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Automotive Ignition Coil Mods

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Speedaddict62

Mon Sept 14 2009, 08:14PM

Registered Member #2361 Joined: Sun Sept 13 2009, 09:04PM
Location: SaarbrÃ¼cken, Germany
Posts: 6

Hello everyone,

This is my first post here! I will start off by saying that you have some very interesting and intriguing stuff here, and although a good deal of it is well over my head, I'm sure it will all eventually come in time. Being new here, I don't know a lot, nor do I know good places to look for more info, so what I'm really looking for are pointers on where to learn more. We've all got to start somewhere, right?

Now onto my topic: I was brought here from my car hobby (read: addiction). Interestingly enough, it ends up pulling me into many different fields, the latest being electronics. There are a bunch of different things I'd like to make, but the one most relevant to this board is a way to increase the output of my car's stock automotive ignition coil.

The system uses waste-spark and is distrubitorless. The engine is a turbocharged. Ignition timing is controlled by the ECU and a transistor box. Two coils are used, connected to 2 cylinders each (1&4 and 2&3 are fired at the same time, while one cylinder is on the compression stroke, the other is on exhaust, hence "waste-spark"). The coils are fired anywhere from about 13 Hz (800 rpm) to over 167 Hz (10,000 rpm, well out of range at the moment but possibly attainable in the future). The spark gap is around .028". That is mostly what I know. My goal is to modify the system for a stronger spark.

Here are my questions:
1. Is this possible?
2. I assume that increasing the voltage to the spark plug would help initiate the spark at less than ideal conditions but that more current will result in a fatter, hotter spark, making it easier to ignite the mixture. Am I right in my assumptions?
3. If the answer to number #1 is yes, what would be involved and where would I start?

This being a DIY project, I'm totally willing to completely ditch the stock parts and use anything else that might work better, like converting to a coil-on-plug system (if that would be beneficial, one coil per cylinder). Essentially, I would like to make a DIY version of an MSD ignition without the bells and whistles. You can view one here: http://www.msdignition.com/Products/Sport_Compact/Import/Ignitions/6212_-_Programmable_DIS-2_with_Boost_Timing_Master.aspx. Interesting info from that page is that that unit delivers 500V to the coil primary and has a spark energy of 190 mJ. The reason I'm not just simply buying one is because firstly, I don't have much money, and secondly, it isn't fun that way! I've done some searching on here and google and found nothing, so since this technically HV, I thought I'd start off by posting here first.

My other electronic project (not HV) is figuring out a way to open my huge 1600cc injectors faster (they're just solenoids). Maybe step up the voltage perhaps? I've heard that V10 F1 cars used 90V triggering systems...but this isn't quite as relevant to this forum as my first project is.

Any comments/info are appreciated, I really need to be pointed in the right direction. I don't have any prior experience with HV projects (little of electronics at all, I'm afraid) but I have taken some college courses (electrical fundementals and physics) which cover the basics.

Proud Mary

Mon Sept 14 2009, 09:25PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Hello Mr Speed, and Welcome to our demesne!

Nothing at all can be done without some simple measuring instruments. Measurement is at the heart of all that we do. Costly kit is only a just a little bit better than your $20 el cheapo.

So what are L and R of your primary, and your secondary? Then we have stuff to talk about.

lpfthings

Tue Sept 15 2009, 05:43AM

Registered Member #1361 Joined: Thu Feb 28 2008, 10:57AM
Location: Cairns, Australia
Posts: 305

I think I remember reading that spark plug cables are made from carbon? If this is the case, you could use something better. Not sure how valid that is though, I only remember hearing it once.

Proud Mary

Tue Sept 15 2009, 08:51AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Nowadays, and depending on your jurisdiction, both plugs and cables may have resistive anti-RFI elements in them. Measure them to be sure.

