Ignition and Ignition modules

[kb1gtt]

So what's a good ignition module? There are many OEM options which can often be obtained for the cheap with a harness connector from a salvage yard like the J701. For me, I've generally built my own, I have found chips and used them on a PCB I designed. Others have simply manipulated the OEM low voltage signals and used what ever was in the vehicle like the HEI systems. Seems there are lots of approaches in how you go about getting ignition. So I wonder what's a good suggestion for someone with an engine that has a spark plug and that's about all. Things like a water tight connector can be really handy, as well having a proven history of working is also really handy. So my option is often not so friendly to many DIY'ers.

Here's a used J701 that appears to come with a harness connector, from e-bay for under $25 http://www.ebay.com/itm/89-95-Mazda-Protege-MX3-323-B2200-B2600-MPV-Ford-Aspire-IGNITER-J701-BP0118251-/111252460348?_trksid=p2054897.l4275 This seems a bit high when I know the chip found on an OEM 5554 ECU I have kicking around, is less than $1 http://octopart.com/ngd18n40clbt4g-on+semiconductor-343155

There are lots of options including the J701 listed on this page, this page is nice as it includes pictures with pin outs. http://www.iftim.cn/IgnitionSystemParts/IgnitionModule.htm

So I wonder, what would be considered a good ignitor? I also wonder if some of these modules might have some kind of feedback that could be handy. So I say start a discussion here and we'll see what others have for suggestions.

[AndreyB]

No idea is it is good or bad, but I know that it runs on 3.3v - toyota 89621-33020 igniter
+ it is 6 channel

On the car it is located under the hood on the driver side strut column.

[AndreyB]

Vehicle:Mini_Cooper_2003 has coil controlling stuff inside the ECU - the thick wires go directly to the coils. Can you please elaborate on "I have found chips and used them on a PCB I designed."? Is it time for a high-power ignition module?

For start I will simply use external ignition module.

[puff]

COPs controlled by logic signal?
Am I right in my believe that the greater the voltage in the coil (the more energy), the better? or there is some certain threshold, and further increase is unnecessary?
does it somehow depend upon plugs?
btw, all these words about iridium(?) sparks with multiple electrodes igniting the fuel-mix at the ion level - is it true or just marketing bullshit designed to push up sales?

[AndreyB]

COPs controlled by logic signal?

I've edited the previous message to make it less confusing. No, not COP - it has wasted spark and it looks like the stuff which controls the coils is inside the ECU. This ECU uses tiny wires for injectors and thicker wires for coils.

[puff]

russian, that was sort of my answer to jared, not a question regarding your cooper
this page is strange
http://www.iftim.cn/IgnitionSystemParts/IgnitionModule.htm
so plenty of them - what's the difference?

to jared
25$ for such a thing could be a good price, but shipping costs to here would be another 50$ (or even more).
mine cost me ~40$, it looked something like this:

25102012784_cr_result.980x735w.jpg (387.29 KiB) Viewed 20180 times

and here I've found some porn:

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ign4.jpg (45.52 KiB) Viewed 20180 times

[puff]

and more (sorry for these strange letters):

ign5.jpg (101.89 KiB) Viewed 20180 times

ign6.jpg (97.77 KiB) Viewed 20180 times

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[puff]

and here's its schematics:

SensLanos-1.4i-143.jpg (106.69 KiB) Viewed 20180 times

(i believe it's from my module)
so the question now is if powering it for some time without 5v impulses is okay for the module.
and how fast power on and a constant 5V logic level on one or both channels will ruin the module…

I also got a nice graph illustrating dwell time dependency upon voltage (thanks to some man with an oscilloscope)…
however I guess it could be different for each very instance of this device, so the best bet would be measuring this dwell time individually for each particular coil…

here are its specs:
Work temperature: - 40 °С to + 130 °С.
Nominal voltage: 12В.
Weight < 1.32 kg.
Dimensions: 110x117x70 mm.
Primary current: < 6.4 А.
Secondary voltage with primary current of 6.4 А and shunt load(?) 50 pF: 28 kV.
spark discharge energy (>): 50 mJ.
duration of spark discharge (>): 1.5 мс.

