Ignition coil

[azhodge]

Looking at coils for my 88 911. noted that the pelican offerings include an epoxy filled version. wondered what the dope was on that as opposed to oil filled?? of any..

[GH85Carrera]

I looked all over for a good coil. The new Bosch silver is universally considered junk. The old German made Bosch black coils are available used, but they are 30 years old. Good luck with finding a good replacement. Let us know if you find a good coil.

[LucaScali]

MSD Blaster High Vibration is a good alternative to the silver Bosch. Epoxy can be mounted in any position, including upside down. Oil filled are more sensitive to orientation and can leak.

[GH85Carrera]

Originally Posted by LucaScali

MSD Blaster High Vibration is a good alternative to the silver Bosch. Epoxy can be mounted in any position, including upside down. Oil filled are more sensitive to orientation and can leak.

That coil will work, but it is a decent amount smaller in diameter. You will have to add some rubber bushing of make an adapter to get the standard bracket to tighten up and hold the coil, and still mount to the position.

I don't have any evidence, but my car was running great, but before I left on my 5,500 mile 15 day journey I replaced the working coil with a MSD Blaster High Vibration coil and a few weeks after getting home my DME started having issues. I sent it in to Steve Wong and he checked it out and sent back this:

You had a failed ignition circuit and part of your problem was due to an out of spec capacitor that just ages out with heat and time, so that has been replaced with a new Japanese made Nichicon high temp capacitor which is the highest grade and temp rated capacitor available. I might suggest to ohm and check the resistance of your coil primary and secondary to make sure they are in spec, just in case so it’s not a contributor or stressing out the ignition circuit in the DME.

As I said, I can't say for sure it was the MSD Blaster, but I found a used 30 year old Bosch black OME coil.

[scarceller]

DO NOT just put any coil in the 84-89 911 Carrera, that DME has a dwell map optimized to charge coil to about 3.8milliseconds at system voltage of 14.0vdc and unless you are certain that the replacement coil has that same charge times you can overcharge the coil or undercharge it. Most replacement coils like MSD have lower charge times and you'll force the DME ignition driver into overload current protection mode, not a good idea!

The new silver coils are not as good as the old stock original black ones.
But the 964 coils are the exact same coils! So go hunt for a used set of 964 coils and you'll get 2 of them!

Bottom line is that to use an aftermarket coil you need to recalibrate the dwell map on the chip, you need to really understand the DME to do that. Just find decent set of 964 coils.

To the OP 'azhodge', Why are you changing the coil? Do you suspect the current one is bad? The stock coil setup is perfectly fine for a stock engine, you will gain nothing by changing the coil. Just be sure you are using standard spark plugs with gap set at 0.8mm. DO NOT use any fancy multi electrode spark plugs!

[scarceller]

I created this video as part of a research project when I created a new twin plug solution for the 3.2L engines. This video gives you a decent idea of what it takes to gather dwell time data on a test bench with custom circuitry:
https://www.youtube.com/watch?v=a7dFdIdsZeU
Once you gather this data for a given coil you then need to alter the dwell map in the DME with the new data.

[GH85Carrera]

Sal, it sounds like from what you are saying the MSD Blaster I put in my 911 to have a nice fresh coil and not a Bosch Silver likely killed my DME. I guess I will take that coil to my buddies target range and have fun blasting the MSD Blaster with lead.

It was in my 911 for under 6,000 miles. 5,500 of those miles was driven in 15 days. I am sure glad the DME was able to get us back home before it gave up and died.

[Rawknees'Turbo]

I can't speak to its longevity as I've only owned it for a short bit, but ************ makes a 911 coil that looks almost identical to the black Bosch ones (price is about the same as the junk silver coils).

https://www.************.com/p-1586-cdi-ignition-coil-by-************.aspx

[mysocal911]

Originally Posted by GH85Carrera

Sal, it sounds like from what you are saying the MSD Blaster I put in my 911 to have a nice fresh coil and not a Bosch Silver likely killed my DME.

Bad guess!

[scarceller]

I have no idea if that coil hurt the DME without knowing the optimal charge times so I can't say for sure. But the transistor driver is hefty and should remain safe if the over current protection works. However, if you charge the coil for more time than optimal the coil will heat up and likely fail early.

But I see a lot of DMEs with vibration failure solder joints at the large coil driver transistor. It's very common failure so it's possible the DME simply failed because of age and vibration.

Originally Posted by GH85Carrera

Sal, it sounds like from what you are saying the MSD Blaster I put in my 911 to have a nice fresh coil and not a Bosch Silver likely killed my DME. I guess I will take that coil to my buddies target range and have fun blasting the MSD Blaster with lead.

It was in my 911 for under 6,000 miles. 5,500 of those miles was driven in 15 days. I am sure glad the DME was able to get us back home before it gave up and died.

