: Iradium Ix Spark Plug



94CaddyConcours
10-04-04, 07:52 PM
What do you think of Iraduium sparkplug?
-BILL SONG
-AOL:KHM3KALIKING

94CaddyConcours
10-04-04, 07:53 PM
The brand is NGK
-BILL SONG
-AOL:KHM3KALIKING

dkozloski
10-04-04, 11:34 PM
It is common in aircraft sparkplugs to have the side electrodes made from platinum and the center electrode from iridium. The iridium erodes slighlty less than the platinum so this evens up the wear. I would expect iridium plugs to last somewhat longer than platinum. Because either will last 100,000 miles it's going to take a long time to get your money back.

Geno Castellano
10-05-04, 11:39 AM
It is common in aircraft sparkplugs to have the side electrodes made from platinum and the center electrode from iridium. The iridium erodes slighlty less than the platinum so this evens up the wear. I would expect iridium plugs to last somewhat longer than platinum. Because either will last 100,000 miles it's going to take a long time to get your money back.


Not to start flaming but I have seen the OEM dual platinum plugs go WAY past 100K with no problems. Usually the only problem that occurs is if one of the platinum pads falls off eventually and the gap starts to open up as the base material then starts to wear. As long as the platinum pads are there the plug is virtually unscathed at 100K and well beyond. The platinum just does not erode like the parent material of the plug.

Not sure about the aircraft plugs but I have never seen any spark plug with pure platinum electrodes. They would be quit expensive. Light aircraft plugs are a poor comparison anyway as they are designed quit differently and those engines run on leaded fuel. There is nothing magic about platinum, iridium or anything else with regard to lead fouling. Aircraft plugs will fail due to lead fouling (just like auto plugs did back when lead was in auto fuel) regardless of platinum or anything else. This happens to auto plugs in Saudi Arabia and other countries where leaded fuel is still available. The dual platinum plugs fail quickly due to lead fouling...not the erosion of the gap.

Iridium plugs work well because the center electrode can be made quit small in diameter creating a "sharper edge" for the spark to form at. The iridium will still conduct heat away and allow the correct heat range even with the sharper tip so as to eliminate any preignition problems.

Iridium plugs are fine I would say but the problem the poster is referencing has nothing to do with chaning to another spark plug design. He has a problem with either a failed injector or failed spark plug wire or fouled plug or something. If the root cause is determined and fixed then the OEM plug is perfectly satisfactory. Conversly, if the root cause of the problem is not fixed then then changing plugs is not going to correct the problem regardless of iridium or anything.

dkozloski
10-05-04, 01:28 PM
Precious metal reclaimers pay top prices for scrap aircraft sparkplug platinum electrodes. They are near pure platinum but are very small pieces welded to base metal. I have been collecting them for years and it takes hundreds of electrodes to produce an ounce of metal. With the current price of platinum on the world market there is about a dollars worth in each plug. Aircraft plugs are cleaned and inspected on a regular basis. In addition to long life the major reason for using them is that compared to massive electrode plugs there is much more circulation of combustion gases around the insulator and electrode area keeping them more free from fouling. It's a reliability as well as a wear issue. The cleaning causes more wear than the running. I have seen electrodes worn down to needle size that still fuction well. The plug is usually rejected when it can no longer be gapped correctly.

Spyder
10-05-04, 01:45 PM
"This happens to auto plugs in Saudi Arabia and other countries where leaded fuel is still available."

Oregon, some say, is another country. :)

Geno Castellano
10-05-04, 02:55 PM
Precious metal reclaimers pay top prices for scrap aircraft sparkplug platinum electrodes. They are near pure platinum but are very small pieces welded to base metal. I have been collecting them for years and it takes hundreds of electrodes to produce an ounce of metal. With the current price of platinum on the world market there is about a dollars worth in each plug. Aircraft plugs are cleaned and inspected on a regular basis. In addition to long life the major reason for using them is that compared to massive electrode plugs there is much more circulation of combustion gases around the insulator and electrode area keeping them more free from fouling. It's a reliability as well as a wear issue. The cleaning causes more wear than the running. I have seen electrodes worn down to needle size that still fuction well. The plug is usually rejected when it can no longer be gapped correctly.


You're describing the OEM dual platinum plugs exactly. The platinum is just tiny pads welded to the center electrode and to the ground electrode. You need to clean the aircraft plugs because of the lead in the fuel. Running unleaded plugs will allow them to go forever with no gap wear and no cleaning.

Ralph
10-05-04, 03:04 PM
OK, so can there be any detrimental damage to the top of the pistons, etc. if these pads fall off? If so, I might get rid of the new Bosches I put in last year! I know they are supposed to run hotter to burn off any carbon deposits but I don't want to rish engine damage if they fall off. I read about some motorcycle applications of Bosche plats tips falling off but that was years ago.

