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Old 12-28-2014, 08:57 PM   #1
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Can Anyone Explain This?

I've noticed this trend as of late and it goes as follows:

1) Acquire new-to-me used DIC cassette of unknown mileage and varied vintage after increase in knock counts, and noticeable lack of power.

2) Car runs MUCH better with the replacement unit. I then proceed to make 10-40WOT pulls over a course of several months. LOTS of power, even at ~10psi. Is faster with half the boost of phases 3-5.

3) Knock counts come back, noticeable drop in power, and then past ~15psi, it starts to make what sounds like compressor surge (shhhch chchchchchchc)

5) Starts to stumble on startup. Engine runs noisily. Spark-out at higher boost pressures

6) I call it quits and get a new-to-me DIC, with the lowest possible mileage and newest vintage.

7) Cycle repeats.

I am running NGK BCPR 7ES-11, gapped to .031". Light Dielectric paste around base of coil.

Dielectric doesn't seem to prolong the lifespan of the DIC.

What is going on here?
Thanks,
-Cm
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Old 12-29-2014, 06:54 AM   #2
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just a shot in the dark, but maybe it's just that the tune is changing how the DIC would operate under normal conditions with a stock tune and in a sense wearing it down before you would expect. I don't really know, just a thought. how new of a DIC do you usually get?
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Old 12-29-2014, 01:51 PM   #3
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Where are you injecting the water/meth?
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Old 01-03-2015, 03:24 PM   #4
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I am injecting the water meth right into the throttle body.

I am running straight methanol, because water really screws with the DIC. They work as a camshaft position sensor by constantly feeding current to the plugs. The amount of voltage sensed by function of the resistance across the plug gap, which is itself a function of the ion composition of the cylinder atmosphere, enables the DIC to tell the ECU where the firing position of each piston is. When you inject water, the voltage goes way up in accordance with Ohm's law=badness.
FYI, the CPS tells the ECU that either #1 or#4 are in firing position, but the DIC determines which of the two it actually is.
-Cm
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Old 01-05-2015, 06:15 AM   #5
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Have you tried cutting some of the cover away to allow heat to escape?
The only thing I would suggest would be checking grounds to the engine/trans to be sure you have a good, clean circuit.

I can tell you that every used red DIC I purchased, no matter how new, failed within a month, even on my stock-turbo 9-3. I don't know if it's from sitting, or what, but I ended up biting the bullet and bought a new one after 2-3 failed used cassetts.
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Old 01-05-2015, 08:43 AM   #6
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Quote:
Originally Posted by g96nt View Post
Have you tried cutting some of the cover away to allow heat to escape?
The only thing I would suggest would be checking grounds to the engine/trans to be sure you have a good, clean circuit.

I can tell you that every used red DIC I purchased, no matter how new, failed within a month, even on my stock-turbo 9-3. I don't know if it's from sitting, or what, but I ended up biting the bullet and bought a new one after 2-3 failed used cassetts.
yeah, I feel your pain! I really don't want to shell out for a new DIC considering they are worth 30% of the total worth of the car. May come to it tho.
I have not "vented" the DICs, though this may be a good idea as sometime the boots warp and distort from heat. Sometimes from me, sometimes from their previous life.
-Cm
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Old 01-05-2015, 08:44 AM   #7
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The people on Saabcentral think it might be a poor power or control wire or ground to/from the DIC causing excessive resistance and thus more thermal-electric load. Does anyone know where the DIC wires ground TO? I know the ECU grounds are on the plenum, but the DIC may ground elsewhere given its load.
-Cm
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Old 01-05-2015, 09:03 AM   #8
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Not I.
I'm sure the WIS has the info, but short of that, you may be un-wrapping loom to find the source.

You've seen how the "test" cassettes are cut, right? They've got some meat taken out between the bolts so heat can escape straight-up a lot quicker.
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Old 01-07-2015, 07:10 AM   #9
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Meh, I was afraid of that....
-Cm
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Old 01-08-2015, 05:21 AM   #10
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i doubt this is a heat problem with the DI.

i would check one of a few things, first, what do you torque your spark plugs too? they are very easy to overtorque, and when they do they can cause these types of issues, you will see hairline cracks in the porcelain when this happens .

Second, is the misfire on one specific cylinder, or all cylinders?

Third, it kills me every time somebody complains about the cost of a DI, Yes, they are 280-390$ depending on where you get them, but to never have to worry about it again is worth it. If the part was harder to change most people wouldn't think twice about only using a new one, but because it's so easy we are all Car-whoreing second hand DI's around, then wondering why things don't work right. on a tuned car a new DI is becoming a "must have".

Low voltage can do these things, a good sign of a low voltage car is when the scan tool/t5suite looses connection at upper RPMs
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Old 01-08-2015, 10:07 PM   #11
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I seldom get to the misfire stage. More frequently the car becomes so miserable to drive that I turn the old DIC into a candelabra or simply toss it out of blind rage. I always get knock in cylinders 1 + 4 and then it will start to lose power and get progressively louder and grumpy. Sometime after that, I'll get spark out at higher boost levels, but no recorded misfires. Whenever I change to a new ignition cassette I pick up no knock counts and it runs really well, so I don't think it is hardware related.

The plug theory is a good one, but I don't torque them very much at all and have not noticed any cracking on the porcelain or any arcing. I carefully examined them for such evidence after going through these stupid cassettes so quickly.
I have not noticed that I lose connection with RPM with T5 suite dashboard, but, I have noticed that when I rapidly accelerate I do. I always attributed this to the hard drive protection system I have on my ThinkPad laptop. Whenever it detects acceleration consistent with free-fall or impact it locks the HD to protect it.

As I said, I am fairly sure it is DIC related, as when I put the newest one on there it could spin 4th gear with a T28 and w/m. When the cassette wanes, I struggle to spin 2nd. HUGE power losses we're talkin about here.
-Cm
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Old 01-08-2015, 10:11 PM   #12
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My injectors are correctly indexed and I have plenty of fuel. Compression as normal across the board when I tested it a year ago. My head gasket has 20k on it and the cylinder head bolts are tight as hell. CPS has 35k on it.
This problem presents with different ecu's...
Car runs like massive ass in the rain or snow or humidity. A new ignition cassette fixes this, more or less. Hard to remember.
-Cm
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