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Coil on Plug options for Electromotive XDI2

I'm starting to gather the information and parts needed to convert my 2.7 with Webers to electronic ignition. My original plan was to use the complete Electromotive XDI2 three coil setup and Clewett parts, but the less cluttered look of a coil-on-plug solution would be nice. I have already purchased the XDI2, and now need to decide on which type of coils to purchase.

Can the XDI2 be used as-is to drive an on-plug coil? I've read a few of the threads here and see there are "self" vs "internal" ignitor systems - which would be needed for the XDI2? Has anyone made a plug-and-play kit for a COP setup on a 911 yet?

My long term plans are to eventually twin-plug the motor. Would the coils on the bottom plugs be subject to too much heat?

Thanks for any advice. If there is a good link that explains all this, you can just point me there.

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Old 11-11-2012, 08:40 PM
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I wish I could point you to a thread where somebody had documented the whole process.

Where I think the state of the art is presently is with the Denso coils.

However nobody has been able to post the resistance and inductance specs of those coils.

There are two versions, one without an igniter, and one with. Obviously the one without the igniter must be used with an external igniter. If you look at the AEM coils, they are "required to be used with a CDI" because evidently the ignition energy using them as inductive coils is pretty low. It takes 30mJ to get the fire to light, they are less than that. Hence the "use with CDI" program.

That seems to me a retrograde step-- if you need to use a CDI box to fire the plugs, why bother with a pencil coil at all? Also, I can't name a true six-channel CDI that's out there-- every one I've seen, like MSD, requires that you use three channels in a waste-spark setup.

SO: here's the technical writing challenge, if I may:

1) What are the output specs of the XDI2? What are the alternatives, like Megajolt?

2) What are the physical dimensions of the pencil coils appropriate for this application?

3) How are the pencil coils affirmatively secured to the valve covers, top and bottom?

4) What are the primary and secondary resistance, operating voltage, inductance and the ignition energy of the proposed pencil coils?

5) What are the actual part numbers and applications for the pencil coils? How much do they cost, and where do they come from?

6) How do you tune the system? What are the appropriate maps? and finally:

7) What's the difference? What is the improvement in terms of ignition accuracy e.g. reduced spark scatter? What flexibility does the system offer in terms of varying individual cylinder ignition timing, and what is its effect on the peak pressure point (PPP) for that cylinder, on engine smoothness, and on overall dyno results?

To FrankC-- I hear you, wouldn't this all be great to have in a single place? I've been looking but haven't been satisfied. I know it's been done successfully, I just haven't found the trail of bread crumbs. . .
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Old 11-12-2012, 03:55 AM
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Hey guys,

I'm using the Denso CoP's...12 of 'em...along with Bosch amplifiers (igniters). I can actually drive up to 8 CoP's directly from the MBE ECU, it has integrated power amps, and that would've been fine if I hadn't later decided to go twin plug. MBE very kindly made me a Rev B ECU so that we could fire the external amps, bypassing the internal ones.

In terms of tech spec John, sorry, not a scooby....these are what my mate at SBD uses with great success with other MBE projects; I tried understanding ignition a few months ago, ended up doing my melon in so I moved onto other items of the build, lol.

I bought mine from Chris @ TurboKraft; I'd give him a shout to get latest pricing. They ship in a Honda box; IIRC they're FireBlade items, but again, couldn't tell you which vintage.

Haven't got around to fabricating anything to hold them in place just yet...but coincidentally was mulling this one over again the other evening. I'll probably replicate something I saw in a pic I saw of one of the 70's vintage cars....934 or an RSR perhaps?....where they kept the spark plug leads clamped down using "finger" clamps, mounted off of the valve cover studs.

It'd be easy to make plastic or ally collars to hold the top 6 CoP's central, as the valve cover holes are round, but the exhaust cover holes ain't, so that wont work too well. In terms of how they locate on the plugs, you remove the tip from each plug, and the CoP's push down with a serrated engagement onto the exposed plug thread. It is nice and secure, so I can't imagine that for road use they'll come off, but they will wobble around without some kind of locator/clamp.

Cheers
S
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Old 11-14-2012, 10:32 AM
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Spencer, thanks for weighing in. You are not YET an ignition expert but will become one along the way. . . once you start building spark tables for that aluminum monster.

And these details do help: "Fireblade" means they are honda CBR motorcycle coils. Driving them from the box itself without external ignitors suggests they are inductive, not CDI transformers. However, a lot of the motorcycle coils are intended to run off of 80+ volts, some 100+ volts. That suggests that given the size of the coil, it won't make the requisite ignition energy without a high-voltage pulse.

I suppose the way to find this out is to buy one on eBay and test it and do the math.

Unless somebody has the tech specs?
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'66 911 #304065 Irischgruen
‘96 993 Carrera 2 Polarsilber
'81 R65
Ex-'71 911 PCA C-Stock Club Racer #806 (Sold 5/15/13)
Ex-'88 Carrera (Sold 3/29/02)
Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04)
Ex-'89 944 Turbo S (Sold 8/21/20)

Last edited by 304065; 11-16-2012 at 05:11 AM..
Old 11-16-2012, 05:01 AM
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I've not got the tech specs, but I can supply the part number....





