Originally Posted by
aaronc7
The limiters can be a little tough-- there's so many of them and different calibrations have some maxed out and some actually use them for some purpose etc. For example generally speaking the Golf R/S3 tunes have many more 'layers' of limiters in place and the GTI/A3 has a lot of these limiter type tables maxed out. Different tuning teams I think, so you see different approaches (which is also kind of neat to look at / compare).
Anyways, to increase boost/power, it goes something like this.
- Torque Management -> Driver Request -> Max torque table is what the ECU requests at WOT
- Torque Model -> General -> TTA converts requested torque to Airmass desired or set point. Spark efficiency comes into play depending on your ign timing, so you'll likely see higher airmass desired than you'd expect, based on the requested torque value alone.
- Airmass desired goes thru the VE model to come to a MAP desired to hit said airmass target.
- Airflow -> Pressure Control - TIP desired -- MAP desired gets converted to TIP desired. Generally nothing fancy here, but this table can act as a limiter too.
- Now you have a basic TIP desired..however there's many other limiters that get calculated and the min airmass/min TIP desired is the TIP desired actual
- Most common other limiter you see used is Airflow -> Turbocharger - Max PR, to set a max pressure ratio for boost.
- Other limiters can come into play, such as turbo speed, charge air temp limits, etc.
You can generally go about tuning in 2 main ways that I've found
- Torque target
- Pressure/boost target
Torque target is kinda what you'd expect, put the 'torque' (keep in mind it's an internal ecu calc, not actual engine or wheel torque) in the request table and that's what the ECU will go for. Nice thing about this is that it will automatically try to compensate for high IATs, higher elevation etc to shoot for a target torque value.
Pressure/boost target, generally the idea is to set your torque request to some value that will result in MAP desired being a little higher than you'd ever want it to be, and generally set the torque request high and constant value to redline (even if you're tapering boost).
Then, use the TIP desired and/or Max pressure ratio tables to "bring down" that MAP desired request to what you want. This maybe is a little more 'simple' approach to things, but many of us like to deal with tuning this way, since we can directly measure MAP/boost and work it that way. Vs torque which is kind of a made up value anyways. There are other tables that you can have the ECU reduce torque target with high IAT etc., so there's ways to make it a little more 'advanced' technique.
And you can layer these approaches too-- that is what the stock tune does. Personally I do the latter- high torque request, bring in my desired boost vs TIP desired and max PR tables. I'm at 4300', so I generally just have it ride the max PR table and my TIP desired table is more of a 'max boost in any scenario' limiter.
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