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Wirings LS1 / LS2 coils 
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QFP80 - Contributor
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Joined: Sat Aug 16, 2008 4:39 pm
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Hi. Since usage of LS1/LS2 type coils probably isn't specific to any one EMS product I'll go with General section.

Information on http*//www.megamanual.com/seq/coils.htm says adding two capacitors for each of these coils to provide "brief energy storage" and to "eliminate back-fed noise" is recommended. I assume caps should be close to coils itself and not just placed where they're easiest to install? This would probably mean soldering them to wires near coil connectors and covering caps with heatshrink tube. Mounting capacitors with wiring straight to connectors would be closest, but after passing extra pins thru same water seals as wiring it wouldn't be properly sealed anymore. They would also be vulnerable to mechanical stress when connectors are removed from coils.

My setup is going to be wasted spark V8 at this time, but I'd still prefer running separate signal wires for each cylinder to avoid rewiring needs in future. Above page says signal ground should be wired to EMS. Can I combine these grounds on engine side and then bring to EMS or do I really need to have separate signal+ground run for each coil? Installing 16 separate wires from engine compartment to computer just for coils is something I'd like to avoid.

I'm also, perhaps incorrectly, assuming that it's ok to split signal wires near coils because this engine has dual sparkplugs per cylinder so I have 16 of these coils. If splitting is not ok then in worst case it would mean 32 wires to computer and that would be quite challenging to route nicely and require some huge bulkhead connectors on firewall.

My final question at this time is about providing power and related ground to coils. Assuming wire used is not too thin can I combine these to fewer wires to avoid running 16 separate power and 16 ground wires?


Fri Jul 03, 2009 12:51 pm
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LQFP112 - Up with the play
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I think the capacitors could be closer to the ECU as their purpose would be to protect the ECU from noise.

Yes you can group wires together, the idea is to keep the power ground and signal ground seperate.
Try wiring:
1 x Signal ground (ground at ECU)
1 x Power ground (ground near engine/coils)
1 x Coil Power (+)
8 x ECU signals ( or 4 x for wasted spark)

Others have split the signal to two coils for wasted spark, so I can't imagine you would have trouble running two coils.


Mon Jul 06, 2009 4:55 am
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The capacitors are standard fitment to most modern vehicles and are simply for noise suppression. They definitely belong at the coils, but how close is up to you. I personally think that the at connector idea is too extreme. Most OEMs have them within the vicinity of the coil with maybe 200mm of loom separating them, max. The idea is to stop the noise being radiated in the first place, not to protect the ECU from it, per se.

With respect to combining wires :

* Power and ground should be kept in a star pattern. If you can combine them and maintain this attribute, use sufficient wire and go for it.
* Forking the signals to control the coils will be fine provided the ECU has the current drive required to switch two at the same time.

Generally, keep separate loads separate. These signal feeds to the coils are not really loads so combining them shouldn't be an issue. The power and ground feeds to the coils shouldn't be much of an issue either provided they are large enough.

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Mon Jul 06, 2009 1:56 pm
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QFP80 - Contributor
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Thanks. What would you consider sufficient for power and ground wires?


Tue Jul 07, 2009 7:28 pm
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Roughly, 10 Amps per square millimetre. You want to have average current match the wire for wire heating and reliability reasons, but you may be able go get away with less (because of normal rpm vs peak) or need more (because of sag).

I really do not know how much current they draw when dwelling, I could guess, but it would be random... maybe 8 amps peak, 4 average during a dwell, then if you are going to rev it high you have 1/3 duty cycle and you are looking at 4/3 amps per coil average and if you have 8 coils thats around 10 amps, or with 16, around 20 amps.

I'd probably go with something around 2mm sq for the 8 coil setup if the above figures are close to correct.

You have some method and rule of thumb application, now do some research on the coils and go nuts :-)

Fred.

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DIYEFI.org - where Open Source means Open Source, and Free means Freedom
FreeEMS.org - the open source engine management system
FreeEMS dev diary and its comments thread and my turbo truck!
n00bs, do NOT PM or email tech questions! Use the forum!
The ever growing list of FreeEMS success stories!


Tue Jul 07, 2009 7:59 pm
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QFP80 - Contributor
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Great, that should be enough for me at least for now. Also found some test results for these coils. Here's link in case someone else needs it in future. http://forums.hybridz.org/showthread.php?t=120533


Wed Jul 08, 2009 6:03 am
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