Do those shiftkits work?

[SVXtacy]

Say, do those smallcar Automatic shift kits work? I think I have to replace the stock part on my car, and would like to know if upgrading would kill 2 birds with one stone.

[Earthworm]

They do have to be wired correctly. I've never installed one myself but many other members like what the shift kit does for their transmissions.

[Trevor]

Originally Posted by SVXtacy

Say, do those smallcar Automatic shift kits work? I think I have to replace the stock part on my car, and would like to know if upgrading would kill 2 birds with one stone.

The shift kit will not cure an existing fault. It can raise the line pressure to make shifts more severe if this is what is desired, but is not a good band aid.

[Sov13t]

Ive ordered one recently.. just to keep my transmission in one piece till i can afford a 5 speed wrx manual conversion.

[Trevor]

Originally Posted by Sov13t

Ive ordered one recently.. just to keep my transmission in one piece till i can afford a 5 speed wrx manual conversion.

Please explain what is wrong with your transmission and exactly how the mod will keep it "in one piece"

[Sov13t]

by lowering/increasing the pressure there is less wear on the gearbox... thus it lasts longer... is the way I see it. maybe I am wrong

[Trevor]

Originally Posted by Sov13t

by lowering/increasing the pressure there is less wear on the gearbox... thus it lasts longer... is the way I see it. maybe I am wrong

DUTY SOLENOID VALVE "A".

This is a pulse width modulated duty solenoid valve, ( Sometimes known as a pulsoid). The device is incorporated in the SVX transmission control system in order to adjust line pressure in the following manner :-

The fluid line is provided with a bleed or bypass via an on/off device, in the form of an electrically operated valve. This solenoid valve is opened and closed repeatedly, in a rhythmical manner by a control current which is turned on and off by the transmission control unit (TCU) at a very fast rate. The valve is a normally closed device, and remains closed in the event of the loss off a control current.

After passing through this modulated solenoid valve, the continually interrupted pressure is in the form of a pulsed flow. When the peaks level off with the troughs, there is a resulting overall steady reduced pressure. The level of this pressure is adjusted by varying the on/off intervals. Most often the length of the on time is adjusted and the number of on/off pulses per second is kept constant. The usual rate is around 50 cycles per second.

The resulting adjusted output pressure is therefore delivered as a rapidly fluctuating stream. The system incorporates an expansion chamber as a smoothing element, which works as a sort of cushion. This device is usually in the form of a cylinder and piston or diaphragm, backed by a coil spring. In the SVX system the component is described as a Pressure Modifier Accumulator. The high pressure peaks in the stream press the piston outwards and become rounded off, while the low pressure troughs are filled in as a result of the piston moving inwards under spring pressure. The end result is a smoother level of pressure, such that controlled devices are not materially affected.

An increase in the volume of fluid controlled, is achieved by transferring the solenoid regulated pressure, to a pressure modifier valve and a regulator valve.

It should be clear that by “chopping” the fluid supply in an adjustable way, pressure control is achieved economically using a simple poppet type solenoid valve, with few mechanical or electrical complications. However the valve remains in a continuos cycling mode, which imposes rather arduous mechanical stresses.

THE DROPPING RESISTOR CIRCUIT.

It will be immediately apparent that a sudden on off cycle tends to cause what could be called a hammering of the valve seat, even though this is largely checked by the viscosity of controlled fluid flow. The dropping resistor introduces a second series of current pulses applied in parallel with the control signal. These shorter pulses are applied during the off cycles and timed to check the travel of the armature as it reaches the closed position, thus reducing both shock and noise. These secondary parallel signals in effect, “round off” the closing period and reduce the closing shock. This arrangement can be made even more sophisticated and configured so as to soften the the opening cycle, as well as the closing of the valve.

It will be appreciated that reducing the resistance in the circuit, or opening the circuit by omitting the dropping resistor, has two outcomes. Firstly the relative electrical off time is increased thus increasing the line pressure and therefore makes shifts more abrupt. Importantly as a second issue, increased shock loads are applied to the valve.

The factors I describe will apply in the case of a device which varies the resistance according to inlet depression.

[Sov13t]

Thank you for such a great explanation trevor.

But one question arises... technically no matter with a shiftkit or not... you will have wear on the transmission/valve so what I was thinking is putting the shift kit on and having it at a moderate level of pressure not too abrupt and not too soft.

Compromise?

Or do you still think its totally useless?

[Trevor]

Originally Posted by Sov13t

Thank you for such a great explanation trevor.

But one question arises... technically no matter with a shiftkit or not... you will have wear on the transmission/valve so what I was thinking is putting the shift kit on and having it at a moderate level of pressure not too abrupt and not too soft.

Compromise?

Or do you still think its totally useless?

The shift kit can only do one thing, i.e. INCREASE the existing line pressure by cutting out the resistor under controlled conditions. In the event that line pressure is below normal due to a fault, and sluggish abnormal shifting has been a problem, this can be a temporary fix. (A band aid.) However in doing so, it will increase the demands on solenoid valve "A" (i.e. IN EXCESS OF NORMAL), which could be the original culprit causing the low pressure, and will therefore exacerbate what was a fault. The fault inferred is a faulty valve "A" seat. This will not register as a diagnostic signal and there will be no flashing indication.

