DIY DBW

[coyote]

I keep seeing people talking about DBW, be it lag, signal amplifiers or tuning.

DBW is really, really simple to learn, really time consuming and really hard to get right * ... but probably a good thing to start with if you want to ease your way into tuning your own car.

* There really is no right and wrong. Most tuners who charge money and want you to think they've given you heaps of power make the throttle very sensitive, Subaru do exactly the opposite to help you crawl around in traffic. Unlike timing, fuel, etc .. what is "right" for one driver is rubbish for the next.

So, if you have your tatrix cable, installed the software, have downloaded your rom file and are looking at making your DBW just how you like it, ask away.

[coyote]

I good way of understanding what is going on with the DBW is to plot it on a graph.

Below is a graph of the stock SI Drive Sport DBW table from an MY08 GTB.
X axis is rpm, Y axis is requested torque, each line represents a percentage from 0 to 100 of possible accelerator pedal angle.

[Lukovitch]

n00b question: How does lag factor into this?

I understand the response to throttle position bit, don't understand how this can be used to remove the perceptible delay between putting your foot down and the car deciding to do what you asked it to....

[teK--]

There is no lag, it's perceived lag due to the factory mapping. i.e. we're talking a matter of a few milliseconds for the command to be sent from the ECU and for the throttle to respond.

[coyote]

There is no lag

Correct

[Lukovitch]

I figured that since you could remove it by tuning the DBW, it was a result of the factory tune, however I still don't understand how the factory maps achieve this.

You talking about the initial part of the graph and the way it ramps up? What would a more responsive curve look like?

[coyote]

The lazy way is to make the tables completely linear, resulting in a graph this is just a series of straight horizontal lines.

A hybrid between the two is the way to go, but the exact balance is a matter of personal preference.

[senator]

So, if you have your tatrix cable, installed the software, have downloaded your rom file and are looking at making your DBW just how you like it, ask away.

you make it sound so easy..........

[coyote]

I figured most people would find it easier to use a Windows computer than I do.

Note that RomRaider works really well on Linux, you only need to go through the painful process of using Windows for ECUflash and learning view.

[Robbks]

OK Guru's
School me a little on this...
i'm looking at some DBW maps (of an MY07 2.5NA) but the theory would be the same for anything

we have two maps that relate
Accelerator Angle (%) to Requested Torque
and
Requested Torque to Throttle Plate Opening (%)

Now for an example, i'm looking at a 50% Accelerator Angle @ 1600rpm
this sounds like a reasonable way to get the car moving from a stand-still in a timely fashion.
this gives us a torque request of 170 (raw value)

ok so looking to the second table
pick up 1600rpm, go across to the torque request of 170 and we're given a real throttle opening of 66%

again, move up to 60% throttle, which gives a torque request of 175
that translates to an 85% throttle opening.

Now my real question here is why would you not have the maps setup to give a 1:1 relationship between Accelerator Angle and Throttle Plate Opening
I see there's points to fuel economy, but a lot of that can be compensated with the tip-in/ enrichment maps.
On the surface it just appears to be an extra step that doesn't need to be there?
if the driver wants 60% throttle (requested with the accelerator) why not open the throttle plate 60%
I may be missing something completely basic here.

I'm a complete n00b at this, but I can see the DBW maps being my intro to RomRaiding my 3RB. as i always feel that DBW cars are always missing goo throtytle response

And another question.
for us pre-SiDrive owners
does someone have a copy of an 07+ MT ROM that we can use to model our DBW maps on the S# ones.

[coyote]

PM me your email address.

I can probably give you what you're after.

Don't worry if I'm slow to respond, I don't check here much.

[BJ]

Does anyone who has done tuning with Open ECU know how to remove the delay in closing of the throttle in a car with DBW? When you lift off the accelerator pedal the throttle does not close instantly, it stays open for about a second or so which is really annoying. How do I make it close instantly? My car is an 06 3.0RB.

[kiks]

Does anyone who has done tuning with Open ECU know how to remove the delay in closing of the throttle in a car with DBW? When you lift off the accelerator pedal the throttle does not close instantly, it stays open for about a second or so which is really annoying. How do I make it close instantly? My car is an 06 3.0RB.

I dont have this issue, certainly not for a full second. Try being far less smooth with the right foot.

[coyote]

Does anyone who has done tuning with Open ECU know how to remove the delay in closing of the throttle in a car with DBW? When you lift off the accelerator pedal the throttle does not close instantly, it stays open for about a second or so which is really annoying. How do I make it close instantly? My car is an 06 3.0RB.

Except for when running increased idle under startup (choke) conditions, there is no such delay.

Check for a sticky pedal, dodgy TPS, etc ... but it's not in the tune.

[BJ]

I am not the only one with this problem, it is common to all 3.0RBs. The following is from the S&J website, note the no. 1 problem:

Liberty 3.0 R spec B
Public demand has encouraged us to give this beautifully appointed non-turbo 6 cylinder a tune-up.

The three main complaints from owners of these prestigious sports cars are:

■Throttle hanging on after lift off.
■Surge at full throttle.
■RPM limiter is too violent.