3T GTE - Wasted spark??

[TA22 GT]

I'm currently running a Microtech LTX8 on my 3T GTE and want to convert over to a CAS and individual coils. Most likely 4 twin post coils.

Question is regarding direct fire and wasted spark. I see people talking about the stock 3T GTE set up as wasted spark. Given the stock system has both plugs firing at the same time, how can this be wasted spark?

I always thought wasted spark is when there is a secondary "wasted" spark fires on the exhaust revolution on the crank?

OK, so if I buy new twin post coils, can I make the Microtech fire the 2 plugs for each clyinder at the same time or do people set it up so the second plug fires on the exhaust stroke?
If it fires at the same time, I assume it's best to wire the coils so the 2 charges come from different coils?

Hope this makes sense,
Cheers,
Simon

[rob1]

just as a note, my brothers 3tgte was running wasted spark with a micro mt4. wasted spark means that 2 cylinders are firing at the same time, although one cylinder is on its ex revolution. i am pretty sure using twin post coils the idea is for the wasted spark to come from the same coil as the one cranking the engine, otherwise both coils would be firing on every revolution.

[thechuckster]

yep - a twin-post coil can only create one strong spark and a weak one (for the cyl at the zorst stroke).

you'll still have a bit of a rats nest of ignition leads coming out of 4 twin-post coil packs.

You should be able to either adapt another dizzi that has a 24 tooth wheel and a single-tooth trigger wheel - or a single 24 tooth wheel with 2 opposing teeth knocked out. Either will give you enough timing resolution and a home trigger - assuming the ECU supports a 12-1 wheel as well as the Toyota 24+1+1 wheel setup.

[TA22 GT]

I have already fitted a 24 tooth wheel etc from a 3SGTE into my stock 3T GTE dizzy.

So, is running wasted spark on exhaust cycle better than firing both plugs on the firing cycle as it does with the stock system?

I was thinking of using either the Haltech quad coils or the Wolf coils, anyone know if these will run on the Microtech LTX8?

Cheers,
Simon

[rob1]

the wasted spark is going to be on firing the two plugs on the cyl rotating on exhaust cycle, and both plugs on the cyl cranking the engine must also fire. i don't think you could run one of the two plugs as wasted spark, and the other plug on the same cylinder as a full fire. it would contradict the design of the twin spark head.

[sideshow]

ring microtech and ask them cause u might have to get the ecu modified
and sometimes its like 400 bucks for some mods

[TA22 GT]

the wasted spark is going to be on firing the two plugs on the cyl rotating on exhaust cycle, and both plugs on the cyl cranking the engine must also fire. i don't think you could run one of the two plugs as wasted spark, and the other plug on the same cylinder as a full fire. it would contradict the design of the twin spark head.

This is what I'm trying to understand. The stock 3T GTE ECU fires both plugs in the same cylinder at the same time. So if you call it wasted spark it doesn't fire on the exhaust stroke.

With my new set up I could fire both plugs at the same time or just one plug and the wasted spark on the opposing cylinders exhaust stroke. Not sure which is better and why?

For example, a Hyundai excel runs 2 twin post coils and seems to be firing number 1 and 4 cylinder from one twin post coil at the same time. If the wasted spark is weaker, how does the Excel type arrangement work so well? I swapped the leads over on one coil and there is no difference. Is there something special about these coils?

Cheers,
Simon

[TA22 GT]

I always assumed the wasted spark set up had the "wasted spark" firing a little behind the primary spark.
After running some tests today on my wifes excel, I can confirm that twin post coils do actually fire at exactly the same time. Just not sure if one of the sparks is weaker. For an excel I assume it isn't because it is all that fires 2 of the 4 cylinders....

Maybe the excel coils are a good choice to use on the 3T GTE?

