Does anyone know how you are supposed to update this on the later E38 computers? There isn't a place to change "min fuel" under the transient tab.
69 Suburban Bagged & Blown: http://67-72chevytrucks.com/vboard/s...d.php?t=200387
68 Farm Truck build thread-LS3/6L80/TVS1900: http://67-72chevytrucks.com/vboard/s...d.php?t=358692
Didn't even notice that, LOL. Since I can't drive mine yet, if you want to come over some time, that would be cool. I live in Pace, just north of Spencer Field. LMK.
69 Suburban Bagged & Blown: http://67-72chevytrucks.com/vboard/s...d.php?t=200387
68 Farm Truck build thread-LS3/6L80/TVS1900: http://67-72chevytrucks.com/vboard/s...d.php?t=358692
Wait.....and you are from Oklahoma and a Sooner fan? So am I.
69 Suburban Bagged & Blown: http://67-72chevytrucks.com/vboard/s...d.php?t=200387
68 Farm Truck build thread-LS3/6L80/TVS1900: http://67-72chevytrucks.com/vboard/s...d.php?t=358692
Great reading.
Any more info on how we tackle changing these table to fix a problem we identify?
I seem to get large lean spikes when lifting off the throttle.
Cheers
Benno
Good read. Still can't say I have my head around how to change what though. What would be KILLER is developing some histograms that would drive changes to the transient tables. IE: plotting AFR error against the evap factor table or fuel mass impact table filtered to only show data during tip in/out. Just a thought.
Bill Winters
Former owner/builder/tuner of the FarmVette
Out of the LSx tuning game
Great post sir!
Thanks
lwrs10 ,
Excellent post! Thanks for sharing.
I'd like to get this figured out, but it seems we've got some conflicting opinions on this.
I'm a bit skeptical of both opinions seeing that both are off an order of magnitude when converting from seconds to milliseconds...
03 Avalanche Z66
5.3L, Vortech supercharger, water/meth injection, circle D 3200 stall converter, truetrac diff, shorty JBA headers
Replaced 5.3 with ATK 6.0 460 hp crate motor - haven't put sc and w/m on it yet
00 vert vette
Rebuilt LS1 with large cam, injectors, ported and slightly milled 243 heads, Weiand/Lingenfelter Intake Manifold, Vararam Ram Air Intake, LT headers, no cats, Corsa Indy exhaust, higher stall converter
Computations to dial in fuel injectors attached; essential 1st step to tuning.
I'd like to try those transient settings in my '98 tune. Are any of those changes parts or configuration specific?
Sounds like I'm going to need Calibrated Success Advanced and not just Basic to figure out the specific workflow. Basic is enroute now.
Sigh.....it really sucks that these transient tables aren't in the 2004 Z06 pcm. I've been trying to get my 36 lbrs perfect for the longest time. :/
I'd like to work on this today, are you able to provide specific config files or specific steps to optimize the transient fuel settings? I guess for now I'll just use the Z06 Impact Factor Gain table and use the same Min Fuel Milligrams that you used (0.0012). However, comparing my factory transient tables to the 408 tune you posted earlier, my stock transient tables are also different here:
Warmup Transient Fuel:
Delta Min Incr
Initial time
time decay
previous
Transient Fuel Mass:
Fuel Boiling
Fuel from wall Stabil.
Transient Fuel Mass Gain:
Fuel to Wall
Should I leave those additional settings as original factory, update them to values used in a later model, calibrate them somehow...?
I found this on another site:
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So I screwed with it by decreasing the Transient Fuel Mass Gain-Fuel to Wall Impact Factor AND the Impact Factor-Gain. The problem got worse. COOL, go the other way then! So I took it back to stock, added 10% to both those tables and started my drive home from work. WOW! A ton better. I pulled over half way half, added another 10%. HOT DAMN!!! Pulled over again, added another 5%. WOO HOO!!! I figured I was getting greedy so I thought I'd leave it alone for awhile. Let's see how that works for a couple days. Well, the rest of the way home I couldn't help but notice, I didn't have lean spikes as bad anymore.
