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Yanked open a Celica 2ZZ ECU last night, and took a look..

From what I can see, The VVTL Sol Coil is is driven with a transistor from the +12 inside the ECU, and then the Return Curent is passed across a 1/2 Ohm resistor.. It looks like a Voltage measuring Circuit is checking the Voltage above Ground Potential of this Return Path..

The Coil average resistance ( Per BGB ) is 7.5 Ohm.. the return path resistor is 1/2 ohm.. so that makes the Total circuit resistance of 8 Ohm..

Thr transistor will have about a 1/2 Volt foreward voltage drop, so if the Circuit Voltage is 13.6 Volt, then the Coil+ Dropping Resistor will be seeing 12.9 Volt running.

That is 21 Watt of Heat.. with a little over 1 watt being dissiapated inside the Dropping Resistor, and about 19 Something watt out at the Coil..


The 'Dropping Resistor' inside the ECU is using the 1/2 Ohm resistor so the ECU can see a return path voltage of about 0.75 volt.. If the ECU see's this 0.75 Voltage on the return Path, it's happy..

If 'We' were going to simulate a Sol Coil with a relay, ( So the ECU can see the 0.75 Volt ) it would have to have a 7.5 Ohm Coil, or be Paralelled with a resistor to make the ECU 'See' the 7.5 Ohms.. Not a big Problem.. BUT.. the heat generated at the Relay woul be still 20 Watts.. ( that gets hotter than a Tail Lamp Bulb! )..

Another way is to Do it 'Electronically'.. Cut out the 1/2 Ohm Resistor, and Replace it with something like a 100 Ohm resistor, then do the Voltage Calcs on a Loading resistor ( to Simulate the Oil VVTIL Coil ) so the ECU can still see the 0.75 Volt it's happy with..

If the the latter project is undertaken, then the 'Ground Pin' (C-21 ) that normally goes to the Oil Switch, could be taken to ground with a Biasing Resistor.. Say 4.7 K Ohm.. then the ECU would still see a ground potential on the Oil Swith line.. Then take another resistor ( About 1K or So ) from the C-21 line to the New C-7 ( Positive on the Sol Coil ).. then when the ECU heates up the C-7 Line, the Load Resistor will caise the 0.75 Volt to be produced across the new Dropping resistor, ( The one that replaced the old 1/2 Ohm Unit ), and the now Over-Biased ground line ove the C-21, will be taken to some voltage above ground ( About 9 Volt or So ) and the ECU should be Happy with that..

I am presently hacking up my Celica 2ZZ ECU for install in my 1ZZ Spyder.. I'll post updated ad to this part of the progress.. as I am doing this anyway to keep the 2ZZ ECU happy running a 1ZZ what does not have all the Lift Stuff..

Cap
 

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Limited Success

I reworked the Resistances involved, and came up with a Plan, to Multiply all the Values by 200.

This will allow the Values to be something the Local Radio Shack Electronics store will have..

The 1/2 Ohm Dropping Resistor located in the Return Path of the Sol Coil, becomes 100 Ohm..
The Old Sol coil resistance of 7.5 Ohm becomes 1500 Ohm..

This part of the Scheme worked as Planned. But I'm now Stopped on the Oil Switch. I was not expecting such LARGE resistors involves in the Oil Switch Circuit. They put a hell of an Electrical load on that switch. I'll need to go back and refigure the Resistances involved, and change them..

I just soldered the Oil Switch leads to the Ground for now. And the old Lift Sol Wires are terminated internally on the PC Board. By cutting a few traces, and using a few 1/2 watt resistors.

I was able to take the 1ZZ out for a drive, and it did not have a CEL at all!.. No I did not take it past 6.5k RPM!..

I'll figure out the Switch mod, and then get it warm and take it to 6.5 and see if that part works.. It'll be in a week or so.. a few projects are planned for this weekend & week..

Cap
 

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This is close, but not correct.

The VVTl solenoid is driven with square wave 0-10v signals. .
I'm not dealing with the VVTI.. I'm Defeating the Lift Sol Circuitry, so it will not toss a Cell at you when something else is driving it.. or in my case, when it not even there!

They are Similar Circuits, and use the Same type of Power Supply, but I doubt the Lift sol is Pulsed.. I've not hooked a scope to it .. Have you?.. do you have a Switching Frequency?..

So far the 'Defeat' that I have used, has worked.. I have not tackled the Oil Pressure Circuity yet.. That is next on the 'List'.. After this is Finished..

http://spyderchat.com/forums/showthread.php?42326-Torque-Reading-Motor-Mount&p=707995#post707995

Cap
 

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If it is Pulsed, then the Wattage is a bit less.. Thats Comforting..

Make sense if they are using the Same Sol Coil, to drive it the same way.. Probably only really needs a Steady DC of about 6 Volt to actuate.. Might as well use a PWM to get it..

Do you have the 'General Idea of the Cycle' of the VVTI Pulses?.. I'm looking to Log the Duty Cycle of the VVTI pulses to the Sol Coil, and I'm just wondering what range I'll be dealing with.. So I don't have to drag my Scope into the Moving Car.. < My Extension cord is not that long>

Cap
 
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