Increase torque split in auto??

[TomsSVX]

More or less this would be solving an issue many people have come to me with. Their transfer clutches(ie rear wheels) do not engage properly. this is a common issue with the new models. So I am looking for a way to have them partially engaged all the time in order to decrease activation when it is needed. I know there is more to these issues like bad clutch packs and maybe bad Sol. C's but it is still worth looking into

Tom

[NiftySVX]

Originally Posted by TomsSVX

More or less this would be solving an issue many people have come to me with. Their transfer clutches(ie rear wheels) do not engage properly. this is a common issue with the new models. So I am looking for a way to have them partially engaged all the time in order to decrease activation when it is needed. I know there is more to these issues like bad clutch packs and maybe bad Sol. C's but it is still worth looking into

Tom

I am unsure what you mean. In this full time system, the rear wheels are always engaged, at least if operating as designed. The rear wheels are not switched on and off like in the honda real time system, instead the "torque split" to them is varied. This is the whole idea behind the duty solenoid c. There would be no need for a duty cycle, only a on/off signal if it operated in that manner, right?
I do agree with something LAN said tho. Upon consulting the service manual, you can see that the graphic depiction of the duty ratio to the transfer clutch is in no way a linear function, and a "linear modification" doesn't seem like it would be effective.

I think that a cycle generator would be on the right track, but again, I don't think that the duty cycle follows a linear curve in regard to torque applied to the rear output. I really think that the only answer may have to be revealed when we can examine the code stored in the computer.

Thoughts?

[TomsSVX]

There seems to be engagement issues with the newer model transmissions and fitting a resistor to increase pressure applied would make it much easier to "temp fix"

Tom

[Trevor]

Originally Posted by b3lha

Forgive me for asking this Trevor, but it was my understanding from your discussions with Harvey that a solenoid could not be made to partially open. Have I misunderstood?

Phil,

Sincere apologies as I missed replying to your post as above. The thread has become somewhat convoluted.

You are exactly right. Note that I said “such that it did not open fully for the complete duration of each voltage pulse.” i.e. It would fully open, but not for the duration of the complete pulse as a result of being inadequately energised, inertia and fluid resistance being involved. Not an easy situation to express in writing. Sorry that the description was not exactly clear.

You will have noted that I have indicated reservations in regard to this proposal and your doubts are well founded. That said it is an interesting prospect.

Cheers, and pleased you got laugh from my email. Trevor.

[Trevor]

When the car is travelling on an even surface and in a straight line, the road and forward motion in effect lock the front and rear wheels as if they were connected by a chain or a toothed belt.

Torque can be applied to the front wheels with less to the rear because the rear can be partly coasting and be pulled along i.e. driven by the front. In this situation the clutch need not be applied at full pressure and a state of tension can exist between the plates but there will be no real slip.

Say 90% torque front, 10% rear. This results in the missing 80% to the rear being provided by the coupling provided by forward motion. When the car enters a corner in these circumstances, and the situation changes, there is surely the foregone conclusion of initial understeer.

It will be seen that much of the possible issue of clutch wear which has been suggested is probably negated.

P.S. This is becoming a very interesting thread,
__________________

[b3lha]

Originally Posted by Trevor

When the car is travelling on an even surface and in a straight line, the road and forward motion in effect lock the front and rear wheels as if they were connected by a chain or a toothed belt.

Torque can be applied to the front wheels with less to the rear because the rear can be partly coasting and be pulled along i.e. driven by the front. In this situation the clutch need not be applied at full pressure and a state of tension can exist between the plates but there will be no real slip.

Say 90% torque front, 10% rear. This results in the missing 80% to the rear being provided by the coupling provided by forward motion. When the car enters a corner in these circumstances, and the situation changes, there is surely the foregone conclusion of initial understeer.

It will be seen that much of the possible issue of clutch wear which has been suggested is probably negated.

P.S. This is becoming a very interesting thread,
__________________

I believe you are right Trevor. The most important point being "in a straight line".
As I understand it, the clutches are used in lieu of a centre differential and must therefore slip during cornering. Increasing the torque split in the way suggested will presumably result in increased binding up on corners and resultant strain on the drivetrain.

[Trevor]

Originally Posted by b3lha

I believe you are right Trevor. The most important point being "in a straight line".
As I understand it, the clutches are used in lieu of a centre differential and must therefore slip during cornering. Increasing the torque split in the way suggested will presumably result in increased binding up on corners and resultant strain on the drivetrain.

Thanks Phil,

I was rather sticking my neck out in making the statement. I am glad to have confirmation from a man of thought.

