Amen!

WOW just WoW
This is a car forum where car guys talk about horse power, building engines, hot chicks and the smell of race fuel in the morning. Where bragging about your last monster build is regular fair.
Since when did everyone get so sensitive.
Next thing you know, swear words and girly posters will be banned from the garage.

Every one of you has had a more heated discussion over turkey dinner......

hey, seeing as all the brightest minds are in this thread, reckon you could have a squiz at this for me ....
https://forums.pelicanparts.com/911-engine-rebuilding-forum/1084339-another-964-through-bolt-question-o-rings.html#post11221493

So I have a question about this discussion, but it would seem to be in "reverse" fashion because I think, but i'm not certain, i'm thinking about an inductive ignition with two coils and one ignitor.

I believe both Jeff Alton and Neil Harvey mentioned in this discussion here that running two coils from one ignitor doesn't go well. Neil mentioned the ignitor tends to overheat and that's why a conductive paste is used to transfer the heat to a sink. I've seen this ignitor and conductive paste design in a Mitusbishi 2.0L 4 cyl. turbo ignition (distributorless and multiple coils) and a 1980s GM HEI TPI V8 ignition (single coil). I openly admit that this is bringing up more old technology inductive stuff and that does not imply i'm trying say it's great, nor am I trying to crap on it. Reason I ask is because it then made me think of the 993 ignition. Aren't the two coils fired by one ignitor the way a 993 twin ignition is arranged? I know for certain it is unlike the 964 setup with two ignitors. I also see Steve Wong has developed an alternative to the famous Andial signal splitter by modifying the Motronic ECU and incorporating a single 993 ignitor


911Chips.com - Porsche 911 Performance Engine Components

I'm not trying to say that if the 993 has such an ignition, it must be great. My question is actually, is this approach inherently flawed because it employs an overworked ignitor with a conductive paste + sink. It would appear the paste & sink are a compensator for the shortcoming of too much heat?

Please know that I don't mention Jeff and Neil to call them out. I totally respect their knowledge and input here, and i'm not questioning if they were wrong. I'm just trying to see if I correctly understand what they said. Their mention of the ignitors triggered (pun intended) my memory of the ignitions I have encountered on previous cars of mine and then I thought of the 993 setup, which is sort of pertinent to the conversation. Is one ignitor for two coils the inductive version of using one CDI to fire two coils?

Kevin,

Against my better my better judgement I am posting again on this thread.... I am fine with having to block some members... lol

It is pretty simple. There are those who build engines and test our results (regardless if they could be better) and then there are those that build and have results that are good and meet their needs and then there are those that read what other's post, ask questions and create an "informed" opinion. There is room for everyone to post on these topics, and in fact each post can add value to the discussion. Regardless of the experience of the poster.

I hope to not get into anymore debates with those that have no actual experience building and testing engine combinations. That does not mean we think we are right. It only means we have data that backs up what we do, regardless of whether it conflicts with what other folk's data that is based on a white paper or is based on "What they heard". William, Henry, Neil etc and any one else with true experience are who to listen to and would exchange ideas with to perfect our craft. We are always in a state of learning, if we were not we would be standing still at best. We value the input of those with far more experience than we have to the 10th power, even if we disagree or question them at times.

On our Twin Plug builds using 12 COPs with AEM Infinity ECU we are using 2 ignitors. I don't think we are down any power (though maybe we are?). Happy to be proven wrong. I can (RE) post the dyno sheets of a 3.8, a 3.4 and a 3.2SS again but not interested in the feedback from those who don't know what they are looking at and have zero experience in building performance 911 engines..... (I don't mean you by any sense). Forget the numbers on the sheets (it is not my dyno) but look at the curves and ask one's self if more HP is on the table in terms of ignition capability....

Again, I am open to this great dialogue. We always learn something in these friendly debates. If we were building a twin plugged carb motor with a 964/jarvis/jb/superterch or whatever distributor we would be asking questions of those that have actually done it. We only offer our experience to the board where we have actual experience.

