First of all, I know what the ECU does (computer controlled timing device?) but what does ECU stand for?

Secondly, it is known that the STi can lock 65% power to the back while the remainder is upfront in manual mode. Can you reverse this? How much can you lock up front? 65% front and 35% back?

 

Electronic Control Unit.

Second, I don't believe they set up the DCCD to do that.

 

Essogas,

You're misplacing the word "lock" where you really are meaning 'apportion'.

The DCCD apportions power to the front and rear axles via their diffs. The limit is 65% rear though the DCCD can lock itself out to 50/50. From there its up to the diffs front & rear to handle any locking effect per axle and wheel (side to side).

Reversing the proportion (percentage) of power apportioning (65/35 vs 35/65) would result in the driving sensation of a FWD vehicle or a front biased AWD like some Volvo's.

- Janq

 

Exactly. That's what I was wondering. So it's primarily a RW drive? (in a perfect world without the diffs kicking in and transfering power where needed.)

 

It would be most accurate to say rear drive biased.

Kind of like a dog as they use their hind legs more so than front (as based on musculature deveopment) although they do of course use their front legs too.

The front wheels are under power and at any given time pulling the car along. Its just that the bias is toward the rear not front.
Of course we're not accouting for differential action.

- Janq

 

Janq, what is your take on this pinging and knocking issue that has been going around? Do you think it's just the tuners who are all fired up over nothing?

 

I've been monitoring the grapevine and holding my opinion on this item.

I'm going to talk with my ex-coworkers from Subie as well as my local Master Tech buddy who works on all my personal Subaru's.

I'm thinking that the pinging (detontation) is localized to use of low octane fuel (91 or less)...although it shouldn't be happening at all. At NASIOC '944 Turbo Guy' provided an exhaustive detail of his own experience with pinging and he could actually duplicate it at will within the 4K rpm band. He found that cooling off the IC with the water spritzer did the trick.

Overall though, I'm not too concerned at this moment about it as it seems to be both sporadic and only affecting a small percentage of owners. Also keep in mind most folks don't know what detonation is or sounds like so there are bound to be some false positives reported.

- Janq

 

I read 944's account as well. I certainly know what it is because my Mustang once did it. It was fixed by changing fuel brands not Octane level (87). Also, it may still do it on rare occasions on very hot days under high RPMs. It would really suck to have the STi do that as well. At least I was able to source out some good 93 octane near my palce. Fo rthe times I can't get it and must use 91 I might want to keep a few bottles of octane boost kickign around the trunk.

The guys that are mixing fuels and buying it by the drum is a little ridiculous to me. I don't need or want that aggravation! Ireally hope it works fine on 91, though.

 

I bet the owners manual indicates 91 as the minimum required fuel.

I have two gas stations in my community and they both serve up quality 91 & 93 sourced locally from Mobil Corp. A few miles away I can also get my hands on AVGas at 100+ octane for a decent price.

I've been feeding my '93 Legacy 93 octane for 12 years and she runs like a top even with 180K hard miles. There is no way I'll be breaking EPA laws though to ship & store barrels of fuel in my backyard. Thats crazy.

I wonder if a change to a hotter plug and/or a split plug anode would cure this issue. Its interesting/strange how folks ECU is not retarding things to prevent detonation...as an ECU would normally do.

- Janq

 

A hotter plug is a good idea. I don't know what the other thing is you speak of...

 

Here is some info from the OEM supplier Nippon Denso on there irdium sparkplugs; http://www.densoiridium.com/heatranges.htm

I mistyped the wrod "anode" as I meant 'electrode'.
And I was referring to the split electrode models available from folks such as "Split Fire" (splitfire.com) and i know their is a convetional mfr. supplying these too but its been sometime since I was last at Auto Zone.

Another thing I'm thinking is I haven't heard of anyone witht his detonation problem actually pulling a plug or two to visually inspect it and verify that the gap was set correctly from the factory. I wonder how many of our plugs are properly gapped to spec from the factory. (?)
Improper gap in and of itself canbe a cause for detonation/pinging which back the day (before the advent of ECU's) we used to refer to as "dieseling" which n extreme cases was resolved using water injection direct to the cylinder.

- Janq

 

sorry to change the subject, but would the USDM sti ecu be interchangable with the USDM wrx (EJ20)?or how about the jdm sti ecu on the usdm ej20?

 

^^ No.
They are two totally different engines.

- Janq