Quote:
Originally Posted by Stan Weiss
Tom,
I know you have seen way more dyno sheets than I have, and what I have seen is only N/A. I am used to seeing BSAC of 5.5 or higher. Is a blower motor different?
Stan
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Yes, just like every dyno is different.
A Superflow Dyno Cell using ambient air is not going to be the same as a Ford Research Cell that has a controlled cell environment around the engine.
The Superflow Dyno typically uses a Turbine Device to read airflow entering the engine.
A Research Cell might use equipment that reads the actual "Make Up Air" going into the cell room vs the exhaust flow out of the cell.
Hard to use a Turbine Meter set-up on a Twin Turbo Boosted Engine Dyno Test.
I agree that 5.5 is a REALLY GOOD air consumption number.
Heywood mentioned that is some of his lectures.
Once you get past 6.0 you start wondering if you have the right parts in the engine when running NA.
We tested the boosted engine in both the NA and boosted modes.
The mass flow number just went up due to the density change when the boosted device was added.
The cfm thru the engine stayed, for the most part, the same. Basic Physics.
Air Mass is more difficult to measure with a high HP engine.
A street engine with a 80 mm mass air meter can take care of most NA street engines.
No real "very high HP" (generally available) mass air meters are out there in common OEM use.
There was one company who did larger Mass Air Meters in the Detroit Area in the 90s but I believe he passed away years ago.
We do air flow calibrations on Mass Air Meters using a very large Flow Stand in our air flow lab. Again though it just gives the calibrator a curve to compare with his test data as a generic check if the data is valid. He does not care about the decimal point errors.
He wants to know if "he is in Cleveland" vs Detroit. Not what city street he is on.
So Brake Specific Air Consumption either NA or Boosted is a compass that says we are "Facing North" but not nearly the same as a Coordinates: 42°29′16″N 82°53′48″W like you would see from a GPS type position sensor.
So to answer your question,
Boost guys, because they are talking for the most part to people with minimal Air Flow'/Engine knowledge, just say One pound of Air Mass makes 10 HP and call it good.
Air Mass is Air Mass (does not care if NA or Boosted. One POUND of AIR Molecules = one Pound of Air Molecules. The actual HP per pound of air could be 9.7 or 10.3 pounds.
It depends on the SPECIFIC engine
Tom V.