[Gmecm] Ideal gas law and $58

[Rob Handley]

Yes it is a turbo calibration - and I want to use it for a NA engine.

Cold start enrichment is applied via the desired A/F ratio. If it was down 
to the F31M array it would be cold start enleanment!

Curious what you mean by non-linearities. Could you expand?

Rob

----- Original Message ----- 
From: "not a webot" <not.webot at gmail.com>
To: <gmecm at diy-efi.org>
Sent: 24 September 2007 20:04
Subject: Re: [Gmecm] Ideal gas law and $58


> compressor (it is a turbo cal right?) nonlinearities? It might also be 
> cold
> start enrichment related.
> just the 2 first thoughts I had
>
> On 9/24/07, Rob Handley <Robin at furyworld.fsnet.co.uk> wrote:
>>
>> Don't know whether anybody's interested :-) but I have now perfectly
>> matched
>> every factor in $58's steady state (meaning: no acceleration enrichment
>> or deceleration enleanment or closed loop or any other special
>> contributions)
>> injector base pulse width calculation with its equivalent derived 
>> directly
>> from the ideal gas law. It is now absolutely clear that the (F31M) 
>> inverse
>> MAT/IAT
>> look-up array has been 'adjusted' from theoretically correct, for 
>> whatever
>> reasons.
>>
>> This plot: http://213.162.107.39/temp/GM_inverseIATfactor_vs_IAT.gif 
>> shows
>> the only contribution that the MAT/IAT makes to the steady state BPW
>> calculation. The contribution is made via a multiplying factor in the
>> range
>> 0 to 1.
>>
>> The magenta line is the multiplying factor arising from the values that 
>> GM
>> put in the (F31M) inverse MAT/IAT look-up array for the Sunbird. The dark
>> blue line
>> is the theoretically correct multplying factor.
>>
>> The GM contribution stops changing at 23.5C but only matches the
>> theoretical
>> line at 50 C. So why would GM make it such that the mixture was lean 
>> below
>> 50 C and rich above it? Is 50 C the normal running air temperature for 
>> the
>> Sunbird?
>>
>> Rob
>>
>> ----- Original Message -----
>> From: "Dig" <turbodig at yahoo.com>
>> To: <gmecm at diy-efi.org>
>> Sent: 17 September 2007 18:37
>> Subject: Re: [Gmecm] Ideal gas law
>>
>>
>> Yup.  In fact, if I remember the Sunbird cal correctly, they're exactly
>> the
>> same.
>> Given that one application is intercooled, and the other isn't, you would
>> have thought these would have been markedly different.
>>
>> ----- Original Message ----
>> From: Rob Handley <Robin at FuryWorld.fsnet.co.uk>
>> To: gmecm at diy-efi.org
>> Sent: Monday, September 17, 2007 12:18:23 PM
>> Subject: Re: [Gmecm] Ideal gas law
>>
>> I have no reason to think the lookup isn't working. The values in the
>> standard Sunbird F31M array are fixed for MAT = 23.5 C and above. Is it
>> the
>> same for the Sy/Ty ?
>>
>> Rob
>>
>> ----- Original Message -----
>> From: "Dig" <turbodig at yahoo.com>
>> To: <gmecm at diy-efi.org>
>> Sent: 17 September 2007 14:37
>> Subject: Re: [Gmecm] Natural gas law
>>
>>
>> Are you talking about the values in the table, or are you saying the
>> lookup
>> isn't working?
>>
>> The factory calibration was, "less than perfect".
>>
>> The other thing at work here, is the fact that when temps heated up, they
>> wanted a bit extra fuel to keep the detonation demons away.  24 c is a 
>> bit
>> low to start doing that, IMO.
>>
>> Later,
>>
>> Dig
>>
>>
>> ----- Original Message ----
>> From: Rob Handley <Robin at FuryWorld.fsnet.co.uk>
>> To: gmecm at diy-efi.org
>> Sent: Saturday, September 15, 2007 10:15:46 AM
>> Subject: [Gmecm] Natural gas law
>>
>> I've been trying to match the $58 BPW calculation with a hand made BPW
>> calculation spreadsheet - which is based on the natural gas law.
>>
>> What's confusing me ATM is that, in $58, the inverse air temperature
>> correction factor (array F31M) does not change when the MAT value is 
>>  >23.5
>> C.
>>
>> Since gas mass is inversely proportional to gas temperature (if pressure
>> and
>> volume are constant), the MAT contribution should have an effect at all
>> temperatures, and this effect IS significant above 23.5 C.
>>
>> What am I missing?
>>
>> Rob
>>
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