And yes HENRY, you are quite right. None of this is worth getting butt hurt about. My goodness. This is a forum for enthusiasts looking to learn and offer experiences. Be it professional, hobbyist or clueless. We all learned somewhere. Just because someone with a "username" didn't agree with us should have no bearing on how we feel or how we react to posts. But it really is not a place for people who have no experience to post as someone with experience. By all means post what you heard or talked about with person X, we can all use that information.

This is the engine rebuilding forum after all, right? AMEN to you Henry, brother.

Kevin,

It isn’t the number of igniters.....it is the number of channels per igniter.

My race engine has 4 3-channel igniters so each of the 12 CoP sticks has its own channel.

The Bosch 0-227-100-200 used in the 993 is a 2 channel igniter designed to handle 2 coils.

http://forums.pelicanparts.com/uploa...1613206712.png

Kevin,

The Bosch 0 227 100 124 igniter has a single channel and there are 2, one for each coil, used in the 964.

HI Kevin,
This is a long answer to your question but hopefully clears some things up.

Is one ignitor for two coils the inductive version of using one CDI to fire two coils?

Not really. If we think of the most basic inductive ignition it has points and a coil. When the points are closed electric current flows into the coil. When they open the field falls and you get a spark. The limit of this design is how much current you can run thru the points without burning them up. Plus points require constant adjustment.
Many manufacturers switched to “transistorized ignition”. This changed the system so that the current flows thru a transistor. The amount of current is only limited by the size of the transistor. A transistor is just a electrically controlled switch. The on/off “trigger” for the transistor can be multiple things. For some ignitions there is a optical or magnetic “trigger” built into the distributor. For most later cars this trigger signal comes from the ECU.
An ignitor is just a transistor or group of transistors with each channel being a transistor. The important thing is that the transistor in the ignitor needs to be able to handle the amount of current going to the coil.
Bosch 0-227-100-200 used in the 993 is a two channel ignitor. I could not find the specs on that unit to use as an example, but I could for the 227-100-203 from Bosch motor sports referenced on Steve Wongs site (911chips).

Full specs here.

https://www.bosch-motorsport.com/content/downloads/Raceparts/Resources/pdf/Data%20Sheet_68570379_Ignition_Module_IM_3.2.pdf

The 227-100-203 is a three channel ignitor. The maximum recommended current for each channel (transistor) is 10Amps. If we look at the recommended coils for this ignitor the p50 is listed as a recommended coil.

Looking at the P50 coil (full specs below) technical specifications we see that the current for that coil is 5-10Amps which matches with the ignitor max of 10amps.

https://www.bosch-motorsport.com/content/downloads/Raceparts/en-GB/50280203208699019.html#/Tabs=50291595/

However if we look at the C90i coil which is a high power coil (90Mj vs 50Mj) we see from its specs that the current for this coil is 10-20Amps. This is more current than the 227-100-203 is rated for and the transistors would most likely overheat and fail.

Its also interesting to note that the 227-100-203 is rated up to 8000RPM.

So for the inductive ignition using two p50 coils and a single ignitor with a rating of 20 amps or a two channel ignitor with each channel rated at 10 amps the result would be approximately the same as there would be sufficient current capability from the ignitor for both coils in both cases.
So its about matching the parts to the application.

The CD ignition works different than inductive. The CD ignition first raises the voltage to several hundred volts and charges capacitors (capacitors work kind of like batteries that can release energy very fast). When the ignition signal is sent to the CD box (instead of ignitor) it connects the capacitors to the coil (probably thru a transistor). The other side of the coil is connected to the other side of capacitors and capacitors release their energy into the coil.

For the CD ignition with one coil vs one CD with two coils the two coils will have approximately half the energy and half the spark time. This is because the two coils will drain the capacitors in the CD ignition in half the time and the energy from the capacitors will be split between the two coils so half the energy output.

Just like inductive ignition the components need to be sized to the system so do CD. By changing the coil specs and CD specs you can affect the amount of energy and time of the generated spark.

