Hello!
Quick questions about Boost Control in my 2012 Chevy Cruze.... If anybody has experience with this engine, what are your recommendations on controlling boost ramp-in. Is modifying the Base DC table a viable option? Are there any other tables I should be looking at?
If anybody could help me out, I would appreciate it! This has been a fun car to tune, but I would like to have a little bit more control on how my boost ramps in.
Thanks for your help in advance!
First before making changes to the DC Tables, start by upping your torque limit tables, upping the knock airmass table, and you can up the driver demand(be careful with this table, only adjust top end of table 86-100% ranges). Then depending on how much boost you want to run, then you can up the Boost Max Limit Table(in less you are not wanting more boost that the current value in that table).Originally Posted by alawrence
Start there and watch your actual boost vs desired boost.
Thanks Mark, I thought that I had already gone through torque management in detail but I went back through them and found that I never modified the max engine torque tables and before I was experiencing this strange surging (probably due to throttle actuation by torque management)! Now I no longer experience that and the changes I made to my Driver Demand tables are probably working as they should.
Now everything is running great! It has been a learning experience tuning this car, but once you understand how all of the limiters work, it's not so bad right?
Thanks!
I'm still learning this stuff myself, but as you said, driver demand and torque limiter tables seem to do most of the work. You have another input with turbo overspeed (set to .40 on my Sonic, stock) that you can manipulate if you overshoot target boost on spoolup; go lower if you're spiking too much. Other stuff like knock retard airmass can also be changed, but I don't think it's a limiter unless you're seeing KR (makes sense to me). I'm going to play around some with max grams/cycle increase (can't remember the name of the table offhand) to see if I can get the turbo spooling up quicker. It starts coming in plenty early, but the transient spool up time seems slower than I'd expect.
There is a table that deals with the pressure delta factor, mess with that one, it has to do with the max amount of boost that can be gained per cycle. That definitely helps!
The Base DC table is something to look at too, as you could probably manipulate how the Boost ramps in by controlling the solenoid.
Torque Mamagement is crazy on this engine, but it has to be in order to bring compliant with emissions I suppose.
The Base DC table should he used sparingly and only after you get your desired boost to where you want it. Use that table to increase or lower your actual boost KPA to match your desired. Make small adjustments and only where they need to be made. Otherwise you will get a heavy surge from the wastegate actuator adding and taking boost pressure.
Set your boost limit max table to what you want as far as boost pressure.
The Knock Airmass table will 'cap' the Cylinder airmass. I'm guessing that this table is there for the ECM to limit boost by looking at airmass. If, for example, you have .8 in the 0* field, and conditions are right (boost, timing, fuel) enough to exceed that, then the ECM will pull throttle.
Be careful with the pressure delta table. If you add to much down low then the turbo will build more boost than it should at lower rpms. That doesn't sound that bad but for example, if you're trying to pull a hill in 6th gear it'll start building boost to make plenty of power. Then you let off a little to keep from accelerating to much and you can literally feel the engine bounce from one side of the mounts to the other.
That's what I've learned from re-tuning mine here recently.
There's another table, I'm not sure how it comes into play exactly but I set mind a little higher than the desired boost. In the Turbocharger section of TM, the Pressure Ratio Max, I set it .1 higher than the KPA in the boost max table. Such as ... 2.1 where boost max is at 200 kpa. (not actual numbers).
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