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  #16  
Old 09-01-2006, 06:31 PM
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Quote:
Originally Posted by b3lha
Dammit Joe! Don't you ever read any of my posts? LOL I actually traced the wiring for the JDM TCU in my 94.

The power switch on the JDM car grounds pin 4. The SAME PIN as the economy switch on the UK/Aussie car. If you swap your UK TCU for a JDM one then your econ switch will become a power switch.

If you want a JDM diagram, take the UK diagram and modify it as follows:

(i) The switch connected to a4 is labelled "power" rather than "econ", there is no wire to feed the econ light on the dash.
(ii) The speed sensor 2, being a hall-effect type comes straight into pin a11 rather than going into pin a17, out of c6 THEN into a11. The circuit a17-c6 appears to convert the inductive signal to a hall-effect signal on UK cars. The JDM TCU seems to have this circuit but it is not connected.

Phil.

Phil,

Apologies, I DO read your posts, but having connected up the JDM control unit, and finding the speed signal giving me a very "fast" signal on the mileage, i.e. the mileage was clocking up at non-representative rate, I disconnected it, and put back in the Euro one.

Now I appreciate the fast mileage thing was caused by the SS2 signal being fed in whereas the box was set up for the Hall effect one, so my subsequent search for a forced Power mode solution was based on the expectation that the JDM and Euro TCUs are largely the same, and it would be good to find the switching mode to make the Euro box have Power mode full time.

If what you are saying is correct, and possibly also if the US TCU control box is wired similarly to the JDM one because of the Hall effect VSS2 sender, then it is actually possible that grounding a4 on the US one will activate full Power mode, where I would have been expecting Econ mode. {It might be difficult to detect if the US boxes switched on Econ from pin 4, as I imagine their combination meter is not wired up for the Econ light. If grounding the a4 pin switched on the Power light for them, then you would know which way things were hanging}

As I have already tried your JDM solution, and determined that the Power light comes on when the Econ switch is on, can you now tell me how the JDM TCU will accept the in-gearbox SS2 signal, and not give a crazy speed/mileage output? In other words, if I plug in the JDM TCU, do I also need to sever some of the Hall effect connections that are redundant in order to get a meaningful and usable speed signal?

Is it even possible we would need the US TCU to make this Pin 4 grounding give us Power mode without getting a distorted speed output?

Joe
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  #17  
Old 09-01-2006, 10:00 PM
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Woke up early!

Such a lot of controversy and confusion .

Thanks for volunteering to try it out on a U.K spec box Joe.
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  #18  
Old 09-02-2006, 09:33 AM
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Quote:
Originally Posted by svxistentialist
Phil,

Apologies, I DO read your posts, but having connected up the JDM control unit, and finding the speed signal giving me a very "fast" signal on the mileage, i.e. the mileage was clocking up at non-representative rate, I disconnected it, and put back in the Euro one.

Now I appreciate the fast mileage thing was caused by the SS2 signal being fed in whereas the box was set up for the Hall effect one, my search for a forced Power mode solution was based on the expectation that the JDM and Euro TCUs are largely the same, and it would be good to find the switching mode to make the Euro box have Power mode full time.

If what you are saying is correct, and if the US TCU control box is wired similarly to the JDM one because of the Hall effect VSS2 sender, then it is actually possible that grounding a4 on the US one will activate full Power mode, where I would have been expecting Econ mode. {It might actually be difficult to detect if the US boxes switched on Econ from pin 4, as I imagine their combination meter is not wired up for the Econ light. If grounding the pin switched on the Power light, then you would know which way things were hanging}

As I have already tried your solution, and determined that the Power light comes on when the Econ switch is on, can you now tell me how the JDM TCU will accept the in-gearbox SS2 signal, and not give a crazy speed/mileage output? In other words, if I plug in the JDM TCU, do I also need to sever some of the Hall effect connections that are redundant in order to get a meaningful and usable speed signal?

Is it even possible we would need the US TCU to make this Pin 4 grounding give us Power mode without distorting the speed output?

Joe
Don't get excited. I was just kidding. Looks like I was wrong about the JDM and UK TCUs being compatible . I didn't realise you had already tried and discounted that approach.

