legacycentral bbs

People have been saying this around here lately.

What the hell is the power light/mode?

I think its mainly in or only in 4EAT when you jam on the accelerator it lights up and makes the car go fast and pull harder, also drops it into a lower gear.

Ahh, like a power button in Saturns eh? Lights turn on and make you think you are going faster?

My power button is the clutch

Like that, but this light actually makes you go fast, well in the turbo at least, when this light kicks on you get mashed into the seat

yeah it's a 4eat thing only. I'm not sure if newer 4eat's have them still or not. It doesn't make you think you're going faster it makes you go faster. It switches from regular mode to an aggressive map. It's based on how quickly the tps changes I believe. Most the time it'll downshift to a lower gear but not always. It's basically like adding a few psi of boost

LegacyPunk555 wrote:Like that, but this light actually makes you go fast, well in the turbo at least, when this light kicks on you get mashed into the seat

in any 4eat

Yeah, a lot of cars with automatic transmissions have this functionality. Most of them have a switch you can switch between "power" and "economy." Subaru just decided to have the TCU guess when you want "power" mode instead of making it determined by a switch.

From what I hear, the Nissan 4-speed electronic automatic transmission from the same era is pretty much the same as the FWD Subaru 4EAT, and it can do the same thing (although it still has a switch).

Ahh. So I can downshift any time I want and be in "power" mode, and the 4eat has to floor it and wait until the light comes on?

well it's not simply a downshift, it's actually a more agressive shift map. There is no power mode on a manual transmission. You have no tcu to control it. Picture it like this, (all made up numbers) in normal mode you can accellerate from 0-100 in say 25 seconds in power mode it'd be 15 seconds. The light comes on instantaneously so long as you change the tps position quick enough. You can activate power mode going from closed-wot or even closed-half throttle or less. You can even go to power mode from half throttle-wot if you do it right. It will only downshift if it needs to and the gear you'd be downshifting to has enough rpm left to warrant the change. Like it wont downshift to 1st if you were cruising at 35 and activated it. That's only like a couple hundred rpms left in 1st.

Also I believe there were ford 4eats like this aswell.

That is how ALL automatic transmissions will operate. Floor it, and it downshifts. That is standard operating proceedure. You floor it, and it will shift within parameters set by the ECU and based on vehicle speed and engine RPM, it will swap gears accordingly.

Ford's auto trannies are adaptive learning. You disconnect the battery and drive around at WOT a lot, it'll hold gears longer in the rev range than if you grandma'd around. Solely a comfort feature rather than a performance feature.

It seems as if Subaru's "power mode" is simply another name for "performance mode" which does nothing other than shift closer to the concrete parameters of the ECU. Now my REAL question is, does Power Mode do anything other than adjust shift points? Does it alter fuel maps? I don't see how it would really do this, as fuel delivery should be set by RPM and airflow, not by whether a switch is turned on, or a power mode is engaged. Doesn't seem like Power Mode is anything other than a standard proceedure that the car should be doing anyway.

Power mode doesn't change anything about the engine. It's entirely contained within the TCU. So, clearly, the only thing it can affect is shifting.

There's a difference between power mode and kickdown, though. Kickdown, which pretty much all automatic transmissions do, is just a downshift when the throttle is almost fully open. Power mode, like THAWA said, can be engaged without even getting close to full throttle.

If I recall correctly I used to be able to get my automatic BCs to kickdown without engaging power mode, if I didn't press the pedal too fast.

You're right, though, that "power mode" is another name for a feature many automatic transmissions do have.

yes vikash it is possible to have the car downshift without going into power mode. I've done it too many times to count.

Toyotas have this too. When my Celica was an auto i could hold the shift all the way to redline with the ECT power button on, where the regular mode would make the car shift 5-700 rpms sooner. It also increased the line pressure in the transmission, making the shifts quicker and more firm.

So basically, it's just a light that really doesn't mean anything as "power mode" is nothing spectacular and has no performance gain.

no, it changes shift maps to allow for better accelleration.

yep if i ease on the gas it shifts at 3k but if mash on the as it shifts at near redline in my 95.

Lol, but EVERY automatic transmission does that Hardy. Some have adaptive personalities, like Ford, where if you see WOT a lot, it keeps aggressive shift maps on call and almost always turned on. Some are standard and will touch near redline on every WOT pull. There is nothing that the "power mode" can do that will improve acceleration beyond what any transmission will do. There is no added performance (i.e. fuel map changing), so all it does is move around a shift point. At WOT, this is exactly what a transmission does.

I've only gotten my power light to come on a few times, but when it does, its more than just a downshift. It shifts/drives a whole lot harder than when its in normal mode.



Kevin

Phil, nobody's saying "power mode" is unique to Subarus. It is indeed something that all well-designed modern automatic transmission control systems include. BC/BFs just tell you when it's engaged, that's all.

It's not as simple as WOT kickdown, though. Power mode allows for spirited driving even when you're not at wide open throttle.

ahh, ok, that's what I was thinking (exactly like ford's adaptive system).