Cheers,
Simon

[sideshow]

its not called wasted spark


if just like extra spark duration or better spark on the 3t

watsed spark on excel fires on compression stroke on cyl 1 and ex stroke on cyl 4
this also helps burn the exhaust mixtures abit again

if u want to use all 8 plugs on yr 3t and then also go wasted spark u need

4 doulbe ended coils or 4 excel coils

you would fire both spark plugs in the same cylinder at same time

where as the factory toyota ecu might fire the 2nd plug afew degrees later than first

so then u will need to hook up the cyl 1 and cyl 4 twin post coils together in parallel

u will have tomake sure the coil charge time or dwell is set properly with this setup on the microtech

[TA22 GT]

Just for my understanding, the excel set up fires each clyinder every 360 degrees?

So it turns out to be once on the compression stroke and then again on the exhaust stroke?

I still dont get how this is wasted spark because wouldn't it mean that number 4 clyinder is always going to be a weaker spark? Aren't twin post coils made of 2 windings? The primary winding gives most spark, if so how does number 4 get wasted spark on the exhaust stroke and then a strong spark on the next stroke from the same coil supply?

Hope this makes sense,
Simon

[Hen]

Simon, it sounds like you have the right idea.

Wasted spark is when 2 cyclinders are run from the same (twin post) coil (eg 4AGZE). So every time the coil fires one cylinder will be on compression and go bang, another will be on exhaust and do nothing.

Twin spark is what a 3TGTE has, with 2 spark plugs per cylinder. I'm not familiar with its intricacies, but I don't think this is waste spark. The only plugs that fire are the two in the cylinder on compression.

Due to the different gas densities and makeup, it is easier for a spark to jump through the exhaust gases than through the compressed charge. So there is less "load" on the coil if you are running waste spark with 1 plug in compression and 1 plug on exhaust than if you are trying to spark with both plugs on compression.

I think it'd be nicer to run a twin post coil for each cylinder and have both plugs run from the one coil. However as said above, this may be more of a load on the coil. Whether this really is a problem I have no idea.

Hen

[rob1]

yeah the fact your looking at a twin plug engine is confusing. regardless of how the stock setup works the theory of wasted spark stays the same. 2 cyls firing then the opposing. like sideshow said, as you have the twin plug head you will need 4 excell coils.

[TA22 GT]

I agree I need 4 excel coils.

I might be wrong, but I some options

- Run one twin post coil to each clyinder, this will spark both plugs at the same time in the compression cycle.

- Run one twin post side to the cylinder on the compression cycle and the other side of the same coil to the opposing cylinder on it exhaust stroke.

Now I just checked my 3T GTE with a timing light and find the LTX8 has it firing both plugs on number 1 and 4 at the same time. So this is option 3, fire both plugs on each clyinder at the same time as well as run wasted spark to the clyinder on the exhaust stroke.

I'm assuming the last option has to be the way to go?

Now if a twin post coil provides one strong and one weak spark how do I know which side has the strong spark?
I tested the excel coil and each twin coil fires at exactly the same time and even when I swap the leads over there is no difference. Can't say the whole strong and weak signal from a twin post is making sense to me ATM.

Cheers,
Simon

[Hen]

It's not anything in the coil that causes the strong and weak spark, it depends on the gas the plug is firing through.

I'd vote for pissing off the waste spark part of it and just running a coil for each cylinder.

Hen

[TA22 GT]

OK, well now its making more sense.

I think I'll run one twin coil for each clyinder and set it up to fire both plugs on the compression and exhaust cycle. That has to be the best option....

As you said, I'm also not sure what running one twin post coil to each plug on the compression cycle will do, but I'm guessing it won't make much difference.

I think I've got it...

Now I just have to decide which twin coils to use. The hyundai ones look the same as the Haltech. Not sure if Haltech is better. Have also seen a nice set used on a 3000GT, would be nice to know if "coils ain't coils" or if they are all just as good as each other.


Problem is that the 3000GT have 3 twin coils (and I need 4) and Mitsubishi don't sell them broken up.

Cheers,
Simon