On the UK wiring diagram, the only thing between the speed sensor and the speedometer is that circuit a17-c6 that converts the speed sensor signal to a square wave suitable for the speedo. From what you've discovered, the circuit in the UK TCU must divide the signal by the final drive ratio but the JDM one doesn't. Possibly it's done in software and the constant is missing because the circuit is not connected on JDM cars.

I don't see any easy way to work around that problem, other than fitting a JDM speed sensor.
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  #19  
Old 09-02-2006, 10:05 AM
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Agreed Phil

That's why I have resorted to trying to impose Power mode on the UK variant, long term it would be more useful to more people.

I might try earthing those pins to see what would happen.

The other thing that occurs is that the Econ mode is the obverse of the Power mode. Do you think it might be a runner to offer say 5v to that same pin, to see if that might trigger Power mode, or would I be playing with fire and blow the box?

Joe
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  #20  
Old 09-02-2006, 02:16 PM
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Quote:
Originally Posted by svxistentialist
The other thing that occurs is that the Econ mode is the obverse of the Power mode. Do you think it might be a runner to offer say 5v to that same pin, to see if that might trigger Power mode, or would I be playing with fire and blow the box?
I don't think that is a good idea.

The way that transistor electronics normally work is that the inputs are either in one of two states. Either "grounded" (ON) or "not-grounded" (OFF). The TCU "floats" the pin at 5v and then it detects when the pin is "pulled down" to ground. Not that I really know anything about electronics.

The ultimate solution would be to reverse engineer the software in the TCU. It's just a simple 6800-based computer. I wrote an OS for a similar board for my final year project at university. If I knew how to download the code onto my PC then I would spend a little time disassembling it. It would be cool to be able to customise the shift maps, particularly for the guys who have changed their diff ratio. There are solder tags on the board that could be some sort of serial or jtag interface for diagnostics. But I don't have the hardware expertise to figure it out.
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Last edited by b3lha; 09-02-2006 at 03:04 PM.
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  #21  
Old 09-03-2006, 02:31 AM
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Quote:
Originally Posted by svxistentialist
The other thing that occurs is that the Econ mode is the obverse of the Power mode. Do you think it might be a runner to offer say 5v to that same pin, to see if that might trigger Power mode, or would I be playing with fire and blow the box?
Joe
Er.. I would imagine that absolutely nothing will happen. If you put a very high impedence voltmeter on that pin whilst it's 'floating' I'd be willing to wager that you'd measure 5 volts, give or take a gnat's whotsit. So fixing it at a definite 5 volts won't do anything.
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  #22  
Old 09-05-2006, 04:57 PM
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You are sure to be correct Pete. Adding 5v to that pin would be pi$$ing in the breeze.

I have a new plan that takes account of Mike's advice that will work for UK cars. [The US cars can use a variant of it also if they want]

Using the Econ switch I will feed the 5v line to the TPS pin of the TCU. To stop the 5v going back up the line to the ECU and causing problems, I will be adding an in-line diode to the connection so the 5v can only go one way to the TCU, and not feed back to the ECU.

In addition I will put an interruptor in the line, so the TPS pin is reading 0-5v rather than a steady 5v. This will ensure Power mode is permanently on. I am not sure what Mike means by a "555 timer", but if it is simple and easily installed, that is what I will use. Something like what breaks the circuit for the indicators or the hazard lights would do nicely, but of course no way I would accept the clicking. An inaudible device would have to be found.

I find it interesting that in the JDM TCU that has switchable Power mode, the speed sensor two input is a 5v square wave. Connecting this square wave internally in the box to the TPS input would have the same effect as described above. I wonder if this is what is done internally in the JDM box to turn Power mode on, when pin 4 is earthed?

We will never know, I suppose. Anyway, I now see a way forward. I will rewire it when the new gearbox is in. I don't want to do any messing with the wires until I am sure all the readings and input/outputs are in the correct range. That way I won't compound a felony.

Joe
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  #23  
Old 09-06-2006, 12:57 AM
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Quote:
Originally Posted by svxistentialist
In addition I will put an interruptor in the line, so the TPS pin is reading 0-5v rather than a steady 5v. This will ensure Power mode is permanently on. I am not sure what Mike means by a "555 timer", but if it is simple and easily installed, that is what I will use. Something like what breaks the circuit for the indicators or the hazard lights would do nicely, but of course no way I would accept the clicking. An inaudible device would have to be found.
A good place to look at 555 circuits is http://www.uoguelph.ca/~antoon/gadgets/555/555.html - look at figure 9b on the page. I'm still not convinced that you need a pulsed input to the TCU, but then I'm an idiot .

