Turbo effenciency horespower equation ?

[chanley talon]

OK this thread sounds horrible . My question is . What is the airflow formual and how do you find it. If im flowing 32lbs a minute i making 320 horsepower. How do they get these numbers ? I have a logger is there a way for me to look at it and see or do some math?

Most turbo have a flow rating per min . How do i see what mine is flowing on my car? Thanks i hope you understand me.

 

[99gst_racer]

Rule of thumb is:

airflow * 10 = crank HP

and then:

crank HP * .80 = rough estimation of WHP

(substitute .85 for FWD DSM's)


This rule of thumb is very accurate with my car.
I was flowing 48 lbs/min, and made 403 WHP.
Using the calculations, I come up with 480 BHP and 408 WHP, so it's pretty close.

 

[chanley talon]

How do you find out what you're flowing?

 

[99gst_racer]

How do you find out what your flowing?

Well, here's a fun question. Get out your pencil.


airflow (lbs/min) = (AP * EVC * 29) * (10.73 * Rankin)

AP = Boost + Atmospheric Pressure
EVC = Engine Volumetric Flow



But, I just use DSMlink to figure my airflow numbers.

 

[cool_g_83]

Logger

 

[chanley talon]

ok i have a logger so what do i log?

 

[kenamond]

Your logger will give you volume flow rate, not mass flow rate (correct me if I'm wrong). The logger doesn't know what the pressure of the air is at that flowrate (it knows the temperature), and you need both to compute the density - which would be needed to convert volume flow rate to mass flow rate.

The ECU knows this (needs to in order to properly control the injectors), but it's not provided to the OBDII port.

Edit: Sorry: you're a 1g, so maybe that info is available to the OBD1 port.

 

[chanley talon]

Ok maybe im not asking the question the right way? What i would like to know is how you get the equation . First you must have a place where you can see what your flowing in and out of the motor i think , either by injector fuel flow or by air read at the mass air fow sensor. Then you need some type of math ? Basically i want step by step instruction to see what lbs/min my engine is doing. Also i would like to know how you can tell if your maxing out your injectors? Thanks and keep this going . I might learn something here.

 

[dsm-onster]

A suggestion. . . tunerstein can log a gram/revolution number. This can be directly converted to lbs/min with a little mathematical ingenuity (just algebra). You'll have to use rpms (revolutions per minute) to convert grams/rev to grams/minute. Then knowing 1 kg = 2.2046 lbs, you can yield lbs/min.

Converting Karman to AirFlow-- Wading through the clutter, you will find a way to calculate the mass flow w/ hertz count, intake air temp and baro input. You'll need all three variables plotted over the rpm range to get a massflow over rpm range chart or graph.

3000GT MAS Karman Hz to Air Flow Conversion-- You can guess CFM (cubic feet per minute) by subtracting 20% from your 1G hertz reading since a 2g maf reads ABOUT 20% lower hertz number for the same CFM. You'll still have to record intake air temp and baro input.

NOTE: this link states that hertz count is affect by temp. But, I've always been told that the ECU uses the air temp signal to calculate the mass flow (lbs/min) not that the temp signal and volume flow (hertz count) is combined to yield a new hertz count corrected for air temp.

I don't bother w/ the discrepancies because I have DSMLink or have used tuerstein and don't do this math below.

Using the second link charts and the ideal gas law we can calculate mass flow. TheIdeal Gas Law provides: PV=nRT

P=Pressure
V=Volume
n=number of moles
R=Gas Constant
T=Temperature in Kelvin

Convert your Baro reading to ATM (atmospheres or bars) and plug in for P (unless your logger records bars directly).

Convert your CFM to litres per min and plug in for V. 1000 L/min = 35.3 cfm.

R = 8.3145 J/mol K.

Convert air temp to Kelvin:

[5*(ºF - 32)/9] = ºC
ºC + 273.15 = K​

Plugging in to the ideal gas law will yield moles/min for "n". After you get the "n", convert to lbs/min knowing that 1 mole of atmospheric air = .0289 kg. Remember, 1 kg = 2.2046 lbs.

Plot your boost and airflow on the compressor map and see where you are. . . Your engine determines airflow.