29.2 temp 93.4 ,dew point 72.6, 600ft elv. Density altitude
3524 dry density 4006, correction factor 1.104

[vortecpro]

29.2 temp 93.4 ,dew point 72.6, 600ft elv. Density altitude
3524 dry density 4006, correction factor 1.104

For years I've asked SF dyno operators to input my typical baro when testing in Colorado 23.60, of course no one would to this day, could you input this baro 23.60 into your dyno and tell us the correction factor?

[David Redszus]

29.2 temp 93.4 ,dew point 72.6, 600ft elv. Density altitude
3524 dry density 4006, correction factor 1.104

For years I've asked SF dyno operators to input my typical baro when testing in Colorado 23.60, of course no one would to this day, could you input this baro 23.60 into your dyno and tell us the correction factor?

It is a very simple matter to use a baro sensor at the inlet along with an inlet air temp sensor, fed into a data logger.
The logger software can then compute actual air density and correction factors, both on the dyno and on the engine at the track.

Correction factors in excess of 3% are bogus.

[David Redszus]

Why are dynos typically inaccurate?

The dyno itself only performs two operations.
It loads the engine using a measurable restraining force.
It allows a measurement of engine speed.

The problems arise due to sensor accuracy and operating conditions.

Sensor accuracy requirements per SAE J1349.
Torque......+- 0.5%
RPM.........+- 0.2%
Fuel.........+- 1.0%
IAT...........+- 0.5%
InP, OutP....+- 0.1 kPa (0.0145 psi, 0.4 inH20)
IAT and IAP sensors must be within 0.15M (5.9") of air intake.

As if these sensor requirements are not stringent enough, consider the effects of stacking errors.

To be elegible for SAE J1349 certification the following data must be provided.
Measurements
Engine Speed (may be obtained from engine controller)
Observed Brake Torque
Friction Torque
Air/Fuel Ratio
Spark Advance / Ignition Timing (may be obtained from the engine controller)
Ambient Temperature and Pressure
Inlet Air Temperature and Pressure
Inlet Air Water Vapor Pressure
Intake Manifold Air Temperature and Pressure (may be obtained from engine controller)
Temperature of Fuel at Fuel Flow Meter
Fuel Rail Temperature and Pressure
Engine Coolant Inlet and Outlet Temperature (water cooled engines only)
Oil Sump Temperature and Oil Gallery Pressure
Exhaust Gas Temperature at the manifold outlet (Left & Right)
Exhaust Pressure at the manifold outlet (Left & Right)

[RCJ]

95 degree,29.23 baro, 80% relative hum.= c/f of 1.07
95, 23.6 , 80. = c/f of 1.393
Sae j1349
I'm no expert on this stuff but there are some numbers for you.

[vortecpro]

Thanks, but again I'm looking for someone with a SF 901 to input my baro of 23.60 and post the correction factor. BUT they will not do it been asking for years.

[vortecpro]

I dyno tested one of my 467 with a 228 @ .050 hyd roller, 10.1 comp, 049 oval port head, performer RPM intake here inTexas about 890 feet elevation, Dynamite dyno STP, conditions were:

890 Elevation approx
28.99 Baro
120 grains
97 Degrees
Horrible air flow through dyno

588 Corrected HP
515.6 Observed or Measured, or in the room HP

I should note this dyno is the only dyno I've tested on the that has shown less HP than my dyno, and I've tested on a lot of other peoples dyno, I believe this is due to the design of the dyno cell which has very little air movement. I test again today, I will bring my weather station so I can get a good read on the conditions. This should answer the OP question.