understanding coils

[lanceslambos]

can someone explain which of these coil specs would yield "higher" performance if any? i don't know what the primary resistance and secondary resistance means, nor the inductance.

coil #1 -
40,000 volts
primary resistance 0.350 ohms
secondary resistance 7.8k ohms
inductance 4.2 mH

coil #2 -
40,000 volts
primary resistance 0.380 ohms
secondary resistance 5.850 ohms
inductance 4.5 mH - 5.6 mH

[sall]

The ratio of secondary to primary with ignition coils is usually 80:1. The higher the ratio, the higher the output voltage of the coil. Both have output of 40,000V. So, neither has an advantage to my knowledge.

The Accel # 140017 is the 'performance' coil out of all available for the Classic AFAIK. They output max 45,000V. Accel # 140017 has a ratio of 75:1. The MSD coils are just a direct replacement at 80:1, 40,000V.

[bobsblue95]

Right, and technically, they will all yield pretty identical performance. The 45KV coil isn't going to burn the fuel any more efficiently than a stock setup in good condition (the computer will see to that) and may actually shorten the life of your plugs due to hotter spark.

[lanceslambos]

i just googled those sall and they have horrible reviews. everyone says they work for 2 weeks to 2 months before pooping. i thought the same thing Bob!

[oldwino]

Inductance has to do with the rate of current change in a coil. The lower the inductance, the faster the field can collapse. The faster a coil has to charge and discharge, the lower inductance is needed.

[sall]

Jun 4, 2012 21:26:08 GMT -6 lanceslambos said:

i just googled those sall and they have horrible reviews. everyone says they work for 2 weeks to 2 months before pooping. i thought the same thing Bob!

I was not recommending them as I have never used them. Only saying that since they are 75:1, they would be considered the 'performance' option.

I only see a review on Amazon with a brief search. Eleven reviews out however many hundreds of thousands they sold is not a very good sample anyways. That's what warranties are for. I wouldn't bother anyways as Bob is probably right about the PCM and plugs.

[lanceslambos]

Jun 4, 2012 17:45:31 GMT -6 sall said:

The ratio of secondary to primary with ignition coils is usually 80:1. The higher the ratio, the higher the output voltage of the coil. Accel # 140017 has a ratio of 75:1. The MSD coils are just a direct replacement at 80:1, 40,000V.

seems like you contradicted yourself then. is 80:1 not a higher ratio than 75:1 or is it like a shotgun where 12 is bigger than 20 and 10 is bigger than 12, etc.?

isn't 7.8k = 7,8000 if not then what's the k mean? the secondary resistance seems to be the biggest difference. by the way coil #1 is msd blaster and coil 2 is summit racing brand. i never mentioned msd though - you must be psychic sall!

to keep from burning out the plugs, couldn't a person just switch to hotter ones?

i read somewhere online but don't know where...that changing to a different voltage coil than factory can "hurt" the engine. is this true and how so?

[bobsblue95]

isn't 7.8k = 7,8000 if not then what's the k mean?

you have one too many zeros, 7.8K = 7,800

to keep from burning out the plugs, couldn't a person just switch to hotter ones?

I don't think that would work in this case as I believe the plug's heat range has more to do with fuel burning than spark. Seems to me it would actually be easier than that though. Just increase the gap by about 10% - proportionally the same as the voltage increase. Given the coefficient of resistance through air and using Ohm's Law, this would result in a slightly longer spark at the same current as stock, so the plugs should then wear the same.

This is assuming that a longer spark is better than a fatter spark in terms of plug life. A fatter spark may or may not result in faster/better ignition (there are a lot of other variables in there!) but I still believe that the original configuration is already designed to ignite as efficiently as possible, otherwise the car wouldn't pass emissions from the factory, or get 28-30mpg on the highway.

[sall]

Sorry Lance, I should have been more specific. Typically the higher turns ratio will provide provide more voltage. Those Accel specs are probably like 1000 lumen XML Chinese flashlight producing a 3000 lumens haha.

There are other factors to consider with coils. One of the main things of a coil is to provide amps, not just volts. The higher the turns ratio the less work the coil has to do to get to its rated voltage. As well as the lower the resistance in the coil the less heat that will be produced by the coil. Cooler electronics work more efficiently. Hence heat sinks on most of my LED projects with lots of copper pad to disperse heat.

I really do not think the 'extra' voltage is going to help much as it only takes a certain amount of voltage for the spark to jump the plug gap. Similar to Bob's last paragraph.

Here are the increased gains Accel claims:

Peak Increase in Energy vs. OE 11%
Peak Increase in Voltage vs. OE 10%
Peak Increase in Dwell vs. OE 21%
Peak Increase in Current vs. OE 12%

The summit house brand coils actually look pretty good to me.

...although psychic abilities would come in handy time to time... this is in the performance section So, I figured MSD.

[shelbyracing]

I had accel and returned them. They weren't consistent with each other. 1 would jump a spark an 1" and I was like holy crap, another would only go about a 1/4" and didn't even look as hot. Or feel, I got zapped lol.
+1 on MSD, what I plan to get if I have a oem fail. Not sure any gain is really to have been had, the factory have some pretty good voltage.