P.S. As you point out a mod which increase clutch pressure overall, will increase possible wear at any time when the clutch is slipping, e.g. cornering. The driver would have to use any control with diligence and only intermittently.

Cheers, Trevor.

[Trevor]

Tom, have you lost interest.

I have a C solenoid so have experimented a little. Mine measures 16 ohms, the book says 8 - 15 ohms.

In a dry state the solenoid operates and the valve closes at the application of 8 volts DC, and releases and the valve opens when the supply is at 1.8 volts. It will therefore be apparent why the modulated supply is required to constitute a full on/off cycle.

A resistance of 4 ohms in series with the solenoid increased the above figures to, 10.5 volts and 2 volts, so that this would represent a good starting point for experiments.

I would reckon on using string say 6 or so one watt carbon film resistors, at a cost of less than a couple of dollars, as an adjustable trial set up. These could be fastened down a length of screw strip connector. They may get a little hot but will be OK for a short period.

N.B. All the pros and cons have been set out in this thread and no more than an experiment is suggested at this stage. Over to you.

P.S. It is likely that the adjustment of resistance could be rather sensitive and critical. This may or may not represent a problem and testing will disclose same.

[crazyhorse]

When I get my trans swapped out I may experiment with this. I like the idea of a DCCD type setup for the 4EAT.

Now that all of you that are smarter than me have chimed in with interest; Am I on the right track with a variable tone generator?

[b3lha]

Originally Posted by crazyhorse

When I get my trans swapped out I may experiment with this. I like the idea of a DCCD type setup for the 4EAT.

Now that all of you that are smarter than me have chimed in with interest; Am I on the right track with a variable tone generator?

I think you need a duty cycle generator. Look at these badly drawn waveforms:

____--____--____--____--____--____--__ low duty cycle
_--------_--------_--------_--------_--------_-------- high duty cycle

____-------____-------____-------____-------__ low tone
_--_--_--_--_--_--_--_--_--_--_--_--_--_--_--_ high tone

A signal produced by a tone generator had pulses at varible frequency, but the "on" time is always equal to the "off" time. A signal produced by a duty-cycle generator has differing "on" and "off" periods.

The duty cycle is the "on" time as a percentage of the "total" time for each wave. I think your tone generator will always produce a 50% duty cycle.

[Trevor]

I agree Phil,

I have looked at the suggestions of a “tone” generator but this is not what is required. As you point out, the frequency should be constant and the on time the variable factor. What is more the off period must be exactly that and zero voltage.

A square wave generator could be constructed with a variable on time but does involve complications. The most obvious is a separate driver adjustable signal would be involved, rather than a modification of the existing automated signal. The simple resistor idea retains the original signal at a reduced amplitude.

It could be possible to devise circuitry which would reduce all existing on pulses by a percentage, if the resistor idea will not work, but this is much deeper water.

[crazyhorse]

I have access to an electronics engineer, and some small, but obsolete PLC's. I also have some time to play with this at work at the moment.

So, what I need is a variable pulse generator. One that's programmable for a percentage. This will give me the ability to modulate the duty cycle.

I can lay hands on a portable O-scope as well. After the holidays, I'll get my SVX fixed, and borrow the O-scope. After that, all bets are off. We'll figure this out one way or another. At the very least, we'll figure out what the wave form looks like.

[Trevor]

Originally Posted by crazyhorse

I have access to an electronics engineer, and some small, but obsolete PLC's. I also have some time to play with this at work at the moment.

So, what I need is a variable pulse generator. One that's programmable for a percentage. This will give me the ability to modulate the duty cycle.

I can lay hands on a portable O-scope as well. After the holidays, I'll get my SVX fixed, and borrow the O-scope. After that, all bets are off. We'll figure this out one way or another. At the very least, we'll figure out what the wave form looks like.

It will be necessary for any wave form generator to drive an electronic switch, capable of switching the current involved and the nastiness of a highly inductive load.

[crazyhorse]

I thought induction was an AC phenomena. I could see if we were creating a positive to negative wave form, but were doing a simple digital switch. Granted there is quite a load, but I think the PLC's I have access to are capable of handling it.

I don't fool myself, I'm no expert. So enlighten me if I'm wrong.

[Trevor]

Originally Posted by crazyhorse

I thought induction was an AC phenomena. I could see if we were creating a positive to negative wave form, but were doing a simple digital switch. Granted there is quite a load, but I think the PLC's I have access to are capable of handling it.

I don't fool myself, I'm no expert. So enlighten me if I'm wrong.

When a DC supply to an inductive load is interrupted, there is revers discharge which must be dissipated. Where contacts are involved arcing occurs. In the case of AC, phase reversal during switching prevents the problem.