Harveys QC
 

Anyone this side of the 'pond' instaled/tried OAB_AU quick change?, sounds interesting;)

p.s I dont want to start a yet another 'debate':rolleyes: on wether it works or not, or if it will blow your auto box....just constructive

John:)

Re: Harveys QC
 

I don't know of anybody over this side who may have installed it yet John.

:)

Re: Harveys QC
 

I'm planning to install it, but I am hampered by the fact that the car I am currently using [over here] has a bad gearbox.

I have another SVX here with a good gearbox, but I don't use that car.

Without getting in to a flame war I think it is probably a good upgrade for anybody who has a car with a fully working and in good condition transmission, and with the proviso that the car is not used brutally at track days or on the drag strip.

My knowledge of automatic gearboxes does not extend much beyond the dipstick. From what I read the QC seems to remove some of the slow and slurring protection the engineers built in to save the box clutches between changes. This results in snappier changes using the QC. If a gearbox is wearing out or partly worn, these full power changes may hasten the demise of the clutch packs.

A good gearbox used normally for commuting and not being trashed should last OK with the QS. At least it would not bother me too much, once I knew I was not on weak clutches. That's why I intend to get one. I want to rebuild the original gearbox belonging to Jersey Girl so that she is "original" and with "matching numbers" as our across the pond brethren are so fond of quoting.

This bad gearbox I'm suffering with is also stopping me from trying the new software Phil wrote for UK gearboxes, which as you probably know have some functional differences from the US ones. [The US ones are rear assist Mickey Mouse gearboxes like you get in the Honda C-RV :rolleyes: ]

That's my take on the controversial subject. ;)

Joe :)

Re: Harveys QC
 

That's news to me... Can anyone confirm this?

Re: Harveys QC
 

There are threads on this going back to before the Flood, if you care to run a search.

In the US transmission the rear drive is operated by an electro mechanical clutch. Your power distribution is normally about 85/15 % with front bias, and the TCU uses the solenoid duty cycle to give more power to the rear as required up to a maximum of 50/50.

This gearbox is described by Subaru as "Active Torque Split AWD system".

The gearbox fitted to Japanese and UK cars, and certain other markets, is different. It is a full-time 4WD gearbox with similar power distribution to the manual system as used in the WRX. It uses a centre differential [as opposed to a rear take-off] which normally sends 64% of the power to the back and 36% [approx] to the front.

As the rears start to slip under power, the TCU can randomly divert power to whichever wheels have grip up to 50/50.

This type is described by Subaru as "VTD-AWD system"

This difference is notable also by the use made of the AWD fuse under the hood. In the US car, like yours, Snow, if you insert the AWD fuse it turns the AWD system OFF. You end up with a car driving 100% of the power to the front wheels, it disengages the rear take-off clutch.

In the UK cars if you insert this same fuse it locks the centre differential at 50/50. Effectively this means we could not drive our cars too far with the fuse in, at least unless we were on the loose. You guys could actually drive yours with no real problems, this is a bonus your SVXs have that ours don't enjoy.

With the US type AWD fuse turn-off system it is possible to test your cars at a test centre having only one roller for the dyno, by fitting the fuse temporarily. It is postulated that this is the reason these gearboxes were supplied in the USA, but nobody has ever confirmed that.

With my car it is permanent AWD and the local test centres are unable to test it on the rollers [they don't have double rollers] for brake function and so on. In order to complete the tests, the guys have to bring the SVX for a short drive. They seem quite happy to do this. :rolleyes:

Joe :)

Re: Harveys QC
 

Perhaps the comparison is meant only in one aspect of stateside AWD? The CRV begins at 100% power to the front wheels, sending it rearward on demand. As described <here>, the CRV system is very different from any Subaru running gear, continent indifferent. A twin-pump system cares not about a fuse. ;)

(Side note: My SVX doesn't care about FWD fuses, either. MTX on board! :cool: )

Re: Harveys QC
 

Actually the US AWD SVXi have varying split with a front bias.
But under normal driving the signal usually tells our transmissions to be about 65% front and 35% rear.
On the level or downhill, under light throttle conditions you could see 90% fwd and 10% rwd...
(I can't say that I have ever seen that.:o)
Under WOT conditions the signal tells the trans cluth to be as much as 49% fwd and 51% rwd.
I have seen that.

Re: Harveys QC
 

[QUOTE=svxistentialist;580796]I'm planning to install it, but I am hampered by the fact that the car I am currently using [over here] has a bad gearbox.

