Advanced Engineering Tech - removing the second spark?

hey im totally new to this forum but i have a question that you guys might be able to answer.

Coils fire twice during a four stroke engine cycle; once when it counts and another time when the piston is back at tdc and has pushed exhausted gas out.

this is cant be controlled with a distributor but with electronic ignition it can

this second spark reduces emissions by igniting some unburned fuel in the exhausted gas

my question is has anyone removed this spark to release that unburned fuel to the exhaust to cool it?

any info would be great...and if im an idiot you can tell me

Wrong section for this question.

In unrelated news, I've heard people say the stock computer can't handle above 7000 rpm. is this due to not being able to trace the reluctor wheel at that rpm, or because it can't generate sufficient spark at that rpm?

Actually, you're wrong because on a typical 4 stroke engine the cam turns at half the RPM of the crank. Therefore, each spark plug only fires once per two revolutions of the crank. It does not fire when the cylinder is in overlap, otherwise it would backfire through the intake every other revolution.

hey im totally new to this forum but i have a question that you guys might be able to answer.

Coils fire twice during a four stroke engine cycle; once when it counts and another time when the piston is back at tdc and has pushed exhausted gas out.

this is cant be controlled with a distributor but with electronic ignition it can

this second spark reduces emissions by igniting some unburned fuel in the exhausted gas

my question is has anyone removed this spark to release that unburned fuel to the exhaust to cool it?

any info would be great...and if im an idiot you can tell meYou are talking about waste-spark DIS as used on GM's 2.8L-3.4L V6... this is different than the sequential ignition system described by ss1;

there are only 3 coils for 6 cylinders, and each coil is fired twice every 2 revolutions; each coil fires 2 plugs, the one at TDC compression (this spark ignites the A/F mixture), and the one at TDC exhaust (this is the wasted spark);

the wasted spark is necessary in this system to allow a path for secondary current to flow thru the coil, otherwise the other plug won't fire;

by the time the waste spark fires the cylinder exhaust content has already been pushed out of the cylinder, so the waste spark won't ignite any unburnt fuel (but the catalytic converter will promptly oxidize any unburnt fuel which results during misfires).

Thank god this was cleared up or everything i've ever learned was about to :barf:

It was a really good question by the OP. Not sure where he was going with it but good thought process nonetheless. For what it's worth, my Ranger does the same thing. It helped me decipher a bad coil pack issue too. It made troubleshooting so much simpler.

In unrelated news, I've heard people say the stock computer can't handle above 7000 rpm. is this due to not being able to trace the reluctor wheel at that rpm, or because it can't generate sufficient spark at that rpm?

I would think a 24x reluctor wheel would do a better job than the 58x.

I would think a 24x reluctor wheel would do a better job than the 58x.

You think less teeth offers better resolution than more ??...err nope.

58x is a simpler and superior setup

And the typical LS fires the spark ONLY when it is required at each cylinder.

Many engines do fire a wasted spark, and it is nonsense this is a bad setup. it works just fine, the only real downside is the coils have less time to charge as they are firing twice as often for any given rpm.
But it would only be an issue in very extreme examples

I am one of the members of the 60-2 (58x) DIS inventors (Alex Long) patent.
The project was for the Buick GN using a Waste Spark "twin post" DIS coil.(1980's)

WE specified a 60-2 TW (1/4 degree@2500 RPM acceleration) in 1983.
GM chose their 6+1 with NO acceleration measurement.
GM upgraded to a 24xe TW (1-2 degree@2500 RPM acceleration) in 200?.
GM now uses a 58x (60-2) TW (expired patent 60-2) in 2006.

The reason, correct crankshaft position measurement required by OBD-II.

The first "twin-post" coil I designed for the Buick has been improved today for use in the USPS LLV DIS upgrade.
The "rare earth" was installed in the smaller new frame, output increased.

Waste Spark coils are GREAT for low cost, the problem is the Spark Polarity.
One sparkplug fires normal, the other backwards. (ground to center)

The ability of Ion Sensing is also not possible with waste spark coils.

Lance

...
GM upgraded to a 24xe TW (1-2 degree@2500 RPM acceleration) in 200?.
GM now uses a 58x (60-2) TW (expired patent 60-2) in 2006.

The reason, correct crankshaft position measurement required by OBD-II.
...That's right, the 24x encoded wheel lets the PCM locate the crank position within 90 degrees on engine startup, which is not good enough for the later revisions of OBD-II... the newer ECM's using the 58x (60-2) wheel count the pulses on engine shutdown and store the resulting crank position in memory, so they already know the crank position for the next engine startup, thereby meeting OBD-II requirements.

:cheers:

You think less teeth offers better resolution than more ??...err nope.

58x is a simpler and superior setup



No because at high RPM less teeth means less blur to the sensor.

No because at high RPM less teeth means less blur to the sensor.

If your ecu thinks its a blur, stop using a shitty ecu and fit a proper one.

If your ecu thinks its a blur, stop using a shitty ecu and fit a proper one.

Less teeth would mean the ecu would handle more rpm IF blurring was a problem. I also think it wouldn't be the ECU that thinks it's a blur but the sensor. And in any case it was in response to this post:

In unrelated news, I've heard people say the stock computer can't handle above 7000 rpm. is this due to not being able to trace the reluctor wheel at that rpm, or because it can't generate sufficient spark at that rpm?

Less teeth would mean the ecu would handle more rpm IF blurring was a problem. I also think it wouldn't be the ECU that thinks it's a blur but the sensor. And in any case it was in response to this post:

In many ways rpm isnt the sole issue. It is wheel diameter, tooth size etc etc.

But 7000rpm on a wheel the size the LS uses should be no issue at all. Any decent ecu could run a wheel that size well over 15k if needed the tooth sizes gaps are so big.

Obviously a smaller diameter wheel would have more chance of teeth not getting recognised. A lot boils down to common sense. But it would take a very small diameter wheel or one with very bad teeth cut from it to pose a problem

In most cases, there are few positives from running a small number of teeth