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

[Charles McDowell]

Not questioning you, since I don't know, but that's not obvious to me.  =
The
venturi effect when the exhaust is going fast (high RPM) would be much
greater too, so more outisde are might get drawn in. Of course, at =
higher
pressures, it seems like the exhaust would just want to go _out_ anyway, =
not
draw fresh air in.

-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org] =
On
Behalf Of David Cooley
Sent: Monday, January 03, 2005 10:59 AM
To: A list for Do-It-Yourself EFI
Subject: RE: [Diy_efi] Re: (was: IAC counts) VE tuning issues


 that and a lower volume of Exhaust is created so the amount of air is a
higher percentage than at higher exhaust flows

=20
-------Original Message-------
=20
From: charles at taildragger.info
Date: 01/03/05 11:48:31
To: A list for Do-It-Yourself EFI
Subject: RE: [Diy_efi] Re: (was: IAC counts) VE tuning issues
=20
Is there a reason why an exhaust leak would be significantly more =
relevant
at idle? Low RPM pulsing draws air in vs. pushing exhaust out?
=20
> I don't think a non-heated O2 Sensor is my 160 problem. My BLM goes to =

> 160 almost the instant, if not slightly before, my engine goes to=20
> idle. I just can't see the sensor cooling off THAT fast. I've got a=20
> used four wire heated O2 sensor from a fourth-gen F-body that I plan=20
> to install but I don't want to introduce any more variables at this=20
> time.
>
> My idle counts are staying around 11 and my MAP Sensor doesn't=20
> indicate a vacuum leak so I am going to do some more looking for=20
> oxygen leaks into the exhaust manifold and another plumbing which goes =

> into the exhaust manifolds. It's gotta be something as stupidly simple =

> as those backed off manifold bolts. Perhaps a crack in the cast iron=20
> or a cracked AIR tube weld...hmmmm...
>
> Mike
>
> At 03:55 PM 1/2/2005, you wrote:
>>you can avoid the O2 cooldown problem by installing a heated O2... run =
=20
>>the heater from Switched 12V and ground
>>
>>
>>-------Original Message-------
>>
>>From: <mailto:charles at taildragger.info>Charles McDowell
>>Date: 01/02/05 16:33:49
>>To: <mailto:diy_efi at diy-efi.org>'A list for Do-It-Yourself EFI'
>>Subject: RE: [Diy_efi] Re: (was: IAC counts) VE tuning issues
>>
>>Let us know if you figure out the idle. I also have what seems to be=20
>>excessively high BLM right at idle. I have close to 128 all over but =20
>>when I stop I can watch the idle cell BLM just creep up to 140 or=20
>>more. It seems that the other cells within the same BLM grouping are=20
>>fairly happy, but when it goes all the way down to idle it gets messed =

>>up. I haven't had time to mess with it for a while but I was guessing=20
>>maybe the O2 sensor just cooled off or something (I have headers). Or=20
>>possibly it  just
>>needs more VE. I have to work on it to see, but I'd be curious what =
you
>>figure out.
>>
>>I know my 7747 can be set up to go to open loop at idle, but I don't=20
>>have it set up that way. Is this why they have it, because closed loop =

>>is flakey at idle? I'm not sure how you'd tune your idle though=20
>>without O2, unless just by feel. -----Original Message-----
>>From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org
>mailto:diy_efi-bounces at diy-efi.org">diy_efi-bounces at diy-efi.org
[mailto:diy_efi-bounces at diy-efi.org] On
>>Behalf Of Mike Frels
>>Sent: Sunday, January 02, 2005 3:08 PM
>>To: A list for Do-It-Yourself EFI
>>Subject: Re: [Diy_efi] Re: (was: IAC counts) VE tuning issues
>>
>>AIR valve is working as it should. I checked the diverter valve with=20
>>vacuum on the manifold side and it doesn't bleed air into the exhaust. =

