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Question Running COP ignition with Motronic DME

Looking for data and feed back from anyone running COP or wasted spark ignition with Motronic DME

I know there are a lot of aftermarket systems out there, just curious on what can be done with the Motronic.

My 3.2 motor is currently single plug N/A with the OEM DME
Iím planning a Turbo conversion and looking for cost effective solutions to improve the duration and voltage output to the plug, with the ability to later expand the system to twin plug.

Is it possible to split the Motronic DME ignition signal into the 3 channels needed to drive a single plug COP system?
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Thank You for your time, Paul. We do because we can.
87 911 3.2 (Turbo conversion, build in progress, Thermal Barrier Coatings, High Pressure Dry film coatings) Modified heads, boat-tailed case, ARP hardware, OBX Header, 930 clutch disk, G50 Trans
89 5.0 Mustang convertible (For Sale)
Old 02-02-2010, 08:46 AM
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Here is link showing the inside of a Motronic DME Inside a Carrera ML3.1 DME - The Land of NoVA/DC/MD area Porschephiles Item # 9 is the ignition driver.

Is it possible to split and use this signal for COP?
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Thank You for your time, Paul. We do because we can.
87 911 3.2 (Turbo conversion, build in progress, Thermal Barrier Coatings, High Pressure Dry film coatings) Modified heads, boat-tailed case, ARP hardware, OBX Header, 930 clutch disk, G50 Trans
89 5.0 Mustang convertible (For Sale)
Old 02-02-2010, 09:05 AM
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A lot of what you are saying is over my head I think.

However, I believe the stock ignition is CDI and hard to beat as to intensity.

I think many of the wasted spark systems do not generate as hot a spark but not sure.

If you are staying single plug adding MSD seems to be an improvement. With this you can also get pressure based boost retard. Or even go fully programmable.

There is a company that taps into the signal from the Motronics to coil for the advance curve and from the crank sensor to know which cylinder is up to feed their own box for driving a twin plug wasted spark system.

Me I would stay with the single plug factory or add on MSD unless going for over 500hp or lowering compression to under 7/1. If I was going to go twin plug I would probably get a twin plug dist or just change over the whole EFI to a programable.
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Quote:
Originally Posted by 911st View Post
A lot of what you are saying is over my head I think.

However, I believe the stock ignition is CDI and hard to beat as to intensity.

I think many of the wasted spark systems do not generate as hot a spark but not sure.

If you are staying single plug adding MSD seems to be an improvement. With this you can also get pressure based boost retard. Or even go fully programmable.

There is a company that taps into the signal from the Motronics to coil for the advance curve and from the crank sensor to know which cylinder is up to feed their own box for driving a twin plug wasted spark system.

Me I would stay with the single plug factory or add on MSD unless going for over 500hp or lowering compression to under 7/1. If I was going to go twin plug I would probably get a twin plug dist or just change over the whole EFI to a programable.
911st,
Thanks for your input,

To clarify the 84 - 89 Motronic ignition is an Inductive system using a coil not a CDI unit.
The ignition driver item #9 in the DME from the link Inside a Carrera ML3.1 DME - The Land of NoVA/DC/MD area Porschephiles shows that it is a power transistor on the Digital side of the DME. In hind sight, I think that's where my confusion started lol

From your post, Motronic's turbo conversion thoughts? mentioned using the adjustable MSD boost retard system as a method of controlling ignition boost retard, so I decided to check it out. After reviewing their installation diagram, I questioned whether it would work, since their wiring diagrams http://static.summitracing.com/global/images/instructions/msd-5462_frm28661.pdf show the white trigger wire hooked up to the distributor pic-up and since the Motronic system has no dist pic-up it left me wondering where would the signal come from. So I sent an email to the supplier and apparently according to them it will work and this is what they had to say;

"It will basically wire in between the ECM and coil.
The white wire will connect to the wire that is currently connected to the coil (-)
The Orange wire will then connect to the coil (-)
The small red wire will connect to switched 12v+ or the coil (+)
The black wire to ground."

Nice to know as this looks like a fairly inexpensive solution to having variable control of boost timing externally of the ECM ignition tables.
It's piggyback and and some what of a band aid but a solution, but still a means to the end result.

I know we are getting a bit off topic here, but its all tied together.

One of problems with doing your own turbo conversion is with working out all the variables in managing the new fuel and ignition needs, however for me that's part of the fun.
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87 911 3.2 (Turbo conversion, build in progress, Thermal Barrier Coatings, High Pressure Dry film coatings) Modified heads, boat-tailed case, ARP hardware, OBX Header, 930 clutch disk, G50 Trans
89 5.0 Mustang convertible (For Sale)
Old 02-02-2010, 05:24 PM
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We are lucky to have Steve Wong to burn chips for us if needed.
Old 02-02-2010, 06:15 PM
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Quote:
Originally Posted by 911st View Post
We are lucky to have Steve Wong to burn chips for us if needed.
Yes we are, I'm thank full for that and will be keeping that option open.

In the meantime I'm interested in learning more about the inner workings of Motronic system.

It seems that most people doing EFI conversions on their 930 are going to aftermarket systems where they can program their own fuel and timing maps. This makes sense when you need to buy pretty well everything, but for those that already have a working Motronic EFI system, well why not use it.

There is a lot of bad rap about the Motronic and the barn door restricting flow but for a modest build I don't see that as much of an issue. Look at the race cars that are forced to use restrictor plates, they seem to be able to work around this problem with the location of the restrictor (see pg 121 Bruce Anderson 3 edition) " Several teams figured out that they could run the correct size restrictor as far as they could get it away from the throttle, and they could almost eliminate the effect of the restrictor"
Less intake restriction is better but at what cost?

Getting off topic again, lol

This leads me back into the Blow through VS Suck debate.
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Thank You for your time, Paul. We do because we can.
87 911 3.2 (Turbo conversion, build in progress, Thermal Barrier Coatings, High Pressure Dry film coatings) Modified heads, boat-tailed case, ARP hardware, OBX Header, 930 clutch disk, G50 Trans
89 5.0 Mustang convertible (For Sale)
Old 02-03-2010, 08:27 AM
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Back on topic,

I found this last night DIY Wasted Spark for 84-89 Carrera
Fantastic reading, valuable information on Motronic

Also found this link from that page about CDI vs IDI Capacitive or Inductive Ignition?

More on CDI vs Induction ignition systems EFI University Electronic Fuel Injection Tuning :: View topic - Is CDI ignition necessary


Bottom line if it's doing the job, be happy with it.
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Thank You for your time, Paul. We do because we can.
87 911 3.2 (Turbo conversion, build in progress, Thermal Barrier Coatings, High Pressure Dry film coatings) Modified heads, boat-tailed case, ARP hardware, OBX Header, 930 clutch disk, G50 Trans
89 5.0 Mustang convertible (For Sale)
Old 02-03-2010, 08:46 AM
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I do not know of any mfg using a blow through metering system. However, Protomotove has been quite successful doing so and I think makes up to 475hp with such systems.

The 944-Turbo is a pull through.

With a blow through the BOV can be to atmosphere. On a suck through it should loop around the turbo compressor.

I suspect minimizing any restriction after the turbine or before the compressor wheel possible improves a turbos efficiency but can not say that for sure.

On a pull through there is a lot of intake volume (including the intercooler) that might dampen the AFM's responsiveness v having it just in front of the throttle body.

The AFM's were not designed to be pressurized so some efforts may be required to hold them together.

Not sure any of this helps.

I think I vote for the simplicity and ability of the AFM to more quickly sense changes in air flow of a blow through.
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