Ok, you first Joe, i'll let you be the guineapig:p

I'm tying not to go down the road of attempting to make a 318iBMW into an M3.....would be cheaper to buy an M3!, SVX been a one off gives way to temptation to make changes or improvments, to have a firmer shift when required would give it a more modern feel.

John:)

Re: Harveys QC
 

Well, as you have a 5 speed, your driving characteristics will be closer to the UK spec and Japanese spec VTD transmission. :D

My comment was off-the-cuff, as illustrated by the smilie, and not meant to suggest the Subaru system is the exact same as the CRV system. It is similar, in that a primarily front drive gearbox has some power tapped off and fed to the rears. It is, however, totally superior to the Honda gearbox because of the better Subaru traction. The driving experience remains predominately front drive, though, which is why the VTD gearbox is superior and a little more sporty.

Very interesting that Tom has monitored 51% rear split on your system. I thought 50/50 was an absolute limit. I'm pretty sure 50/50 is an absolute limit with our VTD type as it is due to mechanical considerations in the gearing.

Joe :)

Re: Harveys QC
 

It is impossible. physically speaking there can be no more than a 50/50split on the US tranmsissions. The front drive is directly proportionate to the output shaft of the transmission as it is directly driven. The only thing that can be changed is the output to the rear wheels up to 50% in a full lock.

Tom

Re: Harveys QC
 

Both Joe and Young Tom are correct.:)
The mechanical limit is 50/50.
But the signal given has been monitored to 51/49.
It was just an observation that I've seen and I thought that I would share it.
I should have been more clear.
Old Tom:o

Re: Harveys QC
 

Well my point is that it is interesting you noted 49/51 in the data read-off.

If nothing else this implies that the sensor signals are not accurate to 1% limit, or, alternatively that the control system is subject to transient current or voltage surges which can give these readings.

In either event it does mean we need to take these single readings with a pinch of salt when we are datalogging. Average states will be more important than spikes.

Hope I'm not treading on duty cycle territory here, and re-ignite an old holocaust about steady state solenoids :eek: :eek:

:rolleyes:

Joe :)

Re: Harveys QC
 

[quote=blueji;580880]John

Phil has reprogrammed my UK TCU so that Power mode can be forced on, and left permanently in the on position.

This can be achieved by a console switch in the JDM cars. It is much more difficult with the UK gearbox because the firmware is different. Phil monitored all the functions and has re programmed it to allow Power mode in the place of the Econ mode that UK gearboxes are saddled with.

If you're game I would be happy to send you the re-programmed TCU to try out, or "guinea pig" in your Northern parlance. :p :lol:

Having used Power mode full time in my jdm car, I'm willing to bet you would be happy with the change it will make. Phil and Belha run their jdm cars all the time in Power mode. I'm fairly sure anybody who has done the Power mod in the US leaves theirs on all the time as well.

It just makes the car feel like a sporty drive. You get rid of the "lazy" feel that is there in the UK gearbox.

Do you want to try it? This is a one time only offer.

Joe :)

Re: Harveys QC
 

I have seen this reading on several SVXi.
It is usually during a WOT downshift on an asphalt, uphill.
Less than perfect traction conditions.
And it is a very brief spike.

Re: Harveys QC
 

Very interesting Tom. It's starting to make sense.

The percentage torque distribution [between the front and rear axles, ignoring side to side for a moment] is decided by the speeds shown to the TCU by Speed sensor 1 and Speed sensor 2. Differences between these signals will cause the power to be sent from the slipping axle to the one with grip [the slower one]

The conditions you describe are perfect for such a spike. Powering uphill on slippery asphalt weight goes to the back, front end will start to lose traction if enough power applied. In this scenario under steady state strong acceleration in whatever gear [WOT] it will be normal for the computer to sense slippage at the front axle and send as much as possible to the rear. This should be as near as dammit to 50/50.

Now a change of state is applied; downshift at WOT. We are so used to the SVX not breaking traction because the computer works so well at traction distribution that we expect the torque percentage to be always within the envelope. But in this 50/50 state as the downshift happens and the revs go up to a higher power and torque level, both back wheels break traction momentarily when the clutches bite.

The unthinkable happens and the rear axle revolves faster than the front for a moment or two, hence the 51% spike. As it bogs down it reverts back to its natural state in the lower gear.

Well, that's how I see it. Any better ideas?

Joe :)