$36 Replacement ignition coils?

[LastSVXintheChi]

did you buy the plug wires separate? if so what kind did you use?

[huck369]

This is a Good alternative ideal for the coils, but there is no good place to mount them if you have all the stock parts under the hood (Air Filter Box, Overflow Jug, and Windshield washer jugs)
I bet there are a ton of stock 6-cylinder coil packs from other brands that could also be used too, just a mater of wiring them up.

[oab_au]

Originally Posted by smc

Its been stated in another forum that I have a complete lack of understanding of the subject matter in regards to the coil swap. Very well. A few quick figures relating as to why I decided to do such an install.
Stock coil: 60 ma, 36,000 v maximum output with a short duration spark. $100 to $200 each.
High End Aftermarket subaru STI coils: 120ma, 50,000 v. output with modulated multi-spark capabilities. However they cost $700 for a set of 4.
My alternative: 310 ma, 51,000 v output with long duration spark. Cost, $36 each.

The remote coils are now mounted away from heat and vibration, have a more substantial spark that is less likely to be "blown out" when in a forced induction situation and are readily available and of lower cost than any alternative with a *subaru* label on them.

Oh, I wonder who that could be.
If you are going to modify a system, it is best to know how that system works before you go changing it, or it may not be a good move.

Using separate High Energy coils, with Hi Tension leads is a retrograde step. The manufactures don’t go to the expense of fitting a coil on each plug, to be generous. They do it to solve a couple of problems that come with Hi Energy ignition. First to prevent the shorting and burning of the coil towers and leads, that happens when a separate coil, and plug wires were used. Any body that worked on GM, Ford etc, engines that used these would know the problems.

Secondly putting the coil on the plug prevented the electrical interference that Hi Energy, flowing through a wire transmits, to all the other wiring in the engine bay. With an increasing amount of analogue and digital signals, like crank sensors, airflow sensors, temp sensors, etc, which the engine relies on, this type of interference will cause increasing problems, so coil on the plug solved these.

If you are fitting different coils to this engine, they have to be the same as the originals that the ECU is set to work with. The particular coils that you have chosen have a primary resistance of 0.4 ohms; the standard coils have a primary resistance of 0.7 ohms. This means that when the ECU turns the coil on for the dwell period, a primary current of 30 amps will flow, instead of 17 amps. This current is flowed by the Ignitor till the amperage reaches about 4 amps, when the Ignitor holds it at this level till the ECU turns it off to fire the coil, due to the lower primary resistance, it will rise to this level faster, and is held at this amperage for a longer time.

This presents two problems; First the coil or the Ignitor will finally burn out from the extra current. Second, because the coil has on lower primary resistance, the rise time, to build the magnetic field will be faster, and as they don’t have a diode in the secondary to prevent the coil from firing, on the field rising, the plug will fire at the start of the dwell period and again at the end, advancing the spark.

If you and going to use different coils, the dwell period of the ECU will have to be reduced to suit the coils primary resistance, and use the diode to protect against firing on the start of the rise time. If they are used with Capacitive Discharge ignition, they can be used without the dwell change and the diode, but the wires will still be trouble.

Harvey.

[smc]

The wires are just a universal kit for a v8. 8mm hd wire. Nothing unusual. ACCEL kit. # 5040B The problem is, it tends to be rather difficult to get the leads connected to the sparkplugs due to how far they are located into the heads. They plugged right in on my project engine, however in practice in the SVX is has proven to be a bit more difficult to hear that satisfying *click* of a plug lock.
In the future, I will change out to a v6 kit with longer plug leads to make things easier.

Indeed, this swap is not for everyone. Space is at a premium under our hoods. Mine becoming more spartan as its intended for track use, is most likely not the best example. However in many ways it was just proof of a concept and an alternative to other coil options

oab_au, that is a beautiful response, mate. To which I will fully take to heart! I truly love information like this. Thank you and I will continue to refine this as my build progresses.

