Tuning supercharged C7 - Weird issues

[Eric@HPTuners]

Andy, have you pulled the plugs out to inspect them?

[Area47]

this is what i feared on ls1tech when everyone was questioning the tuning on the lt1. you can not treat this as a port injection engine, you will lose the motor if you do. just because the afr doesn't change does not mean the fuel pressure didn't tank on these engines. on the previous FI di motors from gm i have cranked 27psi on them at 12.8 afr with zero issues. 12 degree's of max timing zero knock anywhere. 80k miles later still living just fine. on e85 im at 13.0-13.2 and 25psi and 24 degree's of total timing. even diablo sport looked at me funny when they posted their dyno graphs for the new silverado 5.3 and i told them to lean it out. get away from the port injection knowledge and think outside the comfort zone. the di is a much more precise and controlled way of fueling an engine than hosing down a bowl.

[carlrx7]

I wonder if Greg Banish (eficalibrator) has any insight to this new ECM and tuning technique? Andy, it may be worth it to hire Greg and have him setup your company up with a great base tune. I'm sure it would help sell your kits exponentially!

[josh@lashway]

I didn't get a chance to look at the scans but I can safely assume you are getting "injector window misfire", your spraying too far into the compression stroke pretty much leaving a puddle of fuel on the piston that the spark plug can't ignite. You can't see it in the scan but it will loose all its power and break up. There are a couple ways around it, call me at the shop if you want and we can see what options this car has, I'm Sure I'll have the same problem with my c7 soon, might as well figure it out now, like we did with the LNFs 954-971-4383

[JakeM]

You guys talking about LNF's, do you have any data as far as EGT's when you are running the cars leaner like you say? I think it would be a really quick way to tell the story of why DI motors would like to run leaner than port injection. Also, as already alluded to, the plugs will tell the tale as well. I would like to see a plug after a WOT run with the motor being shut off after the throttle is released.

I would think EGT's would be a quicker way to come up with more tangible data though.

[JakeM]

I would be willing to bet that a DI Motor running leaner will have very similar EGT's to a port injection motor running known good AFR's.

[black06g85]

I did, have to see if I can dig up some old datalogs from my buddies car. Stock motor, meth injection (single 5gph nozzle) 34psi boost 12.6:1afr (.86 lambda) gt3076r.
on my old laptop hard drive, gotta see if I have the adapter for it,

[JakeM]

If you have one for gasoline that would be better as it would be closer to comparing apples to apples. But any data is better than no data! Thanks Black.

[Area47]

The only data I have available is the "ecm egt sensor" which is more or less measured like a fart in the shower. Couple of the lnf's I did back in 08 had egt's but I have slept since then.

[black06g85]

talked to a buddy that some of the old logs (Was his car anyway) was hitting 1430 ish on straight pump and was in the low 1320 1350 range with the methanol injection running. unfortunately the straight pump gas we only pushed to 26psi though.

[mowton]

I didn't get a chance to look at the scans but I can safely assume you are getting "injector window misfire", your spraying too far into the compression stroke pretty much leaving a puddle of fuel on the piston that the spark plug can't ignite. You can't see it in the scan but it will loose all its power and break up. There are a couple ways around it, call me at the shop if you want and we can see what options this car has, I'm Sure I'll have the same problem with my c7 soon, might as well figure it out now, like we did with the LNFs 954-971-4383

If that be the case (puddling) wouldn't that show as a lean WB reading as un-burnt fuel thus having you add more and more fueling?

Ed M

[Andy@A&A]

Andy, have you pulled the plugs out to inspect them?

Yes. They look fine.
I just got some new ones (colder) to install later today.

I wonder if Greg Banish (eficalibrator) has any insight to this new ECM and tuning technique? Andy, it may be worth it to hire Greg and have him setup your company up with a great base tune. I'm sure it would help sell your kits exponentially!

That did come to mind. He owes me anyway. He uses an A&A Supercharged car (the yellow Z06) in his DVD and I have yet to receive my royalty check.

I just got back from SEMA and have to tune another car before I can get back on mine.
Colder plugs and leaner AFR are on the agenda.

Thanks Guys.

[Z06-Hammer]

"The driver demand (predicted) torque request must always exceed the calculated engine torque."