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Last edited by JimMueller; 09-14-2014 at 09:44 AM.
Yeah, the MAF/VE are dialed in. I made a couple changes to the 02 sensor values to help with gas mileage(lower values) when I originally tuned it. I just changed them back to stock along with lowering the min inj pulse and default inj pulse from 1200 - 2400 rpm from 1.2xx to .927 and that seemed to make a substantial difference in part throttle and decel rich swings are gone now.
I'm happy for now. I think that lowering the 02 sensor values screwed up my part throttle. Perhaps it was too lean on tip in. Much better now with stock values.
Last edited by SVT_Z06; 09-18-2014 at 09:31 AM.
Recent tuning work resulted in a better understanding of how the transient fueling tables work, and I thought I would share this
simple summarization of what I learned tuning these tables on my 408 stroker motor. While reading this summary please keep
in mind that the purpose of the transient fueling tables is to correctly predict the impact MAP changes during throttle position
changes have upon intake port wall fuel film by formulating a model to accurately predict the rates at which fuel is deposited upon
and evaporates from the intake port walls. To maintain proper fueling, injector pulse width must be modified during throttle
position changes to maintain a consistent film of fuel on the intake port walls at all times. When tuned properly, the transient
fuel tables will ensure that evaporation and deposition of fuel on the walls are occuring at the same rates so that wall film
remains relatively constant.
IMPACT FACTOR - During acceleration I found that LESS fuel was being deposited on the intake port walls than predicted by the
factory GM settings. This created a rich condition because the fuel injectors were attempting to compensate for more fuel building
up on the intake port walls than was actually taking place for the modified motor. This means the numbers in the Impact Factor
table were too LARGE and needed to be reduced to eliminate transient rich fueling. Multiplying by lambda error in this case moved
transient AFR in the right direction (except for 60 MAP which had to be increased).
BOILING RATE (EVAPORATION) - During de-acceleration I found that fuel was evaporating from the intake port walls SLOWER than
predicted by the factory GM settings. This also created a rich condition because the fuel injectors were attempting to
compensate for more fuel boiling off the intake port walls than was actually taking place for the modified motor. This means
the numbers in the Boiling Rate table were too SMALL and needed to be increased to eliminate transient rich fueling. Dividing
by lambda error in this case moved transient AFR in the right direction (except for 60 MAP which had to be decreased).
TUNING TRANSIENT FUELING - The purpose of tuning these tables is to maintain stochiometric fueling during changes in throttle
position; tuning in this case effectively removes the rich and lean spikes that would otherwise occur even though the MAF and
VE tables have been properly calibrated. Transient fueling is crazy difficult to tune because these "spikes" occur so quickly and
because an error in either table affects the operation of both tables for the specific MAP and ECT region impacted. Tuning two
tables simultaneously which have opposite impacts on non-steady state fueling is considerably more difficult than the more common
chore of tuning a single table during steady state conditions.
The GAIN tables for EVAP and IMPACT can be used to modify the values in the base tables for various MAF rates, since the velocity
of the air flowing through the intake ports during transient conditions can necessitate adjustments to the base table values to
maintain proper fueling. The higher the MAF the higher the velocity of air through the intake ports, and the less fuel that can
hang onto and build up on intake port walls as compared to that for lower air velocities. As air velocity increases, GM decreases
the Impact Factor gain values to account for this and prevents the rich transients that would otherwise occur at higher air
flow rates. GM set the gain for EVAP RATE at unity (1.0) for all MAF rates. Evidently, evaporation/boiling rate has the most
impact on fuel wall film as the throttle is being closed (de-acceleration), and air flow rates/velocities when the throttle
butterfly is nearly closed do not impact boiling rates that much.
Last edited by JamesLinder; 01-07-2015 at 07:30 AM. Reason: REVISED FOR ACCURACY 1-5-2014