Resolution.

[Greg Hermann]

>But, but, what about the filtering?.  Doesn't that fly in the  face
>of needing absolutely accurate MAP sensing?.
>  **Notice the question mark, I'm asking.
>  This "filtering" is a funny animal, in so far as using larger ID/
>loner sensor lines can make a vast difference on some
>applications, and I've always had better response with smaller
>shorter lines.
>Bruce

There are strong fluctuations in MAP, size and frequency of fluctuations
depends on design of motor. Ecu needs an average value to perform its fuel
rate calcs.

Sooo--you can filter between the motor and the sensor or between the sensor
and the A/D converter or digitally after the A/D converter. (Or any
combination you want of these.) If you do it on an analogue electrical
basis between the sensor and the A/D converter, you would use an R/C
network--and the math of different size/length tubes between the  motor and
the sensor,  for doing it there, is virtually identical to that of an R/C
network should you choose to do it electrically. All kinds of ways to
accomplish the job digitally, if you choose to do it that way (look at
knock sensors).

If your sensor's response rate is not up to the frequency of the MAP
fluctuations from the engine, you will HAVE to use some mechanical
(connecting tube variations) filtering to avoid getting garbage output from
the sensor.

Regards, Greg
>
> more accurate input
>>data, and that the auto mfgrs are not bloody likely to spend the money
>>required to be any more accurate than they need to be in order to meet
>>emissions regs with an average HP engine!!
>>
>>Real questions here are :"How many bits wide are the A/D converters in the
>>ecu?" and "How many mapping points does the load/rpm matrix need to
>>contain?" and "How many bits wide is the fuel rate calculation (and tables)
>>in the ecu?" and ""What is the minimum time increment to injector pw which
>>the ecu will implement?" and "How many bits wide does everything need to be
>>in order to obtain the desired level of turndown to give your high HP
>>engine decent street manners?"
>>
>>Staging injectors, and rising rate fuel pressure control are certainly a
>>help, particularly if there are fuel rail pressure and temp inputs to the
>>ecu for fuel rate corrections on the fly!
>>
>>Regards, Greg
>>
>>