Tuning supercharged C7 - Weird issues

[mowton]

i am still leaning towards fuel pressure issue. it can not sustain 11.2 afr. it's not a port design.

How would you calculate Delta pressure across the injector at what point in the piston travel, injector timing etc.....?

[LSxpwrdZ]

Well stated. GM has the engine model calculated out for there intentions not for ours. The engines are run on steady state engine dynos where they take measured airflow vs power output at random spots to what's called at Design of Experiment....there is no way with VVT to possible map out every VE spot which is where the 7 string polynomial calculation comes into play. Google the concept of Kriging.....read up....http://en.wikipedia.org/wiki/Kriging

Time to start separating the hackers from the calibrators...........

HT

I like it. I believe this platform is going to be one to bumfuzzle quite a few.

[frans96ss]

I like it. I believe this platform is going to be one to bumfuzzle quite a few.

You got that right... It took me some time but i got it down now.

[JakeM]

I love this thread! It's feeding my brain and I can't wait to get my hands on a C7 with forced induction.

Redline - When you say you've seen this on the TT Caddies, do you mean this problem or that you need to make sure you are monitoring the correct airflow PID's to get a accurate summation of what is happening in reality as apposed to what you are commanding?

[Area47]

How would you calculate Delta pressure across the injector at what point in the piston travel, injector timing etc.....?

how many Gdi motors have you worked on that could sustain this.

[Area47]

I like it. I believe this platform is going to be one to bumfuzzle quite a few.

It is already starting to show.

[mowton]

how many Gdi motors have you worked on that could sustain this.

Non obviously, just trying to figure out how they manage the injector flow while the intake stroke is occurring and how boost might disrupt the OEM calibration levels to fill the cylinder with the correct AFR mixture. I am learning as are most of us and need to rely on the more experienced to bounce our confusion against.

Ed M

[DSteck]

I'd imagine that as the intake valve is open, cylinder pressure is assumed to be manifold pressure.

[Area47]

Non obviously, just trying to figure out how they manage the injector flow while the intake stroke is occurring and how boost might disrupt the OEM calibration levels to fill the cylinder with the correct AFR mixture. I am learning as are most of us and need to rely on the more experienced to bounce our confusion against.

Ed M

the biggest factor i have run into the gdi setups is the dropping of the fuel pressure under wot conditions. normally it would peak at say 2200psi, but the midrange would drop to 980 and then the misfires and loss of power would happen, such as the situation andy is running into. mine being the extreme side of the spectrum on the fuel supply. if the pressure tanks in the midrange it's out of flow from the hpfp, if it tanks on the high side, its out of supply pump. the misfires would not always trigger a code, as one would be lead to think, it would show up in the logs as an airflow drop for a split second. counteracting this would be injector timing. in a nutshell, opening that small window up a smidge, assuming the fuel pressure is steady all the way to this point, if the fuel pressure is not and you're still trying to command say .75 lambda, i would try and lean it out and see if the pressure stabilizes enough to make a full run, then work from there.

you're not going to see a lot of timing in these motors as they do not need it to make power. if you're still seeing this issue and the fuel pressure is steady across the board and it does the same thing, work the injection timing tables under the fuel system tab and see if it will smooth out. the ecm is pretty good at protecting the engine from destruction, but can only go so far.

step one, log fuel pressure. there should be a PID for it
lean it out till pressure stabilizes. {be uber conservitive with the timing, may require an egt as well to be sure}
see if the pressure is dropping, if not, and it still falls over, work the injection tables a bit under the fuel system tab.

still dies up top. check the commanded torque tables.

have to keep in mind, you're not flooding the back side of a valve anymore, this is precision injection directly into the cylinder. the game is different now.

::shrugs:: thats all i got.

[Area47]

Something else to look into, do you have the multiple injection events turned on? you would get a bigger single shot instead of multiple little shots.

[Blingole]

I think the injector "Split pulse" is disabled.