Pete.
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  #24  
Old 09-06-2006, 02:51 AM
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Quote:
Originally Posted by ItsPeteReally
A good place to look at 555 circuits is http://www.uoguelph.ca/~antoon/gadgets/555/555.html - look at figure 9b on the page. I'm still not convinced that you need a pulsed input to the TCU, but then I'm an idiot .

Pete.
Magic Pete.

Thanks for that.

Just in case the dropping off after 10 seconds is peculiar to the USA tranny computer, it will make sense for me to just try the solid 5v feed first. If it remains stable, then Bingo, problem solved.

If it drops off after X, we won't even ask Y, we'll 555 it.

Ta

Joe
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  #25  
Old 09-06-2006, 01:33 PM
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If You Really Want Power Mode All The Time Just Adjust Your Tps Sensor To Far Found That Out By Accident.power Mode Is On As Soon As The Car Is Started.
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  #26  
Old 09-06-2006, 02:26 PM
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Quote:
Originally Posted by poweredx2
If You Really Want Power Mode All The Time Just Adjust Your Tps Sensor To Far Found That Out By Accident.power Mode Is On As Soon As The Car Is Started.
Hmmmm

Sounds interesting. Thanks man, I might give it a go.

Did you adjust your Caps Lock too far at some stage also maybe?

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  #27  
Old 02-02-2007, 03:48 PM
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Some clarification needed:

Quote:
Originally Posted by rmjjensen
I've done this with a simple voltage divider and a switch.

Yes it works, but you can't simply hold +5V to the TPS input. The power light will eventually shut off after 5-10 seconds or so if the voltage is remained constant.

However, what you can do which DOES work is pulse +5V to the TPS input on the TCU with a 555 timer. I gaurentee that will work 100%.

Here was my original post: http://www.subaru-svx.net/forum/showthread.php?t=20197
Mike
Can you throw some light on this question for me?
You described using a pulsed or interrupted 5V signal to the TCU pin for the TPS signal. You may have used a voltage divider to provide 5V, and interrupted the 5V using a 555 timer.

Now you say this genuinely works, and turns on Power mode.

However, in your earlier descriptions, you mention that showing the TCU this WOT voltage also sends the gearbox into defcon 5 mode, i.e. it activates kickdown to the lowest gear.

Can you please verify if this is the case? If the TCU needs to see variable voltage there on that pin, so it can decide when to activate kickdown, then this applied fluctuating 5V to the TPS input pin will give Power mode OK, but may also apply kickdown full-time, which is a little less desirable for those who want to live.

What's the story? How did it work for you?

Thanks

Joe
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  #28  
Old 02-03-2007, 11:33 AM
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Quote:
Originally Posted by svxistentialist
Mike
Can you throw some light on this question for me?
You described using a pulsed or interrupted 5V signal to the TCU pin for the TPS signal. You may have used a voltage divider to provide 5V, and interrupted the 5V using a 555 timer.

Now you say this genuinely works, and turns on Power mode.

However, in your earlier descriptions, you mention that showing the TCU this WOT voltage also sends the gearbox into defcon 5 mode, i.e. it activates kickdown to the lowest gear.

Can you please verify if this is the case? If the TCU needs to see variable voltage there on that pin, so it can decide when to activate kickdown, then this applied fluctuating 5V to the TPS input pin will give Power mode OK, but may also apply kickdown full-time, which is a little less desirable for those who want to live.

What's the story? How did it work for you?

Thanks

Joe
Sure ...it's not necessarily sending +5V to the TCU that initiates power mode. It's the theory that power mode is engaged when there is a sudden charge in throttle (TPS). Pulsing +5V to this wire will make the TCU think you keep flooring the gas pedal ...then letting off ...flooring it ...letting off. Now, if you physically do this in the SVX, you'll get the TCU in power mod, but you'll also be driving like a moron and get engine surges and wouldn't make any sense.

