Duty solenoid and the resistor
 

We all know about the solenoid "controlled" by the resistor behind the battery. My question is: Is this solenoid either "ON/OFF or are their degrees of pressure it will supply?

Randy ii

I hope I asked the question clearly enough?

I think it does both. It will cycle when engaging the solenoid then maintain a specific "degree of pressure"

Don't quote me cause I could be wrong.

HA...I quoted you!


Randy ii

Randy cleared up one point...

I don't think you could be wrong, because that's what people always call me - well maybe you could be - they usually say, "wrong, wrong, wrong" - that's when I know they're referring to me - hey, that makes me Wrong III :) (see below)

Wrong I: I'd like to apologize for this shameless post count enhancement
Wrong II: and for lack of contribution to this thread.
Wrong III: I always thought solenoids were an On/Off device, but since the TCU modulates current and voltage, there must be another way of using them.

I dunno, I was pretty excited to see another response and then I find this. I dunno...I just dunno...

Randy (Think I'm gonna cry now) ii

It adjusts pressure by duty cycle or 'pulse-width' - the duration of time that the TCU applies voltage to the circuit (or ground, for those that know the difference. ;) ) When problems occur with the shifting it has probably switched to 'doodie-cycle', making the owner use words such as "crap' and "s**t".

So, if I get you right, if I increase the resistance the "pulse Width" would increase? I'm thinking of a variable resistor to combat a hard 1-2 shift. All the rest shift nice and firm. (I like things nice and firm) :D


Randy ii

I'll answer this without looking at a schematic, so it might be wrong. If necessary I'll look it up. Most automotive electronic systems have power applied with the ignition and circuits are controlled by switching the ground on and off. Adjusting the resistance only changes the 'strength' of the voltage at the solenoid, it doesn't change the time on/off. So, adjusting the resistance will vary the line pressure constantly, as a result of the solenoid exerting moreor less force per cycle, unless you twiddle the knob between each shift.

I'll go with that guess. It make sense. Nope I won't be twisting it with each shift. I want to just slightly increase/decrease resistance to smoooooooth out that first shift. One of the mods in the tranny has caused it to "clunk" from first to second after warming up. Kinda rough on the drive train during stop/go traffic I think.

Thanks again, and again, and again...etc. Beav

Randy

Randy,

Do you have the resistor in place? If so then I can't offer any advice to smooth it out (see below on why),

If you're running with no resistor, then you may wish to try values other than 10 ohms (the stock resistor). No resistor is essentially equivalent to infinite resistance. Down somewhere around 400-500 ohms the blinking light doesn't occur, but the solenoid receives very little voltage/current and shifting is almost as firm as no resistor. A value of around 60 ohms is what I calculated from an article in Gears Magazine (Auto trans rebuilder trade rag) for a sporty shifting car that still exercised the solenoid.

Going below 10 ohms would soften things more, but the same article warned of excessive current flowing through the solenoid - BTW, 10 ohms is what I calculate as the lower limit he thought should be allowed for operation.

[does this make up - a little - for my earlier worthless post]

You might try calling these guys and see if one of their pressure risers will work with the SVX tranny:

http://www.bulkpart.com/cgi-bin/miva...ry_Code=PressR

YES IT DOES! Actually I have the stock resistor in place but that info is very valuable. Thanks

Randy ii

That's kind of a cool concept. Probably more than I need to do. I'm thinking of more of a one time tweaking.

I've learned of a new device however. :cool:


Randy ii

Not the full answer but some extra info.
 

The following information although secured for another thread may be of use to those perusing this one

In an effort to find out exactly what is occurring in the resistor and solenoid circuits I hooked up my scope and had a look at things.

Unfortunately I was on my own so was unable to run the car in drive against the brakes as I had hoped to do. I admit being chicken as I was conscious of the garage wall and shelves containing valuable stuff in front of the car, as well as my own neck ! As a result the car was run in neutral and I could do no more than increase revs while checking the scope trace and taking measurements.

Static, all voltage measurements coincided with specifications.
The resistor measured 12.3 ohms and the solenoid 3.4 ohms.

With the engine running and the resistor in circuit the output from C7, i.e. before the resistor, showed a pulsed signal at a constant approximate 13.5 volts and at a rate of around 50 hertz. This was not in effect a square wave as the voltage fell to zero between pulses and the solenoid EMF was completely disrupted resulting in a substantial reverse spike. The frequency remained constant as did the voltage but the length of the pulses became shorter as the revs rose.

Tested as above, the output from C 8, i.e. the direct circuit to the solenoid, showed a similar signal but with shorter pulses. The pulse length did not vary with throttle opening and increased revs. Once again a significant negative spike was observed.

It was noted that the resistor ran extremely hot .

With the resistor open circuit, the same pattern was registered showing that feed back had not effected the individual circuit measurements.


N.B. Beav if you are looking,

It is hard to fathom how the system actually operates. One would expect the direct circuit to impart primary control and the resistor circuit to have some sort of auxiliary function, but who knows do you ? I now realise that I should have checked the relationship between the two signals. It could be that the two are in synchronism and one overrides the other and so lengthens each pulse, but this is a rather weird concept. I have designed systems involving the control of solenoid valves in industrial plant but have never seen or used anything similar.

Harvey has on several occasions stated that the signal from the resistor circuit is constant but at a varying voltage and is designed to provide a platform which prevents the solenoid from completely bottoming. On the basis of the above measurements this does not hold water.

Beav please throw in your $1000 dollars worth !

Regards Trevor. *<)