Throttle Linearity Settings
 

I would like to discuss what tables and settings in the ROM can be modified to effect the throttle linearity or how throttle pedal % equates to throttle plate opening %. I currently feel like I have a much too ramped up throttle setting where 50% throttle pedal input feels much closer to 100% throttle opening. I know that we can log two different Throttle/Accelerator %s in EcuTek and is there anyway to look at those and determine a throttle curve to see how linear it is? The end result is I want a perfectly linear throttle response. I doubt the OEM/Stock throttle mapping is perfectly linear, and I know my current one isn't.

The most obvious answer is the requested torque tables for the throttle drive-by-wire:

Stock:
http://i.imgur.com/Onc3bdm.png

Shiv's current ROM:

http://i.imgur.com/tzYamop.png

you will find if you actually make the pedal to TB a direct correlation that 50% is essentially the same as 100%

As with most modern engines the TB is simply WAY TOO BIG for the actual airflow demands...

For example, I have a S13 track slut, it makes 450hp 390 ft lbs, I have a ~70mm TB on that car...after ~60% you achieve the same exact power curve as WOT. I use this range to setup boost VS TPS...works great

Alot of people complained early on that the throttle pedal wasn't linear in the twins...so it is likely that alot of the tuners "linearized" the pedal VS throtle tables...but as described earlier the valve (Throttle body) isn't effectively throttling the airflow anymore.

and yes i 100% realize that didn't answer any of your questions...sorry

Is that related to the torque dip (I know, two peaks) to the right in the first pic?

It looks like a contributing factor. Fixing this table to be more linear is one of the more obvious changes required to address the dip. As you can see Shiv's is much more linear.

- AdrianG

This is a great thread to get your head around how the DBW tables interact:

http://www.romraider.com/forum/viewt...hp?f=15&t=7960

I bet if I tracked down the part numbers the FA20 N/A motor and the FA20DIT turbo motor by Subaru uses the exact same throttle body so they can reduce production costs. They'd just be using the DBW control to make up for the difference between applications.

Yes, I would be surprised if that wasn't the case.

However, a TB flows a volume not a mass...so even at an increased pressure ratio the TB is still larger than it needs to be given the displacement and VE of the motor

The problem is that all those threads mostly focus on how the tables work with the OEM Subaru boost control and WGDC which most of us even with aftermarket turbo kits don't utilize. I would really just like to see what other people are running for tables on BRZs and how linear they feel their throttle response is.

That's a big difference from stock. Can you give us further written analysis of the differences between stock and shiv's tuned throttle maps?

Can someone explain to this noob why there are two tables, A and B?

Does the fact that the tables have 16 columns imply the throttle only has 16 positions, or the ECU does interpolation?
:thanks:

What does the ECU do with those requested torque values?

Tut, thanks for starting this thread.
Skull, right on.

DriveByWire is my #2 most disliked design on our platform.
I'll be watching.

I'm still learning myself, so this is probably a shitty explanation.

Calculations are run using values in other tables to calculate engine load, which is then used in calculations to determine all the right settings for each part of the fueling, intake, and exhaust system. Engine Load is related to throttle position (along with a bunch of other variables no doubt) and then Engine Load and RPM determine which values are used from the tables for things like Intake & Exhaust Cam Retard/Advance angles, Ignition Timing, Fueling targets, etc etc.

RomRaider can see ~328 tables at this time, and I wouldn't doubt there's more that haven't been added to the definition yet. It's a big complicated beast to wrap your head around. Luckily we have our factory ROMs as well as Shiv's open maps so we can identify the areas to focus on.

When I run a comparison on a factory ROM VS Shiv's latest release, it identifies 39 tables which are not equal. This is my starting point to compare differences and learn why those differences improve the car's performance.


http://f.kulfoto.com/pic/0001/0042/ru20U41175.jpg