How do I reduce the amount of fuel when throttle is applied?

[TCSS07]

all good man lol - id add engine oil temp also to your channel list pids and always start your log session when it reaches operating temp around 170-180 degrees which would be probably about 20 min of driving roughly from a cold start for fuel trim tuning for idle and part throttle because the trims will be different when the oil temp is colder and it'll have you chasing your tail trying to dial them in - other than that your logging the important stuff
make sure your not getting knock and after a flash drive for about 5-10 min to get rid of the heat soak and reset the fuel trims

don't hesitate to come back if you need further help - also the pe ratio is good where its at for a direct injection setup - happy tuning

[codename Bil Doe]

Nice car (I read the article today). Unfortunately, you picked an amazing engine with a very difficult ecu to learn for your first tuning effort. If this was an LS1 you would have it understood in a few hours (ve tables, maf, timing). The newer ecu's are torque based and much more complicated but very powerful and adjustable once understood.

You should really post your tune for everybody to help you out quickly. From the 8.0-9.0 afr dip I think the comment may be right that your COT may still be on. I've seen stock C7Z's dip below 9.0 aft on dynos because standard GM practice is to dump fuel and pull timing on WOT under load, tip in throttle, etc

As a quick FYI, you shouldn't have to run race gas on that motor to make good power. My dyno numbers on my road race engine (bone stock engine and turbo, just pulled cat and tuned raced for 3400mi) are:

91 octane : 315/345
100 octane: 345/389
110 octane: 390/4xx

Anything above e10 is illegal in SCCA road racing.

I don't want to speak for you, but I believe you're trying to prep for nationals. For the tuners here, it's not just a local event or normal request but national championships. There are great tuners and a lot of knowledge here. Maybe someone can give a little more time to help you out with your time crunch.

[marksawatsky]

Thanks Bill Doe. We did a lot of dyno tuning on 91 octane and power was good (330 hp/330 ft/lb) but the 100 octane race gas gained 50 ft/lbs of torque. Should I turn off my Cat Over Temp protection? The local club has cancelled the test n tune today so I'm not sure what I'll do for testing. Attached is my tune if you want to look at it

[codename Bil Doe]

My tuning laptops are at work, but maybe someone else can take a look. It's been well over a year since I've tuned newer turbo ecotec or ttv6 am would have to refamiliarize myself with the ecu. Also have to update my software
but if no one answers this weekend I will take a look during the week.

What is your current peak boost?

Is it flat or does it peak and drop off?

How long does it take engine to recover from 0-20psi from off throttle to full throttle? 0-20psi is an arbitrary range that I chose a long time ago and am familiar with. You'll want it to be around 0.7-0.8sec. Any faster is a little uncontrollable.

What is your overshoot past your target boost?

Some things to look at. PID tables are important for turbo response characteristics, especially for autox.

[TCSS07]

under engine diag/air flow for tests p0101,p0106,p0121 - set min ECT to 493 and for p0068 set enable rpm to 8k
i run maf only but if you want to keep a blend of speed density and maf that's fine but id lower the dynamic airflow (under engine/airflow/dynamic) to 4k for rpm disable and 3900 for rpm re enable so it uses the maf only for upper wot fueling to make it easier/little more accurate because the vve tables get a little wonkey because there not a true ve table and use coefficients
for pe - set the eq ratio to 1.176 (12.5) - direct injection can run leaner than a traditional port fuel injection and be safe (forgot to mention that before) - i like to keep the enrichment rates the same so if you have ramp in at 1 set ramp out the same to 1
cot over temp comes into play when the cat reaches a high temp and the ecm dumps fuel to cool it off - turn it off for tuning it messes with the afr and then turn it back on if you want - piston protection is off so thats good
spark advance - i like to have a smooth transition instead of blocky/dip into wot spark
spark retard - disable burst knock - set to 0 for base,base deca and base dod and just make the recovery rate .5 from 2k to 8k
as long as your not having trouble with boost whether reaching max boost, overshooting target boost and holding boost or surging just leave the turbo settings alone - or explain what issues your having

[marksawatsky]

I made those changes and will call that my TCSS07 tune. I'll test it when I can. My TNT was cancelled this morning so I had to test at an undisclosed location. I tried several changes to the tune and was able to recreate the stumble with a couple of the changes made. It is always when rapidly coming off the throttle then mashing it quickly again and from what I can tell, it's in the 3000 to 4000 rpm range. Could this be a bypass valve problem?