Another thing I cannot figure out still is that my buddy who mines says that he cannot understand spark plug manufacturers claims that iridium is harder than platinum. He says the opposite is true and that platinum should last longer.

Geno Castellano
10-05-04, 03:21 PM
The platinum pads are so tiny they will not hurt anything if they fall off. The Bosch platinum plugs are not like the OEM plugs at all. The bosch plugs have the platinum only on the center electrode and it is a tiny piece of platinum embedded in the porcelean tip. The ground electrodes do not have platinum so they wear. This is important on the Northstar (93-99) since half the plugs fire positive-to-negative and the other half fire negative-to-positive. The ones that fire negative-to-positive will wear the ground electrode excessively without the platinum. The Bosch plugs have never shown to be the equivalent of the OEM plugs on the dyno for power or economy. Especially the Bosch+4 plugs with all the extra ground electrodes. They impede the flame propogation and cause a significant loss of power. The reason Bosch makes the +4 plugs is because they don't have the dual platinum technology so they put extra ground electrodes on to account for the wear. The spark plug "heat" has absolutely nothing to do with carbon buildup in the chamber or anything like that. Nothing. The Bosch plugs do not "burn hotter" or anything like that. It isn't the hardness of the material anyway. It's the reactivity of the metal with the plasma created at the spark/arc point. Platinum is very inert in that sense.

Ralph
10-05-04, 03:31 PM
The platinum pads are so tiny they will not hurt anything if they fall off. The Bosch platinum plugs are not like the OEM plugs at all. The bosch plugs have the platinum only on the center electrode and it is a tiny piece of platinum embedded in the porcelean tip. The ground electrodes do not have platinum so they wear. This is important on the Northstar (93-99) since half the plugs fire positive-to-negative and the other half fire negative-to-positive. The ones that fire negative-to-positive will wear the ground electrode excessively without the platinum. The Bosch plugs have never shown to be the equivalent of the OEM plugs on the dyno for power or economy. Especially the Bosch+4 plugs with all the extra ground electrodes. They impede the flame propogation and cause a significant loss of power. The reason Bosch makes the +4 plugs is because they don't have the dual platinum technology so they put extra ground electrodes on to account for the wear. The spark plug "heat" has absolutely nothing to do with carbon buildup in the chamber or anything like that. Nothing. The Bosch plugs do not "burn hotter" or anything like that. It isn't the hardness of the material anyway. It's the reactivity of the metal with the plasma created at the spark/arc point. Platinum is very inert in that sense.

What would you recommend from GM then Geno? Rapidfire? What is GM's name for their platinum plugs? If they are significantly better than Bosche I will get them.

Ralph
10-05-04, 03:33 PM
Also, how could we know if the tips fell off? Would there be any symptoms like rough running, bad fuel economy, etc?

Geno Castellano
10-05-04, 04:11 PM
I recommend the OEM dual platinum plugs. Period. They run better than any other plug in the Northstar engine because they were developed for that engine.

The likelyhood of a platinum pad falling off is miniscule. I happened on some of the original plugs installed in the factory back in the early 90's. The process for attaching the platinum pads has improved significantly since then and it is highly unusual for them to come off anymore.

The plug still works fine if the platinum falls off. It'll just start to wear and the gap will open up and eventually it will cause a misfire. It probably takes about 40-50K for a misfire to show up if the platinum does fall off depending on whether the center electrode or the ground electrode lost the platinum and which cylinder it was (due to the electrical polarity of the coil winding for that cylinder) so I wouldn't worry about it.

The Rapid Fire plugs are ok but they erode the gap fairly quickly since they are not a platinum plug so I wouldn't expect them to be at the top of their game for over 10-15K. Stay away from the Bosch plugs unless you don't want full power.

Ralph
10-05-04, 04:15 PM
Thanks Geno!! :yup:

dkozloski
10-05-04, 07:45 PM
How fast a material erodes in a high temperature atmosphere such as a combustion chamber doesn't depend on its hardness but rather on its resistance to oxidation. Iridium is more resistant than platinum so in platinum/iridium plugs the side electrodes will be platinum and the center electrode is iridium to balance the wear. As a point of interest iridium was suggested as a material for a component part of the first atom bombs and was being considered until it was discovered that all the refined iridium available in the world at the time (1944) made up a cube about 2 inches on a side. Since then better sources have been found.
Geno, if the correct heat range plug has been selected
and it is operated under the proper conditions, lead fouling of aircraft sparkplugs is self cleaning. If the plug insulator is too cool, lead compounds will accumulate, when power is increased the compounds will melt and form conductive deposits. A further increase in power and leaning of the mixture will burn the deposits off. What we were more likely to find was clinkers that we mechanically removed with probes and needles as opposed to abrasive blasting. Ananysis showed that the major component of the clinker was silicon from dirt ingestion plus some carbon. I have seen aircraft plugs operated for over 2600 hrs. in the same engine without ever using an abrasive blast and then being transferred to a replacement powerplant. The engine in the example was a Lycoming IO-540 K1A5 that we overhauled. In that run it never had a component part replaced except for the normal consumables. That same year our shop sold more aircraft sparkplugs than any other shop in the world. We were supplying plugs for a virtual airforce that was fighting over 5 million acres of forrest fires with borate bombers. Most of these were converted WWll aircraft such as PB4Y-2 Privateers, B-25's, Boeing C-97's, DC-6's, PBY Catalinas and a host of others. Some aircraft required 144 plugs per change.

