steps to grams per sec.

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Nov 13, 2007 | 08:47 PM

Dale

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From: AR

Car: 1991 Camaro RS Vert

Engine: 350 S-TPI

Transmission: T5

Axle/Gears: GU5/G80/J65

steps to grams per sec.

Does anyone know how many step(s) the TPI throttle body flows in GPS?

example idle is 16steps=8GPS?

Thanks

Nov 13, 2007 | 10:30 PM

RednGold86Z

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From: Corona

Car: 92 Form, 91 Z28, 89 GTA, 86 Z28

Engine: BP383 vortech, BP383, 5.7 TPI, LG4

Transmission: 4L60e, 700R4, 700R4..

Axle/Gears: 3.27, 2.73

Re: steps to grams per sec.

Do you mean the IAC??

The flow through the IAC will vary depending on vacuum and baro conditions.

You could calculate it yourself (if you have a MAF), just change the target idle speed, note how many steps change, note how much airflow changes, divide. If only have MAP, use VE to calculate it - knowing displacement, VE, RPM and MAP should get you all that you need. Do the same test.

BTW, the IAC resolution is much much more better than 2 steps / 1 g/s.

Nov 14, 2007 | 07:03 AM

Dale

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From: AR

Car: 1991 Camaro RS Vert

Engine: 350 S-TPI

Transmission: T5

Axle/Gears: GU5/G80/J65

Re: steps to grams per sec.

Yes I was talking about the IAC in a TPI throttle body. Didnt even think about baro effecting.

I'm not even sure my maf reading is right, but I'll give that a try.

Nov 16, 2007 | 06:55 PM

dimented24x7

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From: Moorestown, NJ

Car: 88 Camaro SC

Engine: SFI'd 350

Transmission: TKO 500

Axle/Gears: 9-bolt w/ 3.23's

Re: steps to grams per sec.

GM has calibration curves to linearize the IAC flow for the PID idle control routines in the later computers. If you knew generally how much the IAC flows when fully open, you could use the curve to estimate the airflow based on counts. Ill post up a curve for a standard IAC.

Nov 16, 2007 | 10:35 PM

dimented24x7

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From: Moorestown, NJ

Car: 88 Camaro SC

Engine: SFI'd 350

Transmission: TKO 500

Axle/Gears: 9-bolt w/ 3.23's

Re: steps to grams per sec.

Code:

;
;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
;-IAC counts vs. % desired airflow
;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
;
; Used to linearize IAC action
;
; IAC counts  ;% airflow
;
L4E88   FCB  0   ;  0.0
 FCB  9   ;  6.3
 FCB  19   ; 12.5
 FCB  27   ; 18.8
 FCB  37   ; 25.0
 FCB  46   ; 31.3
 FCB  56   ; 37.5
 FCB  64   ; 43.8
 FCB  72   ; 50.0
 FCB  79   ; 56.3
 FCB  84   ; 62.5
 FCB  89   ; 68.8
 FCB  94   ; 75.0
 FCB  100  ; 81.3
 FCB  109  ; 87.5
 FCB  125  ; 93.8
 FCB  150  ;100.0
 
;
;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
;-IAC baro compensation factor vs baro
;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
;
;  factor = val/128 ;kPa
; 
L4E9C   FCB  166  ; 60
 FCB  160  ; 65
 FCB  155      ; 70
 FCB  151  ; 75
 FCB  147  ; 80
 FCB  143  ; 85
 FCB  138  ; 90
 FCB  130  ; 95
 FCB  128  ;100
 FCB  128  ;105

Not gospel, but should be good enough for estimating. The IAC baro compensation is used to increase the desired airflow rate. Invert the number (128/value) to get the flow reduction.