Si Drive & the Track

I'm new to Subarus and you guys are helping me learn a lot. After some quick searching on this I couldn't find an answer to my question.

 

Since the Si Drive is just a throttle map as I understand it, and "sport" mode allows 100% throttle when the pedal is all the way down, does it make sense to use "sport" and not "sport #" when racing? More pedal travel to achieve 100% throttle would in theory give you finer control of throttle modulation.

 

Or does "sport #" do something else besides just a throttle ratio?

maybe if you have very powerful NA or tubro car with anti lag On stock to stage 2 setup there will always be a lag in overall reaction time, especially turbo so I would say anything that can actually minimize ratios, pedal travel, reaction time would be much preferred.

also applies to the LGT:

http://i48.photobucket.com/albums/f215/spaceman838/4e603420.jpg

This is a good topic... and I've never seen that graphic before. Interesting. So how does S# provide "greater torque at lower engine speeds"? Ehhhh?

 

I drive mostly in S#, because it's fun... it doesn't provide "close to the feel of an Impreza WRX STI," but it's getting there. However... for the track... would S not be the better choice? Anywhere that greater throttle control/feathering the pedal is desired seems like would be more appropriate in S.

Would you want to use the full pedal range to feather throttle or, since you are already very used to S#, use the 54% travel to feather the throttle?

 

A personal choice.

Use S if the track is wet, or maybe if its your first time ever on track.

Use S# if it's dry.

Use i if you're driving on snow/ice.

 

Your idea of how SI affects throttle mapping is slightly off. It's not 100% pedal = 100% throttle, 50% pedal + 50% throttle. That linearity depends on your tune. What SI does is limit how soon you get max power at each RPM. At 2.5k rpms, 100% pedal may give you 60% throttle in S, where in S# it may give you 75% throttle.

 

Next time you're getting on a freeway on ramp, shift into 3rd early and push the pedal down to the floor from 2k rpms to 6k. Do that once in S and once in S#. You will hit a higher boost sooner in S# than you will in S.

 

Now translate that to the track, and you will lose around .5 seconds per turn because there's about that much WOT delay between S and S# after you straighten out. This isn't a RWD Ferrari that is oversteer happy if you're a split second too quick rolling on the throttle, you have a spec.b. with a torsen rear diff AND traction control.

 

If you're worried about safety, traction control will take away throttle response mid turn if you're going too fast (very annoying). If you're trying to theorize which is faster, the benefit of having an AWD car AND having the torsen rear is that you can put more power to the ground sooner during turns. Driving in Sport mode will mute the top 2 benefits of driving a spec.b. When you get to know the car better, you will actually need the throttle to help your car rotate and turn (throttle oversteer), and Sport mode will make that harder as well because of the muted response.

Would you want to use the full pedal range to feather throttle or, since you are already very used to S#, use the 54% travel to feather the throttle?

I suppose--although to say I'm "already very used to S#" is probably a stretch when I'm not even used to stage 3... but I'm not the one asking, anyway. I'll just do whichever feels right. That's the beauty of having the button right there on the steering wheel.

What SI does is limit how soon you get max power at each RPM. At 2.5k rpms, 100% pedal may give you 60% throttle in S, where in S# it may give you 75% throttle.

 

So you are saying that it is more than just a ratio and that there are maximum throttle values for a given RPM?

A traditional cable throttle can provide 100% throttle at 500 RPM, but the SI drive is programmed to limit maximum throttle based on the RPM, and it is not just a pure function of how far depressed the pedal is?

I think it might actually be more accurate to say that "max throttle" or "WOT" as the commonly used term here in subie land, has a different effect on the car depending on i/s/s#. s# will have a higher requested torque value (more power) sooner in the power band. That is what the graph that SLA posted earlier.

 

Going back to your original questions:

1) It does not make sense to use S over S# on the track in HPDE's, it will not help you get faster unless you are racing on a slippery surface.

2) Using electronics (the si mapping) to get better pedal modulation will not help you get faster. Use your legs to get smoother pedal modulation for both gas and brakes.

3) I do not know what you mean exactly by throttle ratio. The graphic that SLA posted pretty much explains as clearly as possible what the different modes mean. The key take away from that graph is that under WOT at 3k RPMS, you will get more power (torque) in S# than you will in S. Why? Because S mode takes away torque from you, even if you are 100% throttle. It's not just a function of how far the pedal is depressed.