[Pstallo]

DO NOT get the silver coil! I replaced my old one with a new silver one because I thought I was replacing potentially worn parts with new. Coming home from a car show, my daughter and I had to be towed home.

So, I found a 30 year-old black one on EBay (like the one I never should have replaced) and haven't had a problem since.

[scarceller]

The silver coils seem to fail very quickly, if they don't fail right away they tend to last. I've seen some work fine for years yet other fail within hours of use. Not sure why that is?

Originally Posted by Pstallo

DO NOT get the silver coil! I replaced my old one with a new silver one because I thought I was replacing potentially worn parts with new. Coming home from a car show, my daughter and I had to be towed home.

So, I found a 30 year-old black one on EBay (like the one I never should have replaced) and haven't had a problem since.

[Reiver]

One of the primary reasons I went to an MSD streetfire box and MSD coil.....about the same size and easily reversible (box unit)...get a female plug and it is a piece of cake.
I also figured a 33 year old DME might not be running optimally and for the price of a rebuild I could buy two streetfires and a coil (did) and have a spare in the frunk I'll never use.
No more coil dilemma's.

[scarceller]

You are using the MSD CDI box like the 6AL box, correct?
If you did that then you can actually open the plug gap a bit more from 0.8mm to 1.0mm possibly even more. This is a decent option and a safe one for replacing a bad stock coil with something aftermarket.

Originally Posted by Reiver

One of the primary reasons I went to an MSD streetfire box and MSD coil.....about the same size and easily reversible (box unit)...get a female plug and it is a piece of cake.
I also figured a 33 year old DME might not be running optimally and for the price of a rebuild I could buy two streetfires and a coil (did) and have a spare in the frunk I'll never use.
No more coil dilemma's.

[scarceller]

Here's another option from Crane, this one is inductive (NOT CDI based). It's called a Crane Fireball HI-6S here's the docs:
http://www.cranecams.com/uploads/instructions/9000-6320_.pdf
It has a few extra bells and whistles we don't need but you can just turn those features off.
What I like about this product is that it's Inductive based and produces longer spark events than CDI.
It's used with Crane's LX-91 or PS-91 coils.
Here's the kit with box+coil:
http://www.ebay.com/itm/Crane-Cams-6000-6302-HI-6S-and-PS-91-Coil-Kit-/400303482688?hash=item5d33f26740:m:m8YvIvdnkUgHV4Q C7f_Y-nw&vxp=mtr

[mysocal911]

Originally Posted by scarceller

I have no idea if that coil hurt the DME without knowing the optimal charge times so I can't say for sure. But the transistor driver is hefty and should remain safe if the over current protection works. However, if you charge the coil for more time than optimal the coil will heat up and likely fail early.

But I see a lot of DMEs with vibration failure solder joints at the large coil driver transistor. It's very common failure so it's possible the DME simply failed because of age and vibration.

The MSD coil has about 10 - 15% more inductance than the stock 911 3.2 coil, which will result
in less peak current & thus less stress on the coil driver.

[Reiver]

Originally Posted by scarceller

You are using the MSD CDI box like the 6AL box, correct?
If you did that then you can actually open the plug gap a bit more from 0.8mm to 1.0mm possibly even more. This is a decent option and a safe one for replacing a bad stock coil with something aftermarket.

No the MSD Streetfire...it is 'hotter' than the original CDI but not overly so, closer in specs.
The smaller streetfire has a built in rev limiter you can set and it fits in the original box position...paint it silver and it is hard to notice. It works in the same fashion as the 6 series.

[mysocal911]

Most likely the problem, i.e. about a 75-90% of all 911 3.2 DME failures, was a marginal solder connection
at the ignition coil driver where it connects at the circuit board:



That is one of three solder connections that most all DIYs can easily repair (about 15 minutes)
and save the cost of a very simple "rebuilding" that most "rebuilders" charge $400 - $500 for.
These connections should always be checked before wasting money on a rebuilt DME. The typical
symptom is either an intermittent spark and/or intermittent running.

[scarceller]

Dave, this is good to know but what's the charge time at 14vdc? Without knowing this data we don't know if we'll overcharge or undercharge the coil?

Originally Posted by mysocal911

The MSD coil has about 10 - 15% more inductance than the stock 911 3.2 coil, which will result
in less peak current & thus less stress on the coil driver.

[mysocal911]

Originally Posted by scarceller

Dave, this is good to know but what's the charge time at 14vdc? Without knowing this data we don't know if we'll overcharge or undercharge the coil?

T (charge time - milliseconds) = L (inductance - mH) X I (current - amps) / V (battery voltage - Vsat)

Since the MSD coil has a higher inductance, the charge time will take longer to reach the desired
current/energy, potentially limiting the max rev point. This should not be an issue for non-race
engines.