My question, Does 100% idc mean theres precalculated injection window value thats 100% used up or is that mean 100% on time threwout all 4 cylinder strokes as how port fuel injection is?
Example with easy math if we could only inject fuel on the intake stroke that means our injector by thoery would be maxed out at 25% idc from 1 stroke?

[Area47]

when doing the gdi vehicles i do, i don't look at idc, just msec in certain area's. treading that fine line between max power and misfire central.

[jim2092]

Andy, I would imagine your problem lies in the driver demand. If you have even used the torque model stuff to hold a FI car back on the gen IV stuff, the way the ETC reacts looks very similar. Neat that the pedal relation to engine output is tied to "power" and not "torque" though. Guess that has to deal with how the blade position is more relevant to power than torque on a gas motor. Just more common to seeing this logic tactic implemented on a diesel. The Ford guys already have to look at it this way.

Regardless, if full pedal is supposed to mean "500" HP to the ecm, there is a point its going to hold you back. I think the warning listed with those tables is more relevant to the danger of run away cars. Its probably not that you'll end up with a bricked piece of hardware. Id imagine at some point your going to have to increase the numbers in the 100% area on those tables, like you would with any other vehicle that uses a system like this.

Bill says these PIDs exist. Logging these might shed some light.

PIDs to log in the scanner:
◾ETC Pedal Average Position: The position of the pedal, 0 - 100%
◾ETC Desired Position: The desired throttle position, 0 - 100%
◾ETC Position: The measured throttle position, 0 - 100%
◾ETC Source: The control source of the throttle. During normal operation it should be "Torque"
◾Driver Pedal Power: The power request from the driver demand tables
◾Driver Pedal Axle TqReq: The axle torque request from the driver demand tables
◾Driver Final Axle TqReq: The final axle torque request from the driver demand calculation
◾Predicted Axle Torque Cmd: The commanded axle torque request (after limiting)
◾Predicted Axle Torque Src: The control source of the axle torque request. It should be "Driver"
◾Predicted Engine Torque Cmd: The commanded engine torque request (after limiting)
◾Predicted Engine Torque Src: The control source of the engine torque request. It should be "Axle"
◾Maximum Engine Torque: The maximum possible engine torque, this should be higher than Predicted Engine Torque Cmd otherwise it is limiting
◾Engine Torque: The current calculated engine torque

[Andy@A&A]

I just put the blower back on the car last night after copying the brackets and making jigs for the tubing. I've been kind of tied up with that for the last week or so.
I set commanded AFR at 12.2 and the big glitch is totally gone. I guess it just didn't like being so rich.
The throttle still partially closes at 6000 or so but I only see it as a percentage in the scan. I don't see a reduction in airflow or power. Could it be commanding the blade to close but somehow it's not actually closing?
This seems to be speed related as it stays open on a 3rd gear pull but closes on a 4th gear pull. Any ideas on why that would be?
Overall, it's not moving a lot of air. I barely see 500 grams. It made 510 RWHP and 520 RWT, or thereabouts. Not too impressive but at least it's making a smooth pull.
I seem to have misplaced the belt I was using and put a slightly longer one on so I may have some belt slip going on.
I need to get a boost gauge hooked up to see what's going on.
I don't see much difference when adding or removing timing either. Going from 12* to 15* doesn't seem to change things much. It has KR even if you put 10* in it so I'm just sort of ignoring that for now. I figured if it were real knock, I would have blown it up by now.
I do appreciate the input. I've just been tied up trying to get the pieces together to be able to make more systems and haven't had time to look at the tuning and all your suggestions.
Thanks, Andy

[Redline MS]

Bill says these PIDs exist. Logging these might shed some light.

