I've been spending some time trying to learn about tuning. I'm even thinking of starting up a little website of techinical information that is easily available to the public. It's not up yet, so I thought I'll post it here and get some opinions. Someone asked me what SI-Drive does after I told them I was trying to learn about the ECU with my open port cable. I never saw a good (or decent) post on any forum that had any example. So I threw this together really quick. This is the "almost"-complete story of how SI-Drive works. I've spent quite a bit of time looking through the tables that I pulled out of my 09 STi, and discovered all the wonders of SI-Drive... **If you have a hard time focusing on large charts with many numbers, really just try to read the text in the examples lightly. The charts are there for my support/evidence The Requested Torque Map Starting with a table that describes one of the modes, here is the "Requested Torque" map for the SI-Drive Sport mode. You don't have to remember anything, it's just to give you a taste. Now would be a good time to explain Requested Torque: Requested Torque is pretty much a "theoretical"/magical number of torque you want to try to get out of the engine. It isn't meant to be a literal number of torque you are expecting. Which may seem weird, but it is perfect for situations like this (SI Drive). You will understand why in the examples below. It may also help to understand where this number is used. The first and most important table that references this "theoretical torque" is the table that controls the throttle plate position. The second table is the "Target Boost" table. Both accomplish exactly what they sound like they are trying to do. Before I try to give a full example of what happens in the same situation but in the three different modes, it's slightly worth noting that you can set the top speed limiter to a different speed in each mode. This is so useless that Subaru has even set them to the same speed... What the difference is Let's start..You're driving around in three different SI-Drive modes. You slam the accelerator to the floor. Sport@3600 RPM: We look at the requested Torque for Sport at 3600RPM and we get 428.9 at 100% pedal (to the floor). The "Requested Torque Base" table shows so we take the number 292.0 at 3600 RPM. We use both the requested torque and the base torque and compare it to the "Target Throttle Plate Position" table. 428.9/292 > 1.000 so the drive by wire system opens the throttle plate 100% Now that we've got our throttle open all the way, the computer checks how much boost we want. 428.9 >380 so we get 2.013 bar as our target boost (+atmospheric) so 14.50 psi Summary: Throttle plate fully open, 14.50 psi of boost and all the fuel/timing needed based on the boost only Sport Sharp@3600 RPM: We look at the requested Torque for Sport Sharp at 3600RPM and we get 428.9 at 100% pedal (to the floor). The "Requested Torque Base" table shows so we take the number 292.0 at 3600 RPM. We use both the requested torque and the base torque and compare it to the "Target Throttle Plate Position" table. 428.9/292 > 1.000 so the drive by wire system opens the throttle plate 100% Now that we've got our throttle open all the way, the computer checks how much boost we want. 428.9 >380 so we get 2.013 bar as our target boost (+atmospheric) so 14.50 psi Summary: Throttle plate fully open, 14.50 psi of boost and all the fuel/timing needed based on the boost only I KNOW WHAT YOU'RE THINKING! That I just copied and pasted those numbers!...well I did , but that is in fact the Sport Sharp map. About this time you might want to look at the "100.00" pedal angle column on both maps and compare the numbers. You'll be just as disappointed as I was. (you can also wait till the Full Conclusion section to see them next to each other). Intelligent@3600 RPM: We look at the requested Torque for Intelligent at 3600RPM and we get 319.9 at 100% pedal (to the floor). The "Requested Torque Base" table shows so we take the number 292.0 at 3600 RPM. We use both the requested torque and the base torque and compare it to the "Target Throttle Plate Position" table. 319.9/292 > 1.000 so the drive by wire system opens the throttle plate 100%......... /facepalm Now that we've got our throttle open all the way, the computer checks how much boost we want. 319.9 (we'll round to 320). So we have 1.573 bar as our target boost (+atmospheric) so 8.12 psi Summary: Throttle plate fully open, 8.12 psi of boost and all the fuel/timing needed based on the boost only If your eyes are stinging because of too many numbers: IN SUMMARY, With your foot pushing the accelerator against the floor there is NO difference between Sport and Sport Sharp if you ride it throughout the entire RPM band. In intelligent, at full pedal it is trying to give you maximum power...but for only 8 psi. **Technical note (covering my ass): There's much more involved because the intelligent mode has just requested less boost and so less fuel is needed. So it technically isn't as simple as setting the boost lower....but it is. Also, if you take the SI-Drive from one of Subaru's other vehicles, that has an Automatic transmission...You will see that they claim it improves shift response too. This article is for my 2009 STi...sorry, only got enough time for one vehicle at this time. Full Conclusion: So at full pedal to the floor action. There is no difference in Sport and Sport Sharp. However, look at the two maps next to each other and you can see why they say it "improves throttle response": because it does. It essentially just gives you full throttle even if you have the pedal down 2/3 the way. Lower than ~70% it does give you a little less boost but still full throttle. At around 50% pedal (it becomes similar to intelligent mode), you have your throttle plate open fully, but are only requesting about 7-8 psi. You should now completely understand why SI-Drive Sport # feels like you just instantly turned on the power. You can even recreate this feeling in Sport mode, just slam your foot obnoxiously to the floor every time you want to accelerate.... If you see anything wrong in this quick article, call me out. I'm learning...But I wouldn't have posted if I didn't believe I was 95% sure. I don't really have too much to reference for this either, I learned 90% of this from staring at a map I pulled out of my car. The rest I learned from the "An Intro to Subaru Tuning" by Bad Noodle. Also remember I'm trying to give a quick description of SI-Drive, not a full description of the ECU...yet.
I love this stuff in a street car but its the first thing I want taken out of my track cars. To much B.S. going on
it's almost like traction control, but with fuel/power. you don't have to think and you'll get better MPG . But you can drive around in different modes and accomplish the same with just controlling your foot
When you tune a car with SI drive, how does that work. Does the tune overwrite one of the modes? You could keep your intelligent mode for economy and then have the killer SS or TS (Doug) tune to change to?
one of many new 'features' subaru is introducing to compete with acura and the like. not a big fan but +1 on taking the time to delve into it. thankfully my right foot decides my boost and throttle response.
some different tables, specifically ignition advance and target boost. you can however overwrite and fiddle with the modes and effectively get rid of the SI drive options AFAIK (ie they all act the same). I'll let doug or sarge chime in here though
Drivers aids like this do nothing but promote bad driving habits. I'm not a fan of most drivers aids, people should learn to drive without traction control, abs, stability control, etc...
You can write over any and all of them. Nicad had it right. I don't think I would get rid of them though. Might as well leave the option unless you just hate the idea. I kinda feel the same though...I let my foot control boost and economy. Nice write up though!
turning to Sport # has become habbit...I also think "my foot" gets better MPH in Sport # Very Very nice write up my friend...and nice tail lights
yea there's something magical about turning the dial to Sport # when youre about to get on the highway lol...i catch myself doing it even though i know better. never use "intelligent". and i think i might put some JB weld or locking screws on my tail lights before the next time i go out..:squint:
So is the Si drive programmable? It looks like there might be some pretty awesome possibilities with boost control to keep traction.