Geno Castellano
10-05-04, 11:32 PM
and a B29 would have 224 plugs wouldn't it?

Ralph
10-05-04, 11:41 PM
I thought the most each engine was is 24 Cylender? For example the B25 bomber Mitchells. How many sparkplugs are we talking about for each cylender? P38's had V8's.

Geno Castellano
10-05-04, 11:44 PM
I believe a Mitchell had 2 engines with 14 cylinders each for 28 cylinders with 2 plugs per cylinder that would be 56 spark plugs. Those were radial engines with 7 cylinders per bank and two banks of cylinders for 14 cylinders per engine.

CadiJeff
10-05-04, 11:51 PM
two plugs per cyl looks right (lookong at engine pic from grandfather's b-17 1943)

Ralph
10-05-04, 11:54 PM
two plugs per cyl looks right (lookong at engine pic from grandfather's b-17 1943)

A friend told me that the Cadillac powered planes had 24 cyl. engines? Can you confirm?

I think I was wrong about V8's in the P38.

dkozloski
10-06-04, 12:05 AM
A Pratt & Whitney R-2800 has two rows of nine cylinders for eighteen cylinders total, times two plugs per cylinder for thirty-six plugs. A DC-6 has four engines for 144 plugs per change. A KC-97 can have four Pratt & Whitney R-4360 engines which have twenty eight cylinders each which gives fifty-six plugs per engine and four engines total for 224 plugs at around $25.00 a shot. A P-38 had V-12's made by the Allison Div. of GM.
The most exotic engine I am aware of was the 24 cylinder sleeve-valve Napier Sabre made in Great Britain. It was 2200 cubic inch, could turn 5500 RPM and on a test bench developed 4500HP for 175 hours straight. This engine was so intense that the cylinders were made from solid copper to dissipate the heat. The limiting BMEP (cylinder pressure) of most American radial engines was about 180PSI. The Sabre could be operated at 450 PSI before it showed signs of distress. Used in the Hawker Tempest.

RAD
10-06-04, 12:23 AM
The P-38's had Allison inline V-12's.


> P38's had V8's.[/QUOTE]<

CadiJeff
10-06-04, 12:50 AM
the pics that I have don't show a good range to tell but give me 24hrs and I will try to find his service manual from the b17, unfortunately my grandfather died 15 years ago so, asking him would proove problematic at best. Also interestingly enough I have my great uncle's tank service manual too, this particular tank was produced by cadillac and used two cadillac v8s.

dkozloski
10-06-04, 01:06 AM
B-17's had 1820 cu. in. Wright engines of nine cylinders each.

dkozloski
10-06-04, 01:10 AM
The tanks had flathead(L-head) V-8's. Both the exhaust and the intake ports came out between the cylinders. I used to have a 1939 LaSalle ambulance with the same engine but a little smaller.

CadiJeff
10-06-04, 05:46 PM
acording to the manual (b-17-f) the engine had 9 cyl w/ a front and rear spark plug on each, w/ a total displacement of 1823 ci and maximum emergengy HP rating of 1200 a piece @ 2500 rpms on 100 octane fuel and 1100 hp @2500 rpms on 91 octane fuel

the tank was the m5 light tank and it does have the flathead cadillac engines

realhighpockets
10-06-04, 10:59 PM
A KC-97 can have four Pratt & Whitney R-4360 engines which have twenty eight cylinders each which gives fifty-six plugs per engine and four engines total for 224 plugs at around $25.00 a shot.

Same engines in a B-36 but add 2 more =336 plugs. Awesome powerplant with a wet takeoff rating of 3500hp and add 4 J-47 turbojets with ignitors (like a spakplug) for who know how much $$ to replace. I had an auto shop teacher in high school who was a mechanic on them. The engines are inside the wing and that's were you access them for inflight service.

dkozloski, it looks as though you have a wealth of aircraft knowledge. Are you a rated mechanic? I am currently working on my A & P certificate from Embry-Riddle and the Air Force. I take my general test next week. After 22 years of aircraft maintenace, I should have learned something.