The proper use of the shift kit if there is one, would be to make normal shifting firmer, if this what is desired, but it is important to establish what is normal and not a faulty condition. In any event an increased load on the seat of solenoid valve "A" will occur, as I have detailed.

[NikFu S.]

I installed mine after my transmission was freshly rebuilt.

I find it shifts a little harshly at times and not so much other times.

[Trevor]

Originally Posted by NikFu S.

I installed mine after my transmission was freshly rebuilt.

I find it shifts a little harshly at times and not so much other times.

------ and at the same time you are giving your hopefully new solenoid valve "A" a somewhat hard time. The question is, what advantage is being provided over and above that which is a properly operating original system?

Nick, please be sure that this is not a critical reply, as I respect your always thoughtful posts. Your observation and reasons will add to the facts which are involved in practice and preference. There are swings and roundabouts.

Cheers, Trevor.

[NikFu S.]

No you are right to question the logic in using such a thing.

I did it solely for the superficial feel of firmer shifts.

My plan is to swap in an MT when this tranny is unable to operate, which is why I haven't fixed the AWD.

I do however have the severity of the shifts turned down because I am worried over the constant jarring in and out of gear.

[oab_au]

Originally Posted by Trevor

DUTY SOLENOID VALVE "A".

This is a pulse width modulated duty solenoid valve, ( Sometimes known as a pulsoid). The device is incorporated in the SVX transmission control system in order to adjust line pressure in the following manner :-

The fluid line is provided with a bleed or bypass via an on/off device, in the form of an electrically operated valve. This solenoid valve is opened and closed repeatedly, in a rhythmical manner by a control current which is turned on and off by the transmission control unit (TCU) at a very fast rate. The valve is a normally closed device, and remains closed in the event of the loss off a control current.

After passing through this modulated solenoid valve, the continually interrupted pressure is in the form of a pulsed flow. When the peaks level off with the troughs, there is a resulting overall steady reduced pressure. The level of this pressure is adjusted by varying the on/off intervals. Most often the length of the on time is adjusted and the number of on/off pulses per second is kept constant. The usual rate is around 50 cycles per second.

The resulting adjusted output pressure is therefore delivered as a rapidly fluctuating stream. The system incorporates an expansion chamber as a smoothing element, which works as a sort of cushion. This device is usually in the form of a cylinder and piston or diaphragm, backed by a coil spring. In the SVX system the component is described as a Pressure Modifier Accumulator. The high pressure peaks in the stream press the piston outwards and become rounded off, while the low pressure troughs are filled in as a result of the piston moving inwards under spring pressure. The end result is a smoother level of pressure, such that controlled devices are not materially affected.

An increase in the volume of fluid controlled, is achieved by transferring the solenoid regulated pressure, to a pressure modifier valve and a regulator valve.

It should be clear that by “chopping” the fluid supply in an adjustable way, pressure control is achieved economically using a simple poppet type solenoid valve, with few mechanical or electrical complications. However the valve remains in a continuos cycling mode, which imposes rather arduous mechanical stresses.

THE DROPPING RESISTOR CIRCUIT.

It will be immediately apparent that a sudden on off cycle tends to cause what could be called a hammering of the valve seat, even though this is largely checked by the viscosity of controlled fluid flow. The dropping resistor introduces a second series of current pulses applied in parallel with the control signal. These shorter pulses are applied during the off cycles and timed to check the travel of the armature as it reaches the closed position, thus reducing both shock and noise. These secondary parallel signals in effect, “round off” the closing period and reduce the closing shock. This arrangement can be made even more sophisticated and configured so as to soften the the opening cycle, as well as the closing of the valve.

It will be appreciated that reducing the resistance in the circuit, or opening the circuit by omitting the dropping resistor, has two outcomes. Firstly the relative electrical off time is increased thus increasing the line pressure and therefore makes shifts more abrupt. Importantly as a second issue, increased shock loads are applied to the valve.

The factors I describe will apply in the case of a device which varies the resistance according to inlet depression.

There is reason to believe this post to be inaccurate and misleading. Further info can be found in this thread.
http://www.subaru-svx.net/forum/showthread.php?t=35942

Harvey.

[Trevor]

Originally Posted by oab_au

There is reason to believe this post to be inaccurate and misleading. Further info can be found in this thread.
http://www.subaru-svx.net/forum/showthread.php?t=35942

Harvey.

Members will understand that Deceit is the object here, the object being to distract readers from this thread :-

http://www.subaru-svx.net/forum/show...306#post442306

[Trevor]

Harvey,

The following is an extract from the opening post in the thread you have suggested by way ot a reference.
Do you continue to claim that what you state is correct?

Quote ---”When full throttle is used, the solenoid stays as an open drain, and the pressure is held high. As the throttle is closed the Throttle Duty Cycle current, is increased to reduce the solenoids drain on the Pilot pressure that acts on the Regulator Pressure Modifier valve and Line pressure is reduced.”