Taking the mystery out of tuning the 1.4

[Stew]

Per Scot's suggestion I updated the Turbocharger Knock Max Airmass table, I also updated another table which was one of the first ones I had changed when I got HPTuners but I wanted to revisit it with a minor update now that I've gone through several tune revisions.

I'll be taking a test drive later today to verify the changes after the mail gets here, that way I can write off the miles for my test drive since I'll be running a work errand! Upon successful verification I'll update the first post with the revised data.

 

[Swordsmith]

Wow.. ssoo much info.. I just got my 2014 1.4 lt and the main issue i have is the turbo lag when going WOT. I want to tune (nothing big or extravagant) it but not lose my warranty... any suggestions?

You cannot tune, at all, without potentially losing your warranty. Any modification you do to your car COULD result in the service techs claiming that your mod caused whatever broken part they are looking it. They could say "your bumper fell off because your car accelerated harder than a stock Sonic could accelerate."

They can Also deny you warranty coverage because of your driving habits; they could say that you were "racing" and thus broke your car.

You might be able to argue effectively that your changes or behavior were not at fault... but to do that you might have to take them to court, spend time and money, on a gamble that the judge would agree with you and not them.

Right and wrong have little to do with this, it all really comes down to the individual techs', or possibly the service manager's, personal decision, on a case by case basis, whether they want to extend you coverage or not.

If you want to tune your car, go ahead, but understand that you increase the risk that some breakdown will not be covered.

If, like me, you are treating the Sonic as an incredibly cheap midlife crisis sports car substitute, then the hell with it, throw any mod in there you want, it's probably still cheaper than one tire on a Lamborgini. If like Preloader your wife has a baby on the way and you want your Sonic to be a cheap reliable way to get you from point A to point B, keep it stock.

I hear if you buy the SRI from Chevy it comes with a very mild tune... that one shouldn't violate the warranty, look into that!

 

[Stew]

Ok I did a test drive and have some preliminary results. I made two updates:

First, in the Turbocharger Knock Max Airmass table I put the OEM values in the -25* column and interpolated from the -5* column. So the -25* column is OEM, the -5* column is the 1.50 and it scales down in the in-between columns.

Second, in the Allowed Pressure Delta Factor table I simply upped the 1.75 value to 2.50 and left the value in cells for 1000 rpm and 1500 rpm as they were. The reason for this is a pressure ratio value of 2.50 equals about 19.5 psi and I wanted to eliminate potential conflicting values between this table and other tables.

These changes had two results. First, upping the values in the Allowed Pressure Delta Factor raised my peak boost from the high 20's to the high 21's. I'm ok with this for now as long as I don't see 22 psi but I may tweak the Turbo Base DC table to lower it down just a hair, I just don't want boost any higher because reliability!

Second effect is something that had already been happening but it's doing it a little more with the adjustment to the Turbocharger Knock Max Airmass table, and that is occasionally boost would only peak around 17.5 psi and now it's down to around 16.5 psi with this most recent update but mostly it's right up where it should be.

I know others have reported experiencing this as well, regardless of who the tuner is. My suspicion was the ECM intervening due to knock but I don't think that's the case. When I was getting 21 psi, timing was around 4 but when boost was being limited to 16.5 psi, timing was 6. If boost was being limited due to knock then it would stand to reason that the advance would be lower with the lower boost levels, not higher.

I don't know yet what is causing this, if anyone has an idea don't be shy. Also, there are three tables that I would like to learn more about, I don't know if they factor in or not, they are Proportional Gain, Integral Gain and Derivative Gain. There are a few posts over on the HPTuner forums that attempt to explain them but I'm still not fully grasping what they do and if they factor in.

 

[Italianjoe1]

You kinda have a sledgehammer approach to the boost control but it works. I have followed some of the other 1.4 tuning guides to start with and used my previous HPT experience on other platforms and have had pretty good success.

Boost limiting is still torque management, I was getting it with the a/c on and heavy accel until I made some limit adjustments, as it is now the car pulls steady at 22psi ac on or off.

Follow scot's suggestions on the knock table, only change the right column or two, if the car is detecting several degrees of knock let it take the boost out. Then solve the knock problem via tuning timing/fuel/boost.

The cars do respond nicely to some midrange timing adjustments but it needs to be small, as the boost comes in hard and fast and it will just knock and pull out all the boost/timing if it can. I had the car pinging loud enough I could hear it with one trial, it ran like a raped ape but it would not be safe at all to leave like that.

Trial and error is the best way to learn, make small changes and log them repeatedly to see the results.

 

[Italianjoe1]

I don't have the files on this computer but i'll try to add my screenshots when I get back to my tuning laptop for comparison's sake.

 

[Stew]

I don't have the files on this computer but i'll try to add my screenshots when I get back to my tuning laptop for comparison's sake.

ItalianJoe1, good to hear from you, thank you for the input! Yes, please post as much of your tune as you feel comfortable posting, comparing what I've done to other peoples tunes will help not just my understanding but hopefully other peoples too! Each time I make an adjustment I get a better understanding of how the tables interact, and you are right - small adjustments then test, then more small adjustments.

