Wiring schema for converting 4EAT to full-time Power Mode

[svxistentialist]

Having kicked around the idea of converting US cars to have a switch like JDM cars for activating Power mode full-time, I now have established what way it needs to be wired so you can convert your cars.

I know some of you will be keen to make this conversion, particularly those that have done engine upgrades and still retain the auto gearbox.

I'm going to copy over the relevant posts from Zavikan's thread so you can see where the idea is coming from.

Joe

[svxistentialist]

I have just done some study on the US wiring diagram vs the Australian one, and I now have almost sorted out how you US guys can wire up permanent Power mode.

The TCU makes its calculations on when to employ Power mode based on input from the TPS. This is a white wire that connects to B67 Pin 8, the smallest connector into the TCU, the 12 pin one.

What we have to do to trick the TCU into switching on the Power mode is to feed this white wire a 4.8 to 5.0 volt signal. The TCU will assume the throttle is wide open, all the time, and will leave Power permanently on.

Next, how do we feed a 5v signal to this line? Well, this is my idea. There are three wires going from the MPFI unit to the TPS, Red, White and Black. The white wire is the variable voltage signal that the TPS returns to the ECU and the TCU. The black wire is the earth. I'm willing to bet that the red wire is a 5V feed from the MPFI unit that the TPS modulates through a resistor.

Now if this red wire is a 5V feed, then what we do is connect a switch between the red wire and the white wire. When the switch is ON, the red 5v wire is fed to the TCU, voila!, full-time Power mode. When the switch is OFF, the white wire is fed to the TCU, and we are back to normal, Power will come on when the demand is beyond the set levels.

I'm willing to bet this will work, and tomorrow I will check the TPS red wire voltage to see if my calculations are correct.

However, we are taking Zavikan's thread way off topic, so when I check the voltage tomorrow, I will put up this how-to in the Technical forum so you guys can do a guinea pig with the wiring, wire in a switch and try the system out.

It will be fun if it works!!

PS I'm also fairly sure that grounding pin 4 will cause the TCU to go to Economy mode, no Power shift map.

[svxistentialist]

A couple of points.
Joe first I think there Are 3 maps, may be 4, in the TCU. Normal. Power and the one used be the Cruise Control. As our Aussie model does not use the Economy switch, this may be the same map as the cruise map. If it is not, then there are 4 maps.

The other is if you switch the white wire to 5V to hold the Power map, it will also hold the ECU at full throttle signal all the time. You would have to isolate the 5V signal from the ECU, and only allow it to the TCU.

Harvey.
__________________
One Arm Bloke.
Tell it like it is!

95 Lsi. Bordeaux Pearl, Aust. RHD. Subaru BBS wheels. 117,000Kls
97 Liberty GX Auto sedan. 125,000Kls.

[svxistentialist]

The first bit is about 4EAT shift modes. The important bit about the Power mode is in the last paragraph:

Mind mapping!
Quote:
Originally Posted by oab_au
Joe first I think there Are 3 maps, may be 4, in the TCU. Normal. Power and the one used be the Cruise Control. As our Aussie model does not use the Economy switch, this may be the same map as the cruise map. If it is not, then there are 4 maps.

The other is if you switch the white wire to 5V to hold the Power map, it will also hold the ECU at full throttle signal all the time. You would have to isolate the 5V signal from the ECU, and only allow it to the TCU.

Harvey.

Hi Harvey,

I am not so sure you are correct in this, but I think I see what you mean.

What I said was there are only two shift maps in the software, Normal and Power. These two maps determine when the upchanges and downchanges happen depending on a number of inputs, and relating to the demand from the driver.

In the case of the cruise control, this controls the gearbox by the application of a voltage from the cruise control computer to B66 pin 3. When cruise is ON, this voltage is <1 volt. When OFF, it is variable from 6 to 10.[interesting that it is over 5 v, the range which reads the TPS, is it not?]

What Econ does is deny the use of the Power shift map, so I'm saying it is not a shift map in itself, just a blocking circuitry.

Likewise with the cruise control. It does not redetermine shift points. It merely sets parameters for steady speed driving conditions, and for over-ride of these conditions, but using the Normal shift control map. It may also deny access to the Power shift map, that would seem to make sense too, but I'm only guessing on that.

Spot on agreement on your last point. The variable feed voltage on the white wire has to be fed at all times to the ECU. The divert we make is only to the TCU feed, B67 pin 8. We feed it variable voltage for "on demand" Power mode availability, and steady 5 v for full-time Power mode. The ECU will not be affected, it will be reading the throttle position requirement through the white wire variable voltage feed on B60 pin 2.

