Post by
PeterJL »
https://forums.nicoclub.com/peterjl-u50399.html
Fri Nov 10, 2006 2:14 am
When I poke around under the hood of my 2000 Nissan Maxima, it strikes me that the the Nissan A33 3-litre V6 engine is a nice piece of design work. The mix of high-tech and "ordinary" seems to hit the right balance between performance and utilitarian reliability. ... Except for important bit the end of the ignition system.
Most car manufacturers now use the same setup to fire a sparkplug, the thing is simplicity itself, a natural progression from the old Kettering ignition, but making the most of the reliability and speed of solid-state components. Instead of the spark being generated from a single coil driven by breaker points and sent to each plug with a distributor, the new systems use a single coil for each plug.The coils are smaller and sit on top of the plug. Similar to the old method, when you switch on the ignition key, 12v is supplied to the coil primary winding, which is grounded at the other end, so that a magnetic field is generated that "saturates" the more numerous secondary windings that surround the primary. When this current flow is interrupted, the field collapses, and the energy dumped into the secondary windings produces a high voltage pulse to fire the plug.In older systems, the breaker points carrying the current were pushed open by a cam, in the new ones, it's a switching transistor mounted in each individual coil housing and triggered by a precisely timed pulse from the engine management computer so as to ignite the fuel-air mix at a time that is optimum to the microsecond. Great stuff huh!
Well, so it should be. The first power switching transistors of 50 years ago were fragile things, but not so these days. If I browse the catalogs of electronic parts suppliers, I can spec a power transistor that can handle massive current at high voltages while heated nearly to incandescence. The term appears to be "ruggedising". In a harsh environment like an engine bay it's tough for any electronic component, but not for something like a simple good quality switching transistor, they're about as complicated as a hammer. Motorola used to make old metal-canned 2N3055s that you could darned-near cook with, and yet have lasted forever in all kinds of horrible industrial environments. This is the sort of proven-reliability component you find in aircraft.
How is it then that a company like Nissan cannot build or source an igniter coil unit that lasts.GM, Ford and Mitsubishi don't seem to suffer from the problem locally.The switching transistors in the coils in the old (?1980) Nissan EXA used to burn out one by one, and it appears that those in the Maxima twenty years later still do the same. They seems to take 3-5 years to go. Presumably the same can be expected for the 2007 Maxima. Here in Australia the part alone costs around $200, or 6 for $1200! Even the guys in the dealer service area are embarrassed when they quote the pricing.
Lets see, a Motorola 2N3055 sells for $1.50, a standard old fashioned automotive sports coil costs around $25.00. Hmm .. seems to be a bit of margin there in the pricing for an unreliable component that has the life expectancy of a hamster.
My problem is that I have a 30-odd thousand dollar car that I like, and bought new to serve for my retirement (Only 32000km so far), but can't trust enough to take on an interstate trip. I'd replace all 6 coils if I thought that new ones would be reliable, but it looks as though they were specced by a cost-accountant from Osaka rather than an engineer. What I'd like to do is cut one open and solder in a better quality transistor, maybe even a $5.00 one (wow!). Problem is, I can't find the one that's failing, the ECU only reports that the ignition failed, and it's intermittent. I have to wait until it fails completely.
Murphy's law suggests that the culprit is probably one of the back 3 buried under the inlet mainfold.
Best RegardsPeterJL