[Diy_efi] DIY-WB -- Rcal vs. Ip samples

[Peter Gargano]

was Re: [Diy_efi] DIY-WB question

bcroe at juno.com wrote:
> 
> Anyone mistrusting the Rcal circuit could put in about a
> 10K ohm pot instead of the sensor resistor, and adjust
> it to get the specified open air voltage.

I'd suggest a larger value pot as I've seen Rcal values as high as ~30 k.
 
> If quite a few users would compile their J9 to J8 voltage
> in free air, along with the ohms of their sensor Rcal, we
> could compile some kind of statistical error record for
> the design. Make adjustments if indicated.  Or perhaps
> just show its doing the job.

Here are 11 sensor free-air Ip values against Rcal. 10 are straight
out of the box, and another has less than an hours use, mostly on a
bench. For the record (and not that it matters), the circuit used to
measure the values was the Oz version of the DIY-WB, with a DVM across
the 100 ohm Ip sense resistor (R13 here) :

  http://techedge.com.au/vehicle/wbo2/const/ipsense.gif


sensor	Rcal	Ip mA
#	k ohms	free-air

1	29.9	5.07
2	23.9	5.08
3	14.9	5.24
4	11.9	5.42
5	7.55	5.49
6	6.16	5.52
7	6.16	5.64
8	4.28	5.70
9	4.28	5.71
10	2.40	5.93
11	1.98	5.99

As will be seen by plotting Rcal (or 1/Rcal) against F/A-Ip, or by looking
at sensors 6 and 7, the factory Rcal will not exactly compensate for the
initial free-air Ip, and the Rcals seem to be only available in a limited
range of values.

As the sensor ages, you can expect some variation from the initial free-air
Ip, so any kind of serious tuning use should be periodically checking (and
adjusting) the free-air Vout to be 1.50 Volts above the Vstoic value.


Peter.

-- 
Tech Edge Pty. Ltd.     http://techedge.com.au
(02) 6251 5519          Int'l +612 6251 5519
37 Jalanga Cres.        PO Box 288,
Aranda, ACT 2614        Jamison Centre, ACT 2614

_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi