Considering 2008 LGT Limited

[SWP-LegacyGT]

And this doesn't tell you something about the worthiness of SI-Drive?

you mean worthlessness of it?

 

It's going to be interesting to see what cobb does with it. Also the throttle control is a LOT better on the '08's that it is on the '07's. Go figure.

[wags528]

you mean worthlessness of it?

 

It's going to be interesting to see what cobb does with it. Also the throttle control is a LOT better on the '08's that it is on the '07's. Go figure.

 

yeah, im anxiously awaiting that . . . i will purchase an accessport as soon as they have maps for a 08

 

also, I FULLY agree with BigInALegacy - - SI Drive is a quality feature and makes driving the car that much more fun

[SWP-LegacyGT]

SI-Drive in the 5EAT's along with the improved throttle control is a step in the right direction. It'll be interesting to see what happens in '09/'10 with the Legacy platform.

[Crawdaddy79]

you mean worthlessness of it?

 

No, I mean worthiness. I do not know enough about it to say that it's worthless. All I know is that in using it, I don't see the point. I'm very open minded to see any advantages it has other than giving an impression of being more powerful by giving you 50% throttle at 25% pedal push in Sport Sharp mode, and more fuel efficient by giving you 10% throttle at 25% pedal push in I mode.

 

I know that I get no better mileage in long trips with I mode. I will admit that I get slightly better city mileage but that's because you're just about forced to be lighter on the gas pedal in moving from a stop.

 

At a steady throttle (gas pedal down equally through all 3 modes), try changing the modes, you will certainly notice a difference in power output through all 3 modes at the same throttle level.

Oh I am familiar with that very much. I use when I complain about engine response, and someone says that it's turbo lag - and then I ask well why is SI-Drive more responsive than my gas pedal? No one really knows what I'm talking about at this point so I usually drop it.

 

You need to know your gas pedal is nothing more than an electric analog "controller" for your actual throttle opening. When you say "same throttle level" it's not really a throttle level - just where you have your foot on the pedal. The throttle level instantly changes when you move the SI-Drive knob.

I mean, just look at the graph on the dash and you'll see what I mean. It clearly shows exactly what I just explained. When that line straightens out at it's peak, that's your powerband.

 

Sorry but I don't trust that graph for anything.

[turbo427]

I have had my 08 5EAT for about month now the SI is nice but not anything great unless COBB can make something cool, gas doesn’t change just limits your throttle if you keep your foot out of it, will do the same thing. Would be happy with good throttle response The I is so sluggish, but you only get 40% throttle in I drive, I drive in S mode and manual shift.

[BigInALegacy]

You need to know your gas pedal is nothing more than an electric analog "controller" for your actual throttle opening. When you say "same throttle level" it's not really a throttle level - just where you have your foot on the pedal. The throttle level instantly changes when you move the SI-Drive knob.

 

 

Sorry but I don't trust that graph for anything.

 

 

Exactly my point, it changes the amount of throttle response in relation to your gas pedal. So right there is a difference.

 

And as far as the graph goes, it might not be 100% perfect, but even so it gives you something to compare what the different modes offer. Say Intelligent is a 'benchmark' if you will, it's saying that with the other modes, the ECU/engine is tuned to give that much better performance in relation to that graph. Each of those drive modes had to have been measured on the same scale, so even if you don't think it's an accurate representation of performance, think of it as a guide to how the driving modes differ from each other. For example, when they benchmark PC video cards, they compare them on a level scale (benchmark), how they stand up against each other. At the very least this is what your getting with the graph.

 

And I have to say I think the graph is pretty accurate. If you use the X axis (left to right) as horsepower, and the Y axis (up and down) as RPM, it's pretty darn close. In I-mode, you don't get all the power, and it shows in the graph. The plateau is halfway down the Y axis. In Sport-mode, the horsepower goes up to the max, according to the graph, and the powerband kicks in halfway through RPMs. This is accurate while driving because she jumps at 3000rpm. Same with S#-mode, on the graph you get to the plateau immediately, which while driving is also true.

 

IMHO the graph is a very good representation of the different driving modes.

[Natheya]

Kind of funny how people are buying aftermarket ECU units yet they dont understand how or why SI drive works.. It does.. There is a difference.

[Crawdaddy79]

But what does it do that causes the difference?

 

From Subaru this is all I could find:

Operated by the driver from a rotary dial mounted on the center console, this three-mode performance management system controls engine variables to deliver a range of acceleration characteristics. SI-DRIVE is like having three engines in one.

 

I found some more information HERE, but from there all it says in many words is more power sooner because of a more aggressive throttle response.

 

And then there's this graph that I can't figure out where the source is - what data they used to get it.

 

http://www.crawspace.com/web3/si_graph.jpg

 

It goes against the dyno results someone posted by showing Sport Sharp having more power than Sport.

 

I'm sending World Car Fans an email asking where they got that "data". It looks pretty vague.

