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

Mon Jan 3 17:02:08 GMT 2005

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

-------Original Message-------

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

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?

> 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 idle. I just
> can't see the sensor cooling off THAT fast. I've got a used four wire
> heated O2 sensor from a fourth-gen F-body that I plan to install but I
> don't want to introduce any more variables at this time.
>
> My idle counts are staying around 11 and my MAP Sensor doesn't indicate a
> vacuum leak so I am going to do some more looking for 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 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
>> 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
>>excessively high BLM right at idle. I have close to 128 all over but
>> when
>>I stop I can watch the idle cell BLM just creep up to 140 or more. It
>>seems that the other cells within the same BLM grouping are 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 maybe the O2
>>sensor just cooled off or something (I have headers). Or 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 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 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
>>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
>>nuts. All were tight, except for two. Guess which two? The two that hold
>>the manifold tight against the #7 exhaust port. They were completely
>>loose. Oxygen was coming into the exhaust just inches from the O2 sensor.
>>Murphy's law again I guess. After tightening I took it for a quick drive.
>>The butt scan said it was running much better. I took it for a quick
>>second drive with proper scan tool attached. Much better! Idle is still
>> at
>>160 but all the surrounding rpm/kPa ranges are yielding 130-145 BLMs.
>>
>>I feel like I am now getting somewhere. Thanks for the exhaust leak
>> tip...
>>
>>Mike
>>
>>At 05:50 PM 1/1/2005, you wrote:
>>I have had trouble with the AIR system bleeding air into the exhaust even
>>with the valve "off". Had to plug off the air line whlie tuning. Once I
>>had the idle set, and re-connected everything, it would creep to
>>ritch. Had to replace the valve in the end. Also had problems with the
>>exhaust manifold not sealing at the head on another vehicle and giving
>>lean readings on the o2 sensor. Idle blocks are hard to tune, 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 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.
>>Hmmm...could I have switched the two connectors to the diverter valve
>> last
>>time I reassembled after checking lifter preload?...I've done 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 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 as it
>>should. I have not re-checked that exhaust manifold bolts since spring
>> when
>>I put the engine in. Yes, I am still running cast iron manifolds. I will
>>take a wrench to the exhaust bolts and nuts 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
>> 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 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?
> _______________________________________________
> diy_efi mailing list
> diy_efi at diy-efi.org
> http://lists.diy-efi.org/mailman/listinfo/diy_efi
>

_______________________________________________
diy_efi mailing list
diy_efi at diy-efi.org
http://lists.diy-efi.org/mailman/listinfo/diy_efi
_______________________________________________
diy_efi mailing list
diy_efi at diy-efi.org
http://lists.diy-efi.org/mailman/listinfo/diy_efi