Joe

PS Strange you Aussies did not get the Econ switch. The wiring for it is shown on the diagram you sent me!

[svxistentialist]

OK guys, I have checked on the wiring, and the voltages are as I surmised from looking at the wiring diagrams.

Essentially, there are three wires to the TPS as many of you know. The black one is an earth, the red one is a 5v feed to the TPS from the ECU, and the white centre one is the variable voltage signal wire out from the TPS. This feeds back to the ECU so the ECU can make calculations based on how fast and how far the throttle is opened, and manage the fuelling accordingly.

There is a white wire tapped from this feed to the ECU that goes to the TCU at B67, pin 8. Your TCUs in the US are set up the same as the UK and Euro versions. It will assess how much demand for overtaking speed is required, and switch on the Power mode map if beyond certain parameters.

When this Pin 8 gets the full voltage, about 5v at WOT, then Power mode is engaged.

To be continued...

[svxistentialist]

Next stage:.......


What we plan to do is feed Pin 8 B67 the full 5v signal so that the TCU assumes we are on WOT all the time, and leaves the Power mode shift map switched on.

The way to do this is really simple. We need to tap into the 5v feed that the ECU is sending to the Throttle Position Sensor, and feed this voltage to Pin 8 B67 of the TCU, rather than show it the variable voltage of the white wire from the TPS already feeding Pin 8.

Now if you simply disconnect[ cut] the white wire from Pin 8 B67, tap into the red wire 5v feed from the ECU out of B60 pin 3, and connect this to Pin 8 B67, you now have Permanent Power mode. And I mean permanent in the sense that you can't switch it off. If you are unhappy with it for any reason, then you will have to reverse the wiring, connect back in the white variable voltage wire to Pin 8 again.

Of course, it would be better to have it like the Japanese do it, so we can switch on the Power mode if we want to rock and roll, or switch back to Normal mode if we want smooth shifts and chill out listening to Barry Manilow.

Hey, I know you guys all listen to Barry Manilow when no one's around, so don't try and deny it!

Next stage, switching it on and off.

[svxistentialist]

To make the changes reversible, we need to fit a switch.

As I have the English model at present, I was hoping that I could rewire the Econ switch which is on the selector lever, and is not a function I will have any need for. Unfortunately this is not at all possible, it is the wrong type. Switched on, it diverts Pin 4 to earth and locks out Power mode.

So it only has two poles, two wires going into it. This is known as a SPST switch, Single Pole Single Terminal. What we need is a Single Pole Double Terminal rocker switch. This is an either/or type of switch rather than an on/off switch. It will have three terminals. One will take in the white wire, variable voltage. The other will feed in the red wire, 5v voltage. The third terminal we feed to pin 8. Depending which way the rocker switch is set, the third terminal will feed the TCU with the variable voltage, or the full 5v line.

You can fit this rocker switch either under the dash [near the wiper winter/summer switch?], or if you want to approximate the JDM set-up, cut a hole for it on the gearchange console.

You will need to disconnect the white wire from Pin 8 and extend it to one of the terminals of your rocker switch. You will need to strip a small section from the red wire leaving ECU connection B60, Pin 3, solder a wire to this point [insulate the new connection, obviously] feed this new wire [keep it red, use the same colour code I suggest] to the other switching terminal of your SPDT rocker switch. Lastly, send a new wire from your switch back to pin 8, B67. I would use red and white wire, but any colour will do.

LAST AND IMPORTANT POINT!!!!

I am volunteering this information with no guarantee or warranty. Anybody tries this, and smokes their ECU or TCU or any other damage caused by these modifications, you must be assured you know what you are doing, and that I will not be responsible if it goes wrong.


I'm going to do my own car like this. If you want to wait a few weeks until I have time to hunt up the switch and have time to do it, I'm willing to be the guinea pig and take a few jpegs as I go.

Joe

[ItsPeteReally]

I wait with bated breath.

I'm slowly turning blue.

Pete.

[svxistentialist]

Originally Posted by ItsPeteReally

I wait with bated breath.

I'm slowly turning blue.

Pete.

How long before you are Blue Peter?

[ItsPeteReally]

Originally Posted by svxistentialist

How long before you are Blue Peter?

Get down shep

It's interesting. I would like to know how the system behaves in power mode at less than full throttle.

