3TGTE Ignition - help the n00b!

[sillycar chick]

When the 3TGTE goes in 51LII, im going to ditch the dizzy setup and go with a CAS / coilpack setup. I had a thought on another option, but since I know absolutely nothing about ignition on these engines (my knowledge extends as far as the humble 2T-G engine and the likes) thought I would get some help.

Instead of using spark plug leads to the coils, is it possible to run a direct fire setup like ive seen on some engines? I really dont know very much about these setups, let alone ignition systems at all but hey, ive gotta start somewhere, and im keen to learn.

(See attached photo of a CA18 which shows what im talking about in case what i have called it is incorrect. - courtesy of Izzy's celica, sorry for stealing your pic)

And yes I am aware the 3TGTE is a twin spark engine, but could I still make it work? Im going to be using a Microtech LTX10s ecu with ignitor setup.

Help will be much appreciated, I really would like to make this work.
Thanks.

[skiddz]

i cant help with the CAS and coil pack setup but i can tell you why its a pain in arse with a direct fire:

the problem with going without a lead is that is makes changing the plugs a real bitch, ie on the CA you have the top cover, then a plate thing that holds the coil pack in, then another plate thing then u can get the coil pack and thing out, then u can get to the plug, if ya have the intake going across the top like the exa's did then it takes longer, probably about 30-45 mins just to get it all out, cos there are a shit load of screws, thats why the CA's come with iridium plugs from factory, with 8 plugs at 25 a peice thats gonna be pricey

also that would mean u cant have the intake going across the top of the head cos the packs will foul on it, somthing to think about anyway

[barned01]

i have seen many setups which still use individual coils per plug but they still have a lead going to the plug, ormally the lead is less than 20cm long as well.
the coils are usually arranged neatly along one edge of the rocker cover also this arrangement would allow better placement if the over the top manifold was still present (which it indeed is on a 3tgte).

This is actually a really woeful post however in attempt to thinly disguise my desire to subscribe to this thread as i would like to run a CAS setup on both my 18RG and also on the 3t in much the same way you are talking about, as i can't help but think the dissy is the reason why my car hesitates for a fraction of a second when i boot it.

[The Witzl]

yes you can do this, you just use "twin output" coil packs like from a 4A-GZE instead of single output ones - you'll need 4 of them.

Use the X4 ignition box from Microtech.

Then you are going to need an extra crank trigger signal, because if the ECU is dictating which coil/cylinder is firing (instead of the distributor cap + rotor), it will need two signals:

• Crank position - tells the ECU what position the crank is within a rotation
• Reference - is a signal the ECU uses to determine what cylinder you are up to. Usually pulses at TDC no.1 or thereabouts.

The reference signal is easy - your dissy can do this with some mods to the star wheel (chop off the star points for cylinders 2, 3 and 4).

The crank position signal is harder, but not impossible. A crank trigger disc on your crank pulley is the option of choice

[YelloRolla]

Dana,

This thread reminds me that I was going to send you some pictures of the set up that I run. I was unable to find the pics that I had of mine????

I did send them to someone else on these forums a while back - and I don't remember who. If the person that I sent them to reads this, please email them either back to me or to sillycar chick.

My email is [email protected]

[Soarer_D00D]

Bosch make some twin outlet coils which you can usually pick up relativly cheap. I'm assuming on a twin spark engine, you would have to get 4 x twin outlet coils, and set them up via the ECU in a direct fire mode. On my 1JZ, im using 3 dual outlet coils running wasted spark, instead of the factory derived direct fire via the 6 individual coil packs.

I'm still running leads from the coils as i've heard its better heat transfer not having the coils sitting right on top of the Cyldinder head. As for the ignitor, im using a Haltech igniter (which funnily enough works well with my Wolf3d) and i havent had any spark issues what-so-ever. So, in theory, i cant see any problems running direct fire through 4 dual outlet coils to run on the twin spark, just not sure if it would be sparking on rising edge, or falling edge, you'd have to consult someone whos done this on a 3T already.

Hope that helps a little
Cheers
Shazza

[thechuckster]

twin outlet coils are for waste-spark not firing dual sparks - so they're not ideal for what you probably want to do (using each twin-post coil pack to fire one cylinder). Waste-spark coils only produce enough charge for one plug to spark as the other plug would normally be in another cylinder full of burnt combustion gasses.

You could use the coil-packs in waste-spark mode - but each pack would have to feed two cylinders - with the two being 360 degrees apart (based on camshaft position) - making your connecting of plugs ot coil-packs looking like knotted-up spagetti.


Alternative theory: I think you could run the engine with a single crank trigger wheel (with a single home tooth or missing home tooth) - the trick would be to run the ECU as if the engine only had 4 spark plugs in waste-spark mode with just 2 dual-post coil packs - each ignition output (there would only have to be 2) from the ECU would have to run 2 igniters - which in turn each drive a dual-post coil pack.

This theory will come undone if the igniters are 'dumb' units (e.g. cannot work out how to do dwell) and rely on current output from the ECU to dictate dwell control.

Am still hungover so i wont bother with an MS paint diagram... maybe tonight ;-)

[Soarer_D00D]

twin outlet coils are for waste-spark not firing dual sparks - so they're not ideal for what you probably want to do (using each twin-post coil pack to fire one cylinder). Waste-spark coils only produce enough charge for one plug to spark as the other plug would normally be in another cylinder full of burnt combustion gasses.

You could use the coil-packs in waste-spark mode - but each pack would have to feed two cylinders - with the two being 360 degrees apart (based on camshaft position) - making your connecting of plugs ot coil-packs looking like knotted-up spagetti.


Alternative theory: I think you could run the engine with a single crank trigger wheel (with a single home tooth or missing home tooth) - the trick would be to run the ECU as if the engine only had 4 spark plugs in waste-spark mode with just 2 dual-post coil packs - each ignition output (there would only have to be 2) from the ECU would have to run 2 igniters - which in turn each drive a dual-post coil pack.

This theory will come undone if the igniters are 'dumb' units (e.g. cannot work out how to do dwell) and rely on current output from the ECU to dictate dwell control.

Am still hungover so i wont bother with an MS paint diagram... maybe tonight ;-)

Yeah, fair enough. Learn something new everyda... Cheers for the correctness.

[The Witzl]

Chuckie - yeah i know the theory of wasted spark coils, but i've seen the 4xtwin-out coils in operation on a certain yellorolla above (about 2-3 years ago, when he was running the 3T head)

Perhaps a comment Jason?

[thechuckster]

if he ran 4 coils in waste-spark mode then each coil would have fed two cylinders.

edit: i figured you'd know how they worked seeing as you lurk on msextra.com