[Diy_efi] Re: Minimalist micro based EFI ?

[Mike]

Yes true :)

Well articulated,

<sigh>

rgds

mike



At 09:08 AM 3/11/03 -0700, you wrote:
>At 11:29 PM 3/11/03, Mike wrote:
>
>The basic control theory element you are skirting around here is "dynamic
>range".
>
>The ratio between an engine's minimum and maximum output power is a pretty
>fair definition of the dynamic range which ANY fuel delivery system must
>cover.
>
>Next question is, how much granularity in fuel flow control rate can the
>engine tolerate without getting into either emission problems (an
>artificial constraint), excessive fuel consumption, including plug fouling
>and/or bore washing (valid concerns) , or detonation (a very real and
>immediately expensive concern).
>
>With a boosted engine, the engine's dynamic range is generally wider, and
>the higher the boost level goes, the wider the dynamic range gets--so more
>precision (more bits) MAY well be necessary in measurement of inputs
>critical to controlling the fuel flow rate fpr boosted engines without
>getting into excessive fuel control granularity.
>
>In fact--the need for more precision in fuel metering may well increase
>_geometrically_ with boost, since boosted engines are so much more
>sensitive to detonation than NA engines are !
>
>Greg
>
>>Yes Mos, but not from the perspective of a design decision to
>>run an engine over a certain power come boost range...
>>
>>ie. A Gen III 5.7L V8 uses a MAF sensor 5v max output, 300Kw
>>
>>A RB30 N/A puts out 120 Kw and uses a different MAF sensor also
>>with a max 5v output.
>>
>>Case 1 above at say 100Kw flow has less MAF voltage than the
>>case 2 with 100Kw flow as its a sensor sizing throat/voltage issue.
>>
>>So clearly the sensor is chosen for the range and the a/d resolution
>>is chosen under some other metric, other than the difference in
>>vintage between the 2 samples above, is there a compelling reason
>>the 5.7L V8 *needs* higher resolution if emissions is not an issue,
>>
>>rgds
>>
>>mike
>>
>>
>>
>>At 02:06 AM 3/12/03 +1100, you wrote:
>>>On Tue, 11 Mar 2003, Mike wrote:
>>>
>>>> At 01:38 AM 3/12/03 +1100, you wrote:
>>>> >> <cough> I dont see how boost has anything to do with the number of
bits.
>>>>
>>>> So now you are saying air flow voltage is related to boost pressure
>>>> rather intimately ?
>>>
>>>There's no standard (that I was referring to). I was referring to MAP and
>>>atmo - hence 5V/1bar (yes, very generally). As another poster stated,
>>>there's 5V/3bar (and also 5V/2bar).
>>>
>>>It doesn't matter what you're measuring, but if your range increases, your
>>>resolution will decrease if you use the same number of bits, period. Your
>>>10 bits will not give you the same resolution with 2 bar as they will with
>>>1 bar.
>>>
>>>I was in no way saying that it was insufficient - merely stating that
>>>boost *can* affect the number of required bits - so yes, boost does have a
>>>lot to do with the number of bits.
>>>
>>>Air flow voltage is related to air flow (obviously), and air flow is very
>>>intimately related to boost pressure.
>>>
>>>Mos.
>>>
>>>--
>>>84 AE86, 90 ST185GrpA, 91 MX83Gr, Sydney, Oz.
>>>
>>>
>>>
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>>>
>>
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>
>
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