RB20 / RB25 coil swap idea

[GTSBoy]

That's interesting. I didn't realise there were other non-OEM coils out there. The JJR ones will be at least $100 cheaper than getting Splitfires from Jessestreeter in Japan, and I'm not pushing huge boost into the RB20, so even if they don't have as much guts they're probably going to be fine for me - provided their likely Chinese manufacture has decent quality.

Will consider strongly.

[GTSBoy]

Can get coils from Nengun or Jesse Streeter for <$550. Am going to avoid the Chinese copy ones from JJR just in case.

[dougmo]

gtsboy are you still running the coil cover between the rocker covers?

if you remove it and cut it and leave just enough for the ignitor to mount on to it should help if not cure the issue(unless your coils are totally rooted) obviously doesnt look as clean but does the job.

may be worth a crack.

[GTSBoy]

I normally run the cover. Normally it is fine. Like in the 40°C heatwave recently in traffic it must have been hellishly hot, and it was still fine. Although it is quite likely that those days were the straws that broke the camel's back and took a few months of lifespan off the coil that just died this week.

In the case of this coil, it died on the way to work. And on the way home it died again exactly the same number of km (give or take little bit) after leaving work. So that night I pulled the cover off and the next morning it died in almost exactly the same place as the morning before. So I gather that the coils get almost exactly the same heat treatment whether the cover is on or off.

As RB30-Power said above, the cover is intended to duct the cooling air pumped from the timing cover over the coils. I think this is why the first coils to die on RB20s are #4 and #5, because the middle of the head is hotter than the front or back ends, and the cooling from the air over the coils becomes less effective as you go towards the back. Making #4&5 about the hottest coils. I've had to replace #4 and then #5 and now #6. The front 3 are still going.

I reckon if Nissan had any sense they would have installed a duct between the cabin ventilation plenum and the back of the coil cover and positively cool the coils that way.

Anyway, it makes sense to me.

As to cutting down the coil cover, I have previously made a small right angle bracket to mount the igniter vertically upright over the last two coil cover bolt holes when the cover is off. Only took 30 seconds to find where I had left it in the shed from last time when I took the cover off the other night!

I'll put new coils in it and they will last 15+ years like the Nissan ones and I won't have to worry about it again.

[Bozz]

Do the coils open/short circuit or does the insulation break down?

A mate has RB20 coils that were arcing out the side near the rubber boot for the spark plug, I fixed them by putting regular silicon roofing sealant around them, same trick used in old tellies when the trippler or flyback transformer's insulation would break down. Coils had silicon reapplied once since but are still running to this day.

[GTSBoy]

The RB ones generally show discolouration on their sides, showing that they've seriously cooked. Some of them show arcing/soot on the sides where they've just completely broken down.

I would assume that the coils you siliconed would have been missing even when cold? Mine have been OK when cold but they give up when they get warm.

[Bozz]

I dont recall if they were doing it only when warmed up but they had heaps of soot and shit around the tiny cracks along the side. I glued them all, including the ones which weren't misfiring. Worth a try.

[GTSBoy]

Intriguing update/conclusion to this story.

I bought some Splitfires from Jesse Streeter (big thumbs up for him) in Dec and fitted them at Xmas. I have only had a chance to run 1.5 tanks of fuel through the car since, between being on leave and going overseas for a couple of weeks for work. So results are only just in today. The results? Well, I'll drag it out a tiny bit longer.

If I look back at the fuel consumption numbers for all tanks of fuel that have gone through the car over the last 10 years the vast majority of them are in the 13s. Very early on I had more tanks that were low 13s to high 12s, in recent years it's typically at least 13.5 up to the low 14s. Infrequently recently I'll have a tank that is high 12s.

The first refill after the new coils went in was 12.0. The second tank filled tonight was 12.2. The difference is startlingly clear. I used to hit half tank on the guage at almost exactly 200km, and like almost all Skylines it would be at the bottom of the guage by 370km. This last tank was at least 230km by half tank, and it had 345km at 1/4 full. I would have gotten it well over 400km before bottoming the guage.

So it is using something like 10% less juice.

Not only does it use less fuel, but it runs better in every way. It starts more smoothly (ie crank to stable idle almost instantly instead of fluffing around for a few seconds like it used to). It idles more smoothly, it pulls away from stationary more smoothly, it pulls from low revs more convincingly, is more eager to rev and generally feels a bit stronger. Now this is not an engine that anyone had any reason to suspect that there was any problem. It dynod at ~170rwkW when tuning the Nistune a few months back. That's about 300HP which is where the AFM, injectors and turbo are all reaching their limits. It didn't seem crook in anyway.

So beyond the old coils occasionally just completely shitting themselves when really hot, it would appear that old OEM coils just are not anywhere near as good at lighting the fire as some nice new Splitfires. You'd scoff at the graph on the side of the box that shows Splitfires making an extra 6% power or whatever it was they claim on an R32 GTR. But I would expect my car to have at least another 5kW on the dyno just from how it feels.

So, for once we have a $500+ purchase spent on the car that not only makes it run better and go quicker, but will actually have a payback! It will take about 2 years for the fuel savings to pay back, but that doesn't matter. It's still a free upgrade eventually.

I'm thinking that just about any RB or VG that still has >10 year old coils may well benefit from at least borrowing a set of Splitfires and seeing how it goes. It also possibly puts paid to the idea of trying to silicone up old cracked shitted up coils to keep them going.

/csh?

[Billzilla]

Istuff

Good story mate.
Had something similar happen to the old 3K engine in the racer. We used to run conventional points and a bigger coil. The engine would come on cam at about 6,000rpm. We then fitted an optical ignition system that produced far bigger sparks, and the power then came on at about 5,800rpm Started easier, etc.

[2rismo]

Use BP Ultimate with detergent molecules and you'll go 40% further per tank!

Good result though and something I bet most don't appreciate.

[260BC]

.................................................. ........................................

I'm thinking that just about any RB or VG that still has >10 year old coils may well benefit from at least borrowing a set of Splitfires and seeing how it goes. It also possibly puts paid to the idea of trying to silicone up old cracked shitted up coils to keep them going.

/csh?

Good result, can't argue with that, but I will

COP is a shit of an idea, all the rules say - keep ignition coils away from engine heat as much as possible. Its a piece of piss to mount six coils on the side of the motor and run short leads to the plugs, looks schmick too. LS coils for one have built in ignitors and can be bought on US Ebay cheap.

I know you are a 'modernist' Brad and the above would not have persuaded you but pffft, there it is

[GTSBoy]

Oh, no. Don't get me wrong. If it wasn't fucking ugly and having to use ignition leads and further crowding the engine bay I'd be all over using external coils. I know the reason they die is 'cos they live in the nearest thing to hell right on top of the head. But the old ones were good for 10 years, the new ones will be good for 10 years. I can't see that being a problem (ie either the car or the engine will expire before the new coils do).