LE5 Turbo Drivability (Decel, DFCO, Throttle Follower) [2007 Saturn Sky 2.4 E67 ECU]

[Engnineere]

Hey guys,

I have a Manual Trans 2007 Saturn Sky with a 2.4L, E67 ECU, 60lb Siemens injectors, k04 turbo, straight piped exhaust on 93 octane.

1. When engine braking in gear at greater than 1500RPM and 0% accel pedal, it looks like my DFCO doesn't kick in for like 5 seconds which results in the car lurching really badly. It looks like it's reading from the Idle Base Spark table (which doesn't make sense), and it's at like 20-35 degrees of advance. I flattened the table in that area (2000-5000 RPM x .08-.12 CylAir) to 5 degrees of advance and that seemed to barely start addressing the lurching but the backfiring is violent enough to make me worry about burning my valves. I like the noise, but it seems unhealthy for the turbo.

2. When I clutch in to come to a stop, my RPMs start dropping like a rock and dip down to about 400 RPM and shudder really bad before catching itself and revving up to 1200 then oscillating back to around 850 where it should be idling normally. I tried correcting this with the Throttle Follower Torque table, but I didn't really know what I was correcting for or looking for, so it seemed to not make a difference at all when I snap the accel pedal to 0% while coasting.

I've attached my latest tune, my stock tune, a config/layout file and a log file that shows these issues. You can see in my screenshot where these problems are occur which will save you some time skimming through the datalog. I'm satisfied with the performance under load and WOT, I'm just not a fan of how bad the decel is (especially on road courses when I'm trying to decel into a turn), and I don't think the car should be nearly dying every time I come to a stop. For some reason, no matter what table I adjust, the main spark just does whatever it wants and doesn't seem to follow any table.

Screenshot 2021-12-18 142310.png

Stevens 07 2.4 man k04 3inint 60s 2bar 93 j - Decel.hpt
Leeman_Stevens_2007_Sky_StockTune.hpt
Stevens rev j scan 3 - pulled timing during decel.hpl
2224timing-wideband-throttle.Channels.xml
Charts.Charts.xml
2224.Layout.xml

[Engnineere]

Nobody has any ideas?

[cadillactech]

What happens when you put all your DFCO settings back to stock?

Have you tried increasing your minimum final airflow table in Neutral?

[Engnineere]

What happens when you put all your DFCO settings back to stock?

Have you tried increasing your minimum final airflow table in Neutral?

I've messed around with the final airflow table a little bit, but not enough to notice a difference. I have a manual trans, so does that mean that i should be tuning the Park / Neutral tables instead of the D/1/2/3/4/5/6/ tables/rows?

Also is there a way to have the car ignore the LTFT when the car is in decel? it looks like when I'm in decel, the car reads wicked lean and tries to add 19.5% fuel... it would be nice to just have the car not try to correct the "fake lean" when it's engine braking with negative torque.

[cadillactech]

I've messed around with the final airflow table a little bit, but not enough to notice a difference. I have a manual trans, so does that mean that i should be tuning the Park / Neutral tables instead of the D/1/2/3/4/5/6/ tables/rows?

Also is there a way to have the car ignore the LTFT when the car is in decel? it looks like when I'm in decel, the car reads wicked lean and tries to add 19.5% fuel... it would be nice to just have the car not try to correct the "fake lean" when it's engine braking with negative torque.

I would change all the final air flow tables just to be consistent. Try 15% and see if it changes anything for your condition. If it does they you are onto something.

As far as the DFCO, does it act this way with the settings back to the stock settings? It should ignore LTFT when DFCO is enabled.

How is your turbo system setup? Blow through or draw through MAF? Is the BOV a stock set up like the K04 with it integrated into the compressor cover? How are you controlling boost? What about the PCV system.

[Engnineere]

I would change all the final air flow tables just to be consistent. Try 15% and see if it changes anything for your condition. If it does they you are onto something.

As far as the DFCO, does it act this way with the settings back to the stock settings? It should ignore LTFT when DFCO is enabled.

How is your turbo system setup? Blow through or draw through MAF? Is the BOV a stock set up like the K04 with it integrated into the compressor cover? How are you controlling boost? What about the PCV system.

My turbo system is just the basic K04 with the integrated bypass and wastegate. I currently have it set to 6-8 psi and it's a blowthrough MAF setup. I've also done an EVAP delete by disconnecting the evap vacuum lines and unplugging the purge valve. I'm using the evap manifold inlet as my boost reference for my BOV and for my boost gauge.

So I might've fixed the odd dipping/dying when coming to a stop. It looks like there is a throttle follower torque table that I adjusted upwards so that around 950 rpm, I'm commanding a little higher than idle so it catches the coastdown idle and doesn't dip anymore.

As far as the DFCO, they're basically at stock settings. My bandaid fix is that I changed my base spark table to have a big section at the top of the table just retard the timing like crazy so that when my foot is off the throttle and I'm in gear, it just retards the spark like crazy so that even if the fuel hasn't been cut off, I'm making "negative" torque and engine braking. After about 3-5 seconds of popcorn, the fuel cut kicks in, and it continues to smoothly decel.

Now I just have the hard cranking to try to deal with..

Throttle Follower Torque.png
Spark Table.png