Wasted Sparks VS Sequential Spark

[wilbo666]

I'm trying to quantify the performance gain (if any) of moving from Wasted Spark to Sequential Spark and vice versa.

My thoughts were that there maybe a benefit from moving from a paired coil wasted spark setup (e.g. 7M-GTE) to a COP wasted spark setup. My reasoning is that with COP each coil is only being called upon to supply spark for one spark plug as opposed to spark for two spark plugs at a time...

However I don't really see an advantage of sequential spark over wasted spark with COP...assuming that the ideal dwell time at high RPM is not encroached by the firing of the wasted spark (I haven't researched into if that is the fact of not, but I suspect not?)...

Dyno graphs of paired coil wasted spark vs COP wasted spark vs COP sequential spark would be fantastic (same ignition curves/maps of course)!

I'm looking into aftermarket ECU's and am trying to decide if sequential spark (on a 6cly) is really a requirement for me.

Cheers
Wilbo

[chris davey]

It was for me!

From the reading I did, the US 2jz guys who go to AEM which is waste spark COP have to use a HKS DLI to get stronger spark above about 18psi.

Can’t remember the boost figure, but 1jz747 has made 440ish rwhp with stock coils packs and the microtech x6 igniter.

That was one of the big reasons for me changing from wolf to microtech.

[Bored?]

My thoughts were that there maybe a benefit from moving from a paired coil wasted spark setup (e.g. 7M-GTE) to a COP wasted spark setup. My reasoning is that with COP each coil is only being called upon to supply spark for one spark plug as opposed to spark for two spark plugs at a time...

However I don't really see an advantage of sequential spark over wasted spark with COP...assuming that the ideal dwell time at high RPM is not encroached by the firing of the wasted spark (I haven't researched into if that is the fact of not, but I suspect not?)...

For what it's worth, your logic seems correct to me. So long as the inductor has enough time to charge, there probably isn't a difference.

If you had really bad wiring, it is conceivable that drawing twice the current could cause a slight voltage drop, which would increase the charging time further.

The real question is whether the minimum charge/discharge cycle time is small enough to be able to occur once per revolution. Apparently it's a real issue on some engines, which is why CDI was invented.

[wilbo666]

Well @ 8000RPM, you have
*133.33 Engine Revolutions/Second so
*7.5mS / Engine Revolution
*15mS between spark events using sequential COP
or
*7.5mS for Wasted spark COP

if my quick calculations are correct...(we have our doubtsies! weesss do *golum voice*)

Does anyone have figures for minimum dwell time for toyota coils? Or even better has someone put a CRO on a coil to see how long it does take to charge?

It does seem that there is not much time, but it depends on the coil charge time...

*Giant EDIT (learned to do maths? ))

Cheers
Wilbo

[chris davey]

IIRC my microtech has it set at 3.25ms. I can check tomorrow.

[thechuckster]

from memory... MSEFI suggests 6mS during cranking and ~3mS running.

I have a microtech drawing for wiring various toyota dizzi's and it had dwell times on it as well.... (goes off to search intahnet for a copy)

from : http://www.megamanual.com/ms2/configure.htm#dwell

Maximum Dwell Duration (ms) (max_coil_dur) is the longest period the coil is allowed to charge - too long and it can burn out your coil, too short and the spark may be weak. Normally this value is between 2.0 and 4.0 milliseconds. For the GM HEI 'in-cap' coil, a value of 3.5 milliseconds is typical....

