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Old 08-09-2007, 01:53 AM   #1
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Default Toyota COP dwell curve

Here you go peeps:



The internal driver current limits at 10A. The dwell curves shown are for 8.5A and 9A. (Higher curve is for 9A). These are ideal dwell curves if your wiring can deliver full voltage with no voltage drop. (Typically lose 0.2-0.4V avg over the dwell period).

I'd want to run the coils at 8.5A for safety, but given the loss in the wiring, use the 9A curve.

At 8.5A, coil stored energy is 100 mJ.

The '01 coils store 133 mJ at 6A (current limit is at 6.8A). But some of that energy will be lost in the plug wires. I don't know how much. They can jump a longer air gap than the Toyota coils.

The '00 coils can store 170 mJ at 7A but their plug wires are much longer. I don't remember how far they can jump.

By comparison the GM coils on my TEC3 only stored 50 mJ, but I think they are capable of more voltage than the other coils, as they can jump a longer gap in air.

I couldn't find the 1000x "cattle prod" high voltage probe in the lab, have to ask for it tomorrow. I can measure the coils' max output voltage. That'll be fun.
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Old 08-09-2007, 03:44 AM   #2
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Somewhere I've seen the airgap to voltage table. 0ft altitude, 0% humidity (is that possible?), and 0bar atmosphere. That doesn't really tell how much current was in the ark though. 1kv per mm or something rough like that. I don't know if it was even linear. I doubt it.
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Old 08-09-2007, 03:49 AM   #3
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These are what us AEM owners have for dwell settings.

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Old 08-09-2007, 04:05 AM   #4
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Man WTF does that mean in dwell time in milliseconds for us MS users?

2.2ms assuming a max 14volt system with me assuming my alternator is amazing. 13.5-8v would probably be more realistic. So maybe 2.3ms would be good for us.
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Old 08-09-2007, 11:18 AM   #5
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MS assumes 12v and make corrections, at higher voltages the time is reduced; lower, increased.

So it looks like 2.5-2.6ms would be best.
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Old 08-09-2007, 11:21 AM   #6
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Jason, since the 01 coils are waste spark, does it divide the spark energy in half between the two plugs? so 133mJ becomes 66?

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Old 08-09-2007, 01:38 PM   #7
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[email protected], the energy is divided into 2 plugs, but the "waste" plug gets a small fraction that the other plug gets.

The energy I quoted is that stored in the coil just before spark; I'm not sure how many % is lost in the wires.
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Old 08-09-2007, 01:42 PM   #8
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The AEM should have implemented a dwell correction vs. MAP instead of RPM. More useful. One could then run the coil "cooler" at lower MAPs.
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Old 08-09-2007, 01:44 PM   #9
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What coils do Supras use? EVOs? WRXs? These are high boost factory cars.

If anyone can send samples to me I can test if they're any more powerful than the miata and Toyota coils.
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Old 08-09-2007, 01:52 PM   #10
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how does the waste plug get less juice? the coil has no idea which one is firing...
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Old 08-09-2007, 02:23 PM   #11
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Jason SBB, thanks for all the work. It's much appreciated. You wouldn't happen to know what the 1.6L coil dwell time should be do you?

Lazzer408, do you know how to calculate the dwell time based on those AEM default settings. The manual give very sketchy details as to how to calculate the dwell time. From what I've read, it means that between 13-14V the aem gives about 1.7ms of dwell time with the stock 1.6L miata setup. The default for the toyota coils gives even less. Would this mean that we can safely increase the dwell time when using these coils.
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Old 08-09-2007, 02:27 PM   #12
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Quote:
Originally Posted by y8s View Post
how does the waste plug get less juice? the coil has no idea which one is firing...
Less resistance on an empty chamber compared to a full compressed one. Requires less work.
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Old 08-09-2007, 03:07 PM   #13
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[email protected], the 2 plugs are in series; the "waste" one is practically a short circuit compared to the other one. The energy is not reduced by the fact that the coil has to spark 2x as often, provided you don't run out of time for proper dwell between sparks.
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Old 08-09-2007, 03:12 PM   #14
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So what is optimum dwell time for a '99-00 OEM miata coil?
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Old 08-09-2007, 03:28 PM   #15
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Quote:
Originally Posted by cjernigan View Post
So what is optimum dwell time for a '99-00 OEM miata coil?
Check this link

http://forum.miata.net/vb/showthread...ght=coil+dwell
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Old 08-09-2007, 03:31 PM   #16
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[QUOTE=JasonC SBB;138598][email protected], the 2 plugs are in series; the "waste" one is practically a short circuit compared to the other one.[QUOTE]

This is because the waste gap isn't under compression.

It would be interesting if you could find means to measure it. The current flow is equal thru any electrical path. This includes wasted spark. The current thru both arks is equal but the voltage's across each will be different. Once the ark is formed the current will flow thru it. It's easier to form an ark in the cylinder with no compression so there's little loss happening.
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Old 08-09-2007, 03:52 PM   #17
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Quote:
Originally Posted by Red 90 View Post
Thanks for the link. I don't go go .net often. Looks like I should be running more like 3.1 or 4.1 ms constant for my '99 coils then or is that wrong? I have been running more like 2.0 just because i didn't want to fry them. Not sure if I want to use the 4A or 5A value for 12v.
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Old 08-09-2007, 03:54 PM   #18
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Here's the dwell curve for the '00 coils:

EDIT: the old graph was wrong:
To reach 5.5A:
10V: 5.9 mS
11V: 5 mS
12V: 4.25mS
13V: 3.75mS
14V: 3.3mS
15V: 2.9mS


and for the '01 coils (use the 6A curve):


You can find the dwell curves for the NA 1.8 and 1.6 by looking at the Hydra maps.

Last edited by JasonC SBB; 08-10-2007 at 02:40 AM.
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Old 08-09-2007, 04:02 PM   #19
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Anyone have the hydra maps for the 1.6 and 1.8?
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Old 08-09-2007, 05:16 PM   #20
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he just posted the numbers.. it's easy enough to fill in. btw, FM has started using jason's numbers above in their maps.
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