I'd like to think that the 'power' map is very simple addition to the standard map, effectively delaying upward gearchanges until the engine revs are at 6,500 rpm. If this is so then you could effectively dawdle at low speed while maintaining high revs. But I doubt that this would be a viable way for the JDM standard car to behave. So it probably will do something else! But maybe the JDM TCU has different mappings anyway

Anything that gives you greater control over what the auto box decides to do has to be an advantage. Frankly we need a 'mug' to volunteer to try this out, and it seems like you just volunteered.

[svxistentialist]

Originally Posted by ItsPeteReally

Get down shep

It's interesting. I would like to know how the system behaves in power mode at less than full throttle.

I'd like to think that the 'power' map is very simple addition to the standard map, effectively delaying upward gearchanges until the engine revs are at 6,500 rpm. If this is so then you could effectively dawdle at low speed while maintaining high revs. But I doubt that this would be a viable way for the JDM standard car to behave. So it probably will do something else! But maybe the JDM TCU has different mappings anyway

Anything that gives you greater control over what the auto box decides to do has to be an advantage. Frankly we need a 'mug' to volunteer to try this out, and it seems like you just volunteered.

Thanks Pete.

The prognosis on this has improved since the last post. Phil has PM'd me with A Better Way.

Well, for our European cars it means I can use the Econ switch as a Power switch by rewiring it to feed the 5v line to Pin 8. {The US guys will have to wire in the additional SPDT rocker switch as above, I don't know of a switch they may want to make redundant and use for the Power purpose}

I have looked up the wiring, and I have to use a system where the feed to Pin 4 is left in place, otherwise the Econ mode will shut off Power mode, but this is easily do-able.

Regards how the maps behave, this is well documented. I drove my JDM for years with the Power map permanently on, so does Phil as far as I know. It does not behave as you suggest. It's not actually a simple addition or change, it's a complete other map. The noticable difference is it will hold onto lower gears much longer when you are pressing on, and it will downchange faster [for less than carpet mashing input!] when you want to overtake, like on the motorway. At low revs it will climb all the way to 4 just the same as Normal, but hold the lower gears for longer in between.

The mpg penalty is about 1 mpg extra, maybe 2, depending how you drive. My style is pressing on, but not burning rubber.

The gearbox in Power mode can get into a bit of a dither compared to Normal mode, say in situations where you are hammering on, but slow for a bend or an obstacle. In such situations it may not be sure if it needs to change to 4 or hold 3 and can vacillate. With the Normal mode on, it would already be in top whether you liked it or not, and you would have to select 3 to stay in the power band.

However, if you leave it in Power all the time, this problem does not assert much. I'm not sure if this is because your driving tends to work around the problem, or because the box has a learning mode which adjusts to the style of your driving. I think it's the latter, but I'm not certain. Either way, it's not a major feature, the benefits of the more responsive behaviour far outweigh the foibles.

My gearbox guy won't take my car for two weeks, so I am going to start work on the conversion tomorrow while I have it here. I will document and photograph the progress so it will be easy to replicate.

Joe

G'bye Econ mode!!!!

[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

[svxistentialist]

Thanks for the link to that thread Mike. Interesting reading.

Now you got me worried?

Why do you think it drops out of Power mode after 10 seconds while it is getting a solid 5 v feed? Surely it should presume there is a WOT and the lower gears, more acceleration driving mode is required?

I'm going to see if I can compare with the JDM set-up. I'll post back any changes which that comparison might indicate are necessary.

For Econ to switch on, the switch merely grounds the B66 pin 4, which is not in use in your US TCU.

Having just checked the diagrams [painstakingly!! ] I have deduced that neither the US models nor the Aus models have any connections on the following:
B66, Pins 15,16,18,19 and
B67, Pin 7 and
B68, Pin 9

Now it would be very sweet if the JDM set-up merely grounded one of these unused pins to impose full-time Power mode, maybe one of the 4 not in use on B66, who knows?

I will wait and see. If I can't find a JDM wiring diagram, I might try grounding each of these in turn to see if one of them turns on the Power light.

Thanks for the heads-up

Joe

[b3lha]

Originally Posted by svxistentialist

Now it would be very sweet if the JDM set-up merely grounded one of these unused pins to impose full-time Power mode, maybe one of the 4 not in use on B66, who knows?

I will wait and see. If I can't find a JDM wiring diagram, I might try grounding each of these in turn to see if one of them turns on the Power light.

Thanks for the heads-up

Joe

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.

[svxistentialist]

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, 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