Originally Posted by EvocentriK

Seems this thread died in the ***. Anyway, completed the installation of the GTR coils in sequntial spark mode. Ended up making a bespoke power supply with 14 gauge Raychem #44 wire to the harness plug, dedicated 14 gauge ground strap to the cylinder head, 30A sealed relay with a 15A sealed fuse holder. Built my own coils harness from 18 guage tefzel, spliced power and ground wires sealed with Raychem SCL and everything is then covered with raychem DR25. The harness is terminated into a 6-way Deutsch DT connector. Turned out really nice, fired up today for the first time and it ran well. I elected not to use the stock feed for the relay trigger, as this feed is on its own circuit with the ignition relay, lots of wire and the 10A fuse feeding it. Too many parts to fail that could take out the new system, so I am triggering it with an ECU switched 12v power signal that was previously used to power the narrowband o2 sensor.

I spoke to PRP in australia about the power feed situation and they advised that they don't really consider it a big deal. There's a 1000kw R34 GTR with 18 guage feed and ground apparently and that's doing just fine, so I guess the coil output must be pretty insensitive to dwell time with the GTR coils (or dwell voltage, as the case may be).

Originally Posted by deeman101

If you're running sequential ignition, the question I have is if you have two 16ga power feeds to supply the amperage demands during an individual coil's dwell time wouldn't that split the amps needed by 50% each to charge the coil in parallel? Or 7A and 7A instead of 14A through each of the stock wiring 12V feeds. I can understand if it was still a wasted spark setup simultaneously drawing amps for charging 2 coils could be pretty demanding on the stock wiring.


Edit: I should mention the above is with the assumption you'd be willing to run both power/ground circuits to all the coils in parallel.

Edit 2: I looked up the circuit diagram. The ignition coils have a 12V 16ga wire coming from the positive battery terminal with a 20A fuse and also has a branch from that same wire for the ECU. So.....probably better to run a separate line to the coils if you're drawing a lot of amperage.

Originally Posted by EvocentriK

Just trying to unpack that, are you saying the stock setup has 2 x 16 ga feeds or you would build one with 2 x 16 ga feeds? The stock system has only 1 x 16 ga feed which is spliced to allow one power wire to run to each of the two OEM harness plugs. It's a long feed wire, it's power source is the Omron micro relay in the engine fuse/relay box and it's got a 10A fuse in the cabin as well. Not ideal from a resistance & voltage drop scenario, which is why the testing shows the voltage sags heavily during coil dwell with the stock feed setup.

Yes, running sequential spark vs wasted spark halves the load on the wiring as only one coil at a time is in a dwell state, there is no dwell overlap if you use the commonly found dwell times for the R35 coils. Wasted spark is charging two coils at once and firing one on the exhaust stroke, so it's double the charging load, double the charging/discharging related coil heat, and reduced coil and plug life. Given how antiquated the stock ECU is I changed this out awhile ago, and one of the advantages of aftermarket is the ability to run sequential spark. This also allows per cylinder knock control instead of cylinders being paired which is great too. Be crazy not to! If still on stock ECU, R35 coils in wasted spark mode on the stock power feed line is pretty tough going, they'll work but it is less than ideal.

Originally Posted by deeman101

Yea I checked the wiring diagram. Looks like only 16ga wire for both coils and the "ECS" or basically the ecu. I didn't see on the diagram that it was actually routed through the ECU plugs but that sounds reasonable.

Given that the ECU is drawing power over the same 16ga I'd favor running a seperate circuit to avoid potentially compromising ECU power. Even with a sequential ignition setup.

Originally Posted by Biggiesacks

well bad news is, its not a fuse its a resistor. AFAIK you have to keep it. I'm not sure if the PRP stocks will work with your G37 coils without the GTR stocks. The PRPs retained the top half of the GTR stock but yours looks like its one piece in the picures?

Originally Posted by deeman101

Damn it I was starting to think that was actually a resistor. Not used to seeing one like this. Maybe it's possible to find another stock that's Evo length but just has spring throughout the length (same as GTR/G37/PRP stalk). That way the resistor can stay.

The coil head looks exactly like in this pic from PRP and the resistor is in the same place. I'm highly confident it will work.




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Originally Posted by deeman101

Actually I just tried something. I was able to put the Evo 8 coil stalk on it and the coil pack fit very nicely along with my spoolin up carbon mounting plate. Only thing is I needed to take out this fuse (seen to the left) and I'd need to cut a spring down to make it fit well. How necessary do people think that fuse is? Incidentally I think this one is blown....I'm measuring 1900 kohms right out of the box.

Originally Posted by EvocentriK

Thanks for all the testing. Quick one, you said on page 1 that the GTR coils draw 14A during the dwell period, but here you say the coils are at 11A when saturated. I'm a bit confused by the expression here. Isn't saturation a point at which maximal magnetic field strength has been formed in the coil, and when it collapses it triggers the maximal spark energy output? Saturation may take longer based on the incoming voltage/current fed to the coil from the power supply (ie: lower = longer dwell time required) but saturation is saturation, right?

The most telling detail is the voltage sag to 9.3v that you observed during the dwell period. Even with stock or Yaris coils, especially in wasted spark configuration, the stock power feed is inadequate. 16AWG wire is really only good for 10A constant in free air and it's really surprising to me that Mitsubishi undersized the feed to such an extent. Engine bay temps are high, and the circuit is fused at 10A - upgrading the ignition circuit fuse to 15A is really exceeding the wire rating and I'd suggest isn't a great idea. Was this test you performed where you obesrved the 9.3v at the end of the dwell period in wasted spark mode, or were you isolating a single coil only on the harness with no others connected and measuring it in situ while triggering it manually? I assumed this was in wasted spark mode, and you had all coils in place and the engine running but you were taking measurements from one coil. This would influence the results as you would have 2 coils in their dwell periods simultaneously. Similarly, did you perform the above current draw test in wasted spark mode with all the coils connected and running together?

I have almost finished converting my ignition system to sequential spark configuration, and I am debating the need to run a relay for a dedicated power supply for the ignition coils. I assume the spoolinup power harness is simply a relay with a fused power feed that uses the stock feed as the 12v relay on trigger signal (ie switched 12v trigger).