Footman

iTrader: (2)

07 GT 6speed with 69,000km on original coils. I'm experiencing some slightly rougher idle and I figure it maybe time for coils. I replaced the spark plugs at 48,000km, but not coils.

Referring to this thread: https://www.rx8club.com/showpost.php...3&postcount=12

and in specific, the values as determined by RIWWP:


-----------------------------

I set my digital multimeter to Ohms, and on the buzzer. The test guidelines dictate that
- between terminals A and B, there should not be 0 or infinity
- between terminals B and C, there should not be 0 or infinity
- between terminals A and C there should not be continuity, 0 to several kilohm.

~35,000 miles on them before getting a few misfires up high, no noticable power loss, replaced coils and misfires disappeared. Unknown order in the 8.
Coil #1: 800, 558, 645
Coil #2: 806, 557, 640
Coil #3: 814, 556, 647
Coil #4: 806, 555, 645
Remarkably identical in values across all 4, especially compared with the 2 other sets.

Removed set, ~16,000 miles, I don't know which one was in which spot on the 8. I should have marked them.
Numbers are A to B, B to C, A to C
Coil #1: 804, 536, 608
Coil #2: 805, 540, 629
Coil #3: 770, 542, 620
Coil #4: 805, 544, 622

Installed set, brand new, 10 miles on them, numbered from front to rear in installation position:
Coil #1: 712, 477, 561
Coil #2: 768, 482, 577
Coil #3: 723, 490, 566
Coil #4: 713, 497, 572

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I was only able to test Coil #1 (closest one to the front) because I didn't have time to remove the intake box. My readings were:

A - B, B - C, C - A
795 ohms, 537 ohms, 626 ohms (reverse polarity, otherwise infinite)

Thumper3322 gave me a bad ignition coil that he pulled off of his car and when I tested his, they were:

788 ohms, 548 ohms, 637 ohms (reverse polarity, otherwise infinite)

This is where I want to call upon RIWWP for clarity on procedure when he did the test for "C - A". The instructions call to put positive on C and negative on A. When I did that, it gave me an infinite reading (no continuity) which is what the Mazda manual says it should be. But if I reverse the polarity on the terminals, putting positive to A and negative to C, then I get the 626 ohms.

So RIWWP did you measure it correctly and got those ohmic values for your new coils? cause they should be infinite resistance (open circuit) for C - A.


Does anybody else have some numerical values that they have done tests on their ignition coils to share? Time for new coils? No misfires or CELs, but upper range of RPM doesn't sound right at all...

Footman

iTrader: (2)

No one at all? seriously?

RIWWP

iTrader: (2)

I haven't been on in a few days, but say the title and your 2nd post, and it drew me in to post what you already found





To be honest, I could have done it backwards. I still have all 3 sets, and can re-test the 2 older ones tomorrow if you are interested (not sure I want to pull my installed plugs ). Offhand though, I would swear that I got the same reading regardless of which placement i used for the C - A test.

dannobre

iTrader: (3)

I have tested coils that are non-functional...and new ones that had identical values...not sure what that means exactly

I did have a couple that shorted the windings..they were easy to tell...but the ignitors must fail in some way that isn't evident to the outside world

MazdaManiac

iTrader: (3)

Not a particularly useful test since all you are doing is measuring the impedance of the ignitor transistor.
It's not a particularly high-quality part, so the resistance values will be all over the place with no correlation to functionality.

Footman

iTrader: (2)

So in the end, there is no gauranteed test for coil functionality?

Does anyone know what each terminal refers to in the coil?

I'd imagine to make the coil work:
- one terminal is ground
- one terminal is 12V
- one terminal is trigger from the PCM (to activate a power BJT inside the coil which completes the circuit for the transformer.

Footman

iTrader: (2)

RIWWP, if you have time, can you test those ones that you have on hand? EXACTLY as per instructions... positive terminal on C, and negative on A?

MazdaManiac

iTrader: (3)

"A" is trigger, "B" is ground and "C" is power.

Footman

iTrader: (2)

You mean B is trigger and A is ground?

Mazurfer

^.................Nope, they put "A" in the middle.
"A" is the one with varying colors.
"C" is Black/White
And of course "B" is black.

I update Jeff's pic to show the terminals.

nycgps

iTrader: (1)

a bit too late to find out my friend.

Thats why I now I always do this now :

2 set of spark plugs = 1 set of coil.

Huey52

iTrader: (2)

There is one guaranteed test for coil functionality and that (per TSB) is short or open. Anything in between varies with the part spec variance, which as MM cites is pretty wide.

Terminal Positive Negative
A B Infinity or 0 ohm is not normal
B C

C A 0 to several kilohm (continuity) is not normal

Footman

iTrader: (2)

hahaha, the drawing takes the shape that looks like the COIL plug connector, but yet they put the A connector in the middle of the drawing that corresponds to terminal B on the actual middle connector on the plug..


BTW, where is that schematic from? There is nothing that detailed even in the mega large RX-8 FSM manual... I want a copy of whatever Mazdamanic pulled that from.

MazdaManiac

iTrader: (3)

No you don't.
I pulled it out of my ***. Seriously.
Photoshop and a drawing from another coil.

Footman

iTrader: (2)

Were you able to melt away the epoxy and see the actual components inside the coil in order to get that diagram?

MazdaManiac

iTrader: (3)

No. That is just how it works, though the box in the box is also a transistor.
ALL integral-ignitor coils work that way.

It's just two biased MOSFET transistors (well, the discharge T is a stack) and a Schottky diode.