ECU mods and Engine torque control

[svxboy]

I have the wiring diagram to the SVX's ECU and was wondering what the Engine torque control wire was for and what it went to? Could this be the switch that kills engine power at lower RPM's? It says in the diagram it should read 5 volts off and 0 volts on. I wonder if installing a switch or a 5 volt power supply to this lead would eliminate the "engine torque control". Anybody out there with good electrical knowlegde and is familiar with the SVX's ECU? I am just looking for comments and suggestions on the subject. I am in search of trying to eliminate some of the low rpm lag that this car has and to better its QT's. Thanks, Greg

p.s. I know eddycat and cdigerlando would have some possible knowledge on this subject.

[Chiketkd]

...but I wanted to see if anyone knew how to splice in this switch. thinking about splicing in a switch before going back to the dragstrip in late October.

Longass also mentioned something about the 'torque control' switch in a previous thread:

Originally posted by longassname
I don't know what smallcar offers. I certainly don't need to go to them to find a spst switch (single pole single throw). It's not for changing the shift patterns. That can't be done propperly without reprogramming the tcu and there's no reason to do it anyway. There is however what is called the "torque control" signal sent from the tcu to the ecu during shifting. When the ecu sees this signal (it's actually a pull down = circuit is connected to ground) it pulls out a bunch of ignition timing to reduce torque during the shift. This makes for a soft, silky, luxurious shift which is comfortable for everyday driving and kinder on the transmission. Decreasing torque at any time; however, is not good for drag racing. In fact it makes the sifts seem painfully long when your mind is operating in that hyperfast compressed time drag mode. By putting a switch on the wire for the torque control signal you can dissable it while drag racing. I don't recomend it as the next "free mod" for everyone to run out and do to their svx which they realistically never drag race. If you actually go to the track however it seems like a no brainer. People with 5 speeds of course no longer have the torque control signal as they no longer have tcu's.

Any ideas? Where is this wire that runs from the TCU to ECU?

-Chike

[NikFu S.]

How the heck did you find this?

[mbtoloczko]

The torque control pin is shown on the ECU pinout diagram. There are images in my locker of the ecu pinout. After I switched over to a 5MT, I experimented with disabling torque control. As LAN said, its a pull-down type signal, so it holds high (5 V) automatically, and when torque control needs to be enabled, the pin on the ECU is grounded (normally the TCU). Enabling torque control has no effect until the motor gets above a certain throttle position and/or engine RPM (I've kinda forgotten). When it does enable, the motor falls completely flat on its face. Its so drastic that the first time it happened, I thought the engine had just died. I doubt its the cause of low rpm lag you mentioned. If you want to experiment with enabling the torque control (so you know what it feels like), all that you need to do is splice into the wire going into the torque control pin on the ECU, and then ground that wire.

[Chiketkd]

Mychailo,

Those ECU pinout diagrams are perfect and just what I was looking for. So after I splice into the engine torque control wire, I should ground one of the wires? Would the firewall make a suitable grounding point?

Also, you talked about the motor falling flat when torque control is enabled - what happens when it's disabled? Are the shifts super firm and crisp?

This is the reason why I'm interested in making the switch...

-Chike

[svxboy]

WOW Chiketkd, I barely even remember writing that initial post back in '01! How fast time flies by. It sounds like from the other posts that the TCU is responsible for grounding out the signal of the torque control pin whenever the transmission is shifting therefore causing the retarded ignition timing. The part that I still don't understand is to bypass this, could it be just simply disconnected or a switch put in-line or does a 5 volt power supply need to be connected to trick the ECU. Its already known the wire cannot be grounded, otherwise the torque control would be enabled all the time.

Greg

[Chiketkd]

Greg,

Glad to see you're back from the great beyond.

Yeah, when thinking it over I realized that disconnecting the wire may not be the solution as it'll cause the pulse to drop from +5 volts to 0.

Doesn't seem like a there's a simple solution around this...

-Chike

[b3lha]

Read mbtoloczko's post again. It's a pull down signal which floats at 5V.

The ECU grounds the wire to enable Torque Control while shifting. Just disconnect the wire, or put a switch in line with it if you don't want this to happen.

It might improve your drag times, provided the gearbox doesn't explode the first time it tries to shift at full torque.

