3T-GTE Ignition Systems

[Matt Dunn]

Hi all,

We are building a 3T-GTE and  are planning on running multicoil and are doing away with the distributor cap and rotor.

We have modified a distributor to take the sensor out of a 4AGE 20V dist, so it will have a 24 tooth and a single tooth signal.

First  question is where do we time it?

I think that with the G4+ you can adjust the base timing to where ever,

but we have the ability to place the pickup anywhere on the shaft, so is there any place that is better than another.

Is the single pulse better to ocour exactly at TDC no1,

10 deg before TDC,  20 deg before TDC,

or does it really not make any difference.

 

Second question is,

the engine is a 4 cylinder, but uses 8 sparkplugs, 2 per cylinder.

We were thinking of using 4 wasted spark coils to fire the 8 plugs.

Are we better to run one coil with both leads to the same cylinder,

or run true wasted spark,  and fire two coils each time.

First way would be simplier,  but then the coil has to fire two plugs under compression load

rather than one under compression load and one under almost no load?

 

 

 

 

[Adamw]

For the cas tooth I would go for 90btdc or 90atdc (ie Pistons half way down the bore).  The reason for this is the Toyota sensors put out very low voltage at low cranking speeds, having it at 90 deg is where crankshaft is moving the fastest so you will get better voltage out of it.

For the question about using the double ended coils, I really need to research that a bit more but my initial feeling is the same as yours - having both “ends” in the same cylinder under compression may not work well.  I think you would be better to keep it more traditional wasted spark type wiring then it is proven.

[Matt Dunn]

Ok then sounds good.

So to trigger the coils, we will need to fire two coils at once, 

can I run a 4 channel igniter and use wasted spark mode in the ECU

and split ignition drive 1 to two channels of the igniter,

or is the output of the igniter not strong enough to trigger 2 channels?

 

[Simon]

I would go with both coil posts to the one cylinder and then treat as a conventional coil set up. We have done this a lot of the multi plug Porsche engines.

One igniter channel per coil is required. 

 

 

[Matt Dunn]

Ok, next question 

We have adapted the 4AGE 20V CAS to the 3T dist,

but the dist rotates in the opposite direction.

Will this affect the triggers?

The main 24 tooth wheel appears to be symetrical and looks as though it will output the same signal in both directions,

but the bottom single tooth appear to be ramped in one direction and looks like it builds up the the step on the wheel.

I am unsure what affect this will have on the signal?

We may be able to machine the wheel so that the ramp is gone and the tooth just sticks out, but is it necessary?

 

 

[Adamw]

Im pretty sure it will be fine as is.  Im not really sure why they do the funny ramp thing but the waveform shape of the sync tooth is not particularly critical.  If it turns out to be a drama, you can just grind a tooth off the 24 tooth wheel to make it 24-1 then you wont need the trigger 2 at all.