SI drive and Tuning

From my understanding so far, the SI Drive is basically a change in timing for each setting… is this right?

So here’s my question, it may be stupid but I’m not very knowledgeable about car computers and I’m hoping to learn some new stuff: did some looking and haven’t found anything on this yet.

What will a tune do to my SI Drive? Will it essentially increase the timing for each setting or can each setting be tuned separately, kinda like an access port?

For instance: say I have my car dyno tuned in the sport sharp mode for a performance tune. When I change the setting back to sport or intelligence mode, after the tune, will it just decrease the timing for sport and intelligence modes? Or will sport and intelligence mode still have the stock setting…?

I’m assuming a tune will change all three modes by a certain amount of timing but will still allow for a decrease or increase in performance depending on the setting…

Hope this make sense. Any thing helps, Thanks in advance.

SI drive is a change in throttle mapping and requested torque (and thus boost). Nothing else. Timing and fuel delivery stay the same across all 3 modes.

si drive controls throttle angle (electronically) and boost (electronically) by throttle angle

tuning the ecu will have no effect on the si drive

changing the throttle mapping will have effect on power. what will happen is "i" mode 100% pedal = 60% throttle angle, and so on. thats how power is effected

I was almost 100% positive that SI Drive changed requested torque values, as well.

 

Throttle angle alone doesn't control boost.

si drive controls throttle angle (electronically) and boost (electronically) by throttle angle

tuning the ecu will have no effect on the si drive

changing the throttle mapping will have effect on power. what will happen is "i" mode 100% pedal = 60% throttle angle, and so on. thats how power is effected

 

Almost. As i understand it, these cars set throttle plate angle by requested torque. The RT value is a function of pedal position and rpm. There are three 3D tables to supply those RT values, and those correspond to the Si-Drive selections.

Note that in these later ECUs, boost control is also mapped via RT vs. rpm, meaning Si-Drive affects both throttle mapping and boost control. Even though there only the usual one each initial and max. WGDC tables, the different RT values from switch selection mean different parts of those tables come into play.

 

Hope that clears it up.

Short answer: nothing that you can't do with your foot.

Short answer: nothing that you can't do with your foot.

 

Haha. I hate the factory throttle mapping in Sport# with a passion, at least on the STi. Nothing but smoke and mirrors at the expense of pedal resolution.

 

Bear in mind that the Si-Drive selections can effect boost control so you can use them to set up low, medium and high boost maps. While the stock implementation leaves a lot to be desired, the system itself can used to some advantage.

So to put it in simple terms the SI Drive controls the amount of boost (low, mid, high) and the amount of fuel delivered to the engine or is it the rate in which fuel is delivered to the engine, based on the throttle angle…?

In relation to tuning; if the SI Drive doesn’t control timing for the car and the tune does; the car will essentially perform slightly better/different then stock in all modes due to the timing adjustments from the tune, correct??

Also, will it matter which mode I have the SI Drive in when I get the car tuned? Meaning if I have one performance tune done in Sport Sharp will the SI Drive have to be in Sport Sharp to get the benefits of the tune? Does this make since…. hope so thanks for the info!

So to put it in simple terms the SI Drive controls the amount of boost (low, mid, high) and the amount of fuel delivered to the engine or is it the rate in which fuel is delivered to the engine, based on the throttle angle…?

 

Not really. See the very first reply. That's what SI drive does.

 

In relation to tuning; if the SI Drive doesn’t control timing for the car and the tune does; the car will essentially perform slightly better/different then stock in all modes due to the timing adjustments from the tune, correct??

 

SI Drive doesn't alter the tune at all. There is only one air/fuel/timing map. SI drive just tells you what the throttle response is going to be, and limits boost based on the RT value.

 

Also, will it matter which mode I have the SI Drive in when I get the car tuned? Meaning if I have one performance tune done in Sport Sharp will the SI Drive have to be in Sport Sharp to get the benefits of the tune? Does this make since…. hope so thanks for the info!

 

Again, when you "tune", you are tuning air/fuel/timing. As long as you aren't in I-mode, it doesn't matter.

Again, when you "tune", you are tuning air/fuel/timing. As long as you aren't in I-mode, it doesn't matter.

