Sol. C Switch Observations - Page 2

oab_au · #16 12-09-2006, 04:23 PM

The US transfer and the VTD transfer valve assembles are different. The US valve applies full line pressure to the transfer clutch, as the normal, turning the C solenoid on, turns the transfer pressure off.

The VTD valve assemble is the opposite. It has no applied pressure to the Limited Slip clutch, as the normal. Turning the C solenoid on, turns the transfer pressure on.

I don't know why this is so, it may have something to do with the way they are to 'fail safe'. The US fails to full AWD, the VTD fails to no Limited Slip clutch, as it always has AWD.

The difference, I believe, is the way the transfer spool valve is machined. Being the easiest and cheapest way to change the action in production. The two have different part Nos.

If it is right, and I won't know for sure, till see the spool valve out of a US transfer unit, it means there is a way to fit the JDM VTD box to the US car and have it operate off the US TCU, by swapping the VTD transfer assemble, for a US transfer valve assemble.

Harvey.

Trevor · #17 12-09-2006, 04:30 PM

Quote:

Originally Posted by oab_au

The US transfer and the VTD transfer valve assembles are different. The US valve applies full line pressure to the transfer clutch, as the normal, turning the C solenoid on, turns the transfer pressure off.

The VTD valve assemble is the opposite. It has no applied pressure to the Limited Slip clutch, as the normal. Turning the C solenoid on, turns the transfer pressure on.

I don't know why this is so, it may have something to do with the way they are to 'fail safe'. The US fails to full AWD, the VTD fails to no Limited Slip clutch, as it always has AWD.

The difference, I believe, is the way the transfer spool valve is machined. Being the easiest and cheapest way to change the action in production. The two have different part Nos.

If it is right, and I won't know for sure, till see the spool valve out of a US transfer unit, it means there is a way to fit the JDM VTD box to the US car and have it operate off the US TCU, by swapping the VTD transfer assemble, for a US transfer valve assemble.

Harvey.

Is this a round about way of claiming that the C solenoid valve is normally open?

oab_au · #18 12-09-2006, 06:28 PM

Quote:

Originally Posted by Trevor

Is this a round about way of claiming that the C solenoid valve is normally open?

No I am not claming it, Its a fact.

Harvey.

Trevor · #19 12-09-2006, 08:34 PM

Quote:

Originally Posted by oab_au

No I am not claming it, Its a fact.

Harvey.

Only in the eyes of one.

hexadec0079 · #20 12-14-2006, 10:28 PM

Hate to revisit this again but time for updates:

In FWD mode the Sol. C still varies but will not go off (off=AWD, 50/50).
In AWD mode, it is easy to get the Sol. C to shut off by flooring it or accelerating quickly.

Conclusions:
The Sol. C is not the only determiner of AWD function, but turning it off will put the AWD in a 'failsafe' mode, for lack of a better term. This will force AWD, but the TCU still varies other AWD inputs.

Hope this helps some on...

Trevor · #21 12-15-2006, 02:02 AM

Quote:

Originally Posted by hexadec0079

Hate to revisit this again but time for updates:

In FWD mode the Sol. C still varies but will not go off (off=AWD, 50/50).
In AWD mode, it is easy to get the Sol. C to shut off by flooring it or accelerating quickly.

Conclusions:
The Sol. C is not the only determiner of AWD function, but turning it off will put the AWD in a 'failsafe' mode, for lack of a better term. This will force AWD, but the TCU still varies other AWD inputs.

Hope this helps some on...

You are correct in revisiting this subject in view of the controversy, and you are also generally correct in your analysis.

Inserting the fuse results in the ”C” solenoid being continuously energised, and therefore the normally closed valve is retained open. Thus the pressure bleed is open, reducing pressure to the transfer valve and subsequently the clutch, which is prevented from engaging so as to provide FWD mode.

For take off acceleration, solenoid “C” will be shut off (de energised) and the valve closed, so as to provide full pressure, an engaged clutch and AWD, as is mentioned in data.

Solenoid ”C”, if it has failed, or is de-energised, results in valve closed, no bleed and therefore full pressure, a closed centre clutch and full AWD. Thus as you correctly state, in fail safe mode “this will force AWD”.

