Transient Fuel: Tips, Tricks, and Info. A how-to guide

[ctd]

thanks for sharing James

For sure! Awesome!

My car is bagged & stored for the winter, near ready for a retune as I swapped the cam this fall. A multitude of self enflected problems has left me in a spot if I should pull the heads in the spring or just put new rocker arms on & continue tuning.....rambling on my part....

I've watched this thread & have wondered how this applies, when I'm MAF only I have a very lean condition on deccel as I have slight lean condition on very light throttle acceleration. In SD only the lean condition on deccel is tuned out, the lean condition on very light acceleration is nearly non existent. I've never run a blended tune, I need to. I do prefer the MAF only tune as I feel the car runs better overall. If I were to correct the MAF only conditions with the Transient Fuel tables that would change how the VE table tuned...correct? The Transient Fuel would tune differently in all three conditions.

[JamesLinder]

I spent about 8 hours tuning transient fueling this weekend and have managed to get it very close.

I had to decrease impact factor for 20 (quite a bit), 40, 80 and 100 MAP (too rich) and I ended up having
to increase 60 MAP. I had to increase boiling rate for 20 (quite a bit), 40, 80 and 100 MAP (too rich) and
decrease it for 60 MAP (to lean).

I ended up with Gains for both tables at stock values. It takes a lot of time tuning transients but it is well worth it
because once the transient fueling is correct throttle response is super crisp and the PE vs RPM AFR immediately
hits 12.7 to 1.0 when going WOT and stays there throughout the entire RPM band.

No one has ever stressed how having this tuned properly makes a HUGE difference! Attached is latest tune and
stock tune so you may compare.

[JamesLinder]

After additional tuning, I had to revise my write up for accuracy. Please re-read. Thank you.

If we work together we can do this!

[JamesLinder]

You would be better off to use both MAF and VEs. Yes, transient fueling errors make VE tuning much more difficult
because this makes it much harder to obtain steady state readings for the areas of the curve where magnitude of
these errors are the highest.

If you tune on the street it also can make MAF tuning more difficult since it is not easy to hold everything steady state
when driving on the street while tuning ANY parameters, however it is obviously more difficult for the 3-dimensional
VE table than the 2-dimensional MAF table.

Now that I have gotten transient fueling much closer to ideal, I was able to re-tune the higher flow rate region of
the MAF curve with a great deal more accuracy. With the transients gone it was much easier to see what was really
going on (quantify the AFR errors) at the higher flow rates.

Once you have a perfectly dialed in MAF, it will help get the VEs in line because they are "corrected" on the fly as you
drive by using stead-state MAF values. The PCM has a table of VE correction factors that it updates for several
combinations or "ZONES" of MAP and RPM. Although these correction factors are in the PCM, it appears we can only
see the "starting point" correction factors for each zone, not what they are corrected to over time (which would be very
useful if we had this information). I assume this is how the self-tuning EFI systems work (Holley) because they have a
great deal of freedom to "tune" while you drive.

Oh, if you have headers, I strongly recommend leaving your PCM in open loop mode after tuning. Closed loop fuel
trims simply do not work correctly with headers. Optimal performance will occur once you dial your motor in using
a wide band and going back to closed loop will result in the fuel trims making corrections at the wrong time. Once
you dial everything in using the wide band, and if you have MAF, VE and transients calibrated correctly, then fuel
trims can only serve to degrade performance. I do recommend using a wide band continuously with the alarm feature
enabled for lean conditions (check out Zeitronix and DashDAQ products) so that you will be aware if a fuel injector
starts failing or anything else should cause your motor to suddenly go lean.

Just fyi, I even tried using just short-term fuel trims in open loop, and even these were not correcting fueling correctly
because they simply do not respond at the proper time because of their location in the exhaust being further from the
exhaust valve than GM's stock exhaust location. I also found that installing the wide band oxygen sensor, which I
leave installed and operational at all times, works best if installed in the bung at the header collectors instead of
further back at the second bung when there is one. I highly recommend the Zeitronix wide band controller for its
accuracy, reliability, and alarm programing features. I'm using this unit to trigger a lean cut-off relay to turn my N2O
system off if AFR should become higher than 12.0 WHEN nitrous is flowing, and I log the LCN-2000 timing retard
signal during nitrous runs with this same controller to confirm its doing its job to protect the motor. I also highly
recommend the DashDAQ unit which is easily connected to the Zietronix controller to continuously monitor about 12
key operating parameters in real time continuously. When not logging you can still see what is going on at all times
at a glance; it looks identical to a GPS unit mounted on your windshield, however it connects to the OBDII port and
can monitor (and log to memory card) just about every operating parameter (although not all of those available
using HP Tuners' logging software).