[TCSS07]

I'd probably start by lowering the pressure delta factor its set at 5.0 if that's set to high it can cause boost surge from ramping in to fast ... my buddies lnf tune I set them to 2.8 across the board

[TCSS07]

Pressure delta is how fast boost ramps in

[marksawatsky]

It's funny you should say that, one of the changes I made while testing today was going back to the stock pressure delta factor on my car. which max is 1.16. Last year I experimented with it to improve throttle response and kept increasing it until the car bucked, then backed off a tad. It didn't stumble with the stock setting but it also took too long for boost to come up. I need great throttle response and boost to come up quickly for autocross

[TCSS07]

The only other tables would be Proportional Gain, Integral Gain, Derivative gain tables

[TCSS07]

Or try lowering it down a little bit try 4.0 and see

[TCSS07]

https://forum.hptuners.com/showthrea...LNF-PID-Tables - explains more on boost proportional,integral and derivative tables

[codename Bil Doe]

Quick synopsis:

Prop gain is your boost ramp.

Derivative gain controls overshoot on ramp up.

Integral gain controls how quickly boost drops after pedal lift. Stock you'll have decent amount of throttle hang when lifting. Too much integral gain you will see boost flutter as the ecu fights to cut boost while wot.

That's a very, very quick and understated description. New ecu's reference several tables simultaneously before deciding on an outcome.

Don't worry about throttle blade position in relation to pedal. Worry about boost ramp and timing.

Boost without timing produces no power. This is where your octane makes big gains. Allows you more peak timing for same peak boost.

I've tuned and helped tune several 2.0t's for nationals and runoffs. A tune that's perfectly fine on the street does not work with the quick pedal response needed in autox or on track.

The biggest thing I work toward is a linear pedal response. It's not hard to achieve with these engines if you know what to look for in tables.

Your gain tables should have a single value, for example. Your torque requested should be the same for all rpm and a given pedal position or load (don't have tune in front of me to reference specific tables). These types of changes linearize the response of the ecu based on pedal and load rather than making the response exponential as it comes from the factory.

When set up to be linear you'll hear a lot more boost being recirculated or bled off part throttle depending on your setup.

[marksawatsky]

I have a lot of throttle hang when lifting, it feels like the throttle is stuck. How do I reduce that?

[cobaltssoverbooster]

most of the pedal response will come from adjusting the driver demand maps in tqm. the decel hang is going to come from the reduction of power output under deceleration. you'll likely have to play with defco and/or ignition values at decel. may need to increase the EQ out to make it lean out faster on Tip-out.

its such a pain in the ass to deal with VVE so it is recommended by all the LS E38 tuners to stay in strictly MAF mode. it does help with tqm calculations if you lock the VVE system in since all the coefficients play into the tqm calcs.
lots to be had in PID tables as bill stated from before. also the knock airmass table is a boost limiter in this but adjust as it becomes an issue. its not a table you want to go ham on.

by the way this ecu has been a royal pain in my ass since its release. its a monster of a learning curve so put your brown pants on and don't quit until you got it.

[codename Bil Doe]

^ ?100 this

[marksawatsky]

Ok, let's assume I test the tune and detect no stumble and the car runs strong. I will want to improve throttle response when lifting off the throttle when shifting or adjusting the attitude of the car. Should I just increase the whole Integral Gain table by 10% and test again? If yes, then do I just keep increasing it until I get boost flutter?

[marksawatsky]

I spent 5 hours testing changes in the tune and definitely improved throttle response by messing with the PID Gain values, but I'm not sure I eliminated the stumble problem. Attached is a log from doing 3 laps around a kart track with a mix of on-off-on throttle and longer pulls to redline. Final Tune from MKA track 3 laps no stumble ran good.hpl
Also, here's a video of the test https://youtu.be/wdTvmHOrDFU

[codename Bil Doe]

PID tables will affect boost ramp, release, and overshoot but not fix issues of timing, afr running rich, or various ecu torque management interventions.

[marksawatsky]

How do you know if you have gone too far on the PID tables? I kept cranking up the Integral Gain and suddenly experienced what felt very much like a stumble, then dialed back to previous level and it didn't do it again. I assume I reached max on that table and I was still getting maximum boost (22 psi) so I also assumed that my Derivative Gain table was ok, too.