Alex Sol

having some issues with my ignition and idle.

prior to my reseal, i had a very good running 964 except for oil leaks

i had idle issues on stock dual mass flywheel and fixed them with:

new crank position sensor
new idle air control valve
freshly rebuilt air flow meter

and during the tear down, i must have damaged some spark plug wires because 7 of the 12 had no continuity ... these were the magnecor reds but they would slip out of the lower spark plug holes and did not properly seal out water so the 964 would run very rough in the rain. i had removed the lower plastic covers.

so after a complete rebuild / reseal this summer i am ready to get this old girl out of the garage.

964 works on the street and stalls when coming to stop and cannot hold steady throttle position and is very rough at idle.

sounds like mini explosions in the intake

and when checking the spark plugs, it appears the lowers are not firing though the spark plugs each have spark

i tested the coils and the 1-15 terminal spec is .4-.7 ohms and all my four coils are 2.0 ohm . Are they all fried? the 1 to centre and 15 to centre spec is 5-8,000 ohms and i'm around 5.6-6.6k ohms.

i've checked all the vacuum lines and they look correct. some of my clamps are a little beat up and will replace. i'm told go to bmw for inexpensive and good quality clamps

so:

misfire and rich running would suggest grounding issues to.

i've only checked the grounds on the top of the motor from main harness and alternator. starter wire and engine ground which is near the starter ground.

Any other places to check?

looking up the 944 board, there is a ground for the air flow meter? i can hear the air flow meter slapping around pretty violently back there also... sounds like i dropped a nut or washer in the crank case but i 'm pretty sure i didn't do this... was very careful keeping all openings covered during the entire rebuild process

so getting to the question, anyone try the msd coil?

FeralComprehension

I looked at those coils and at some reference data provided by LorenFB (say what you will, the guy really does seem to understand p-car electrics) and decided "not worth the risk." It could work, but as there's a chance they could damage some of the other bits in the chain (ignitor, ecu...) I decided to go ahead and buy the crappy Bosch coils currently sold as OEM replacement.

Alex Sol

those silver coils are not all that trustworthy?

are the Bosch blue coils a better bet?

I emailed David at Lindsey and suspect they wouldn't sell stuff that would create problems...

I'll check the spec on those as well. Surprised no one has tried the MSD coils on 964s. I have read the odd horror story.

Lindsey suggests they are a good bet on the 944 turbos...

964TOK

I use a MSD 8222 coil on my '72 2.4E.

No problems and apparently more reliable than the Bosch ones (that are made in Brazil).

Alex Sol

i'm reading thru the differences according to Loren's measurements and don't understand them.

the spec range when measuring the Primary for the Bosch Silver/Blacks are 0.4 to 0.7 ohm and mine are at 2.0 to 2.1 Ohms. Does that mean there is too much resistance and that they are shot? and need to be replaced?

It seems the Blues would work but the specs are quite different and could cause issues at the high end of the rpm? (Loren's suggestion) Is this also due to part that the 993's ignition is pretty much identical to the 964s?

The MSD 8222 are also quite different in spec... and operate with some kind of 'blast'... which may damage other components? ie: fry wires prematurely?

More research required here... and more importantly, more understanding of how this stuff works is required...

FeralComprehension

Yeah, I don't have the understanding or the desire to fork out for a new ecu! One thing I did find is that the ignition system in the 951 is different than the one in the 964, so it is quite possible something that works in the 944 platform won't in the 964.

Which sucks, because there are a lot of people who had to replace their new Bosch coils a second time.

When comparing, you also have to compare the inductance (a word that makes my eyes glaze over; I'm a *mechanical* engineer and remain convinced that electricity is black majik.)

Sorry- no help on measuring your coils. Normally I don't like throwing parts at a problem but on my car I replaced cap/rotors/wires/coils over a 6 month span just so that I'd know exactly how much time each had on it.

Alex Sol

thanks feral,

i slapped in a set of msd 8202 which have the same specs as the 8222s that Lindsey racing sells.

there were from a buddy.

so in they went and bam, nice clean start up and no more of that 'popcorn popper, clang, misfire' action.

but still misfiring in a different way. with the car running, i pulled each injector connection off.

pulled number one, no change
pulled number two, no change
couldn't easily reach 3
4, stalls
5, stalls
6, stalls

so i suspect i'm running on only right hand side and have some fuel issues... new post!

to sum up this post... msd 8202 appear to work much better than the bosch black and silver...

might the 45,000 volts!!

concern is: what is the consequences on other parts of the ignition system that were not designed with this type of coil....

FeralComprehension

Alex, please Please PLEASE keep us posted. So far as I know you're paving new ground; I'm sure I'm not the only one that would like to have a non-crap/non-Bosch alternative coil choice.

Lorenfb

Check here for info on ignition coils under 'Typical Ignition Coil Values':
http://www.systemsc.com/diagnostic.htm

As can be noted from the data posted, the key value for a TCI system
(used in the 964/993) is the primary inductance which relates to the
primary resistance. Both values affect the energy developed in the
resulting spark for a TCI system. The minimum needed to fully ignite
the fuel charge is considered to be about 30 milli-joules.

The Bosch blue coil is at the minimum of the necessary energy level
which can be developed given the typical duel times at 6000 RPMs.
That results from its large inductance of 12 milli-henries (mh) limiting
the current during a given duel time. All of the other widely available
TCI coils with inductances of 3-5 mh will provide the necessary energy
at the high RPMs. Those TCI coils will not damage the ignition modules
used in the 964/993 systems.