Sport can be considered the normal mode. "i" uses a pedal angle table which has low values for requested torque... so low that 100% throttle plate angle nor peak boost cannot be reached. The Sport# tables have the same maximum requested torque values as Sport but the shape of table is more aggressive and less linear.

 

As BAC5.2 states, tune is independent of mode. Timing and target AFR are calculated by load and rpm, plus or minus some compensations. While Si mode selection will result in different loads being seen at the same pedal input, the mode selected doesn't affect timing or fuel directly.

If you read a little on how the DBW system works it will help you understand.

 

In practice it seems normal to tune in Sport mode and then verify Sport# doesn't provoke any overboost or fuel cut where the throttle mapping is more aggressive. At least this is my approach.

From what I've read, very simply put:

 

I: When throttle is applied, the SI drive reduces by a factor (half I think), the actual amount of throttle requested and reduces peak boost by 20%. Intended to make for 'smoother' driving dynamics and better fuel efficiency

 

S: is 'normal'

 

S#: exaggerates throttle inputs by a certain factor (2X?), thereby giving the feeling of quicker throttle response.

SI drive does not directly alter boost.

Right, basically SI scales back the input to the boost table, which is either throttle or requested torque, depending on model and year. On some cars the boost tables have throttle and RPM axes, on some cars the axes are requested torque and RPM.

 

Either way, the net effect is that at full throttle pedal, you get less-than-full throttle plate opening, and less-than-full boost.

 

...which you could also achieve by not pressing the throttle pedal all the way down in the first place, hence my previous comment.

SI drive does not directly alter boost.

 

I agree, but it can and does alter it indirectly. I'm not looking to contradict you, just explain things more clearly.

 

The boost target table is 3D, the axes are engine speed and requested torque. The WGDC tables are 3D and have two axes, one is engine speed and the other is requested torque. In the stock tunes I'm familiar with the "i-mode" throttle maps call for far less requested torque even at 100% pedal angle than the other two. In i-mode the requested torque is never a high enough value to allow 100% throttle plate angle or enough WGDC to reach the maximum boost in the (one and only) target table.

 

Si-drive modes do not directly control boost, but boost is controlled by requested torque and Si-drive modes do change requested torque.

Ok, I get that SI Drive does not “directly” affect boost, although, it inadvertently does by changing throttle mapping and requested torque; or how ever anyone wants to word it. I also get that SI Drive has nothing to do with a tune. Furthermore, I understand that a tune does control air/fuel/timing.

I’m not trying to be super specific as much as I am trying to have a general idea. I’m also just wondering what mode to have the car in when it is tuned as some have answered; i.e. not in “I” mode and recommended in Sport (considered normal mode) with verification that Sport# doesn’t provoke over boost or fuel cuts. I will leave the rest to the tuner! Thanks for the info!

It's pretty much a gimmick in OEM form. Your tuner can adjust each mode to hit different boost targets, or different throttle input for the same boost levels.

 

I set mine up so that I-mode is waste gate boost only, S-mode hits around 17psi and S# hits about 19. All modes are about the same as far as throttle input and much more linear than the stock setup.

It's pretty much a gimmick in OEM form. Your tuner can adjust each mode to hit different boost targets, or different throttle input for the same boost levels.

 

I set mine up so that I-mode is waste gate boost only, S-mode hits around 17psi and S# hits about 19. All modes are about the same as far as throttle input and much more linear than the stock setup.

Agree, the stock implementation is gimmickry on the scale of push-button start. The saving grace is it that can be used for good purpose, given the right strategy.

Wow, the search function seems like it actually worked - maybe...

 

I was going to ask how driving an SI Drive car versus driving non-SI Drive car compared. Meaning, what "setting" (I, S, S#) a non-SI car felt like while driving.

In reading this thread it seems like they are the same in 'S', and in 'S#' the SI Drive just makes the throttle response feel faster - as if you pushed the gas pedal down faster on a non-SI (regardless if it is possible for a human to push it down as fast) with 'I' being somewhat inverse to that. Am I correct in thinking that?

That is the dumbed-down version, I know it is not technically accurate.

Subaru seemed to keep the RT in sport and sport sharp the same(350), just with a different transition grade. I mode has much less RT at wot. What I'm saying is the transition to wot is not linear. note the attached pic

axis