Idle Timing

[Ben Charles]

Attempting to figure out more on this E92 ECU (15 C7)
Just installed these mods
TSP heads (360cfm, 12.1 CR)
TSP LT's/no cats
Custom 4" CAI
E85 Flex fuel (93 shows 7% alcohol currently)
160 thermostat
RX Catchcan

Currently car stays around 165 at idle and timing is -1 to 2 and I need to increase this, this new system is tricky to me at idle. I have adjusted my Spark Minimal to 7 degrees and Im sure that will cure the problem of LOW timing, but I assume there is another way.

Ben2015A8H-I-LT-E85.hpt

[Higgs Boson]

you have heads but stock cam?

mine idles around 17ish

I'll open your tune this evening, can't with this computer

[Ben Charles]

Yea I was planning to do a cam swap, but just decided on heads only for the time being. I'm not a big fan of any of the Gen 5 cams at the moment.

Still doing a few cosmetics at the moment, but I plan to target .88 Lambda to be a little safe. I normally target .85 on port injection and probably could target .90 on DI.

[Higgs Boson]

Biggest thing I can see that might affect it is you are MAF only. Try changing back to hybrid at 2000 or something above idle and see if it changes. I only have the stock file for a manual trans.

Did you change your Idle External Load or Torque Reserve?

[Ben Charles]

Higgs I done some reading and seen where Chris posted this

The idle is all torque based, it is controlled by the Torque Reserve and the PID controllers for Immediate (spark) and Predicted (throttle) Torque. Basically the PCM opens the throttle to achieve the idle RPM using the torque reserve as the starting point. If your throttle is flowing too much air at idle its likely at the lower limit and timing is being pulled to achieve the idle (no different to any other idle control system).

Ill play with the Idle Torque Reserve in the morning. I'm around 2150hz moving roughly 9.5 to 10 g/sec of airflow and the stock torque reserve shows 8.48 ftlbs (Ill play with these numbers, I believe raising will help)
External load may help too, Ill do some moving around and see what happens.

I also performed a port job on the TB and the Intake manifold, I'll try a few things and report back tomorrow.

[Higgs Boson]

ok I didn't know you had a ported tb, you should not need to adjust external load just reserve. I bumped mine about 5%

[Higgs Boson]

did you get it solved?

I noticed on my E78 truck that it uses the main spark table as a baseline and adjusts timing to the necessary level based on torque using Torque Mngmt Advance (which shows positive in the scanner but is actually removing timing when it shows a value in the scanner).

My idle cells were 30 degrees and it was pulling about 15 degrees to idle at 15. So I changed my main spark idle cells to 15 and blended them in and now torque management advance bounces around a few degrees instead of 15.

I was getting surging with my ported TB on the truck after a startup and now it doesn't do it anymore since I lowered the values in the main spark table.

[Ben Charles]

Figured this out some and it was Pure Accident. Idle timing of course as well as most things in the ECU are controlled by Tq. I increased my Tq coefficient tables roughly 10% and noticed Tq management spark at idle was not as aggressive. I looked back at some logs and notice Max Engine tq around 330 at idle, timing around 12-16 degrees (15-20 degrees removed for Tq management spark). With the above change max engine Tq is 385 at idle, timing is 20-23 degrees (8-10 degrees removed for Tq Management spark)

Something else I noticed was cruising at 70 mph Max engine Tq was 365 roughly and now with the above changes its 425.

From the E78 tuning guide

◾Maximum Engine Torque: The maximum possible engine torque, this should be higher than Predicted Engine Torque Cmd otherwise it is limiting

I always had trouble making Max engine Tq higher than predicted other than light throttle or idle, now with changes like above I can get Max higher than predicted ALL THE TIME.

For what its worth the A8 transmission shifts Noticeably BETTER.

[Higgs Boson]

I agree, it's funny when we revisit "old" threads after we have learned about Max Torque Timing, Coefficients, Idle Torque Reserve, External Load, etc tables. :-)

I also was able to get mine to idle with the timing I wanted. We will get these completely figured out eventually and it will be like tuning a 2003 Corvette. Pure cake.

[jtrosky]

So I don't quite understand these torque reserve-related parameters. Is there any chance that these parameters could help my situation where I get a driveline clunk when reapplying the throttle after coasting (at lower speeds)? Currently, I'm working around this problem by putting very small positive values (.02 -> .05) in 0 pedal position in the Driver Demand tables for the speed range where I experience this driveline clunk (theory was that if I keep a very small amount of "pressure" on the driveline, that it would eliminate the clunk). Just wondering if I could accomplish the same thing using these torque reserve tables somehow.

I don't want to just start blindly modifying values that I don't understand, which is why I'm asking this question here. Any chance I could use these torque reserve/external load parameters to reduce or eliminate my driveline clunk?

Thank you in advance!

[Higgs Boson]

It could be contributing to it. What is the application?