[mbtoloczko]

Originally posted by b3lha
...
The ECU grounds the wire to enable Torque Control while shifting. Just disconnect the wire, or put a switch in line with it if you don't want this to happen....

Yep, that's how to do it. Chike, I only tried this after I switched to the 5MT, so no data on how it works with a 4eat. I would be curious to see what happens with a 4eat. My thought is that having it manually disengaged is going to be pretty hard on the clutch packs.

[Chiketkd]

Originally posted by mbtoloczko
Yep, that's how to do it. Chike, I only tried this after I switched to the 5MT, so no data on how it works with a 4eat. I would be curious to see what happens with a 4eat. My thought is that having it manually disengaged is going to be pretty hard on the clutch packs.

I'll definitely consider doing this. I'm sure the 228 ft-lbs of torque our engines make at peak would not be enough to cause damage to our clutch packs. But only way to know for sure is to cut that wire...

-Chike

[svxboy]

OK, lets get this straight. If I want to bypass the torque control system with an auto tranny, I would have to disconnect or install a switch between the TCU and terminal #20 on connector B59 to disable the grounding action performed by the TCU. Then I would have to install the splice between terminal #20 on connector B59 and #7 from connector B60, at the ECU, so it reads 5 volts all the time, getting its source from the PS switch supply. With a manual tranny, there is no need to install the switch because the TCU is already removed and no grounding occurs. The grounding occurs at the TCU not the ECU.


Does this sound right? This has been a mystery to me for years.

mbtoloczko, what of power increases did you notice when you did this mod?

Thanks, Greg

[Phast SVX]

Originally posted by svxboy
OK, lets get this straight. If I want to bypass the torque control system with an auto tranny, I would have to disconnect or install a switch between the TCU and terminal #20 on connector B59 to disable the grounding action performed by the TCU. Then I would have to install the splice between terminal #20 on connector B59 and #7 from connector B60, at the ECU, so it reads 5 volts all the time, getting its source from the PS switch supply. With a manual tranny, there is no need to install the switch because the TCU is already removed and no grounding occurs. The grounding occurs at the TCU not the ECU.


Does this sound right? This has been a mystery to me for years.

mbtoloczko, what of power increases did you notice when you did this mod?

Thanks, Greg

Greg!!! whats up man, didnt know if you still had the SVX or not. We should get together sometime, im at school in whitewater. Give me a call
608-712-1906

phil

[svxboy]

whats up man! My youngest brother goes to school their too. I call ya sometime soon.

Greg

[oab_au]

Not a good thing to do on it's own.

The torque is reduced during changes, to allow the box to do a "soft shoe shuffle" during the change. The TCU does other things to make the change unnoticable. During the 1st to 2nd change the TCU drops the line pressure, and pulses the band on and off a few times to slowly brake it down to speed, instead of just banging the band on.

If the torque is not reduced during the change the band will slip due to the low line pressure and the pulsing of the band pressure.

Removing the dropping resistor, does not keep the line pressure high during the shift as the TCU acts on the A solenoid to modify the line pressure, during the shift.

The way around the problem, as I see it, is to leave the resistor connected, so that the line pressure is varied in line with throttle pressure. This allows the TCU to preform the other duties that it does based on throttle pressure, such as engine braking, ect.

The Small Cars vacuum switch is then used to turn the TCUs control wire to the A solenoid off when the throttle is past 20% or so. With this line disabled during the shift, the line pressure will not be modified down by the TCU. It will just be set by the throttle position. As the throttle is down during hard acceleration, the line pressure will remain high during the change, to prevent the slipage.

This TCU line to the A solenoid should not be just disconnected. It should only be switched off under hard throttle. At other times, we need to allow it connected to preform other necessary duties, such as, varing the pressure with cold ATF, dropping the pressure when selecting D or R from cold, ect.

This change on its own will allow the box to survive hard full throttle changes. Then and only then, could the torque control be modified for a full torque change.

I would recommend that the same Small Cars kit be used to switch the Green/Yellow wire, from the TCU plug C wire no.8. off the A solenoid, and through a resistor to ground, when the vacuum switch activates. Otherwise the TCU will see the open circuit wire and post a code.

Worth a try?
Harvey.

[oab_au]

No body think this is worth a try, or didn't I explane it clearly I think it will allow faster, firmer changes and allow the torque control to be switched out for hard acceleration.

Harvey.