[JamesLinder]

Here is how mine is typically configured, but there are 8 or more screens you can scroll through like this or
they can be set up as graphs of RPM and other parameters just like a logger will display and there are other
features that you can use to monitor a ton of things. You can configure it to compute TQ and HP and log
these with other parameters its obtaining from the OBDII port and the AFR wide band.

It is nothing less than remarkable!

[JamesLinder]

Wow, dialing in these tables requires a lot of trial and error. It is a moving target because every change you make
for a specific MAP column affects the behavior of transient fueling in the other MAP columns - because as a previous
tuner mentioned the values entered affect fueling because of their values "relative" to one another.

In order to get the lower MAP fueling values to fall in line I had to change ALL OF THE higher MAP values above them
in both tables. Through trial and error here is the final tune I ended up with. As you will see the changes from
stock values are now much different than before. This is the closest I will probably be able to get to keeping AFR
constant and at stoichiometric during all the full range of throttle tip-in and tip-out at various MAP values.

If not for my DashDAQ I'm not sure I could have accomplished this because logging does not work as well for me
as watching the changes real time on the DashDAQ readout. It takes a lot of trial and error! I would be interested
in knowing if my changes from stock should provide an improvement for most motors that have been upgraded
with cam, heads, intake, headers, MAF, etc to flow as much air as possible. Anyone trying my transient fueling
tables in their tune, please let me know.

[JamesLinder]

please see attachment - this is for latest tune I posted above.

Custom Built, Forged 408 CID LQ9 - TX Speed & Performance
(thank you Gary Luther)

WiseCo 4.030 -8cc Pistons, Lunati Rods, 24x Lunati Crank
199-AsCast, Precision Race Components cathedral cylinder heads 68cc; 10.7:1
TSP Custom Order Comp Cams: 227/235 .614/.621 on 112LSA
GM LS7 hydraulic lifters; 1.7 ratio GM shaft rocker arms with trunion upgrade
PTM 102mm Throttle Body; Fast Toys 104mm Air Cleaner Lid with ram air hood
FAST 102mm Cathedral-Port Intake Manifold (146302)
TSP 100mm MAF, 2006+ Corvette Z06 GM MAF Sensor (recalibrated IAT)
Bosch 41.7 lb/hr at 4 bar fuel injectors #0280155811
Kooks Long-Tube headers with Y-pipe; CATs removed
GZ Motorsports LSX Series Sportsman Crankcase Vacuum Pump Kit
Meziere 680-WP319S Electric Water Pump
Racetronix Fuel Pump Kit (255L/Hr integral Walbro pump)
2000 Camaro OEM PCM (GM service code 09354896)

[JimMueller]

I was not clear that the changes you were making could be directly usable on other vehicle combinations, and it seemed more complicated than what I wanted to deal with. I'll try those tables, what behavior changes should I be looking for (good or bad)? If I need to scan anything, what PIDs would you want to see?

[JamesLinder]

I would think that the values I have spent weeks tuning for my motor would be closer to correct for heavily modified motors than the
stock OEM tables. Transient fueling if correct will bring your tip-in and tip-out AFR closer to stoichiometric (14.7) all the time.
It is possibly impossible to keep it spot on 14.7 all the time, however it should be very close. It will impact how stable your cold and
warm idle is as well as how quickly your power enrichment AFR is reached and becomes stable. Throttle response becomes immediate
when this is dialed in. There simply are no longer any perceivable rich or lean spikes any longer. If you had my set up and could either
watch AFR at all times or watch the log of AFR at all times, this makes it very easy see how steady AFR is during throttle transitions.

[jimmyblue]

I would imagine that the intake manifold material and
surface finish is a big deal here. I do not see declared,
what kind of intake is on JL's "heavily modified motor"
in all of this work.

Having a not-all-that-popular aluminum intake myself,
I wonder how close I could get by copying. Not that I
think the stock values are bothering my drivability any.

[JamesLinder]

I revised above post with information about motor and latest tune file. The one I posted this morning was not the
correct file. I had tried increasing the 100 MAP values for impact factor, however it appears that impact factor is
essentially the same at 100 MAP and 80 MAP.

