MSD Spitfire Ignition

[outlander]

I honestly felt that much of a difference with the truck plugs and big wires(really couldn't believe it myself)........YMMV

 

[TiRod]

I think the proposition that if the spark ignites, it explodes is sound. The point of a CD ignition is to make absolutely sure there is a spark that can ignite a continuing oxidation reaction.

Combustion chambers aren't static or homogeneous. Deliberate swirl designs, the forced draft of the quench chamber contracting to a few ten thousandths, and the continued induction from the closing valve and it's own movement, plus the rapidly slowing piston itself all produce turbulence - which can and does snuff the initial flame front. That's called a misfire - a common complaint in all motors.

When the quickly compressing gas mixture is inadvertently ignited, ping, dieseling, and other uncontrolled flame propagation occurs - some of which is potentially damaging. That's specifically why CD ignitions were developed for on the edge, less than optimum combustion chambered engines - especially those used in racing.

Not necessarily the 4.0's main purpose in life - but in a motor with more than 150k - and there are lots of them now - carbon deposits and less than optimum induction in the ugly log manifolds Chryco abandoned may be reason enough to add the system.

Once the spark has ignited the mixture, sure, it should explode - but it doesn't always do that. So plug makers jumped on multispark plugs - split electrodes, multi electrodes, surface gap plugs, the diamond hole electrode plugs, and now, capacitor discharge plugs - plugs that fire multiple times.

Aside from upping the amperage beyond safe limits, multiple spark discharge is exactly what "Detroit" is avoiding. I believe it's because they can get results cheap with a standard coil and plug.

Kinda like adding an air pump was cheaper than building the engine to closer tolerances.

 

[Fred]

The gas/air mixture does not explode, it burns. It burns very quickly, but it does just burn. If it explodes, you have engine knock.

Fred

 

[89xj]

I'm with you on the aftermarket ignition systems, but do you really think you can feel the difference between spark plugs and wires? It takes a fair amount of power increase to actually be able to feel it. Sounds like the placebo effect to me. Not a big deal, if you do, you do.






Like someone just said, if the spark ignites the mixture, then the mixture is ignited. Unlike a diesel, a gas engine is sensitive to the air/fuel ratio, and once it explodes, it explodes. The explosion will ignite more in the cylinder than another spark will, plus with an explosion it all happens at once. Again, gas is not like diesel, diesel burns and keeps expanding as the piston goes down, but a gas engine has one ignition event so one explosion expands the gasses that push the piston down, once it's exploded, it's exploded. Don't see what a second spark would do, unless the engine is so worn out or out of tune that the first spark didn't always ignite the mixture.



The XJ coil puts out over 100,000 volts, as do all modern coils, unlike old coils that put out around 36,000 volts. You can improve on 36k volts, but it's damn hard to improve on 100+k volts. That mixture is going to ignite unless there's something else wrong.

100,000 volts, i dont think so. xj ignition and most electronic ignitions put out between 40-50k volts. the advantage to msd is at higher rpms, 5000k and up. on an xj that has a good ignition system and doesnt see high rpms, its not needed for performance.

with that said, i have an msd 6 ignition box and ss blaster coil on my 89. i also have upgraded battery cables, added grounds, red top battery.... these are not seat of your pants performance upgrades, but my 89 runs very smooth and starts up on the first turn of the key in under 3-5 seconds, which is good for the renix. i have nothing to say negatively about the msd system as i have not had 1 problem with it since the install about 6-7 years ago.

at the time of the install, my 89 was in need of repair and i had the money to invest. if money is tight, it could be spent in other areas that need it more.

 

[Goatman]

I think the proposition that if the spark ignites, it explodes is sound. The point of a CD ignition is to make absolutely sure there is a spark that can ignite a continuing oxidation reaction.

Combustion chambers aren't static or homogeneous. Deliberate swirl designs, the forced draft of the quench chamber contracting to a few ten thousandths, and the continued induction from the closing valve and it's own movement, plus the rapidly slowing piston itself all produce turbulence - which can and does snuff the initial flame front. That's called a misfire - a common complaint in all motors.

When the quickly compressing gas mixture is inadvertently ignited, ping, dieseling, and other uncontrolled flame propagation occurs - some of which is potentially damaging. That's specifically why CD ignitions were developed for on the edge, less than optimum combustion chambered engines - especially those used in racing.

Not necessarily the 4.0's main purpose in life - but in a motor with more than 150k - and there are lots of them now - carbon deposits and less than optimum induction in the ugly log manifolds Chryco abandoned may be reason enough to add the system.

Once the spark has ignited the mixture, sure, it should explode - but it doesn't always do that. So plug makers jumped on multispark plugs - split electrodes, multi electrodes, surface gap plugs, the diamond hole electrode plugs, and now, capacitor discharge plugs - plugs that fire multiple times.

