Virtual Dyno Day!

[SM105K]

Old post from this thread, but was curious...where does the "0.oo471" come from or what does it represent? Some sort of constant?

I believe that is the constant for equating the air lbs per min.

 

[stripSHO]

This interests me but wanted to get some clarification on this error factor. The way you describe it sounds like it would be written out like this:

((STFT+LTFT)-2)100

Using @SM105K 1st set of results, that would be ((0.92+1.05)-2)100 = -3% error
Using his 2nd set of results, that would be ((0.94+1.05)-2)100 = -1% error

Trying to understand where you got the 0.97 from. I'm guessing you meant that is the correction factor gained from the error and written more like this (2-(STFT+LTFT))100?

That would get you that 3% error (or a 0.03 error factor) from his 1st set of results from (2-(0.92+1.05))100 and this would ultimately give you the 0.97 correction factor (1.00-error factor) you'd use to multiply the raw airflow data by?

Just wanted to be sure. @FiveLeeter918 mentioned averaging STFT and LTFT, using the same values from @SM105K

(0.92+1.05)/2

which would give you a correction factor of 0.985 instead of 0.97. I'm sure I'm splitting hairs here, but just curious. Is this just two ways to skin the same cat with each method having negligible differences? Thanks

If you have a 3% error, then actual flow is 97% of stated flow (100 - 3 = 97)

The .00471 is a conversion factor for a 3.5L displacement engine for simplification. The full equation would be-

Mass flow = LOAD x (RPM/2) x displacement[cubic inches] x (1 cubic foot / 1728 cubic inches) x .0765 lb/cubic foot [standard air density]

For a 2-cycle use RPM instead of RPM/2

I believe you don't need to worry about actual air density since calculated load has already done this for you. A load of 1 means the cylinders are getting filled with exactly 3.5L worth of air at standard temperature and pressure.

 

[High on Ethanol]

Ehhhhh #/min x10..... Ez. Good enough to judge mod gains.

 

[stripSHO]

Ehhhhh #/min x10..... Ez. Good enough to judge mod gains.

NOPE. See post #68. 64 horsepower spread with the same airflow. Also it's been shown that a certain intercooler upgrade actually reduces flow yet still picks up significant horsepower, though only on pump gas it seems. By the same token you could eliminate the intercooler altogether and move more air but I promise you won't make more power. Well, maybe with straight methanol fueling you could.

Stop trying to make fetch a thing, Gretchen.

 

[Ecoboost_xsport]

Ehhhhh #/min x10..... Ez. Good enough to judge mod gains.

Yup, just needing to get #/min, I wasn't logging it in the past and just retro-actively doing some mathenometry on my previous logs...

 

[Ecoboost_xsport]

If you have a 3% error, then actual flow is 97% of stated flow (100 - 3 = 97)

I got that part...just wondering what the actual equation looks like in order to get to that 3%

Is it (2-(STFT+LTFT))100?

And what did @FiveLeeter918 mean by averaging the 2? Is that just a different method to estimate error?

 

[stripSHO]

I got that part...just wondering what the actual equation looks like in order to get to that 3%

Is it (2-(STFT+LTFT))100?

And what did @FiveLeeter918 mean by averaging the 2? Is that just a different method to estimate error?

Ahh. Yes that is it. Or if you're looking to go straight to the correction factor then save some steps and just do STFT+LTFT-1

Of course this is all assuming that the ECU isn't already factoring trims into that airflow PID, which I honestly don't know for sure it doesn't. It also requires your injector calibration be dead on. So as long as the fuel trims are reasonably low then I really think it's not worth splitting hairs over; for a general reference I would just take the airflow PID (or the load math) at face value. Even the most precise and accurate airflow reading is only going to put you within a 20% window of actual power.

 

[High on Ethanol]

NOPE. blibbitttty blaahh

a few light years, a few trucks of beers, and you may catch a response that's less deserving, but this one still filled your plate with 3% of an infants serving.

p.s. i didnt even read what you wrote, did i miss a response worthy of note?