VE and BLM cell edges

[rrauscher at nni.com]

Dave, BW & others (can't keep track, up to 62 emails just
today),

Something kept bothering me about it being in idle. Another
ecm uses tps < 1.5% and mph < 4 to be in idle. Has to be 
less then both the tps% & mph to be in idle. So, I would
have thought that by hitting the gas the ecm would leave
idle, along with the idle cell.

So, I did a little more research (can't help myself). On the
$8D mask, ANHT, idle cell 4 is tied to whether the canister
purge is less than a certain amount. Hmm, interesting. Once
ccp is greater than xx @ $8522, then the ecm no longer locks
to the idle cell.

However, some of the canister purge qualifications are very
similar to what would be idle: if tps% < 3% or mph < 1.8, then
no canister purge. Then cell 4 is selected. There are some
other quals such as coolant temp and map (set to 0).

The most interesting are the blm and int quals. If either of
these drop too low (107 & 90 respect) then purge can be either reduced or stopped
altogether. There are even option bits
at $8016 that can cause open loop purge along with disabling
the low tps% purge.

So looks like not only is the vss required, but don't mess with
the ccp quals and disable it.

This is one complex ecm/mask, no doubt about it! Every time I
look at the anht code I keep thinking about how I like that
simple '747.

BobR.



>that is excellent info bob, thanks for sharing!
>
>----- Original Message -----
>From: <rrauscher at nni.com>
>To: <gmecm at diy-efi.org>
>Sent: Friday, January 19, 2001 5:01 AM
>Subject: Re: VE and BLM cell edges
>
>
>>
>> It is the idle cell. Some ecm's do it differently, the one
>> talked about here uses cell 4 whenever it thinks it is in idle.
>>
>> If the car is not moving, must be at idle. Or so the ecm thinks.
>> The ecm will then lock into the idle cell. This prevents the
>> cell to use from changing due to map fluctuations. Same deal
>> with the closed throttle SA table. Prevents things from moving
>> around too much.
>>
>> On a heavily cammed engine, it can be a good idea to change
>> which cell the ecm uses for the idle cell. Otherwise the cell
>> to use can 'jump' the instant the car starts to move.
>>
>> BobR.
>>
>>
>> >I don't want to sound like a moderator, but the first question that i had

>> >was why would it lock in this block?  Could this be an OR situation?
>what
>>
>> >is the purpose of locking it into a cell?  if this is some kind of safety

>> >or Limp home mechanism then maybe there are multiple situations that this

>> >could occur.  it appears that you both had different situations but the

>> >same result.
>> >
>> >why lock in a cell & why cell 4.  this the cell that is used the most
>> >(common cruising/driving), or ?????
>> >
>> >thoughts?
>> >BW
>> >
>> >
>> >
>> --------------------------------------------------------------------------

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