PIDs to log in the scanner:
◾ETC Pedal Average Position: The position of the pedal, 0 - 100%
◾ETC Desired Position: The desired throttle position, 0 - 100%
◾ETC Position: The measured throttle position, 0 - 100%
◾ETC Source: The control source of the throttle. During normal operation it should be "Torque"
◾Driver Pedal Power: The power request from the driver demand tables
◾Driver Pedal Axle TqReq: The axle torque request from the driver demand tables
◾Driver Final Axle TqReq: The final axle torque request from the driver demand calculation
◾Predicted Axle Torque Cmd: The commanded axle torque request (after limiting)
◾Predicted Axle Torque Src: The control source of the axle torque request. It should be "Driver"
◾Predicted Engine Torque Cmd: The commanded engine torque request (after limiting)
◾Predicted Engine Torque Src: The control source of the engine torque request. It should be "Axle"
◾Maximum Engine Torque: The maximum possible engine torque, this should be higher than Predicted Engine Torque Cmd otherwise it is limiting
◾Engine Torque: The current calculated engine torque

Now your getting closer.........wait until you really start moving some airflow...........

HT

[Area47]

it may require the knock sensors to be clocked different as well. The lnf's suffered from this. There is a higher torque calculation in 4th vs third. every now and then some of us do know what we're talking about.

[frans96ss]

I just put the blower back on the car last night after copying the brackets and making jigs for the tubing. I've been kind of tied up with that for the last week or so.
I set commanded AFR at 12.2 and the big glitch is totally gone. I guess it just didn't like being so rich.
The throttle still partially closes at 6000 or so but I only see it as a percentage in the scan. I don't see a reduction in airflow or power. Could it be commanding the blade to close but somehow it's not actually closing?
This seems to be speed related as it stays open on a 3rd gear pull but closes on a 4th gear pull. Any ideas on why that would be?
Overall, it's not moving a lot of air. I barely see 500 grams. It made 510 RWHP and 520 RWT, or thereabouts. Not too impressive but at least it's making a smooth pull.
I seem to have misplaced the belt I was using and put a slightly longer one on so I may have some belt slip going on.
I need to get a boost gauge hooked up to see what's going on.
I don't see much difference when adding or removing timing either. Going from 12* to 15* doesn't seem to change things much. It has KR even if you put 10* in it so I'm just sort of ignoring that for now. I figured if it were real knock, I would have blown it up by now.
I do appreciate the input. I've just been tied up trying to get the pieces together to be able to make more systems and haven't had time to look at the tuning and all your suggestions.
Thanks, Andy

I would say that its deff closing it... Mine was doing the same thing. I sent you an email... When you reply ill give you a few things to try

[Andy@A&A]

Bill says these PIDs exist. Logging these might shed some light.

PIDs to log in the scanner:
◾ETC Pedal Average Position: The position of the pedal, 0 - 100%
◾ETC Desired Position: The desired throttle position, 0 - 100%
◾ETC Position: The measured throttle position, 0 - 100%
◾ETC Source: The control source of the throttle. During normal operation it should be "Torque"
◾Driver Pedal Power: The power request from the driver demand tables
◾Driver Pedal Axle TqReq: The axle torque request from the driver demand tables
◾Driver Final Axle TqReq: The final axle torque request from the driver demand calculation
◾Predicted Axle Torque Cmd: The commanded axle torque request (after limiting)
◾Predicted Axle Torque Src: The control source of the axle torque request. It should be "Driver"
◾Predicted Engine Torque Cmd: The commanded engine torque request (after limiting)
◾Predicted Engine Torque Src: The control source of the engine torque request. It should be "Axle"
◾Maximum Engine Torque: The maximum possible engine torque, this should be higher than Predicted Engine Torque Cmd otherwise it is limiting
◾Engine Torque: The current calculated engine torque

I see all these PIDS, but I only see the Driver Demanded torque tables in the calibration. If one had all the information from these PIDS, what would you change?

[jim2092]

This is Bill's explanation of what needs to be changed. It shows the path from Driver's demand and what tables can limit the result. It is found at the top of the Gen 5 section apparently also relating to the E92.


http://www.hptuners.com/help/vcm_edi...vanced_e78.htm

[Andy@A&A]

Unless I'm missing something, all those tables are already maxed out.
I've bumped up the Driver Demanded tables, at the top end, by a considerable amount as well.
The numbers at about 85% throttle and over 100 MPH are WAY up from stock.
Does anyone see anything I may have missed?