As for yet, there have been no detrimental affects of this swap. According to the obdII system monitoring, all is nominal. If this does indeed prove to have any ill affects, I will certainly report them. However in a short time, any affects may no longer relate to our cars as I will be changing to a stand alone ecu and the programming can be changed to compensate.

[icingdeath88]

Originally Posted by oab_au

Oh, I wonder who that could be.
If you are going to modify a system, it is best to know how that system works before you go changing it, or it may not be a good move.

Using separate High Energy coils, with Hi Tension leads is a retrograde step. The manufactures don’t go to the expense of fitting a coil on each plug, to be generous. They do it to solve a couple of problems that come with Hi Energy ignition. First to prevent the shorting and burning of the coil towers and leads, that happens when a separate coil, and plug wires were used. Any body that worked on GM, Ford etc, engines that used these would know the problems.

Secondly putting the coil on the plug prevented the electrical interference that Hi Energy, flowing through a wire transmits, to all the other wiring in the engine bay. With an increasing amount of analogue and digital signals, like crank sensors, airflow sensors, temp sensors, etc, which the engine relies on, this type of interference will cause increasing problems, so coil on the plug solved these.

If you are fitting different coils to this engine, they have to be the same as the originals that the ECU is set to work with. The particular coils that you have chosen have a primary resistance of 0.4 ohms; the standard coils have a primary resistance of 0.7 ohms. This means that when the ECU turns the coil on for the dwell period, a primary current of 30 amps will flow, instead of 17 amps. This current is flowed by the Ignitor till the amperage reaches about 4 amps, when the Ignitor holds it at this level till the ECU turns it off to fire the coil, due to the lower primary resistance, it will rise to this level faster, and is held at this amperage for a longer time.

This presents two problems; First the coil or the Ignitor will finally burn out from the extra current. Second, because the coil has on lower primary resistance, the rise time, to build the magnetic field will be faster, and as they don’t have a diode in the secondary to prevent the coil from firing, on the field rising, the plug will fire at the start of the dwell period and again at the end, advancing the spark.

If you and going to use different coils, the dwell period of the ECU will have to be reduced to suit the coils primary resistance, and use the diode to protect against firing on the start of the rise time. If they are used with Capacitive Discharge ignition, they can be used without the dwell change and the diode, but the wires will still be trouble.

Ok Harvey, how would one go about correcting for this? I am planning on running a megasquirt. How would you go about figuring what the dwell time should be set to for this setup?

[smc]

Seems like you would simply retard your timing a little depending on your tuning. o.O

[92snowmachine]

have you considered using a waste spark system? that's the one gm uses on their v6 enignes. it fires two cylinders at a time one at tdc compression and the other that is on the exhaust stroke. not really needed but very simple to operate if you go with an aftermarket ecu. also you can buy coil on plugs for the gm 5.3 and 5.7 engines for around $30 so that may be even easier.

[oab_au]

Originally Posted by icingdeath88

Ok Harvey, how would one go about correcting for this? I am planning on running a megasquirt. How would you go about figuring what the dwell time should be set to for this setup?

If you are going to use Megasquirt, there is a great resource in the forums that are there. Some one will have done it before.

The ignition process is, the ECU turns on the Ignitor, which turns the coil on, the coil's magnetic field rises, when the current gets to about 4amps, the Ignitor holds it by dissipating the excess current. The ECU then turns off the Ignitor and the coil, to produce the spark.

But if I was doing it, I would use a scope to look at the signal from the ECU to the Ignitor. Measure the time from the turn on to the turn off. Then look at the coil primary, and measure the time from turn on till the Ignitor clamps the current. This is the “Rise Time” that the coil primary takes to reach saturation. You will see the current rising, then leveling off to stay the same, as the Ignitor holds the current by dissipating the excess.

Fit the new coil, and measure its “Rise Time”, if this is faster than the original coil. Subtract the extra time from the total turn on time, for the ECU.
Eg. Original coil ECU time, 10ms. Rise time 8ms.
New coil rise time 6ms. So ECU on/off time reduced from 10ms to 8ms.