Regarding the Turbocharger Knock Max Airmass table, I think I'm correctly understanding the concept of what it's supposed to do - as it detects knock and retards timing it limits the amount of air allowed into the cylinders via lowering the boost to mitigate knock. But the confusing behavior is if I do a WOT run where it's obviously limiting boost, and then 5 seconds later do another run it will boost up to the limit in the high 21 psi.

The conditions haven't changed in the 5 seconds from run 1 to run 2, but one was limited and one wasn't. There seems to be something else at play here and I haven't figured out what it is yet.

Cheers!
Stewart

 

[Swordsmith]

Looking for a difference in conditions between two WOT runs 5 seconds apart...Engine temp, intercooler temp, coolant temp?

 

[Stew]

Yeah, there's those, lol.… but I don't think the difference in boost between consecutive runs is any type of heat soak problem because it can be, and often is, the first run that's having the boost limited and subsequent runs boost up to the limit.

A typical scenario would be turning onto a freeway on ramp and nailing it, the first WOT pull could be in first or second just depending on how fast I'm going turning onto the on ramp and it will limit boost, shift up to the next gear and then it'll pull hard boosting up to its max limit.

I've been looking for a common denominator such as what gear I'm in, IAT, ambient temp, etc but I haven't figured it out yet.

 

[Stew]

Over on the HPTuner forum there's at least one long Cruze tuning thread where the guy is experiencing false knock and I've wondered if that might be the problem, or possibly tip-in knock which seems more likely and I think would fit the seemingly randomness to this.

I'm not in front of my laptop at the moment but I'm sure I saw some tip-in stuff in the timing section, I'll have to take a closer look at those tables.

 

[rcmn0022]

The car can limit the boost based on gear. This is likely what you are experiencing... I think it also limits the final torque based on the output shaft torque. I've never tried to calculate it and see what it makes in first gear at the output shaft.

 

[Scot]

Regarding the Turbocharger Knock Max Airmass table, I think I'm correctly understanding the concept of what it's supposed to do - as it detects knock and retards timing it limits the amount of air allowed into the cylinders via lowering the boost to mitigate knock. But the confusing behavior is if I do a WOT run where it's obviously limiting boost, and then 5 seconds later do another run it will boost up to the limit in the high 21 psi.

The conditions haven't changed in the 5 seconds from run 1 to run 2, but one was limited and one wasn't. There seems to be something else at play here and I haven't figured out what it is yet.

Cheers!
Stewart

Stewart -
It doesn't limit boost, it limits cylinder airmass, i.e. look at your throttle angle and see if it is closing when you're seeing the boost limit. I don't have my PC with me, but there is also a way to look at which area is limiting boost (I think - I could be getting confused with my day job )

 

[Stew]

The car can limit the boost based on gear. This is likely what you are experiencing... I think it also limits the final torque based on the output shaft torque. I've never tried to calculate it and see what it makes in first gear at the output shaft.

Good hearing from you! The output shaft torque setting is sufficiently high that that shouldn't be getting in the way. The gear thing I'll look around but it will sometimes happen and sometimes not in different gears, I would think that if that was the hangup it would always happen in a certain gear.

It would be really cool to slightly limit boost in 1st for more consistent launches though!

Stewart -
It doesn't limit boost, it limits cylinder airmass, i.e. look at your throttle angle and see if it is closing when you're seeing the boost limit. I don't have my PC with me, but there is also a way to look at which area is limiting boost (I think - I could be getting confused with my day job )

Once again thank you for the idea Scot! I have to confess the last few times I've been monitoring things like fuel trims and timing it's been with the ultragauge and not the HPT data logger. The HPT data logger is way better but a little more inconvenient to drive around with.

---------------------

I have made a few more adjustments to the tune, including one a few minutes ago. After a day or two of driving around if satisfied with the updates I'll update the tables in the first post.

The changes include making the Turbocharger Knock Max Airmass table safer, matching values in the Allowed Pressure Delta Factor table to be consistent with other tables, lowering the Turbo Overspeed Airmass Limit Minimum to keep peak boost where I want it and lowering the torque limit values in a few tables.

I'm expecting the overall feel of these adjustments to be mostly unnoticeable compared to the tune in the first post and again these are mostly to make the tune safer and to remove the sledgehammer!

Stay tuned! (pun intended I guess)

 

['12Eco]

Stew,

Thanks for sharing.

The limiting of cyl airmass is most likely due to the throttle closing, if you log ETC Position and ETC Pedal Position you should see ETC Position close to ~50% throttle. As you may have noticed it does not do it all the time, you may have also noticed that your actual boost is now higher than your desired boost.

Occasionally, I believe the vehicle sees the higher boost and wonders if something is wrong, as a way of performing a diagnostic check, closes the throttle.
To remedy this, I've modified the engine diagnostic in the attached jpeg and maxed the 100% pedal in sections below it. So far, the throttle has not closed, hopefully it is fixed for good.

^this did not work, but since it has been commented on, I've left it in this post so others can learn. I repeat, no reason to modify P0068.

I've also attached my Wastegate DC table, it is much less aggressive than your your table maxing at 20psi on my car.