I believe, we can make triple sparks during cranking

[kb1gtt]

About spark heat, that's a kind of complicated one, with many dynamic variations. For inductive discharge ignition, generally you store energy in the coils magnetic flux then you dissipate most of it across the spark plug gap. The voltage to start an arc generally bump up very high, then drop lower once the air has ionized. The voltage and such is mostly dependent on the gap, compression, humidity, temperature of the fuel air charge and heat of the plug. If you have a hot plug, it may ionize early, or if you fire at a low pressure, it takes less voltage to get the arc started. Remember that once you start combustion, your compression goes up very much. So lots of dynamic items happening all in a sort period of time.

Generally you want to dissipate enough energy to create a spark that is hot enough and long enough to ignite the fuel air charge. You can control the voltage by changing the gap, or by changing when you fire, as you're increasing compression as you wait. Then you can control the amount of energy dissipated by controlling the dwell. The voltage profile will be basically the same so the the dwell really determines how long the spark will be. You want the spark to be long enough such that you get enough fuel and air ignited to get a good flame front. Remember that if you ignite only say one fuel carbon, that will likely either create an abnormally shaped flame front, or it might not ignite enough fuel to sustain a flame front. So you really want to keep the spark long enough to get a more uniform flame front, which will burn more fuel.

If you have to hot of a spark for to long of a time, you can erode your plug abnormally. However a longer spark duration helps ensure the spark doesn't blow our, or that you had a spark for a long enough period of time for some fuel to be present in the gap. Remember that air fuel is inconstantly mixed and swirling violently in the cyl.

So about all these different claims about different plugs being better ect. It's mostly horse shit on modern cars. Almost all the time, you'll see demo's done on old engines with points and distributor and such less intelligent systems. For those systems you control the spark and it's characteristics mechanically, which allows a plug MFG to tune for certain parameters. However this takes less of an effect with modern cars which will often tune the spark to help minimize erosion. For OEM applications, the plug only make a mild difference.

About which module, I only have experience with a small collection of them. Because of that I'd generally suggest the J701, as it's reasonably low cost, easy to mount to a heat sinking plate, and works good enough for most applications. For performance and multi-spark capabilities, I'd generally suggest CDI COP technology, but that's often harder to retrofit on an engine that's not designed for that technology. The transistors integrated into the coils are also reasonably good, and help minimize the RF generated that can be picked up by other devices. However if you get any problem with any part of it, the entire thing has to be scrapped. So it can get to be a bit pricey, for DIY thing as you can easily damage the primary winding's, or you can over voltage the internal transistors.

Yes can you please post the dwell pictures.

[puff]

here are we go (thanks to L.S.Sokolov)

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[Nobody]

Why not use GM L2/3/7 coils (a simple TTL output controls them)? I can supply dwell time vs. voltage...

[AndreyB]

Why not use GM L2/3/7 coils (a simple TTL output controls them)? I can supply dwell time vs. voltage...

Pictures? Price?

I guess it all depends on the stock vehicle configuration. If some coils are already there - most people would want to keep them.

[Nobody]

Why not use GM L2/3/7 coils (a simple TTL output controls them)? I can supply dwell time vs. voltage...

Pictures? Price?

I guess it all depends on the stock vehicle configuration. If some coils are already there - most people would want to keep them.

Above is LS2

Price - I've seen them for $20 each used. Nice thing is it is a MPU TTL output, that's it. They are used by many aftermarket ECUs, even on experimental aircraft.

[AndreyB]

Nice thing is it is a MPU TTL output, that's it.

Even 3.3v TTL?

[Nobody]

Not sure, I'll see if I can dig up cutsheet. Remember these need a dwell (charge time) vs voltage table (this info I have).

[puff]

almost four times more expensive than mine (per plug). although should be more reliable. as far as i got, some of the modern "Soviet" cars are also using somewhat COPs, obtainable at the same price (20$ per plug) new, also controlled with 5v ttl signals (if i'm not mistaken).
considering that the brighter the spark, the better - i'd compare various ignition options. probably CDI would give much stronger spark than any of these systems.

