Re: [Amc-list] TBI EFI tuning...

[Tom Jennings <tomj@xxxxxxx>]

Thanks Glen!! I should have realized they'd be linear, and there's a 
hint in one of the TunerPro info boxes (0v=10Kpa or something). I can 
easily check what full scale is, I will probably due that today.

For now, I'm going slow. My main task, small as it is, is to get the 
base pulse width (BPW) correct, that has engine size coded into it (eg. 
258 for this kit vs. 232 for my engine). It's coming reasuringly close 
to what I calculated it ought to be.

(Is there a Megasquirt packaged to plug right onto a GM ECM harness? Now 
that would be a nice hack :-)





Glen Hoag wrote:
> It depends on the MAP sensor, but most seem to have nearly linear 
> outputs from 0-5v.  0 is 0kPa; 5v is the limit of the sensor.  1 bar 
> sensors are probably 115kPa max, 3 bar sensors are 300kPa max.  This 
> is how the Freescale (ex-Motorola) sensors work.  I think that's what 
> GM buries inside their sensor modules.  If you can measure the sensor 
> output and have an accurate barometer, you can determine the sensor 
> calibration fairly easily by opening the sensor port to ambient 
> pressure.  A 1 bar sensor should read around 4v, while a 3 bar sensor 
> will be about 1.67v.  You can find data sheets for common sensors on 
> Freescale's website.  Look for MPX4115AP and MPXH6300.
> 
> The transfer function for the MPX4115 family is 
> Vout=Vs*(0.009*P-0.095), where Vout is the sensor output, Vs is the 
> supply voltage (nominally 5v) and P is the pressure in kPa.
> 
> --Glen
> 
> 
> At 04:18 PM 11/10/2008, Tom Jennings <tomj@xxxxxxx> wrote:
>> OK, I am now doing the thing I sort of dreaded doing... driving down the
>> road with a laptop on the passenger seat. With a simple mis-click I
>> poked the injector base-pulse number such that it immediately stalled!
>> COol! Um yeah. At least I wasn't driving then.
>>
>> But I did tweak the thing for a far more correct setting for the 232 in
>> the Classic. No more adjustable MAP sensor!
>>
>> You could spend forever tweaking this crap, I can see now. But after I
>> solve a few mysteries (eg. TunerPro RT shows manifold pressure as a
>> voltage reading from the MAP sensor; the fuel tables use manifold
>> pressure, in Kpa (Kilo-Pascals), how to convert?)
> 
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