 

My theory about SI-Drive so far: Basically if you want Sport Sharp and you're in Sport mode, just give it more gas. In I-mode it aggressively limits the maximum throttle, thus producing less horsepower than Sport and Sport Sharp. The far less responsive fuel engagement forces you to drive like a grandma, therefore you use less gas and it's more fuel efficient. I don't think it changes any engine characteristics to produce any of these effects.

[BigInALegacy]

controls engine variables... that means it changes aspects of the engine... so again that provesmy point. things like air:fuel ratio for example.

[Crawdaddy79]

Limiting maximum throttle is an engine variable.

[BigInALegacy]

exactly, so these are the types of things that change when switching SI drive. Sure if you mash the gas in Sport it might feel somewhat close to S#, but the fact is in S# you would have been going way faster if you'd mashed the gas the same because of the different 'engine variables' for different modes. Those things like maximum throttle, turbo spool, air:fuel ratio, etc. etc.

[Crawdaddy79]

WorldCarFans.com got back to me - apparently that graph is from a press release from Subaru. They don't know where Subaru got the data.

 

So now, I'm going to contact Subaru. http://www.crawspace.com/web/type.gif

 

 

PS: I had a closer look at the graph in the car. It has nothing to do with RPMs of the car, but instead everything to do with your gas pedal movement.

[BigInALegacy]

Well please let us know when they get back to you, I'd love to hear their take on this!!

[Crawdaddy79]

Well that was fast.

 

Thank you for visiting the Subaru web site and for your message!

 

The SI-Drive feature allows the driver to control engine variables and transmission variables (when equipped with automatic transmission) which change the response and power characteristics of the vehicle. The ECU or Engine Control Module contains hundreds of variables which are programmed into its memory.

 

There are three separate maps, with different variables. We do not have information on exactly which variables are modified, but as explained in the document in the link you provided, they each allow for a different driving experience and fuel efficiency. I assume that the main variables are ignition timing, fuel delivery, shift points, and throttle control. I am sure there are dozens of other variables also affected.

 

Fuji Heavy Industries, our manufacturer in Japan, researched and developed this system with testing on everyday roads, testing tracks, dynamometers, etc. Based on their results, they were able to provide the information in the press release to the public.

 

The graph is an illustration, not an exact reproduction of the proprietary graphs developed in the testing process, to illustrate the power curve for each mode. The Sport# is more peaky, the Sport is more linear, and the Intelligent is flatter. We do not have the actual proprietary graphs from Fuji.

 

Really, this feature is not much more complex than what is explained in the press release. Thank you for your message and if you have any other questions, do not hesitate to reply to this email.

 

Heh - even they don't know what SI-Drive does exactly.

[BigInALegacy]

That was probably answered by a "web mail representative", hence the lack of superior knowledge (and the ultra speedy response). But it pretty much restates everything I've already said.

 

Send another one to Fuji Heavy Industries... ask them what some of these "other" variables are. If they're the ones that built the system, they oughta know more. It would be cool if Sport Tuner or some magazine did some testing of their own on this!

[Natheya]

Sounds like the average response at many companies after deciphering explanations from most engineering departments.

[turbo427]

New Subiesport magazine has a piece on 08 LGT they did a 100 hp build, ECUTeck did the tune and they are using the S# for race fuel mode, it all has something to do with the new system CANbus it like a network that connects the different OBC sound cool, would love to be able really use the SI

[BigInALegacy]

Found this while searching the web.... they're talking about the SI-Drive in '07, but just abother tidbit to add

 

here's the full review for those who care:

http://www.thecarconnection.com/Vehicle_Reviews/Sportscars_Convertibles/2007_Subaru_Legacy_GT_Spec_B.S184.A10483.html?pg=2

 

Subaru's system, at least so far, only affects the powertrain. Intelligent mode cuts off about 20 percent of overall power and torque, lowers boost and smoothes it out, and is designed to feel much like the normally aspirated 2.5-liter engine. The mode has the gentlest throttle tip-in, and is to be used for more economical driving or in slippery conditions. Sport mode then allows full engine power, and a more linear response leading up to it, with a slightly more aggressive tip-in than Intelligent. Finally, there's Sport Sharp (designated by an S# on the dial), which changes the throttle attitude to be very aggressive, with full power and boost available earlier - with some smoothness sacrificed. Subaru officials said that S# won't bring faster raw acceleration times, but it would improve times during maneuvers that require lifting off the gas and getting back on it quickly. There's much less of a difference between S and S sharp.

 

While SI Drive doesn't actually boost the engine's peak power or torque, it does allow quite different driving experiences from the same car. In our Spec.B test car, we noticed that when making a gentle standing start, throttle/clutch coordination was improved in Intelligent mode, and the car was easier to drive smoothly in the lower gears; while at the opposite end, in S# mode, the six-speed was very difficult to drive smoothly in the lower gears due to the on-off nature of the throttle.