I love my evo x but i do miss my N54 335i, its a torque monster compare to evo x because of its higher powerband and now they honor 10year factory warrenty on turbo and wastegate problems for the owner so i think its sick car

 

Is this quoted somewhere that's verifiable? What is the STI's max lockup compared to the Evos? How much harder does it lock? What are the pump pressures?

Sounds like snow mode might just need some tweaks. Plus tire choice has a lot to do with snow driving. What tires where on the STI that were so much better?

Just curious since this is the first I heard about the STI having more center diff lockup.

 

Pump pressure won't answer your question because the areas of the centers' clutches aren't the same. And I am going with what I've read (in several places), as opposed to direct knowledge, but what I've seen is 50% max for the Evo (without throwing a code) and about 65% for the STi.

But even this - if accurate - is a tad misleading because how much lock is needed depends on the match of the center diff's split to the available grip. The Evo's center is 50/50, while the STi is something like 42/58 (it has been changed a few times, so that might not be correct any more). Depending on the tires and the surface, maybe the Evo's split matches better; maybe the STi's matches better.

But more important than the details of the center is the AYC. Having driven my Evo for several months on many surfaces with no pump, I have to say that I've come to dislike the AYC. Maybe with a Cusco RS in there and less aggressive programming I'd be less down on it, but, as of now, I look forward to trying the car with ACD working and the AYC disabled (somehow).

 

ACD tunes disable the AYC so you're in luck there. I actually was retuning my ACD in the Evo IX. In fact I still have the harness if anyone wants it. No use on my X.

The STI due to having a planetary center has a variable torque split so it's not always a static 42/58 (or whatever) split.

Originally I thought the main difference was the STI changes torque split ratios before it changes lockup, where as the Evo can only change lockup and AYC split. In Snow the STI reverts back to something closer to 50/50 split for stability or so I've heard.

Plus hard lockup tends to be used more for the street. This is evidenced by the lower locking pressures of SNOW mode. Which basically opens up the diffs and avoids harsh locking so each wheel can use it's own traction. Gravel maintains a higher lockup in general, but locks up *less* than Tarmac mode. Unlike Tarmac it doesn't "let go" immediately when the steering angle changes.

So in short the harder locking forces benefit the most on the dry street. Slippery conditions prefer a lesser lockup upon G-Force or braking with a higher "static" lockup.

For a generic idea of what I'm saying think of it like this.... (with made up units)

* Tarmac lock is 0, Upon hard accel/braking it locks up to 8. Upon steering change it instantly goes to 0.

* Gravel lock is 2, Upon hard accel/braking it locks up to 5. Upon steering change it maintains a lock of 1-2 before letting it go if the turn gets sharper.

* Snow lock is 1, Upon hard accel/braking it avoids locking longer, when it does though it's a 4. When the steering changes it keeps the lock of 1.

The default ACD setup in my IX was similar to what I mentioned above. Thus snow mode is not a "4x4" lockup like people want to think. If you want that, drive in the snow using tarmac. You'll see why it's less effective.

 

Thanks for the positive feedback guys

@Kendogg, Yes, the Subies hold their value incredibly well. Your never getting a deal getting a used STI that "someone has taken the depreciation hit for you"

@Alpha X, I had the pics of my previous cars already loaded on my computer! Haven't had a chance to take some pics of the X.

The N54 is an amazing power plant! I do miss the torque, but overall I only drove the 135I 4-5K miles a year. Maybe if I got the more spacious 335, or even an XI things would have been different. However I am loving my new Evo! Can't wait for Black Friday sales in about a month! Going to buy some goodies

Also, the BMW extended warranty covers the wastegate rattle issue 8yrs/82000mls and the HPFP failure for 10yrs/120000mls. If your wastegates start to rattle, you get (2) brand new turbos.

 

Well, if you don't swap in an RS or MZ at the same time, you end up with a wide-open rear, which isn't good for anything other than showering in prison.

(Not that there's anything wrong with that.)

Yeah, it's a popular belief in the Scooby world that a planetary doesn't have a fixed torque split. Of course, that doesn't make it true. And it isn't. All diffs that have gears in them have a fixed "native" torque split. Only by the operation of a limited-slip device, such as an ACD, does the diff produce a torque distribution that is different from the native split.

Stop listening to whoever said that. The center of a Scooby locks, just like our center locks, which allows it to distribute torque at an almost infinite variety of ratios, but the split never changes.

Forgive me, but I'm going to ignore your description of the behavior of the various modes on an Evo X. To be blunt, unless you understand the difference between native torque split and moment-to-moment torque distribution, I can't take what you're saying seriously.

 

Figured you'd minimally put a proper 1.5 way diff back there before the ACD tune....


I read up some more and agree with you. Originally I thought the planetary was adjustable. I stand corrected. I've also apparently read some bad info in the past.

I was only confused about the adjustable split on the STI. I understand quite well how the Evo *always* lays down power 50:50 but can use the *existing* differences in wheel speed as a sort of "inertia-flywheel" when it locks up and forces them to equalize. Depending on how "unbalanced" the wheel speeds are, various things happen when the ACD clamps down.