N.B. A normally closed device has been specifically chosen for solenoid valve “C”, for the very reason that it fails safe closed, so as to prevent an open pressure bleed.

Trevor · #22 12-15-2006, 12:41 PM

Quote:

Originally Posted by oab_au

The US transfer and the VTD transfer valve assembles are different. The US valve applies full line pressure to the transfer clutch, as the normal, turning the C solenoid on, turns the transfer pressure off.

The VTD valve assemble is the opposite. It has no applied pressure to the Limited Slip clutch, as the normal. Turning the C solenoid on, turns the transfer pressure on.

I don't know why this is so, it may have something to do with the way they are to 'fail safe'. The US fails to full AWD, the VTD fails to no Limited Slip clutch, as it always has AWD.

The difference, I believe, is the way the transfer spool valve is machined. Being the easiest and cheapest way to change the action in production. The two have different part Nos.

If it is right, and I won't know for sure, till see the spool valve out of a US transfer unit, it means there is a way to fit the JDM VTD box to the US car and have it operate off the US TCU, by swapping the VTD transfer assemble, for a US transfer valve assemble.

Harvey.

Harvey Quote ---”The US transfer and the VTD transfer valve assembles are different. The US (transfer) valve applies full line pressure to the transfer clutch, as the normal, turning the C solenoid on, turns the transfer pressure off.”

Trevor --- Turning the C solenoid on by energising the solenoid, (N,B. It IS a normally closed device), OPENS the valve so as to drain off pressure and therefore REDUCES pressure to the transfer control valve, which as a result turns off.

Inserting the transmission fuse also results in the C solenoid being energised, thus opening this normally closed valve, resulting reduced transfer pressure and only FWD.

The solenoid fails safe valve closed, resulting in full transfer pressure, clutch activated and full AWD.

Harvey Quote ---”The VTD valve assemble is the opposite. It has no applied pressure to the Limited Slip clutch, as the normal. Turning the C solenoid on, turns the transfer pressure on.”

Trevor --- Wrong, the valve assembly is the same. Turning the C solenoid on opens the normally closed valve resulting in a bleed and transfer pressure OFF. This results in the LSD clutch operation being reduced. AWD is available but in a variable locked up mode.

Increasing the length of the ON pulses within the PWM signal reduces transfer pressure in both instances, by way of adjusting the torque ratio front/rear.

As with the US system, Inserting the transmission fuse results in the C solenoid being energised, thus opening the normally closed valve, but in this case is AWD is not illuminated and is in fact fully locked, as a result of a full application of the LSD clutch. This fact is clearly confirmed within the Japanese owners manual as a feature of the transmission.

Harvey Quote --- “I don't know why this is so, it may have something to do with the way they are to 'fail safe'. The US fails to full AWD, the VTD fails to no Limited Slip clutch, as it always has AWD.”

Trevor --- The VTD solenoid C fails safe closed, resulting in full transfer pressure and a fully ON limited slip clutch. The Japanese owners manual drawers attention to this fact, by way of a caution covering towing arrangements for the Japanese SVX.

Harvey Quote --- “The difference, I believe, is the way the transfer spool valve is machined. Being the easiest and cheapest way to change the action in production. The two have different part Nos.

If it is right, and I won't know for sure, till see the spool valve out of a US transfer unit, it means there is a way to fit the JDM VTD box to the US car and have it operate off the US TCU, by swapping the VTD transfer assemble, for a US transfer valve assemble.”

Trevor --- At long last we have statements of fact by way of an admission that absolute confusion reigns (Pun intended ref. fairy story). A qualified engineer would understand the requirements of a fail safe system and hence the use of normally closed valves.

What is even more amazing, is the stupidity of for years continuing to state that normally open solenoid valves, held statically open at variable intervals, are used for PWM control.

There is no mystery, all is logical. It is easily appreciated that the PWM system can be arranged to cater for what amounts to a reversal of the transfer valve arrangement within the US and VTD systems. Important is that variation will be confined to transmission control unit functions, rather than in respect of the transfer valve.

QED.