The 555 Timer does the TPS blips into the TCU while you maintain control of the engine by way of the physical accelerator pedal (TPS signal to the ECU).

Blipping the TPS wire to the TCU with 0 -> 5 -> 0 -> 5 -> 0 -> 5 does not cause the transmission to kick down gears. It depends on the length of which +5V is applied. If it's for 250 ms (for example) there's not enough time to kick down gears. Now if you maintained constant (or long period of time) +5V to the TPS input, the TCU will kick down ...it will think, "what the heck? this guy is flooring the car, but the RPMs are barely increasing - let me kick down a gear cuz this guy wants to MOVE."

Gear changes are determined more by the RPM signal input into the TCU (which we are not changing).

Does this help?
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  #29  
Old 02-03-2007, 06:44 PM
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Quote:
Originally Posted by rmjjensen
Sure ...it's not necessarily sending +5V to the TCU that initiates power mode. It's the theory that power mode is engaged when there is a sudden charge in throttle (TPS). Pulsing +5V to this wire will make the TCU think you keep flooring the gas pedal ...then letting off ...flooring it ...letting off. Now, if you physically do this in the SVX, you'll get the TCU in power mod, but you'll also be driving like a moron and get engine surges and wouldn't make any sense.

The 555 Timer does the TPS blips into the TCU while you maintain control of the engine by way of the physical accelerator pedal (TPS signal to the ECU).

Blipping the TPS wire to the TCU with 0 -> 5 -> 0 -> 5 -> 0 -> 5 does not cause the transmission to kick down gears. It depends on the length of which +5V is applied. If it's for 250 ms (for example) there's not enough time to kick down gears. Now if you maintained constant (or long period of time) +5V to the TPS input, the TCU will kick down ...it will think, "what the heck? this guy is flooring the car, but the RPMs are barely increasing - let me kick down a gear cuz this guy wants to MOVE."

Gear changes are determined more by the RPM signal input into the TCU (which we are not changing).

Does this help?

Yeah. A lot. Thank you.

If the 0-5v break is short enough, then the TCU circuitry decides that Power mode is required [because of the sudden-ness of voltage rise] but because the 5V is not maintained, it does not cause kickdown to a lower gear.

That is magic in a way.

You are then saying that the shift map uses rpm and road speed to assign gear changes. But these changes are assigned from the Power mode shift map, not from the Normal map.

The key or trick to it is keeping the 0-5V interval very short, using the 555 switch, that presumably has a variable interval.

Thanks Mike, that seems to solve the conundrum.

Joe
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  #30  
Old 02-03-2007, 08:17 PM
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Quote:
Originally Posted by rmjjensen
Sure ...it's not necessarily sending +5V to the TCU that initiates power mode. It's the theory that power mode is engaged when there is a sudden charge in throttle (TPS). Pulsing +5V to this wire will make the TCU think you keep flooring the gas pedal ...then letting off ...flooring it ...letting off. Now, if you physically do this in the SVX, you'll get the TCU in power mod, but you'll also be driving like a moron and get engine surges and wouldn't make any sense.

The 555 Timer does the TPS blips into the TCU while you maintain control of the engine by way of the physical accelerator pedal (TPS signal to the ECU).

Blipping the TPS wire to the TCU with 0 -> 5 -> 0 -> 5 -> 0 -> 5 does not cause the transmission to kick down gears. It depends on the length of which +5V is applied. If it's for 250 ms (for example) there's not enough time to kick down gears. Now if you maintained constant (or long period of time) +5V to the TPS input, the TCU will kick down ...it will think, "what the heck? this guy is flooring the car, but the RPMs are barely increasing - let me kick down a gear cuz this guy wants to MOVE."

Gear changes are determined more by the RPM signal input into the TCU (which we are not changing).

Does this help?
My understanding of what as you state occurs, is that short repetitive pulses of say 250 ms, will not cause a kick down, whereas a longer pulse or pulses will. On this basis, continuous pulses not exceeding say 250 ms, will result only in constant power mode, which is what is desired .

It would not be difficult within the TCU, to separate two such individual signals, so that it would appear that a RPM signal would not be required in respect of the original arrangement.

You have certainly carried out some interesting experiments and the information you have provided is very much appreciated.
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