Since specification for standard OEM automotive parts can be difficult for the public to come by the learned experience of those who have tested by trial and error of what works is often the best guide for making choices.


john

Nothing like having an EE explain things. I'm glad I kept reading this, because I hadn't realized that CDs fired when the coil voltage input happened, rather than when it was grounded and the field collapsed.

The documentation for the Bosch 227-100-203 says the following:

"This module is an external ignition power stage capable of supplying up to three non-transistorized ignition coils."

https://www.bosch-motorsport.com/content/downloads/Raceparts/Resources/pdf/Data%20Sheet_68570379_Ignition_Module_IM_3.2.pdf

It seems Bosch does not intend a single ignitor channel to drive more than 1 coil.

The Bosch 227-100-200 module appears to have the same specs as the Bosch 227-100-203 module:

https://www.pim-engineering.com/tiedostot/ignitionmodules.pdf

You certainly would not want to drive two coils per channel with any of these Bosch igniters.

Thanks to Scott and John for the detailed information on the Porsche/Bosch ignition modules. I appreciate the technical insight as to how these modules are designed to work

Jeff,

What brand and model igniters are you using?

Jeff,

If you are using the AEM 3 channel igniters, I asked AEM about using just two of those on a 12 CoP Porsche dual plug six cylinder setup. Here is what they said:

"We do recommend running four of the 3CH Coil Drivers for this specific
setup. Triggering two coils on a single channel will cause the igniter to
overheat and fail.”

If you are using two 6 channel igniters, great. AEM doesn’t make anything like that though. I think Haltech does.

Looking around at all of the igniters I find people might use in street builds, none have enough current handling capacity on a channel to drive two standard ~10 amp coils. I certainly can't find any documentations from any igniter manufacturer saying it is okay to use 2 coils on a single igniter channel.

The higher performance igniters that I did find that support more current on a channel are designed and intended to be used with higher current coils. So again, a single coil per igniter channel.

Based on this, and the fact that a CDI system using 2 two coils on a single ignition has half the energy and half the spark time, it seems to make no sense to use 2 coils on a single igniter channel with an inductive setup or to use 2 coils on a single ignition with a CDI setup. Even with testimonials that say it "works fine".

Nearly 300 hp on a 3.0 street (10:1) engine on street gas. DC 62 102 lobe center. Single MSD.
Note the max power @ 6500. Factory RSR race engines barely made 315 @ 8000
http://forums.pelicanparts.com/uploa...1614116412.png
http://forums.pelicanparts.com/uploa...1614116412.jpg

3.2 Street engine, Mod S cams, SSI exhaust single MSD. We have since discovered that the M&K muffler in this configuration probably cost us 15hp.

http://forums.pelicanparts.com/uploa...1614116685.jpg
http://forums.pelicanparts.com/uploa...1614116685.jpg

Imagine how much it would make with 2 MSD! :D

And here I thought you had more style than the other squirrels....:D

I should do back to back dyno pulls, I have a 3.0 twin plug with a single MSD, now I'm going to install EFI with crankfire and 6 GM wasted spark coils.

I'm not getting rid of my old kit though, my webers dizzy and MSD will be going onto my new 2.7 project that I'm slowly collecting parts for.

Back to back pulls without tuning for each application will be almost meaningless but it's something.
If I understand the answers to my questions, the previous claims of back to back was simply disconnecting one CD box rendering the engine single plug.....hence the claim of 15hp reduction.
It was valuable information but not as informative as it might have been.

I know it's meaningless...that is except to me. ;)

I just want to have fun, my under sized webers, my crappy repop Jag cap dizzy and single MSD is fun.
I'm only doing the EFI swap because a) I got the system cheap for an excellent price and b) because I need a second intake and ignition system for another engine project.

I wonder If I can run my new ECU ignition only? So I can see if I at least feel a difference between my PMS TP dizzy with single MSD/two coils and the the crankfire ignition system.