 

[Stew]

Hi there '12Eco! I have not looked at the engine diagnostic area at all, I'll look at that. It doesn't limit often enough that it bothers me too much, and if it is indeed limiting because it's detecting knock then I'm certainly ok with that. I just need to get out and do some more logging, I'm going to try and do some logging this weekend.

That is very interesting how much lower you have your Turbocharger Base DC table, with that being lower what other tables did you change to achieve your boost goals?

 

[ScarabEpic22]

Id be VERY careful adjusting that particular Enable RPM diagnostic parameter, it is the RPM value at which the ECM performs the MAP/MAF rationality check. There are some cases where the ECM should see an issue with airflow and then close the throttle. If this value is raised AND an issue occurs, the ECM will bypass the check at whatever RPM is specified and keep the throttle open when it shouldnt...

The term sledgehammer keeps getting thrown around here, I would say maxing this parameter out is a sledgehammer approach. This should only be adjusted as a last resort if the other parameters cannot resolve the issue you're trying to adjust/fix.

The other tables associated with this param (think of it as a master enable/disable at the specified RPM) should indeed be raised to slightly above what the expected airflow values are. You dont want them below the expected values or the ECM will try to intervene and limit power one way or another. Max Airflow vs. Ignition, Max Airflow vs. RPM, Airflow Delta, and MAP delta should be altered to tell the ECM what to expect ONLY if the actual airflow is above the values in these tables. Put the Enable RPM back to 800 (stock) value so the diagnostic test is run continuously when the engine is above idle.

Look under the Engine Diagnostics->Airflow tab. Not sure if anyone's played with the Overboost params, interesting stuff in there for a rainy day...

Scot-Im a bit rusty on this, havent looked at this particular param in a year or so, care to validate? Want to ensure all info is correct on here for the next guy who comes along.

 

['12Eco]

Thanks for the warning ScarabEpic22

It seems as though my editing of the diagnostic did not fix my issue. I've my post above to reflect my finding.

With your comment on the over-boost parameters I decided to give them another look. The first time I looked at it I was in imperial "mode" apparently there is a bug that doesn't change the delta to psi, so I thought it was practically disabled stock with 22 psi of "headroom". In metric "mode" the values don't change so I infer its actually kPa, which makes sense that it could be my issue.

Sorry Stew didn't mean to get so far from the main topic but I hope this will help. I don't think anything I've changed would cause our wastegate DC to be that different perhaps elevation? I live at 400-600 ft above sea level.

 

[Stew]

I have made a few more adjustments to the tune, including one a few minutes ago. After a day or two of driving around if satisfied with the updates I'll update the tables in the first post.

Over the last couple days I've made a few adjustments and have been driving around all day today on the most recent revision and I'm very happy with it's performance.

It behaves virtually identical to the tune in the original post but I've lowered values in several tables after input from a few SOF members and raised values in another table as mentioned in an earlier post.

It does very rarely limit airflow (boost) but that's a good thing since it is doing that to protect itself against undesirable conditions such as knock, so I'm not going to try to tune that out. I will update the first post soon with the new values.

Also, I'm trying to minimize my use of the term 'boost' and use the word 'airflow' instead, so I don't sound like I just walked off the set of The Fast and the Furious. So when you read 'airflow' just think 'positive manifold pressure' or 'boost'. :banana:

 

[Stew]

First post has been updated!

 

[Stew]

So after thinking about this thread for a couple days I decided when I was down to about 8 gallons to top it off with about 4 gallons of E85. My 'back of the napkin' math says that I should have a tank of about 97 octane fuel, and I believe it. It feels like it's pulling harder, and looking at the timing on the Ultragauge it is holding the full advance where it often wouldn't before on 92 octane.

Sooo I got to thinking about those with E85 tunes and wondering just how hard is it to tune for this stuff. Well I did some reading on the HPTuner forum and it actually sounds really easy. I was thinking I'd have to change not only the stoich table but also mess around with a bunch of other fueling tables as well, but fear not, it's not nearly that complicated. You only have to change one table and it's not the one I was thinking.

Here is an excerpt from a thread over at HPTuners:

"When you switch to e85, you have to tell the computer to increase the fuel delivery to make the initial mix 9.8:1. If you change the stoich setting in HPT, you must also change other fueling tables to make sure the calculations stay correct. A simpler method is to tell the injectors to just deliver more fuel. This keeps all the other calculations correct, and only requires changing one table. The rule of thumb is usually to start out by telling the injectors to deliver 30% more fuel, and then tweak from there"

Easy peasy. In fact, that got me thinking back to when I installed the 42 lb injectors and couldn't figure out why MPFab's injector table was so different than mine, if he's running E85 that would explain it.

So, to update your tune for E85 should only take a few log/adjust cycles to get it sorted out and then you can start playing around with more airflow (boost) or start jacking up the timing. I'm not 100% sure I want to run E85 but if I decide to it's nice to know how simple it is!

 

[NewZJ]

Making me wish I could program around the BOV with hptuners. Tinkering sounds fun but I can't give up the pssshhhtttt every time I shift