[Nobody]

almost four times more expensive than mine (per plug). although should be more reliable. as far as i got, some of the modern "Soviet" cars are also using somewhat COPs, obtainable at the same price (20$ per plug) new, also controlled with 5v ttl signals (if i'm not mistaken).
considering that the brighter the spark, the better - i'd compare various ignition options. probably CDI would give much stronger spark than any of these systems.

These ignition coils are used on 1200 HP V8 engines (no joke - camaros and vettes).

Generally speaking CDI is stronger but shorter spark. You can also bump up dwell, but this will shorten life span. CDI is good on really lean mixture or fouled plugs.

[puff]

so, basically, it's not just the matter of intensity. duration is also important! i always knew they won't use non-efficient stuff on modern cars).
longer spark is needed just to be sure you make it right in time, or it's the nature of gas ignition inside the chamber, which needs longer spark duration for improving ignition efficiency?

[Nobody]

so, basically, it's not just the matter of intensity. duration is also important! i always knew they won't use non-efficient stuff on modern cars).
longer spark is needed just to be sure you make it right in time, or it's the nature of gas ignition inside the chamber, which needs longer spark duration for improving ignition efficiency?

OEMs favor reliability/cost. CDI still has many supports, as mentioned generally higher voltage but shorter spark which can help in some instances.

What is often done is as cylinder pressure goes up spark plug gap is reduced if energy is fixed. Combustion chambers have come a long way in last 10 years or so, especially on gas direct injection engines, but this would turn into a very long topic LOL.

[blundar]

There are several coils that I use on just about everything that have built-in ignitors and can be driven at logic level:
1. Denso coil sticks. 01+ Honda K/J/D series, Toyota 1zz/2zz, ... ... Very common well-constructed coil made by denso. Typically happy between 2.5 and 3.5ms of dwell depending on exact coil.
2. LSx coils discussed above. Cheap, plentiful, very strong spark @5-5.5ms dwell (long dwell time!)
3. Pantera EFI coils. Aftermarket coil rebadged by AEM, Holley, ... Basically souped-up version of LSx coil.

I typically see:
-150-200hp / cylinder before #1 has issues
-200-250hp / cylinder before #2 has issues
400+hp/cylinder before #3 has issues.

yes, that is horsepower PER CYLINDER not per engine.

[puff]

what's the correlation between the horsepower per cylinder and issues of the coils? more horsepower => greater the pressure is => more difficult for a sparkplug to work?

[Nobody]

If volume stays fixed then cylinder pressure must go up to make more power.

[puff]

still, what's the correlation between HP and coil issues?

[Nobody]

The higher the cylinder pressure the more dense air/fuel charge is, thus more energy required to ignite charge.

You can compensate a little by closing spark plug gap, but you hit point of diminishing returns.

So biggest single variable is cylinder pressure, then head volume. On small engines it’s reversed.

[puff]

btw, what's the usual pressure in the combustion chamber of an engine with the cr 9.35:1? (I wonder if I want to build a test rig to check if my spark plugs work properly

[Nobody]

140-160 PSI depends on cam.

Edit -
You don't need allot of energy for that low a CR without turbo/supercharger/NO2...

[kb1gtt]

On those systems you might be able to bump up the secondary voltage by using an ignitor that can sustain a larger kick back voltage. However you will approach the insulation limits of the coil itself at some point. Those mentioned systems include the ignitor, as well as the coil, so your max generated voltage is limited by the combined components. As nobody noted, for the pressure you set with your compression ratio, you need a gap that is small enough to allow the coil to make the spark. As you increase pressure that allowable gap gets smaller. Eventually the gap is to small to create ignition, or you simply fail to get enough voltage to make the spark in the cyl.

It sounds like blundar has either done a bunch of testing, or has access to testing that shows the power range per device. This power range can be ball park affiliated with cyl pressure.

[puff]

got it. the idea was to save money on regular spark plug changes on the family car park.
but still I need to check the spark plugs in pressurized environment?

[kb1gtt]

Also note that as the plugs wear out, the gap gets bigger. I've seen coils and ignitors fail because the plugs didn't get changed. The gap grew, voltage went up, and components failed.