Andy, looking at the driver demand tables at 100% even at 363KW that translates out to 486.5 HP. Does the computer realize you have pasted this value and cut fuel etc?

[jim2092]

except he said it never goes lean.

[Z06-Hammer]

except he said it never goes lean.

Sorry meant to say closing throttle which I think he said he has figured out.

Besides the AFR could the CVVT be causing any problems?

[Andy@A&A]

I'm almost leaning towards something mechanical like the valves. It's just too abrupt to be anything else.
I am building another kit to ship to a shop in Texas that I've been working with on this issue. They already have a cam and a VVT limiter in their car.
This way they can work on it at their end as well.

While at the SEMA show, I found out that Comp Cams has cams with 3, 4 and 5 lobes for the fuel pump that can deliver 30%, 45% or 74% more fuel than the stock one. I have a call in to my sales rep at Comp to see how fast I might get one.
I also verified that this is the first supercharged C7 that has actually been driven. Edelbrock just got their car running last Friday and rolled it right onto the trailer. I know the Edelbrock guys and we sort of agreed to help each other with the tuning. If I get it figured out, I'll let them know and vice versa.
Magnusons car may or may not even run. They were kind of sketchy about saying anything. Someone who wasn't supposed to say anything alluded to the fact that it did not run, as far as she knew.
LPE has had theirs on the dyno but are using port injectors and a stand alone controller.
I know this has absolutely nothing to do with this thread, but I'm pretty proud that we actually beat the big boys to it. We got this done in 6 days from the day we started it. Other than the actual welding of tubing, I made everything myself and have the scars to prove it. I was driving it back and forth to work an hour after we fired it up. Other than this glitch, it works perfectly. No belt issues etc.
98% of you all on this Forum are way smarter than I am when it comes to anything computer related. This is the first time I haven't felt like a dumbass on here. :-)

[Redline MS]

Andy,

Thank god for Wifi on this flight back from SEMA.......LOL!

Couple things we have found.....the KR you are seeing is most likely due to noise from outside influences verse detonation. We had done some testing with race gas and found the same issue as we knew the fuel was not going to knock at the values we where at. Some is coming from Burst Knock as DI motors are VERY sensitive to "Charge Motion". This meaning the rate in which the air fly's into the cylinder. Much of this concern vs prior port fuel engine management is biased around the short window of time to fill the cylinder and get it mixed well. I'd log a few of the retard tables and see who's asking for timing to be backed off.

With respect to the throttle; this is an interesting find that may or may not effect your situation but non the less part of the new logic....if you log these engines under WOT NA you will find that the throttle opens in steps from like 50% to 84 % (which is WOT). Its all in by 3500-3800 rpms. Of course our minds are programmed to think....hey! I'm not getting fuel power! Until you look at the KPA and you see that as soon as you mat it the KPA is at 100.....This means you don't need the throttle blade fully open to get max VE. The reason they do this is for the traction control system. One of the ways you reduce engine torque is cut off airflow. If the throttle only has to go from 60% to 10% it will react much faster.....this is way I had a hard time trying to push the car off the road course with all the controls active.

The theory behind torque controlled systems is this;

the pedal is the request....meaning when you stab the throttle it looks at the demand table and says hey I want 280 Kw....the E92 tell the throttle to open to X, tells the cam phaser to rotate to X and tells spark timing to go to X.....if GM's 6 million hours in calibrating is close that combination should make that power.........however it then needs to be checked.....

It then looks at the MAF and says.....hey! How many grams/sec are you moving?? Well since engine torque and airflow move together it can tell if its range....if it is......keep driving....if it isn't screw you! This will show up as throttle closings and/or REP mode..

This is where the complexity of recalibrating comes in.....you can get around it but its all because of the closed loop PID check..... it all has to match up..

I also think you need to start logging the pids that report aiflows used for this model.....your issues are all based on the airflow loop. We have already seen this on the TT 3.6 caddy engine.....


HT

[Redline MS]

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.

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

[danieloneil01]

A GM engineer can't throw you guys a bone and drop some knowledge for you guys or maybe Bill? Or is it the case of I'm not telling and figure it out on your own trials and error?

[Area47]

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