Aside from upping the amperage beyond safe limits, multiple spark discharge is exactly what "Detroit" is avoiding. I believe it's because they can get results cheap with a standard coil and plug.

Kinda like adding an air pump was cheaper than building the engine to closer tolerances.

Just a couple comments, for sake of discussion. Most racing engines do have optimized combustion chambers, those guys buy aftermarket heads and they know how to build motors, ask Russ, so that argument doesn't make a lot of sense. The increased swirl that is designed into newer motors, and into older well built motors, creates a better mix of the fuel and air and contributes to cleaner and more efficient cumbustion, it's not a bad thing that can blow out the spark. Modern engines have increased swirl, it's not a problem that needs to be fixed, rather it solves a problem. In our motors, and a lot of us are building strokers, the tighter the quench height the higher compression you can run and still use regular gas because there is less chance of pre-ignition. More swirl doesn't create a need for a multiple spark system, it sort of eliminates any need for it by increasing the combustion efficiency. If swirl caused a misfire, engine designers have a major problem when meeting emmisions standards. If misfire was a common complaint in all motors, as you say, none of them would ever pass smog. Nothing will fail you faster in a smog check than unburnt fuel, plus misfire in a modern motor usually sets off a check engine ligt.

Car makers don't go cheap on design, they spend millions and millions on engineering and testing to meet federal standards for emissions and fuel efficiency, and to make power to be competitive and sell cars. I think it's safe to say that the modern engine is burning pretty damn efficiently the way it comes from the factory. If getting a cleaner burn was as inexpensive as using a multiple spark discharge, they'd be doing it already, and maybe some of them are.

Also, Detroit added air pumps many, many years ago. Current engines are built to extremely tight tolerances. One reason they run fairly light weight oil, and the factory won't allow dealers to do any engine rebuilding. If a motor has a problem, the factory sends a new motor. Current motors are pretty tight.

CD ignition systems are as old as the hills. We had a CD ignition on the family flat fender Jeep with a Chevy V8 when I was in high school, and that was in the 60's.

Sorry, but your whole argument sounds like it was based on thinking from 30 years ago.

 

[TiRod]

I don't doubt the idea that properly designed heads help promote swirl and combustion. I was pointing out that in the day CD ignitions were first used, properly designed heads were still a hope in the future. So, I was talking about 30 year old technology, and yes, modern designs, machining, and construction are a whole lot better.

Looking at the chambers of the 4.0, you don't see it - and the hp ratings match. A 170 to 215 hp inline six hasn't been the recipient of millions and millions of dollars of development. The HO was a nice high port improvement, the NVR blocks great for what they offer, the '99 up "rainbow" manifold another air flow improver - but none of it really high tech. We're still not even talking a cross flow head, much less an aluminum block. The 4.0 is still pretty much the way Nash started out with it in the '50s.

It's a common statement on other make forums not to bother with the expense of a high dollar CD when the factory did so well. One of the things that has gone along with the improved ignitions is real improvements in engine design and development, just as pointed out. The 4.0 (Nash) motor hasn't seen much of that. In fact, the lack of truly modern, economical updating is what killed it - a roller cam V-6 is a lot more efficient, packages more easily, casts, machines, and assembles on production machines optimally designed for V-engines, not inlines.

So, like the older Chevy motored Jeeps of the 60's, a CD ignition in a Cherokee may have more potential than some other late model optimally engineered coil on plug wonder.

It's all food for thought, will a CD ignition like MSD's Streetfire help our old motors?

 

[winterbeater]

Combustion chambers aren't static or homogeneous. Deliberate swirl designs, the forced draft of the quench chamber contracting to a few ten thousandths, and the continued induction from the closing valve and it's own movement, plus the rapidly slowing piston itself all produce turbulence - which can and does snuff the initial flame front. That's called a misfire - a common complaint in all motors.

Wouldn't that generate a CEL code?

 

[TiRod]

Exactly. Work at a parts counter and you have a daily stream of customers coming in to read codes because of CEL's popping on.

Aside from the gas cap, one of the top codes is "Misfire on cylinder X." At that point the conversation quickly turns to what expensive components need to be replaced, again, and why.

Are iridium plugs with attached individual coils that bad, or is OBD a little too sensitive? Millions of dollars spent in design, and you have to go to the dealer for more worK? :bawl:

Would a CD ignition clear the problem up by firing that plug 15 times and getting some kind of burn?

 

[Johnnie Walker]

I know this is kind of an old thread, but what years of 4.0L do the MSD 8228 coil's work on? Also, where's the best place to get a stock replacement if the MSD coil will not work. I have an 1989 with renix motor.