I don't think changing the 0 row of DD is going to do anything for that. Mine is all zeros.

[jtrosky]

Actually, so far, it does seem that putting small positive values in the 0 pedal row of the Driver Demand tables does avoid the issue. Basically, it just keeps some "pressure" on the driveline, so that when I reapply the throttle, there is no "slack" in the driveline. However, if there is a better way to address the issue, I'd like to explore it.

Application is a 2012 Impala - 3.6L V6 (LFX) and 6T70 trans (E39 ECM and T43 TCM). I'm not clear if this affects all of these cars or not - it seems that some have the issues and some don't. Happens primarily when reapplying the throttle between 10 and 35 mph (approx) - NEVER happens when taking off from a standstill or at higher speeds.

Interestingly, someone on the Impala forums told me yesterday that when she installed a VMAX ported throttle body, the issue seemed to go away. Not sure if that helps potentially identify the cause.

When this driveline clunk happens, the car is NOT shifting - just acelerating in the current gear. Seems to happen almost every time in 2nd gear, sometimes in 3rd and infrequently in 4th (seems to be more speed-related than gear-related).

Not a huge problem, just annoying - makes the car seem so, well, "clunky"! :-)

[Higgs Boson]

my truck does it down low when the 8 speed is trying to get to first gear from 2nd or 3rd all at once around 0-5 MPH and reapplying throttle. DD did nothing but cutting Idle Speed Reserve in half had the most positive effect.

[jtrosky]

This is the driver demand table that I am using and it does seem to be working - at least so far. I might raise the values a little still:

JT_DriverDemand.JPG

[jarrah]

Figured this out some and it was Pure Accident. Idle timing of course as well as most things in the ECU are controlled by Tq. I increased my Tq coefficient tables roughly 10% and noticed Tq management spark at idle was not as aggressive. I looked back at some logs and notice Max Engine tq around 330 at idle, timing around 12-16 degrees (15-20 degrees removed for Tq management spark). With the above change max engine Tq is 385 at idle, timing is 20-23 degrees (8-10 degrees removed for Tq Management spark)

Something else I noticed was cruising at 70 mph Max engine Tq was 365 roughly and now with the above changes its 425.

From the E78 tuning guide

I always had trouble making Max engine Tq higher than predicted other than light throttle or idle, now with changes like above I can get Max higher than predicted ALL THE TIME.

For what its worth the A8 transmission shifts Noticeably BETTER.

Ben,

those coefficient are used to model the engine torque i think what your are getting is a higher value due to higher value of multiplication, the right way to do this i guess is using an engine dyno or chassis dyno and try to match the delivered output and compare with max engine trq. i think there is a PID controller that also is playing in the background to make sure the error between predicted and delivered is within a certain degree.

[Ben Charles]

the right way to do this i guess is using an engine dyno or chassis dyno and try to match the delivered output and compare with max engine trq.

I agree, seen where Banish was talking about this very thing. Going to mess with some more settings and Ill report back what I find. Seems like every few days I figure something else new out on the E92. I literally log everyday, Ill have an A&A kit to play with here soon too. Gotta run 10's first on motor though and I'm waiting for better DA.

[Higgs Boson]

you and me both! waiting for better weather, run 10s on motor, but I am probably going with ECS.

[jarrah]

Guys wat the ecu does it looks at ur air flow lets say u idle at 10g/s this directly proportional to the torque so more g/s means more air means more torque however with a cam swap and ot ported throttle u have less air going in at low speeds therefore think of it like conventional VE with a cam swap we used to lower the VE in idle areas which corresponds to lower torque thats why the fact that when higgs lowered this table or cut it in half his achieving better idle bcz it closer to the actual torque being produced

[Higgs Boson]

Guys wat the ecu does it looks at ur air flow lets say u idle at 10g/s this directly proportional to the torque so more g/s means more air means more torque however with a cam swap and ot ported throttle u have less air going in at low speeds therefore think of it like conventional VE with a cam swap we used to lower the VE in idle areas which corresponds to lower torque thats why the fact that when higgs lowered this table or cut it in half his achieving better idle bcz it closer to the actual torque being produced

which table are you talking about? i didn't cut an airmass table, i cut a torque reserve table used at idle. i have since raised it 25% from the 50% cut value. just experimenting.

[jarrah]

which table are you talking about? i didn't cut an airmass table, i cut a torque reserve table used at idle. i have since raised it 25% from the 50% cut value. just experimenting.

Higgs exactly the reserve table is equivalent to idle airflow therefore what you have to do for example is to disable the PIDs that control Idle, then match all your spark tables in idle area except the minimum then with the scanner raise and lower your rpm and see what timing does if it drops you have to lower your reserve tables or another way is set your rpm and just raise the timing until you get max g/cyl which is directly related to your torque output and I think this is wat the ecm is doing based on g/cyl it back calculates your predicted torque. this is wat I do on cammed trucks