What's the advantage of coil-on-plug?

S

segxr7

Registered
What was Ford's rationale for switching to coil-on-plug ignition in the late 90s?

Switching from 2 to 8 coils almost certainly made the engines more expensive to build. And not only are there 4 times as many parts to potentially break, but they are completely exposed to vibration and heat from the engine.

The only advantages I can think of is that the engine will still run if 1 or 2 coils fail, and there's no risk of current leakage or arcing between the plug wires. But since coils and wires aren't really a problem in modern cars, it seems like coil-on-plug systems fail to solve a problem that didn't exist in the first place. What am I missing?
 
COP is superior to spark plugs wires
1. Ease of service
2. COP rarely fail
3. No wires to worry about, and maintain
4. More efficient due to the fact the coil is right above the spark plug and the current has a much shorter way to travel
 
maxmk8 said:
COP is superior to spark plugs wires
1. Ease of service
2. COP rarely fail
3. No wires to worry about, and maintain
4. More efficient due to the fact the coil is right above the spark plug and the current has a much shorter way to travel
Click to expand...

1. I do not agree. Some yes, others no. I've worked on several Ford COPs that were a PITA to access.

2. I read and hear of far more failures with the COP coils/boots than standard coils.

3. I've seen many GOOD wire sets last 100K plus. What's so unreliable about that?

4. I'll give on that one.

I think one of the bigger reasons for the switch was easier PCM control of spark.
 
1. COPs are easier to service, but your right when they are tucked away somewhere - but that a mute point since coil service can often entail plug service.
2. I have heard of far more coil packs failures than COP failures. But boot failures!!! ya, happens a lot
3. Wires start building up some resistance from day one. Sure, wires can last 100k but if you service them - toss them. Once you move than at that milage they are so baked moving them can risk internal damage to the wire core.

No as for switching from 2 to 8 coils? There have always been 8 coils. Each coil pack contains 4 coils with 2 sets each - that is two of those four coils fires at once - just like COP, plugs are always firing in pairs. And yes, even one of the four coils in a pack can fail - I'e had it happen.

As for cost, it may be cheaper. No wires anymore. No need to pay someone to carefully route them by hand. Once less item to go wrong (ok, so the boot failure rate makes up for that! )

Vibration is all the same, but your right - the coils take much more heat abuse :(

I switched my 96 to COP last year. But only because I had them. I will be making a write up soon if anyone want to do it :) But you need COP valve covers :(
 
I never had the problem people have with the boots, i think they pull them out wrong or something. Also, no wires, short distance, less EMI.
 
Steve...I second that! Carefully remove, and re-install with di-electric grease.

I would rather have a boot go bad than have to buy a whole set of wires everytime one fails.

Being in the business for 10 years....I've seen coil packs fail 25 to 1 over COP coils, but it is a semi-new technology.

I will agree with you on the "heat" portion, but NOT the vibration. Given they are closer to the engine, but that doesn't mean the vibration is worse. The farther off the engine(i.e.brackets/remote mount) the more they will be exposed to vibration. Being almost right on top of the center most part of the engine, they are exposed to the extreme vibration that the outer extremeties(alt/ac/ps/intake/etc.) will be exposed to. Just because they are closer to the detenation, doesn't mean they will vibrate more. Think leverage...the closer to the "pivot point" the more pressure it takes to move something, if you move out farther from that point, it takes less pressure to gain that movement. Man...I ramble about the most random stuff, lol.

"4 times the parts to break" Good theory, but not true, per say. Yes more parts(coils) but more efficient, better quality, better spark(less drain on a coil), and CHEAPER if one coil fails, vs. paying for a coil pack that contains ALL the coils.

If I had access to COP's, I'd swap my car over in a heart beat! Anyone want to trade my Nology wires for the COP setup? :D
 
steve said:
I never had the problem people have with the boots, i think they pull them out wrong or something. Also, no wires, short distance, less EMI.
Click to expand...

The boots are a very well documented problem. They FAIL by themselves, my car still had the spark plugs untouched when one of the boots failed. At 45k miles. The other three fell apart when I was pulling them out of the engine to check to make sure they were ok. Poor design on Fords part, hands down.

My crown vic and the Jeep as well as the bmw I used to have... have far better boots that are known to almost never fail. Never replaced any of those.
 
Do you suppose this discussion was had back when we moved away from a single coil/distributor ignition to the digital ignition system with X number of coils?
 
Quite possibly so JP. :) And I'm sure the old school guys were pointing their fingers saying "this will never work". :tongue-pink:
 
J said:
Quite possibly so JP. :) And I'm sure the old school guys were pointing their fingers saying "this will never work". :tongue-pink:
Click to expand...

And no way you can have an engine that doesn't need a rebuild every 40-50k miles. That is just crazy talk. :roll_over:
 
Chevy has some DOHC engines... like this 370 cubic inch LT5 monster making 660hp NA:
harris_002ver2.gif


I would take that motor over a new LS7 427 any day.
 
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Lol....but its SUPER easy to change, and you know some Jiffy Lube d00d is going to tighten it SUPER tight! Forget reading the side of the oil filter and going 3/4's of a turn after it bottoms out....I'm gonna keep turning it until my arm hurts. Rofl....I HATE those jerks.
 
What about the dumb idiots at Sears who think that they are part of the jack/tire team on a NASCAR team and uses an air gun on the lug nuts...ON A 91 OLDS CUTLASS grandma car!!!! Why in the hell would you do that?!?!?
 
Yeah but I will be!!! Plus they stripped one of the studs on the hub!!! I so ripped that guy and the shop manager hard that day!!
 
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