Mates

Tue Sept 15 2009, 10:08AM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

Iâ€™m not an expert in fuel combustion, but I donâ€™t see a reason why a bigger spark should make any improvement for the engine performance. Simply you make a spark â€“ no matter the size in the explosive environment and you get an explosion. Total energy output will be always the same no matter how big is your spark. The only difference might be in the speed of the explosion. It could be that bigger spark will cause that the energy release will be faster, but this sounds like something you always trying to avoid in the combustion engines. All the shity additives added into the fuel are used to slow down the explosion. I think it is a non-sense, just a commercial trick to make some money on people who are crazy about cars and can triumph themselves by arguments of how big spark energy they have in their tuned puppiesâ€¦

If you want a better theme to explore and which is HV and cars related you could try to look for car ozonizers. They seem to be more realistic devices, moreover should be ecologic (hey car lover - do you even know this word?)â€¦

Btw: I hate cars; mainly those fuel powered. It is a cancer for our planet, such a stupid inefficient piece of prehistoric technology which will kill us all... And why - because of car lovers!

Mates

Proud Mary

Tue Sept 15 2009, 10:14AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Oh dearie me, there's a lot not right in your idea of ignition coils, Hr Mates! Start by Googling "dwell time".

Your pal,

Harry.

Speedaddict62

Tue Sept 15 2009, 12:42PM

Registered Member #2361 Joined: Sun Sept 13 2009, 09:04PM
Location: SaarbrÃ¼cken, Germany
Posts: 6

First off, resistance. These figures are out of the tech manual, I don't have a lot available to me at the moment since I'm out of the country, although I have measured the coil resistances before and they were right in line with factory spec.

Primary: .86 Ohm @ 20 degC
Secondary: 12.1 kOhm @ 20 degC

As for inductance, I'm not exactly sure - I'll try to find some figures. All I have for measurement is a pretty decent multimeter, would that work? I should get it shipped to me...

Yes, both the wires and the plugs have resistive elements. The stock wires (aftermarket are rated at 2.2 kOhms per ft) range from 10.1-13.0 kOhm, depending on the length of the wire. The stock spark plug has a 5k resistor built in as well.

I thought more about this and came up with a few more thoughts. I could use wires and plugs with no resistive elements to help get rid of losses, but that might introduce some detrimental EMI. I was also thinking that the higher the voltage going into the primary, the better, since this would increase the current rise in the primary and also the final current, therefore decreasing the necessary dwell time as well as storing more energy in the coil. On top of that, wouldn't the voltage in the secondary be limited by the voltage needed to jump the spark gap? As in, voltage would increase until it is enough to ionize the fuel/air mixture and start an arc, and then current would flow since the circuit is completed.

The reason I want to do this is twofold. Firstly, the stock ignition system on my car is quite strong, however at higher power levels people do have problems and fix them by installing something along the lines of what I posted about earlier. Secondly, it is for me to have a better understanding of the system and how it can be improved. Half the work I do on my car is when it isn't broken, because I know a part or system can be improved.

Thanks for the helpful comments so far, although I realize I need to get my MM and some spare parts for testing to better answer your questions.

Proud Mary

Tue Sept 15 2009, 02:11PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Speed Man, I don't have a meter to show both L & R of the secondary - my L meter will only show R above 5RK or so.

L & R for the primary are the most important, cos that's how you get your time constant.

Colin 99

Tue Sept 15 2009, 10:31PM

Registered Member #192 Joined: Fri Feb 17 2006, 03:08AM
Location: Canada
Posts: 44

Speed Man,

Besides checking you ignition wires and spark plugs for resistance, you could also get some Higher power / voltage ignition coils, Like Accel, they make many variations of ignition coils and they produce a much hotter spark.

Shaun

Steve Conner

Wed Sept 16 2009, 02:28PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Mates is right, the spark either ignites the mixture or it doesn't. If it does ignite it, you get as much power as you're going to get. If it doesn't, you get obvious misfiring, probably most obvious at high boost, since the higher the compression pressure, the more voltage is needed to make a spark jump.

Therefore, if the spark is already hot enough to ignite the mixture, making it hotter won't somehow "ignite it better".

You can switch to a coil-on-plug system by just connecting the pairs of coils that should fire simultaneously in series. I've done this in the past, when I had four coils, but an ECU with only two outputs.

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