o2 voltages on decel low, because of long tubes?
Thread Starter
Joined: May 2004
Posts: 1,080
Likes: 0
From: Elgin, Illinois
o2 voltages on decel low, because of long tubes? on decel w/ my long tubes my o2 voltages go double digits yet my wideband still reads 14.7. Is this because the o2s are further downstream?
Dave
Dave
As I understand it, the 'Vettes close the throttle on
decel. Not even a bleed hole there. Or so I've been
told.
Anyway, I believe the O2s are like a fuel cell. If you
don't have gas flow that provides a fresh supply of
non-O2-bearing gas, output probably drops. Not to
mention that they probably cool right off with no
exhaust heat applied, while the wideband servoes
the heater continuously.
Just conjecture.
decel. Not even a bleed hole there. Or so I've been
told.
Anyway, I believe the O2s are like a fuel cell. If you
don't have gas flow that provides a fresh supply of
non-O2-bearing gas, output probably drops. Not to
mention that they probably cool right off with no
exhaust heat applied, while the wideband servoes
the heater continuously.
Just conjecture.
TECH Apprentice
Joined: Apr 2002
Posts: 308
Likes: 0
From: Austin, TX
Originally Posted by TT_Vert
on decel w/ my long tubes my o2 voltages go double digits yet my wideband still reads 14.7. Is this because the o2s are further downstream?
Dave
Dave
Here is what I think is happening (need more testing to verify).
Narrow band 02s work fine with LTs and some load on the motor(even idle seems ok), but stop working properly on Decel. This shows up in my car as a super rich STFTs, along with a rich reading on the WB.
This is normally not a big deal since decel is its own special mode with its own special fuel trims.
But, the car no longer goes into decel very easy once you put a more aggressive cam in (since it is triggered by a map reading of about 35kpa and you wont see that without some pretty hard engine breaking with most cams)
This causes a problem in your low RPM/MAP FTCs 1-2, since the trims get very screwed up by the crazy stuff going on during decel.
It seems that hptuners lets you change the MAP enable values for decel, but I don't see how it can be done in ls1-edit
. Our local Corvette club had an engine management engineer talk about the LS6 engine and he mention the following, as best as I can recall.
In designing the C5 GM engineering did a ton of testing and from that wrote adaptive strategy that made assumptions as to air and fuel flow under different engine conditions. Changing those airflow parts, like a larger air bridge, will reduce the velocity of the air flow. The adaptive strategy still functions as if the stock parts were being used and the original programming does not change even with tuning. The OBD II PCM was 510 K and only about 80K can be changed by edit. Most cases when the gas pedal is lifted and goes into decel with the larger airflow parts confuses the PCM and is adding or removing fuel when it really did not have to. Larger airflow requires what GM did with the C6 and that is a new faster PCM with an adaptive strategy software to make use of the additional airflow to help response times. FWIW.
In designing the C5 GM engineering did a ton of testing and from that wrote adaptive strategy that made assumptions as to air and fuel flow under different engine conditions. Changing those airflow parts, like a larger air bridge, will reduce the velocity of the air flow. The adaptive strategy still functions as if the stock parts were being used and the original programming does not change even with tuning. The OBD II PCM was 510 K and only about 80K can be changed by edit. Most cases when the gas pedal is lifted and goes into decel with the larger airflow parts confuses the PCM and is adding or removing fuel when it really did not have to. Larger airflow requires what GM did with the C6 and that is a new faster PCM with an adaptive strategy software to make use of the additional airflow to help response times. FWIW.
TECH Addict
Joined: Sep 2003
Posts: 2,065
Likes: 0
From: Atlanta, GA
TPS = 0%
VSS = decreasing
hi i'm in DFCO mode.
You don't think if we shut off some of the logic its that hard to figure out dfco?
air flow this and that , if the pedal is at 0% TPS and we're moving, preferably slower and vac = x you got 0 fuel to the ecu.
It may be time the hptuner's guys let us hack the software, and build in CRC correction features for segments.
VSS = decreasing
hi i'm in DFCO mode.
You don't think if we shut off some of the logic its that hard to figure out dfco?
air flow this and that , if the pedal is at 0% TPS and we're moving, preferably slower and vac = x you got 0 fuel to the ecu.
It may be time the hptuner's guys let us hack the software, and build in CRC correction features for segments.
TECH Apprentice
Joined: Apr 2002
Posts: 308
Likes: 0
From: Austin, TX
Originally Posted by Gordy M
Our local Corvette club had an engine management engineer talk about the LS6 engine and he mention the following, as best as I can recall.
In designing the C5 GM engineering did a ton of testing and from that wrote adaptive strategy that made assumptions as to air and fuel flow under different engine conditions. Changing those airflow parts, like a larger air bridge, will reduce the velocity of the air flow. The adaptive strategy still functions as if the stock parts were being used and the original programming does not change even with tuning. The OBD II PCM was 510 K and only about 80K can be changed by edit. Most cases when the gas pedal is lifted and goes into decel with the larger airflow parts confuses the PCM and is adding or removing fuel when it really did not have to. Larger airflow requires what GM did with the C6 and that is a new faster PCM with an adaptive strategy software to make use of the additional airflow to help response times. FWIW.
In designing the C5 GM engineering did a ton of testing and from that wrote adaptive strategy that made assumptions as to air and fuel flow under different engine conditions. Changing those airflow parts, like a larger air bridge, will reduce the velocity of the air flow. The adaptive strategy still functions as if the stock parts were being used and the original programming does not change even with tuning. The OBD II PCM was 510 K and only about 80K can be changed by edit. Most cases when the gas pedal is lifted and goes into decel with the larger airflow parts confuses the PCM and is adding or removing fuel when it really did not have to. Larger airflow requires what GM did with the C6 and that is a new faster PCM with an adaptive strategy software to make use of the additional airflow to help response times. FWIW.
I guess I better sell my ls1 and get an ls2 so I can decel. Trending Topics
Originally Posted by samz28
It may be time the hptuner's guys let us hack the software, and build in CRC correction features for segments.
The VCM Editor utility allows for increased vehicle support for tuners, and also access to extra VCM/PCM operating system code modifcations.
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