[Diy_efi] Re: (was: IAC counts) VE tuning issues

[Gary]

Allow me to try this again.
> I look at it this way:  BLM's greater than 128 means the ECM is having to
> add fuel to keep the mixture right.
>
Agree.  According to the O2 sensor(s), ecm was not programed to deliver
enuf fuel, providing no mechanical issues, as noted below.
>
> This means it's getting more air than it should according to the VE
tables,
 > which means the table values need to be raised by the appropriate factor.
>
Actually, I now agree with this statement, because the amount of fuel
delivered/commanded, to attain the neutral point (BLM 128), does not
agree with signal the O2s are sending back to e/pcm.  Being a less
amount than necessary, this implies the amount of fuel the e/pcm is
commanding, should be increased.  Raising the VE % will accomplish this.
>
> If you're getting 160 BLM's and you have 80's in the low-rpm VE table,
> then either your injectors are much bigger than the 24# that you think
> they are....
>
I disagree with this though.  If more fuel is needed, according to O2s, the
injector fuel discharge would be less than e/pcm is programed for, or IOW,
injectors are SMALLER than the 24#s, the ecm is recognizing.
>
> .....or you have a pretty significant vacuum leak, or you're getting
> a false lean reading from the O2.
>
I agree with this possibility.
>
> >  If  a given % VE were increased, this would translate to a need
> > to increase the fuel requirement.  Higher % VE requires more fuel
> > than a lower % VE.
> >
I apologize for the confusion.  I previously stated this incorrectly.  If
the
VE were to be increased, more fuel would be commanded, and LESS
additional fuel would need to be added, with the fine tuning by the O2s.
This would translate into BLMs much closer to 128, in lieu of higher
BLMs which would command additional fuel.
> >
> > With the request for more fuel, the VE, the pcm is recognizing,
> > is higher, than fueling tables able to are satisfy, and still maintain
> > the neutral 128 BLM.
> >
So, this is incorrect also.  If VE, the pcm is recognizing, were to be
raised, the additional fuel commanded by fueling tables, would cause
BLMs closer to neutral, requiring less additional fuel to be added.
> >
> > GAS
> >
Hopefully, if posters party enuf tonite, they will not notice my error.  :(

GAS

----- Original Message ----- 
From: "J" <TheGreatJ at charter.net>
To: <diy_efi at diy-efi.org>
Sent: Friday, December 31, 2004 5:59 PM
Subject: [Diy_efi] Re: (was: IAC counts) VE tuning issues


> I look at it this way:  BLM's greater than 128 means the ECM is having to
> add fuel to keep the mixture right.  This means it's getting more air than
it
> should according to the VE tables, which means the table values need to
> be raised by the appropriate factor.  [(BLM/128)*current VE] is a very
good
> formula for finding how much to adjust it.
>
> If you're getting 160 BLM's and you have 80's in the low-rpm VE table,
then
> either your injectors are much bigger than the 24# that you think they
are,
> or you have a pretty significant vacuum leak, or you're getting a false
lean
> reading from the O2.  First thing to do is check for exhaust leaks
> before/near the O2, as that will REALLY screw with your BLMs.  Where did
> you get the injectors?  Are they new or used, and have they been flow
tested?
>
>
From: "Gary" <gas- at charter.net>
To: <diy_efi at diy-efi.org>
Sent: Fri Dec 31 11:52:42 CST 2004

> > First off, as is probably understood, the higher the BLMs are, the
> > more fuel the pcm/ecm is adding/requesting.  If  a given % VE
> > were increased, this would translate to a need to increase the fuel
> > requirement.  Higher % VE requires more fuel than a lower % VE.
> > With the request for more fuel, the VE, the pcm is recognizing,
> > is higher, than fueling tables able to are satisfy, and still maintain
> > the neutral 128 BLM.
> >
> > GAS
> >


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