Waste spark ignition

[Magnus]

I was wondering how you knew that it only enabled above 3K or so... good example on the dyno.

It is most likely ICM controlled. ICM in iself is a computer, takes signals from various engine components and the PCM itself. It knows when the cyl's are at TDC and knows when to ignite based on a PCM signal.

So, when the ICM knows that its over a certain RPM, it probably goes into waste spark mode by itself.

So... in conclusion, to get wastespark at a lower RPM you have to modify ICM (not likely).. or install DIS-4... not worth it.

The 3.8 ignition setup is VERY good and doesn't need much at all , if any, modificaiton.

I doubt you'll make more power in the lower rpm's with waste spark vs none.

[AllTheGoodNamesAreGone]

<blockquote>quote:</font><hr>Originally posted by Magnus:
I was wondering how you knew that it only enabled above 3K or so... good example on the dyno.

It is most likely ICM controlled. ICM in iself is a computer, takes signals from various engine components and the PCM itself. It knows when the cyl's are at TDC and knows when to ignite based on a PCM signal.

So, when the ICM knows that its over a certain RPM, it probably goes into waste spark mode by itself.

So... in conclusion, to get wastespark at a lower RPM you have to modify ICM (not likely).. or install DIS-4... not worth it.

The 3.8 ignition setup is VERY good and doesn't need much at all , if any, modificaiton.

I doubt you'll make more power in the lower rpm's with waste spark vs none.<hr></blockquote>

BTW I am not sure that is 3k rpm.. But it is at some given rpm X.. that is somewhere around 3k.. becuase i cant exactly rememebr where..

Yeah I dont know if it will give you more power.. or if its really worth persuing, but i may look into it..

i also have noticed that this is around the same time that my magnaflow exhaust gets to sounding "raspy"..

[camaro_speedemon]

<blockquote>quote:</font><hr>Originally posted by AllTheGoodNamesAreGone:


BTW I am not sure that is 3k rpm.. But it is at some given rpm X.. that is somewhere around 3k.. becuase i cant exactly rememebr where..

Yeah I dont know if it will give you more power.. or if its really worth persuing, but i may look into it..

i also have noticed that this is around the same time that my magnaflow exhaust gets to sounding "raspy"..<hr></blockquote>


You know, I've noticed a change in my exhaust tone at around 3k. I always attributed it to the accoustics of piping, ect.

[Guardsman]

Um, "wastespark" is the method by which our ignition system (3.4 and 3.8) operate. One coil fires two cylinders. The cylinder on the exhaust stroke will require less voltage to fire than the one on the power stroke. So, most of the power (voltage and current) will go to the cylinder on the power stroke. Any additional power (voltage and current) will be "wasted" in the cylinder on the exhaust stroke. Hence, "wastespark" ignition.

If you're trying to visualize it, the are the positive and negative posts from the secondary coil, that's what the plug wires connect to. The plug wires connect to the plugs. The plugs connect to the block (the block forms part of the circuit).

[chas]

<blockquote>quote:</font><hr>Originally posted by AllTheGoodNamesAreGone:

From what I recall on the dyno I started seeing multiple sparks at somewhere around 2.5-3k rpm.
This is clear becuase all of a sudden my rpm's that the dyno registered exactly doubled what auto tap registerd.
<hr></blockquote>

that is not waste spark. some people have had success on the dyno by taking the timing signal from one of the injectors (they only fire once!) to get around the multiple spark issue. at higher rpms you have more fuel and more spark (or more sparks in this case) help ensure complete combustion. msd's dis (or jacob's or accel's) aftermarket systems are a good idea for older single spark systems (like the 3.4) but for our cars its probably not worth the hassle (unless you need to retard timing for boost/nitrous).

as for enabling multispark sooner, the only benefit at low rpm might be a smoother idle since it would tend to eliminate misses. more power (at low rpm)? unlikely.

wastespark (the spark on the exhaust stroke) is always present but not visible on the dyno since it fires on a cylinder you arent watching.

[ October 15, 2003: Message edited by: chas ]

[ October 15, 2003: Message edited by: chas ]</p>

[3.4 slow to go]

From what I've read, Haynes only so be gentle, both 3.4 & 3800 have the waste spark, which is exactly as Gaurdsman said. THe wste spark is fiered to the other cylinder that the coil pak is connected to. A "similar looking" design I can think of was in my 82 200SX, 4cylinder w/8 plugs. Under heavy load it would fire off both plugs, but was an entirely different system of ignition.