[Mudweizer]

I wanted to compare your file to a stock file to see what all you adjusted, wouldn't be allowed.

[LSxpwrdZ]

I've worked on these tables a bit on various platforms and generally I don't worry as much about the tip in as long as the tip in isn't lean. If I'm commanding .89 lambda at WOT and on the initial blip it spikes down to .79-.80 lambda I am fine with that as that little burst of extra fuel alot of times will give the car a snappy feel. It's when the tip in has a lean spike that you need to do some tweaking as that'll make it feel like it has a dead spot.

One other tid bit that needs to be known is that the main fuel/VE table needs to be calibrated in steady state to the T before even bothering adjusting for transient fueling as that main VE value is still the base for fuel delivery with the transient settings just being a modifier to that. Sometimes this is hard to do without a dyno because initial WOT hits can occur low in the RPM range meaning a loaded dyno that can hold 1200rpm 1600rpm 2000rpm at WOT is about the only way to properly get the upper load/low rpm portions dialed in.

Same thing for tip out, alot of tip out issues occur because the upper RPM full vacuum regions vary rarely get calibrated. A simple way to do this is to turn DFCO off do a WOT pull and let out of the gas and let the engine slowly come back down recording data. Adjust the full vacuum regions using this data and smooth then check tip out.

[JamesLinder]

Thanks for your advice James. In agreement with your comments, I see the primary problem trying to tune on the street
is that transient fueling can cause bad lambda error readings because it interferes with one's attempt to obtain steady
state readings, which to me is worse when calibrating the VE table than when calibrating the MAF table. I have managed
to dial mine in pretty close now however it probably took me 20 tuning sessions or more whereas this could be done on the
dyno with just a couple of runs. Once transient fueling is closer to accurate, this allows you to reach steady state much quicker
when going back and fine tuning VE and MAF again on the street. For me, transient fueling errors at high MAP prevented me
from dialing in a constant AFR during power enrichment, and once I nailed WOT transient fueling I was able to come back and
calibrate the 8,000 Hertz and higher portion of the MAF curve much more accurately which then yields a very stable
WOT AFR during power enrichment. I found transient fueling tuning on the street to involve a lot of trial and error to
finally get it where I thought it would be very difficult to improve any further. I really wonder how applicable my transient
fueling would be to other similar builds? My end results are posted here, where only a few boiling rates were changed
from prior tune posted.

[JamesLinder]

You could make my changes to one of your actual tunes for your PCM, and then compare with stock file to see the differences.
You should go ahead and try my transient table values since these will not affect the MAF and VE tables you have already
tuned. Transient only affects what happens on tip in and tip out and you can see if your AFR stays closer to stoichiometric
on tip in and tip out than it currently does. If your transient fueling should be very close to correct now, then you may not
want to bother messing with this at all though. Like they say, if it ain't broke, then don't try to fix it.

I wanted to compare your file to a stock file to see what all you adjusted, wouldn't be allowed.

[SVT_Z06]

Great info guys!

"Log IBPW at idle. For example, lets say your idle IBPW is 3.2ms
Divide this value by 31.124308 this will give you 0.1028135. Place 0.10 in min fuel in mg."

Does this still hold true? I'm seeing 1.5 IBPW, so does that mean I need to change my min fuel in mg to 0.048?

[Oleblu]

A very old thread, but a very good thread lost to the ages of time. Bumping this thread as it has helped me a shit ton over the last couple days. Finally getting my transient issues figured out after battling with issues for months after an intake & injector swap on my vortec 5.7

[JimMueller]

I still don't understand the detailed workflow to dial in the transient fueling tables.

[green440]

very good info

[DrLoch]

While old this is very good info indeed.

This is something I'm dealing with on my 383LT1 with 24X conversion using a 411/12212156 -> 1251002 2bar. Thus far all my tuning has been done with the supercharger belt off. My VE tuning was spot on in open loop with the WB except around idle which I attribute to the cam (224 - 236 @ .050, 1.6 Shaft Rockers) and long tube headers. Removed the WB installed the NB put it in closed loop had to make some minor changes to the VE table. After further driving I have this annoying lean condition while cruising at 50 -60 MPH and this almost bog sunsation during cold acceleration, idle surging when coming to a stop. When in open loop I dialed all that out of it, put it back into open loop and it was gone.

My initial guess was that it was in the transients since LT1 intake is far different from LS intake but I hadn't gotten around to trying to tune these tables. Now I have something to refer to when adjusting... Thanks again