When Chris (TurboKraft) supplies them, you also get the all-important plugs and pins....when I spoke to my harness guy the other day, and mentioned Denso CoP's he started to get a little concerned, as *some* Denso parts are starting to prove problematic in terms of getting the plugs...whether thats a UK problem, Ive no idea, but something to be aware of.

A quick google, and found this...not official Denso page, but a good start:

Quote:
Originally Posted by some bloke on t'interweb
Coils tested 129700-3881 J0388 from 1999-2005 Honda CBR 600 F4 (ebay, $30). Measures 4.0" top of spark plug ceramic to below connector. 4.75" total length. Rubber cap adds another 3/4" length, but goes over ceramic and can be removed if desired.
Primary resistance 0.8 - 1.2 ohms (around 1.2 - 1.3 on mine)
Secondary resistance 11-14 ohms (about 11.2 - 11.4 kohms on mine)
Charge time ~ 3.1 ms (from internet search)
Forum thread can be found here

BTW...hearing more and more stories about these sort of parts being cheap Chinese knock-offs on (fle)eBay...potential buyer beware...
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Last edited by Spenny_b; 11-16-2012 at 02:24 PM..
Old 11-16-2012, 02:21 PM
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FWIW,

I too tested these coils and was not at all happy with the spark when hit with 12 VDC, I am under the impression these are CDI coils and need to be hit with a CDI to deliver a solid spark. If Chris at TurboKraft has them working on turbo motors I believe him but would like to see some details. I held off because of this and went to a dizzy from a 3.6, Bosch igniters and spark control via the Haltech ECU.

Stay tuned,

PFM
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Old 11-16-2012, 05:50 PM
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Thanks for all the discussion here. It sounds like I definitely need to research this some more to become familiar with all the components involved for a COP system as it is not as straight forward as I had hoped. I was hoping that by now somebody would have sorted out the details and started offering a kit of some type as an alternative to the traditional Electromotive coils. Just another project to add to my list...
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Old 11-16-2012, 07:45 PM
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I recently completed a COP conversion and thought I would share my experiences FWIW, to help build up a reference for people attempting this in the future.

Brief engine specs: 930 base engine, 3.4L P&C's, twin K24 turbo's, twin plugged heads, Haltech P2000 ecu, single 85lb injector / cylinder.

After several attempts at adapting 12 x 996 COP's - I gave up due to:
- The lack of length of the spark plug boot
- A suitable method of retaining the COP's to the valve covers
- The spark plug not being perpendicular to the valve cover face
- Interference with the oil line to the RHS cam tower.







I was hoping that the 996 set-up would work due to the relatively large inductive coils - but due to the reasons above - I gave up. Although I still have 12 brand new 996 COP's if anyone wants to give it a try.

I then tried to adapt a set of Ford / Accel COP's but had similar problems with the length of the spark plug boot length.



I then looked at "pencil" COP's and found that as most are derived from motorcycles, they require a CDI to provide higher voltage to the coil primary to maintain a suitable level of spark energy. After a bit of research I finally landed on the AEM Twin Fire CDI and the AEM "long" style pencil coils.





There is a fair amount of negative experiences with the AEM Twin Fire CDI's on the internet; however most of it appeared to be with their old version. I purchased two 8 Channel Twin Fire CDI's and 12 pencil coils. One 8 channel CDI powers the lower set of plugs, the other powers the upper set of plugs. Each is wired to be fully sequential (i.e. not in wasted spark). After checking with AEM and Haltech, I wired each Ignition Output from the Haltech (one for each cyliner) directly to the inputs of the AEM Twin Fire CDI's (paired each Haltech Ignition Output to the corresponding input of the AEM CDI's). I was advised to do this without a separate ignition igniter, as the Haltech could handle the current draw to power 2 AEM CDI inputs.

Here is how I mounted the CDI's.


To be continued.....
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Old 11-20-2012, 06:52 PM
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Continued..
The benefit of the Pencil style coils is the relative ease of mounting. I use the term “relative” as nothing is as simple as plugging in a set of spark plug leads. As I already had billet valve covers I was able to drill and tap them in order to fit a pair of studs in each valve cover.



I then made a set of plates to hold the end of the coils in place and fitted them with large rubber grommets that snuggly fitted the body of the pencil coil. Due to the difference in angles of the spark plug axis and the valve cover surface the rubber grommet holds the head of the pencil coil very well - they will not fall out.




I added a heat shield to the lower plug COP's - due to the headers and turbo set-up.


The finished product.


The engine made ~450 rwhp on the dyno at 1 bar of boost with 91 octane pump gas and a rich setup. So far the AEM CDI's/COP's have been trouble free.
In retrospect - I spent far too much time and money chasing my dream of fitting a COP system to this engine, with no measurable performance gain. If I had to do it over again I would most likely go for a Coil Near Plug setup using a series of Chevy LS style inductive coils and a simple set of spark plug leads. Whilst not as cool looking, it would have likely provided a similar level of performance, cost considerably less and packaged just as well.

Richard.
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Old 11-20-2012, 06:57 PM
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Thanks,
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Old 11-22-2013, 07:46 AM
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Richard,

I myself am currently looking at the LS coil-near-plug options for my rally build. Great work!

Old 11-22-2013, 09:46 AM
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