Trial and Error on the Vehicle: To set the dwell, you want to set it as low as you can without misfiring at idle. Generally this is between 2.0 and 4.0 milliseconds. If you start at 3.0 and have no misfires, try reducing it a bit (0.1 milliseconds) at a time until you get misfires, then raise it 0.2 milliseconds. If you get misfires at 3.0, raise it a bit at a time until the misfires are gone (then add 0.2 milliseconds). If this seems familiar, it is very similar to the process of setting the PWM% for low impedance injectors:

- Do not use misfiring and high engine speeds and loads to set the dwell - misfires under those conditions will likely be caused by other factors, and will lead to you setting very long and damaging dwell periods. Recall that the dwell is shortened with higher rpm in any cases, so increasing the maximum dwell setting doesn't help at higher rpms. For example, with a 3.5 millisecond dwell time, and a 2.0 maximum spark duration, the rpm at which the dwell begins to be reduced is just 2727 rpm on a V8.

- Do not increase the dwell to create a 'hotter' spark. Increasing the dwell above the 'saturation point' does not make a hotter spark, it only makes a hotter coil. For example, for a 2.5 millisecond saturation time, the current is increasing to it's maximum for 2.5 milliseconds. If this is 6 Amps, then the average current during this time is about 3 Amps. During this time, much of the energy being supplied is building the magnetic field. However, after 2.5 milliseconds (once saturation of the magnetic field is achieved), the current is a constant 6 Amps, all of which is heating the coil, so it presents a much larger load on the coil. So leaving the dwell too long is a problem. As well, the VB921 goes into current limiting mode if the current gets high (6.5 to 7.5 Amps). If the current is kept below the current limit, the VB921 should not heat up much at all. However, if run with a significant amount of current limiting, it heats up pretty fast (which can ruin it). That's why you should lower it as much as possible without misfires under normal operating conditions. If you need a hotter spark, you need another coil.

[thechuckster]

Usefule Ignition reference info: http://www.tonyfoale.com/Articles/Ignition/Ignition.htm

Microtech's wiring of toyota igntion: http://www.microtechefi.com/pdf/LT84CYLTOYOTAign.pdf

[roadsailing]

a few things to consider (all AFAIK)

in a wasted spark setup, the coil is firing two plugs, but only the plug that is firing is drawing much current (as the fuel/air mix means the plug sees low resistance), the plug that fires during the exhaust stroke has high resistance, and low current flow.

In a turbo engine, it is possible to run a very mild form of antilag, ast the wasted spark will ignite any leftover combustables and possible produce a bit more boost.

on an NA engine i would go coil on plug, for wank factor, on a turbo engine, i dont think there is enough of a difference to worry about.

[6_SPEED]

I have wasted spark setup on my 2JZGTE, with STANDARD TOYOTA coil packs.

presently it is making just on 640 rwhp, with a bit more boost to go it will see some more hp.

it idles like standard and does not foul plugs, even with cams and big injectors.

I run an Autronic CDI ignition system i.e a capacitive ignition system which has a very short charge time in comparison to an inductive ignition system.

I have used inductive style ignitions in waste spark mode before and they are really not a success at all, you get stutter up top as the coils dont get the required rise time and you foul plugs like a bastard, causing bad idle and poor starting.

Inductive sequential setups are better, but in a high performance application you still end up with a plug eater.

if you want to run waste spark, you really need CDI to drive it if you want it to be a success.

oh yeah, testing on an engine dyno, sequential to wasted spark made no difference in hp,
either did plug gap.


cheers

.

[6_SPEED]

UPDATE

On the weekend my car turned 715RWHP, wasted spark setup on my 2JZGTE, with STANDARD TOYOTA coil packs driven by an Autronic CDI ignition system.

Goes to show how good factory Toyota coil packs are in conjunction with a decent ignition system.
I think I can still get some more out of them yet, will keep everyone up to date with the progress.


cheers

[Skip]

IIRC my microtech has it set at 3.25ms. I can check tomorrow.

I used to have my E6X charge time set at 1.5ms on my 1J. The tuner told me anything more than 2.0ms would not achieve anything and would ruin the 1J coils quicker. Any truth to this?

[jonra23]

Maximum spark from a coil will be when coils reach full saturation (primary windings fully charged)
Supplying power longer than neccesary to reach full saturation will not increase spark but will shorten the life of coils by heating them up un-neccessarily.