CadiJeff
10-07-04, 02:17 AM
the p&w r4360 isn't that also known as the wasp major or am I smoking crack? If so, I have seen those at the USAF museam in dayton, they are huge!

dkozloski
10-07-04, 11:33 AM
realhighpockets, I have been an aviation buff since I was old enough to crawl. I have worked in aircraft and aerospace on and off for almost 50 years. I have had an A&P certificate for over 30 years. I am also have a pilot certificate with land and seaplane ratings but I don't fly anymore. I am the facilities manager of a commuter airline in Alaska. I can look out my office window and see probably the two biggest year around operators of large radial engine aircraft left in the world. It's an airshow every day. DC-4's, DC-6's, a DC-4 Guppy, and C-46's land and takeoff reglarly. Some haul cargo and others are fuel tankers. If you like big round engines it is the nearest thing to paradise. We operate Beech 1900's all over the state.
Cadijeff, an R-4360 is indeed a Wasp Major. The comparable Wright engine is a turbo-compounded R-3350 which has exhaust turbines geared back to the crankshaft rather than for turbocharging and is also rated at 3500H.P.

dkozloski
10-07-04, 03:26 PM
The most miraculous feat would be to get them all firing at once. Mechanics who have worked on R-4360's tell me that with just one dead cylinder they run very rough. Next try to identify the culprit. A trick I used was to make a mark on every exhaust stack with a temp stick to find the cold ones. With small engines and autos, saliva on the exhaust will reveal a dead cylinder.
Another issue with one of those monsters is the amount of smoke that comes out of it when you start it up. When Pan Am used to fly Boeing Stratocruisers in and out of here the crash crews were called out more than once when the controllers thought they were on fire. I was a passenger on one trip from Seattle where more than fifty gallons of oil was consumed by all four engines and oil had to be transferred between engines to keep all supplied. The outside air temp was below -50F and one of the transfer pumps burned up pumping the -50F 100W oil and filled the cabin with smoke.

dkozloski
10-07-04, 06:16 PM
I saw Jack Rousch but I didn't get a chance to talk to him when I was at the night Nextel Cup race at Bristol, Tennessee in late August. My nephew and I had pit and garage passes courtesy of DEI and NAPA. That was a trip that was like a dream come true. My nephew manages the second most profitable NAPA store in the world and they let him know that they appreciate it. I knew Jack rebuilt Mustangs. I think he bought one to fix and fly and another accident victim to use for parts but decided to restore it as well. Ain't it great to have buckets of money. Merlin top ends have always had a short lifespan. I read that they got about 250hrs. between ring and valve jobs by the end of WWll. My recollection is that the American counterpart to the Merlin, the V-1710 Allison, had roller cam followers. The A&P school where I taught had a cutaway and I'm pretty sure about this.

dkozloski
10-07-04, 06:23 PM
In contrast to the Merlins, big old slow turning American radials that had been developed initially for commercial use were getting a thousand hrs. + between overhauls. A friend in the business told me he saw Pratt&Whitney R-1830 engines used in Catalina flying boats that got 3600hrs. between overhauls by being operated at very low power settings on long patrols.

94CaddyConcours
10-08-04, 07:06 PM
I'm an aviaton major, yes it is true that all engine have two sparkplugs per cylinder. They are quite expensive price range fom $50+.
I'm not sure how many cylinders does a B-51 Cadillac have but I can tell you the biggest radial engine that was 27 total cylinders, 9 on each bank. These engine are really amazing, well anyway it all about turbine and turbo prop.
-BILL SONG
-khm3rkaliking

rash_powder
10-09-04, 06:16 PM
The platinum pads are so tiny they will not hurt anything if they fall off. The Bosch platinum plugs are not like the OEM plugs at all. The bosch plugs have the platinum only on the center electrode and it is a tiny piece of platinum embedded in the porcelean tip. The ground electrodes do not have platinum so they wear. This is important on the Northstar (93-99) since half the plugs fire positive-to-negative and the other half fire negative-to-positive. The ones that fire negative-to-positive will wear the ground electrode excessively without the platinum. The Bosch plugs have never shown to be the equivalent of the OEM plugs on the dyno for power or economy. Especially the Bosch+4 plugs with all the extra ground electrodes. They impede the flame propogation and cause a significant loss of power. The reason Bosch makes the +4 plugs is because they don't have the dual platinum technology so they put extra ground electrodes on to account for the wear. The spark plug "heat" has absolutely nothing to do with carbon buildup in the chamber or anything like that. Nothing. The Bosch plugs do not "burn hotter" or anything like that. It isn't the hardness of the material anyway. It's the reactivity of the metal with the plasma created at the spark/arc point. Platinum is very inert in that sense.