I was adjusting lockup on my IX in tarmac for correcting understeer without swapping in a true 1.5 way rear or re-aligning the rear clutch plates which is a popular mod on the US-Spec 8-9. Far from clueless....

 

We're getting closer, which is cool, because I'll bet some lurkers also have some strange ideas about diffs.

My main new quibble is with the idea that "the Evo *always* lays down power 50:50"; please don't mix up power and torque. The spider-type center of an Evo has a 50:50 native torque split (as do all spider-type diffs), but that doesn't mean that it's sending 50% of the power to each end of the car. When you're in a corner, for example, and the ACD is unlocked, then a bit more power is going to the front, because the front is getting 50% of the torque but is also rotating faster than the rear. Yeah, it's not that far from 50:50 on power as well as torque, but it can be much more different when you start to get wheel-slip. A DSM, for example, with its worthless VC center LSD would allow something like 80% of the power to go to the front, even though the torque split was still 50:50, as you produced nothing but pretty blue tire-smoke with your inside front at corner exit. (Ask me how I know.)

Also, you seem to be thinking that an Evo's ACD is something different from a Scooby's DCCD. They are 99% the same. They have almost the same set of input parameters, they both are adjustable (albeit continuously for an STi and only three options for an Evo), and they are both externally-activated clutch-type LSDs. Most of all, like all LSDs, they merely lock. Yes, the downstream effect of them locking is that torque (and power) that was going to go to one output is re-routed to the other output, but that's because they are ceasing to be diffs and are becoming more like a spool.

From talking to people and asking where they got their ideas about how these things work, I've come to the conclusion that two things have caused the most grief. The first is the series of ads by Scooby saying stuff like "transfers power from the wheels that slip to the wheels that grip." This seemed to make people think that the system actually knows which wheels have don't have grip and which do, and then makes some kind of intelligent decision as to how much torque to re-route from one to the other. It's nothing that fancy. On older systems, all that really happens is one output starts spinning faster than the other and some locking is applied to stop that. Again, the locking has the effect of re-routing torque, but that wasn't the plan; the plan was merely to equalize the two output speeds.

The second thing that caused grief was Quaife's claim that their helicals are "torque-sensing and torque-biasing." They aren't. At least, it's not like there's a "torque-detector" in there, which is what it seemed to imply. Instead, the use of torque creates a side-force via a worm-gear. One direction of side-force is produced by the torque being used by one output; the opposite direction of side-force is produced by the other output. Thus, if both outputs are capable of using all of their torque, the side-forces cancel. But when one output can't use its torque (because, for example, it doesn't have enough grip), then the side-forces don't cancel, the worm-gear is jammed against a wall inside the diff, and stops being able to turn. In other words, the diff locks when the "reflected" output torques aren't equal. Again, all the thing really does is lock and then allows the torque to be re-routed as the diff ceases to be a diff. Nothing more than that. The only real difference between a helical (like a Quaife), which is what we have in the front, and any old-school clutch-pack diff (as older Evos have in the rear), is what makes them lock. Once they do lock, all LSDs are the same.

 

Yep I think we're pretty much on the same page. Just semantics at that point but we are saying the same thing. I kinda wish the OP would step in and elaborate on the snow qualities of the Evo vs STI as well as if either car had seasonal tires on.

I find the topic interesting none the less. The mapping of the two cars center diffs is what I'd like to investigate further but it's hard when the X is still locked down. After having the harness to reflash my IX, I'm kinda bummed this capability never was released on the X.

 

I can try my best. Okay so on the STI I had the OEM SUMMER rubber on the Enkei wheels that came only on the 2011 US sedan. I drive to work at 4AM, so the roads have not been plowed yet. There were instances when snow here in Utah gets almost two feet tall.

I didn't put the car into any special "mode" or anything. I tried to "slip out of control" because the roads are completely empty in the morning. I wanted to test the worst case scenario and see what this "rally" car, made for the street had to offer. The STI did not budge, it stayed literally GLUED to the road! Also like I said before, this was on summer tires, traction control on, and in the I drive setting. The thing was amazing in the snow.

On the Evo X, I unfortunately haven't driven the Evo in the snow yet. It hasn't snowed here yet. I can't wait to compare how it does with the oem summer rubber. If it drives anything like the STI in the snow, I might not even buy winter tires.

 

Thanks!

I'd warn you not to drive on summers with the Evo. Stock tires are quite soft compared to most cars and will be way out of operating temp in the snow. But they absolutely rock in the summer.

Sure the AWD system gets you going even with summer tires, but you will have a harder time stopping and turning at speed on that rubber.

 

you must have not had the harmon kardon system in the beemer! My 335i sound system was badass!

 

That was it, without the Harmon Kardon it sucked!

Honestly didn't want the 135 with I-Drive/Nav. I wanted the plain jane 6 speed with the M sport seats and M steering wheel.

 

I also came from a bmw. 335i. ALso about 3k in mods also e85. After 2 fuel pumps and all injectors being replaced, decided to call it quits. Evo much more fun to drive

 

Like said before I've driven a 335i and those cars are quick, but not as exciting as my evo was.