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removing the second spark?
Thread Starter
Teching In
Joined: Jun 2012
Posts: 2
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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
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
On The Tree
Joined: Jan 2012
Posts: 158
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From: Elswhere
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.
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
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
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
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).
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.
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I would think a 24x reluctor wheel would do a better job than the 58x.
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9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
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
60-2 (58x) Target Wheel & Waste Spark 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
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
TECH Senior Member
Joined: Apr 2002
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From: So.Cal.
9 Second Club
Joined: Nov 2003
Posts: 13,616
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From: Norn Iron
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
EMS Tooth Count Speed First, the Max RPM IS extracted from sensor switching speed.
Hall sensors are faster/less accurate and VR sensors slower (14k)/more accurate.
There is another limit, processor speed.
There are "aftermarket" ECU's stating 60-2 decode, some just "rule out" teeth thus converting to a 12 tooth TW.
This type of EMS requires a CAS to operate, normally the needed CRIP is a GUI setting.
There are some "aftermarket" ECU's that can decode a "missing tooth" TW and operate an engine without a CAS though stating 7000 RPM max with a 60-2 TW.
This RPM limit is caused by processor speed.
The "math" is there to support a 100K frequency standard for TW counting.
Lance
Hall sensors are faster/less accurate and VR sensors slower (14k)/more accurate.
There is another limit, processor speed.
There are "aftermarket" ECU's stating 60-2 decode, some just "rule out" teeth thus converting to a 12 tooth TW.
This type of EMS requires a CAS to operate, normally the needed CRIP is a GUI setting.
There are some "aftermarket" ECU's that can decode a "missing tooth" TW and operate an engine without a CAS though stating 7000 RPM max with a 60-2 TW.
This RPM limit is caused by processor speed.
The "math" is there to support a 100K frequency standard for TW counting.
Lance