could you explain how half fire pos to neg and the other half fire neg to pos? i thought that the engine was connected to the ground, so that they all had to go + to -, just like basic electricity (ignoring the fact that it actually goes the other way).

thanx,
rash

dkozloski
10-09-04, 06:59 PM
Which direction the spark jumps is strictly a wiring arrangement issue. Back when you started a Chevrolet by stepping on a plunger on the floorboards(1947), connected to the starter switch was another switch that every time you stepped on the plunger it reversed the polarity of the current through the distributor to even out wear on the points. This feature was the first item to fail on the car because the switch was on the bottom of the floorboards and caught all of the muddy spray. I don't think I ever saw one of those switches that wasn't bypassed. A good idea, brilliantly conceived and poorly executed.

dkozloski
10-09-04, 07:07 PM
Come to think about it there were some other crappy ideas on those old cars. The gear shift was on the column and only operated one lever on the transmission. There was also a little selector built into the linkage that made the lever select between low or reverse and second or high. The system had a booster diaphragm that used engine vacuum to help move the lever. This selector type shift made operation vague at best and if the engine wouldn't run, to push start, it took both hands on the gearshift handle and both feet against the dashboard to get it into a gear. It was hard to tell if it was the diver or the diaphragm that made the loudest wheezing sounds. There was a fixation on the use of vacuum. The windshield wipers also ran off of it. When you stepped on the gas and pulled out to pass someone in a rain storm the wipers would slow down or quit. On a hill it was the same story. Eventually a vacuum pump was incorporated into the fuel pump. This didn't help the shifting with a dead motor however. That is what the old fogeys call the good old days.

Geno Castellano
10-09-04, 08:52 PM
could you explain how half fire pos to neg and the other half fire neg to pos? i thought that the engine was connected to the ground, so that they all had to go + to -, just like basic electricity (ignoring the fact that it actually goes the other way).

thanx,
rash


The 93-99 Northstars use a direct fire ignition system with so called "waste spark". That is, each plug fires every revolution of the engine. Once on the power stroke and once on the exhaust stroke (that would be the wasted spark). This is done so that the system only needs 4 ignition coils instead of eight. With 4 ignition coils each coil fires 2 cylinders. If you look at the coils you will see two high voltage towers per coil. The electical winding of the ignition coils is such that one of the high voltage connections is "positive" and the other is "negative". So. the circuit that is completed by the spark plugs thru those particular high voltage terminals is such that the center electrode is "positive" on one plug and "negative" on the other. For each of the 4 coils there is one positive and one negative high voltage connections so half the spark plugs arc from the center electrode to the ground electrode and the other half arc from the ground electrode to the center electrode.

It has nothing to do with reversing polarity to even out wear or anything on any of the parts. It is just the nature of the ignition coils with two high voltage windings in the same coil.

RAD
10-09-04, 09:45 PM
The 93-99 Northstars use a direct fire ignition system with so called "waste spark". That is, each plug fires every revolution of the engine. Once on the power stroke and once on the exhaust stroke (that would be the wasted spark). This is done so that the system only needs 4 ignition coils instead of eight. With 4 ignition coils each coil fires 2 cylinders. If you look at the coils you will see two high voltage towers per coil. The electical winding of the ignition coils is such that one of the high voltage connections is "positive" and the other is "negative". So. the circuit that is completed by the spark plugs thru those particular high voltage terminals is such that the center electrode is "positive" on one plug and "negative" on the other. For each of the 4 coils there is one positive and one negative high voltage connections so half the spark plugs arc from the center electrode to the ground electrode and the other half arc from the ground electrode to the center electrode.

It has nothing to do with reversing polarity to even out wear or anything on any of the parts. It is just the nature of the ignition coils with two high voltage windings in the same coil.

OK, we've got the 'how' but not the 'why'..
Lets get real fundamental here...Whats the ultimate purpose in the duality of this design?

CadiJeff
10-10-04, 08:05 PM
Production economy, this arrangement has been around on other GM cars since well before the northstar.

peteski
10-11-04, 02:03 AM
With this arrangement you don't need a distributor (eliminated several moving parts which could break) and you only need 4 coils in an 8 cylinder engine (saving cost of 4 coils).

So, the engine is more dependable and it costs less to manufacture (less parts).

Quite clever in my opinion...

Peteski

RAD
10-11-04, 09:27 AM
Ok, what I meant was the true engineering/combustion chamber application here...I understand cost of manufacturing and all that, along with present day distributorless ignition systems. Howevewr, there are many applications that work successfully on a single mode fire design. I was wondering what the advantage was with the '93-'99 application of this method...

CadiJeff
10-11-04, 11:25 AM
Ok, what I meant was the true engineering/combustion chamber application here...I understand cost of manufacturing and all that, along with present day distributorless ignition systems. Howevewr, there are many applications that work successfully on a single mode fire design. I was wondering what the advantage was with the '93-'99 application of this method...

