Best way to measure airflow of a running engine

[106-1194218389]

I have a friend that has the airflow measuring device from a dyno that was given to him so he could measure some superchager outputs. It is a 55 gallon drum that has an inclined manometer with it and also a range of different sharp edged orifices. It was used to measure the airflow the engine was using while they were dyno'ing the engine. If anybody wants I will go over to his place and get some photos and pertinent information.

John

[jsa]

[quote="1960FL"][/quote]
[color=#000000][quote]Note the FP1 uses a Freescale MPX5010DP sensor rated to accurately measure 10 KPA range 40

[49-1183904562]

SuperRunner,

How many Cid/CC's is your engine and how high do you turn it up "RPM".

Rick

[ThomasVaught]

Quote:

"I have a friend that has the airflow measuring device from a dyno that was given to him so he could measure some superchager outputs. It is a 55 gallon drum that has an inclined manometer with it and also a range of different sharp edged orifices. It was used to measure the airflow the engine was using while they were dyno'ing the engine. If anybody wants I will go over to his place and get some photos and pertinent information."

I read a Lot of the old NACA (father of NASA) papers written in the early 30s to 1950 when they were testing Conventional "V" engines and Radial Aircraft Engines (pre Turbo prop and turbo jet stuff).

In almost all of the dyno schematics they show a similar device for measuring inlet flow to the engine. A sharp edged orifice is located in the center of the flat surface on the end of the drum. (Room air, then the orifice, then the drum , and finally the engine. Agree, they used inclined and vertical manometers.

Tom V.

[Tony]

That is how I would do it myself.

And if I was really fussy, add an automatic variable speed blower to the drum outlet to restore full atmospheric pressure to the engine.

[larrycavan]

Off the top of my head...here's how I'd do this....if it was to be a test conducted while driving the vehicle down the road / track.

IF you were to use the orifice method inside the airbox then that would be relatively easy to remove from the car and test the assembly on the flowbench prior to using it in the vehicle. The overall flow of the airbox with the installed orifice could be determined that way.

First though, you'd have to know what your max pressure drop would be in inches of water that the vehicle could potentially achieve across the orifice mounted inside the air box. That's where I think the 40" sensor mighe come up short. Testing it would be relatively simple with vacuum taps placed on each side of the current air filter, connecting up the FP1 and fire up the engine. Get pressure drop readings.

Next, put the orifice plate somewhere ahead of the filter and check pressure drop again. That would be followed by removing the filter altogether and retesting.

Once the max pressure drop is determined, the assembly could then be put on the flowbench and tested at that pressure to determine the flow. That's your starting point or known flow value. For sake of debate, let's say it works out to 300CFM with the max pressure drop of 36".

So we have an air box with an orifice installed that's rated at 300CFM at a calibrated 36" of water.

If the airbox is then installed in the car and the engine is run at the same RPM to where 36" of water Delta P is achieved, it's drawing 300CFM.

Below that 36", you simply calculate the CFM using normal test pressure conversion formula.

So when performing a test, you log your RPM and Delta P, then calculate your flow for the RPM.

Seems logical to me anyway......I'm open to debate though...

PS - probably want some help with the data aquisition part...driving the car in any gear at 7500 RPM and watching a laptop just doesn't seem like the prudent thing to do...

[Tony]

The problem as I see it Larry, is anything that drops the incoming air pressure by as much as 36" is going to seriously starve the engine of air, and unacceptably reduce both real flow and real power.

Assuming (absolute) atmospheric pressure is very roughly around 400" , maybe you could get away with dropping 4" across the measuring orifice, and drop engine power by perhaps (?) 1%, but any greater pressure drop than that may seriously skew any measurement.

A pitot type flow measurement may be more suitable for this type of application.

[larrycavan]