The CDI coils listed with their very low inductances can't be used with
most TCI systems.

ja78911sc

Pelican has the same part # for a 964 coil and a 944 coil (944-602-115-00-m14).

Based on this, if the MSD 8222 is a common replacement coil on a 944, it should work on a 964 as well ????

Alex Sol

I can't be the only guy to try msd blaster coils in the 964. and agree with Ja78911 here that they are a 'direct' replacement both from pelican and lindsey racing... that said.. i'm trying to understand Loren's info.

I'm looking at the Bosch Black/Silver - I had one of each in my 964. black on the primary and silver on the secondary.

the blacks have over 50,000 kms on them and may even be originals with 293,000 kms. on them. I wouldn't know because i bought my guards red 964 with 247,000 kms and now have 370,000 kms on it...

The silvers were purchased in 2009 and i put 75,000 kms on them before testing them this week.
1. primary reading (two outer stems) 2.1 ohms secondary reading (outer stem to middle of coil) was 5,600 ohms
2. primary 2.0 ohms secondary 11,000 ohms - so i put it on the shelf, blew the dust off on of the blacks that had same reading as silver coil #1

So if i am reading Loren's info correctly, the bosch blues would work but the specs are quite different from the bosch black/silvers.

Primary R .7 vs 3.5 ohms

Secondary 6,200 vs 8,800

Primary L 3.6mH vs 12 mH

N is 90 vs 65

and finally the milli joules 60 vs 30

to contrast the msd blaster 2, the readings are much more similar to the Bosch Silver / Blacks

I got a different inductance number from the MSD website vs Loren's site.. 8mH vs 4.2 mH... so this figure is quite different from the Bosch Black/silvers. Can we use these figures to calculate the milijoules at 6,000 rpms? I suspect that would have to be measured while the car is running.

From the MSD website....

Blaster 2 RED 8202 $39.00 from summit racing
Currently on my car... must keep this upright as they are oil filled with premium oil (of course) for cooling. Are the Bosch oil filled? I have an out of spec Bosch Silver and a sawsall....

Coil Specs
Turns ratio: 100:1
Primary resistance: .7 OHMs
Secondary resistance: 4.5K OHMs
Inductance: 8 mH
Maximum voltage: 45,000 Volts
Peak current: 140 mA
Spark duration: 350 uS
Weight: N/A

Blaster 2 - 8222 - Silver with Red/Black $49 from summit racing / Pelican / Lindsey
Coil Specs
Turns ratio: 100:1
Primary resistance: .7 OHMs
Secondary resistance: 4.5K OHMs
Inductance: 8 mH
Maximum voltage: 45,000 Volts
Peak current: 140 mA
Spark duration: 350 uS
Weight: N/A

will test the injectors and check for pulse / signal and hope to get my other three cylinders firing this week and will report back. cold in my garage though... brrrrr

FeralComprehension

There you go!

JA, your logic does make sense but given the costly nature of the related bits I was unwilling to risk mine in the absence of greater experience. Now that Loren has stated categorically they'll work my next set of coils will NOT be Bosch.

Thank you Loren.

Olcha911

I have used the MSD coils in my 1993 RS America Race Car for the past few years when I did the complete distributor rebuild, new caps, rotors, and ignition wires replacement. No problems at all.

Lorenfb

For those that want to calculate the primary energy stored in the coil
before the spark occurs:

Energy = 1/2 X L (milli-henries) X I ^ 2 (joules)

1. @ 6000 RPMs each cylinder fires every 3.3 ms (milli-seconds)
2. The dwell time (T- ms) must be less than 3.3 ms.
3. I = T (ms) X V (~ battery voltage) / L (milli-henries)

Then for T = 3 ms & L = 3.6 mh, I equals about 10 amps ideally.

Energy = 1/2 X 10 (amps) ^ 2 X 3.6 (mh) = 180 mj

Assuming 8 mh as indicated from other sources, then:

Energy = 1/2 X 4.5 (amps) ^ 2 X 8 (mh) = 81 mj

Bosch Blue coil - 12mh

Energy = 1/2 X 3 (amps ) ^ 2 X 12 mh = 54 mj

The above is all based on a dwell time of 3 ms which is optimistic.
With a 70% duel (2.3 ms) then the results are significantly less.

Bosch Blue coil @ 2.3 ms dwell (70%)

Energy = 1/2 X 2.3 (amps) ^ 2 X 12 mh ~ = 32 mj

Bosch 3.6 mh coil @ 2.3 ms

Energy = 1/2 X 7.6 (amps) ^ 2 X 3.6 mh ~ = 106 mj

Coil of 8 mh @2.3 ms

Energy = 48 mj

Alex Sol

so... ummmm. it will work?? haha. thanks for the science lesson Loren.

I've lost you here Loren.

The Bosch Silvers at 70% efficiency is 106 mj
Bosch Blue is 32 mj
and MSD makes 48 mj?

So the Bosch Silvers make the most mj but crap out early.. like a candle that burns twice as bright... burns half as long????

I'll keep the MSDs

Olcha - good to hear we have a safe coil option here.. did you notice any iimprovement in performance ie: dyno or more importantly... butt dyno.