Ther is no reason other than the pieces already existed and worked reliably.

Geno Castellano
10-11-04, 02:12 PM
Ok, what I meant was the true engineering/combustion chamber application here...I understand cost of manufacturing and all that, along with present day distributorless ignition systems. Howevewr, there are many applications that work successfully on a single mode fire design. I was wondering what the advantage was with the '93-'99 application of this method...


Not sure what your exact question is so select from the following possible answers: :p

The secondary voltage windings for the two high voltage outputs on each of the coils is actually one continuous winding. ie. if you use a VOM and do a continuity check from one secondary voltage terminal to the other on each coil you should see continuity. So, when the primary field is energized it produces a voltage on the secondary coil and one end of the coil is at one of the secondary towers and the other end of the coil is at the other of the secondary towers. So when the spark occurs it is completing the circuit from one secondary tower to the other - so across one gap the spark is positive-to-negative at the plug tip and at the other plug in series in the circuit the spark is negative-to-positive. :)

The coils are wound this way so as to provide the secondary voltage for two plugs instead of just one. That way you only need 4 coils instead of 8. The coils fire in a waste spark arrangement for several reasons:

The waste spark is also necessary to get away with only 4 coils instead of 8 on a V8 engine. With a 90 degree V8 with a 90 degree crank there are always two pistons at top dead center every 90 degrees. One of them is at the compression/firing position and the other is at the exhaust position. If you hook both of those cylinders to the same coil and fire them both at the same time then one of the "sparks" will be used to initiate combustion and the other will be "wasted". The next time both of the paired cylinders will fire the first cylinder will be "wasted" and the second one will initiate combustion. That way one coil can operate two cylinders.

By wiring the coils direct there is no need for a distributor. And by having two windings in each coil there are only 4 coils needed instead of 8. Both items reduce complexity, eliminate maintenance and eliminate parts that can fail. More reliable, less costly and no maintenance required.

If the ignition system is designed with 8 coils then the ignition MUST know crank position AND cam position so as to sequentially fire the correct coil. As mentioned above, two cylinders of the V8 are at TDC every 90 degrees but only one of them is at the compression/firing position. The ignition system would have to know cam timing and cam position to tell which cylinder is at TDC compression/firing so as to fire the correct coil. This adds complexity to the ignition system. With the 93-99 ignition system the crank position is fed direct to the ignition system from the crank sensors. The ignition system simply looks at crank position and starts firing the next set of plugs that come alone. It doesn't matter which of them is at compression/firing since both of them will spark and one will be wasted. Otherwise the system would have to have the cam signal, process the cam signal as well as the crank signals to determine which cylinder to fire and account for the added complexity and then have 8 coils so that the correct one can be fired. In other words - simplicity! :D The direct fire system with 4 coils is very reliable and simple.

By having the direct fire system it can operate as long as a single crank sensor is working and 12 volts is at the coil pack. It does not need the PCM to fire the spark. There is built in redundancy in the coil pack to operate the ignition independent of the PCM and feed the PCM the crank position info.

Faster starts. Since the ignition only needs crank position and it can determine that within about 120 degrees of crank rotation at start up the ignition can start firing the plugs almost instantly upon cranking for very fast starts. If it had to wait for the cam position sensor this could take at least 360 degrees of crank rotation before ignition could start.

Any of these answer your question? http://cadillacforums.com/forums/images/smilies/drinker.gif

RAD
10-11-04, 05:51 PM
I understand all the previuos technology...(as fascinating as it is..)
(Maybe I should of asked for the 'end purpose')...

THERE'S the answer I was looking for! :

>[Faster starts. Since the ignition only needs crank position and it can determine that within about 120 degrees of crank rotation at start up the ignition can start firing the plugs almost instantly upon cranking for very fast starts. If it had to wait for the cam position sensor this could take at least 360 degrees of crank rotation before ignition could start.<

Thanks!

peteski
10-12-04, 02:55 AM
Ok, what I meant was the true engineering/combustion chamber application here...I understand cost of manufacturing and all that, along with present day distributorless ignition systems. Howevewr, there are many applications that work successfully on a single mode fire design. I was wondering what the advantage was with the '93-'99 application of this method...

To be very direct: This arrangement has nothing whatsoever to do with "engineering/combustion chamber application".

It is only used for simplicity and reliability - nothing else.

Peteski

peteski
10-12-04, 03:04 AM
I understand all the previuos technology...(as fascinating as it is..)
(Maybe I should of asked for the 'end purpose')...