Wasted spark will make as much HP as Sequential spark, only danger is as stated above with high overlap cams you can get enough mixture in the wasting spark cylinder to get combustion.

regards
jon

[monstadore]

I agree with "6 speed", there is no advantage in running sequential spark over wasted spark - unless of course your engine is spinning to 20000rpm with massive cylinder pressures!. As long as you properly set up your coil charge time ( you can check this with an oscilliscope ) either will work. Have a look at some of the 10 sec vl's doing the rounds - a lot still run the single coil and oem dizzy!.

[6_SPEED]

UPDATE

On the weekend my car turned 715RWHP, wasted spark setup on my 2JZGTE, with STANDARD TOYOTA coil packs driven by an Autronic CDI ignition system.

Goes to show how good factory Toyota coil packs are in conjunction with a decent ignition system.
I think I can still get some more out of them yet, will keep everyone up to date with the progress.


cheers

UPDATE#2

On the weekend my car turned 876RWHP, wasted spark setup on my 2JZGTE, with STANDARD TOYOTA coil packs driven by an Autronic CDI ignition system.

As before, it goes to show how good factory Toyota coil packs are in conjunction with a decent ignition system.

cheers
Jo

[30psi 4agte]

Nice effort on the hp! Got pics / dyno sheet ???????

For the record i Tend to disagree with the sequential setup being of no advantage over a wasted spark setup.

A sequential setup will have more time for the coil windings to charge and will have more time between ignition fires to cool over a wasted spark setup witch will fire twice in the same cycle and have half the amount of time to cool down.

This is a tuff subject to prove however as majority of the coils these days are of such high quality they will happily perform a wasted setup in the highest of load / hp application without any probs at all.

I run a CDI wasted spark setup on my car and it has stood the test of time and performed faultlessly with a 1 mm plug gap and the 2 bar of boost. The ecu is set to 0.0mS as the CDI ( M&W)controls its own dwell time.

[1jzracing]

UPDATE#2

On the weekend my car turned 876RWHP, wasted spark setup on my 2JZGTE, with STANDARD TOYOTA coil packs driven by an Autronic CDI ignition system.

As before, it goes to show how good factory Toyota coil packs are in conjunction with a decent ignition system.

cheers
Jo

thats pretty impressive power!!

what sort of rpm and boost do you have to use?

any chance of a little rundown on your setup? fuel, ecu turbo etc

no secrets just the basics, cheers

oh .. to stay on topic.... it makes no difference,
more a case of what best suits your hardware combonation, cdi will always be better for high boost either way

[stradlater]

Something to consider, I know it's not in many peoples cases, but with LPG, wasted spark is a fair no-no, because of the gas floating around in the non-compression cylinder that gets fired.

Many a bad backfire/frontfire has been caused by thus...

[fixeruperer]

wasted spark is useless sequential spark is always gonna turn up on time and not fuk around, with wasted spark it rather just have a few cones and plod along.

[Billzilla]

COP is good for everything, though wasted spark can sometimes make a little more power on forced induction engines.

[thechuckster]

A sequential setup will have more time for the coil windings to charge and will have more time between ignition fires to cool over a wasted spark setup witch will fire twice in the same cycle and have half the amount of time to cool down.

que?? - modern transformer coils take anywhere from 3-5 milliseconds to charge and no more than 1 millisecond to discharge - any longer and all you do is heat up the coil and loose spark energy as you start to increase the secondary winding resistance (from the heat).

You have an arseload more than 6 milliseconds between each ignition event in a 6cyl and a waste spark pack will not fire the same coil twice in succession anyway so the increased charging time argument is bogus.

Sequential spark makes your engine management more difficult because you have to keep spark control constantly in sync with two sensors (cam & crank) instead of just a crank sensor. One erroneous signal and you have to drop back to waste-spark mode until the ECU re-syncs.