Originally Posted by smc

Seems like you would simply retard your timing a little depending on your tuning. o.O

That will only change the advance time, it won’t stop the Ignitor from dissipating the excess current for a longer time. The dwell time has to be changed.

Harvey.

[svxfiles]

Originally Posted by 92snowmachine

have you considered using a waste spark system? that's the one gm uses on their v6 enignes. it fires two cylinders at a time one at tdc compression and the other that is on the exhaust stroke. not really needed but very simple to operate if you go with an aftermarket ecu. also you can buy coil on plugs for the gm 5.3 and 5.7 engines for around $30 so that may be even easier.

What year model?

[icingdeath88]

Originally Posted by oab_au

If you are going to use Megasquirt, there is a great resource in the forums that are there. Some one will have done it before.

Yea, dynomatt is helping me get things figured out. I have had a pretty hard time finding stuff in the forums, so I am planning to get everything documented on the forums so that others will have a tunable, standalone ECU in the future that doesn't cost an arm and two legs.

Originally Posted by oab_au

The ignition process is, the ECU turns on the Ignitor, which turns the coil on, the coil's magnetic field rises, when the current gets to about 4amps, the Ignitor holds it by dissipating the excess current. The ECU then turns off the Ignitor and the coil, to produce the spark.

But if I was doing it, I would use a scope to look at the signal from the ECU to the Ignitor. Measure the time from the turn on to the turn off. Then look at the coil primary, and measure the time from turn on till the Ignitor clamps the current. This is the “Rise Time” that the coil primary takes to reach saturation. You will see the current rising, then leveling off to stay the same, as the Ignitor holds the current by dissipating the excess.

Fit the new coil, and measure its “Rise Time”, if this is faster than the original coil. Subtract the extra time from the total turn on time, for the ECU.
Eg. Original coil ECU time, 10ms. Rise time 8ms.
New coil rise time 6ms. So ECU on/off time reduced from 10ms to 8ms.

Thanks for the great explanation. I d for like an hour and couldn't figure out the role of the ignitor in all of this.

Is there a way to calculate the time, at least to get an estimate, or would you have to measure it?

Also, if I were to add an msd type ignition to the mix, how would that affect things?

[oab_au]

Originally Posted by icingdeath88

Yea, dynomatt is helping me get things figured out. I have had a pretty hard time finding stuff in the forums, so I am planning to get everything documented on the forums so that others will have a tunable, standalone ECU in the future that doesn't cost an arm and two legs.

OK yes Matt used it on his. You might ask him what Dwell he used as, it was probably too much, as he was burning out the coils.
I think Matt was firing two coils together.

Thanks for the great explanation. I d for like an hour and couldn't figure out the role of the ignitor in all of this.

Is there a way to calculate the time, at least to get an estimate, or would you have to measure it?

Also, if I were to add an msd type ignition to the mix, how would that affect things?

Yes somebody could calculate it But you would need a .lot more information on the coil's inductance. Easier to measure it.

Harvey.

[92snowmachine]

Originally Posted by svxfiles

What year model?

not sure which one, just know i've had to replace them. the straight six might be an even better option as the coils are really short.
http://www.carpartswarehouse.com/add...32-70055.html#
the video on the bottom isn't the right coils but click on the picture to enlarge.

[icingdeath88]

Originally Posted by svxfiles

What year model?

Any of the LS1 or LS2 engines. They are Coil-near-plugs, not COPs. Here is an example of how someone did it on an RB25: http://www.rad240sx.com/?p=24

Here is some info on what cars they come out of: http://www.yellowbullet.com/forum/sh...=337602&page=4

[smc]

question is, can we simply run an inline resistor that will bring us back to 7 ohm? Seems like it would be a simple in theory.

[oab_au]

Originally Posted by smc

question is, can we simply run an inline resistor that will bring us back to 7 ohm? Seems like it would be a simple in theory.

The speed of the coils rise time, depends on the Inductive reactance of the coil. (the metal and the windings.) A resistor won't alter that, only the final current flow.

Harvey.