THERE'S the answer I was looking for! :

>[Faster starts. Since the ignition only needs crank position and it can determine that within about 120 degrees of crank rotation at start up the ignition can start firing the plugs almost instantly upon cranking for very fast starts. If it had to wait for the cam position sensor this could take at least 360 degrees of crank rotation before ignition could start.<

Thanks!

You are reading too much into this particular feature. Faster Starts is just one of many advantages of this arrangement, not *THE* advantage. GM Engineers didn't just sit down and said: Lets design the ignition which starts faster...

I think that faster starts is one of the side effect of this arrangement. I'm sure the main goal here was to have a simple and reliable system while using the minimum number of parts.

The fact that the Ignition Module can operate without PCM (in a failover mode) is in my opinion much more important than faster starting. And having 4 coils instead of 8 is also easy on your pocket too...
And so on...

Peteski

RAD
10-12-04, 09:54 AM
You are reading too much into this particular feature. Faster Starts is just one of many advantages of this arrangement, not *THE* advantage. GM Engineers didn't just sit down and said: Lets design the ignition which starts faster...

I think that faster starts is one of the side effect of this arrangement. I'm sure the main goal here was to have a simple and reliable system while using the minimum number of parts.

The fact that the Ignition Module can operate without PCM (in a failover mode) is in my opinion much more important than faster starting. And having 4 coils instead of 8 is also easy on your pocket too...
And so on...

Peteski


Actually Peteski, I gleaned the answer I was looking for from bbobynski's reply. But, your observation about what is being read here may benefit some others reading this string...don't know.

It is apparent that I didn't make my question direct enough (although the information in the response is a benefit to all). Like I said in an earlier post, I understand the design and economic motivations in the cost of manufacturing. I was merely wondering what the beneficial end result would be of the secondary waste spark event that was a product of those motivations. I found it hard to believe that it accomplished nothing.

I might add that is interesting that Cadillac went to an individual coil per spark plug, following this design...

Geno Castellano
10-12-04, 10:56 PM
Well, there's no single reason why the direct fire system was used. Any and every design has pros and cons, of course. The really is no "purpose" for the waste spark. It's just the nature of the beast with an ignition system that uses direct fire coils that fire more than one cylinder. It doesn't hurt anything (although it could be argued that the extra sparks would wear the plug gap quicker but with dual platinum plugs that's a non issue) and using waste spark allows the system to be simpler, less costly, more reliable, etc. ALL those things were taken into account when the ignition system was designed.

Yes, in fact, GM Engineers DO design ignition systems for fast starting. As far as I've been told, that was a "must" in the ignition design. There are other ways to make the system sync and fire quickly but the waste spark, direct fire system fires extremely fast on cranking, is simple, less expensive, very reliable and has no moving parts to wear or adjust or need maintenance.

In addition, the PCM's of the time were controlled using a simple RPM and crank position "reference signal" input. The direct fire system provides that to the PCM as a by-product of processing the crank signals in the ignition module.

It is hard to answer questions like this simply because there are SO MANY factors involved in the design and decision to use one system over the other. None of the answers are simple. The later design shift to coil-at-plug ignition systems (on the 2000 Northstar) came about for several reasons.

One reason is that the state-of-art of ignition coils has improved dramatically since the direct fire system circa 1993 (and designed in the late 1980's). The coils have gotten tiny for the coil-at-plug systems.

The direct fire system radiates some level of RFI (radio frequency interference) and EMI (electromagnetic interference). Increasing power in the ignition system makes this even worse. As later emission requirements and engine designs needed higher voltage levels under high load conditions the need for more powerful coils increased and the chance of EMI worsened. So, bury the coils in the cam covers and the spark plug wells to shield against EMI and the problem dissappears.

With higher secondary voltages the electrical requirements for the system increase. Since the higher voltage is only needed occasionally the coil-at-plug design allows voltage scheduling by the controller (the PCM) to reduce primary voltage and current unless the higher out put is needed. This extends coil life, reduces coil temps and reduces electrical load on the vehicle.

Development of increased capacity PCM's with faster processors and more capacity allowed the inclusion within the PCM of the entire ignition system including deciphering the crank sensor signals, crank position, and firing 8 individual coils. This was not possible with the PCM technology of the 1993-1999 systems. Besides, adding 8 coil drivers in the PCM creats more heat and electrical load within the PCM and also requires 24 more wire connections to the PCM.

Moving the PCM underhood (as was done in 1996) set the stage for the coil-at-plug ignition system as the bulk in the wiring harness and length to the PCM was reduced significantly.

Now for a quiz. :D What is the single most commonly discussed "tuneup" item on Northstars. Okay, forget the quiz. I'll answer... Spark plug wires! As long as there are spark plug wires even a totally bulletproof ignition system will eventually need new wires. And without them the ignition will start to break down. This is an emission item also what with the increasing certification requirements for cars to pass at 150K or further. The only way to eliminate spark plug wire ignition related problems is to eliminate the spark plug wires. Seems too simple of a reason, right? That is one of the main benefits, though. No more spark plug wires to wear out, break, cause problems with moisture, etcetera...