>>Before warming up the engine I checked the exhaust manifold bolts and=20
>>nuts. All were tight, except for two. Guess which two? The two that=20
>>hold the manifold tight against the #7 exhaust port. They were=20
>>completely loose. Oxygen was coming into the exhaust just inches from=20
>>the O2 sensor. Murphy's law again I guess. After tightening I took it=20
>>for a quick drive. The butt scan said it was running much better. I=20
>>took it for a quick second drive with proper scan tool attached. Much=20
>>better! Idle is still  at 160 but all the surrounding rpm/kPa ranges=20
>>are yielding 130-145 BLMs.
>>
>>I feel like I am now getting somewhere. Thanks for the exhaust leak =20
>>tip...
>>
>>Mike
>>
>>At 05:50 PM 1/1/2005, you wrote:
>>I have had trouble with the AIR system bleeding air into the exhaust=20
>>even with the valve "off". Had to plug off the air line whlie tuning.=20
>>Once I had the idle set, and re-connected everything, it would creep=20
>>to ritch. Had to replace the valve in the end. Also had problems with=20
>>the exhaust manifold not sealing at the head on another vehicle and=20
>>giving lean readings on the o2 sensor. Idle blocks are hard to tune,=20
>>in my opinion, since they have to be lean to pass smog.
>>
>>--Karl
>>----- Original Message -----
>>From: <mailto:mfrels at ix.netcom.com>Mike Frels
>>To: <mailto:diy_efi at diy-efi.org>A list for Do-It-Yourself EFI
>>Sent: Saturday, January 01, 2005 5:42 AM
>>Subject: Re: [Diy_efi] Re: (was: IAC counts) VE tuning issues I was=20
>>reading HELMS this morning(couldn't keep the eyelids open past  11:00
>>last night) AIR should only inject into the exhaust manifolds when =
cold
>>and in open loop to help burn converter destroying unburned fuel. When =
it
>>warms and goes closed the AIR should then divert to the converter. I
>>interpret this to mean the AIR system should have no influence on my =
02
>>readings.
>>
>>Just the same I am going to double check for proper operation today.=20
>>Hmmm...could I have switched the two connectors to the diverter valve  =

>>last time I reassembled after checking lifter preload?...I've done=20
>>worse  before!...
>>I will report on progress as it happens. Yesterday's forecast for =
today
>>was 50% chance of rain.
>>Happy New Year,
>>Mike
>>At 10:04 PM 12/31/2004, you wrote:
>>that may be the problem... while tuning, plug the AIR system as it
>> injects
>>air to the exhaust like a giant leak...
>>
>>
>>-------Original Message-------
>>
>>From: <mailto:mfrels at ix.netcom.com>Mike Frels
>>Date: 12/31/04 21:54:09
>>To: <mailto:diy_efi at diy-efi.org>A list for Do-It-Yourself EFI
>>Subject: Re: [Diy_efi] Re: (was: IAC counts) VE tuning issues
>>
>>Don't you mean 'injectors are much SMALLER than #24 they are supposed=20
>>to  be?'
>>
>>Anyway as far as oxygen getting into the exhaust stream the only thing =

>>I have really checked is proper AIR system operation. That is working=20
>>as it should. I have not re-checked that exhaust manifold bolts since=20
>>spring  when I put the engine in. Yes, I am still running cast iron=20
>>manifolds. I will take a wrench to the exhaust bolts and nuts=20
>>tomorrow. Thanks for that possible pointer.
>>
>>The injectors are brand new Accel 24 pounders. No, I did not have them =

>>flowed before installing as I believed I could trust them from the =20
>>factory. Is experience counter to this?
>>
>>Mike
>>
>>At 05:59 PM 12/31/2004, you wrote:
>> >I look at it this way: BLM's greater than 128 means the ECM is=20
>> >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=20
>> >need
>> to
>> >be raised by the appropriate factor. [(BLM/128)*current VE] is a=20
>> >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=20
>> >table, then either your injectors are much bigger than the 24# that=20
>> >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?
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>
=20
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