Hemi Dyno Sheet Thoughts

[PRHeads]

If one wanted to see what the actual power curve of that hemi looked like, without the fk’d up CF, just calculate the uncorrected hp for each line using the bsfc number and the fuel flow.
Then you could also figure the uncorrected TQ for each line of data.

I’m sure most all that jumpiness in the curve would smooth right out.

 

[PRHeads]

One last thought....... imagine trying to sort through some timing and jetting changes with the CF erroneously changing throughout the pull.
Good luck with making any sense out of that!!

 

[dadsbee]

Thanks guys! Why I asked for thoughts as it looked a bit suspect. It is a 6 year old dyno sheet from 2 owners back and at least the engine is still running. If we ever get some dry and sand free streets....

 

[PRHeads]

I did the numbers for the 5000-6391 group.......
Uncorrected based on fuel flow and bsfc:

The beginning of the pull showed a CF of 4.2%.
I added that to the right of the uncorrected numbers:
Rpm—tq/hp ——— CF 1.042
5000-428.8/408.3 - 425.4
5100-432.8/420.3 - 437.9
5200-428.0/423.8 - 441.6
5300-417.8/421.0 - 438.7
5400-410.7/422.3 - 440.0
5500-407.4/426.7 - 444.6
5600-410.8/438.0 - 456.4
5700-397.9/431.9 - 450.0
5800-400.4/442.2 - 460.7
5900-387.9/435.8 - 454.1
6000-382.7/437.3 - 455.7
6100-377.8/438.9 - 457.3
6233-376.4/446.8 - 465.5
6391-357.1/434.6 - 452.8

 

[Jerry Hall]

I did the numbers for the 5000-6391 group.......
Uncorrected based on fuel flow and bsfc:

The beginning of the pull showed a CF of 4.2%.
I added that to the right of the uncorrected numbers:
Rpm—tq/hp ——— CF 1.042
5000-428.8/408.3 - 425.4
5100-432.8/420.3 - 437.9
5200-428.0/423.8 - 441.6
5300-417.8/421.0 - 438.7
5400-410.7/422.3 - 440.0
5500-407.4/426.7 - 444.6
5600-410.8/438.0 - 456.4
5700-397.9/431.9 - 450.0
5800-400.4/442.2 - 460.7
5900-387.9/435.8 - 454.1
6000-382.7/437.3 - 455.7
6100-377.8/438.9 - 457.3
6233-376.4/446.8 - 465.5
6391-357.1/434.6 - 452.8

That's more like what I was expecting to see. That should do what @dadsbee wants to do to the tires.

 

[4mulas]

There's no such thing as "dry air" in Canada.

Come to Calgary, my hands bleed from cracking in the winter. It’s dry.

 

[dadsbee]

Come to Calgary, my hands bleed from cracking in the winter. It’s dry.

Yep, same here... but it was dyno' in October !

 

[dadsbee]

I did the numbers for the 5000-6391 group.......
Uncorrected based on fuel flow and bsfc:

The beginning of the pull showed a CF of 4.2%.
I added that to the right of the uncorrected numbers:
Rpm—tq/hp ——— CF 1.042
5000-428.8/408.3 - 425.4
5100-432.8/420.3 - 437.9
5200-428.0/423.8 - 441.6
5300-417.8/421.0 - 438.7
5400-410.7/422.3 - 440.0
5500-407.4/426.7 - 444.6
5600-410.8/438.0 - 456.4
5700-397.9/431.9 - 450.0
5800-400.4/442.2 - 460.7
5900-387.9/435.8 - 454.1
6000-382.7/437.3 - 455.7
6100-377.8/438.9 - 457.3
6233-376.4/446.8 - 465.5
6391-357.1/434.6 - 452.8

THANKS! for all the work !! MUCH appreciated...

 

[PRHeads]

I looked thru some dyno sheets I was sent from a motor that had been tested on a dyno using a Depac system.
There was a run during that session that also had some notable CF variation, but nowhere near 6%. It was under 2%...... and it only happened on one pull.

The CF can vary through the pull, but it should be well under a 1% variation.

If the “weather” in the dyno cell is changing that much....... you need to work on the air handling situation in the room.

If you look back at the partial sheet I posted, you’ll see the CF changes slightly....... corresponding to the small change to the air inlet temp.
Warmer air, higher CF......cooler air, lower CF.

The vapor pressure(humidity) and baro pressure have much more affect on the CF.
And neither of those atmospheric conditions are going to vary much at all(any?) in the amount of time it takes to make a dyno pull.