We should try not to make all these issues a black and/or white type of deal. There's no simple answer so no one is right or wrong. There's always a compromise in any design. I guess this is what engineers do. Tough job. They come to the most elequent compromise to solve a problem.

[/novel]

RAD
10-12-04, 11:54 PM
Once again I log off, knowing a great deal more on the subject than when I logged in...Thank you Geno.

peteski
10-13-04, 01:09 AM
Yes, another awesome post!

Thanks Geno!
:worship:

wake
10-14-04, 12:29 AM
I recommend the OEM dual platinum plugs. Period. They run better than any other plug in the Northstar engine because they were developed for that engine.

The likelyhood of a platinum pad falling off is miniscule. I happened on some of the original plugs installed in the factory back in the early 90's. The process for attaching the platinum pads has improved significantly since then and it is highly unusual for them to come off anymore.

The plug still works fine if the platinum falls off. It'll just start to wear and the gap will open up and eventually it will cause a misfire. It probably takes about 40-50K for a misfire to show up if the platinum does fall off depending on whether the center electrode or the ground electrode lost the platinum and which cylinder it was (due to the electrical polarity of the coil winding for that cylinder) so I wouldn't worry about it.

The Rapid Fire plugs are ok but they erode the gap fairly quickly since they are not a platinum plug so I wouldn't expect them to be at the top of their game for over 10-15K. Stay away from the Bosch plugs unless you don't want full power.


I've had several GM cars with the factory platinum plugs that were missing their pucks... Both my 96 Corvettes were missing several, and a few plugs on both my 94 and 98 Northstars were missing their pucks... It's a lot more common than I'd like to see... Over on the Corvette Forum, many people there also experienced missing pucks on their factory plugs...

I agree with you on the Rapid Fire plugs... I tried several sets on various cars over the years and they never seemed to last move than 10K miles...

I've never had any problems with Bosch plugs though with exception of one car... On my old Camaro, I just didn't drive it hard so the plugs got loaded with carbon... On all my other cars though, I've had good luck with the +4s and +2 plugs... And if I lost any power with the Bosch plugs, my dyno from my previous 96 Corvette didn't show it...

I think this is the only subject I'd have to disagree with you on... The first thing I've done on the last 4 GM cars I've bought was to pull the plugs and not think twice about seeing missing pucks...

Geno Castellano
10-14-04, 12:12 PM
I've had several GM cars with the factory platinum plugs that were missing their pucks... Both my 96 Corvettes were missing several, and a few plugs on both my 94 and 98 Northstars were missing their pucks... It's a lot more common than I'd like to see... Over on the Corvette Forum, many people there also experienced missing pucks on their factory plugs...

I agree with you on the Rapid Fire plugs... I tried several sets on various cars over the years and they never seemed to last move than 10K miles...

I've never had any problems with Bosch plugs though with exception of one car... On my old Camaro, I just didn't drive it hard so the plugs got loaded with carbon... On all my other cars though, I've had good luck with the +4s and +2 plugs... And if I lost any power with the Bosch plugs, my dyno from my previous 96 Corvette didn't show it...

I think this is the only subject I'd have to disagree with you on... The first thing I've done on the last 4 GM cars I've bought was to pull the plugs and not think twice about seeing missing pucks...


The older generation of the dual platinum plugs had a greater propensity to loose the platinum pads with higher mileage. That has been improved over the years and it is rare to loose a platinum pad on current plugs. The OEM dual platinum plugs in Northstars have changed suppliers over the years 3 times in search of better manufacturing methods and better quality control on the platinum process.

dkozloski
10-14-04, 07:00 PM
The side electrodes of fine wire aircraft plugs fit in a slot cut in the rim of the shell and appear to be bonded in place as you can't get them out whole except in rare cases. To reclaim platinum I had a very small pair of chain nose pliers that would get a good grip and I could pry out the little pieces. The center electrode was bonded into a hole bored into the center conductor that appeared to be made of nickel. The platinum projected through a small hole in the center of the insulator from the larger hidden center conductor. I can't recall more than one or two side electrodes that fell out of the shell in the thousands of plugs I have examined over the years and I don't recall a single center electrode that was missing rather than worn to a knubbin although I did see one rattling loose in the insulator. The brands I can recall are AC, Champion, Auburn, Autolite, and BG. It sounds like the problem isn't that they can't build the automotive variety to last but they can't build them to last for the price they get paid. Back then the cheapest plugs were about $8.00 ea. for massive electrode and the hybrid platinum/iridium sold for up to $42.00 each.