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Originally Posted by bladerunner919
(Post 1892982)
Wow, if you can detect a pause in the pulses you have my respect. If the car is ilding at 1000rpm (and it's probably more like 1200 when cold) each bank of 6 is exhausting spent gas 50 times per second, so you're detecting a 1/50th of a second pause from a single missing cylinder!
Correct me if I'm wrong, but at idle ( 700 RPM here ) the engine is turning 11 RPSecond. And that results in 11 exhaust pulses per second. 5.5 per bank. At least this correlates to my experience. One thousand one, one thousand two. ffft, ffft, ffft, ffft, ffft, ffft, ffft, ffft, ffft, ffft, ffft. Meh, close to that anyway. |
Originally Posted by JigJag
(Post 1895777)
Correct me if I'm wrong, but at idle ( 700 RPM here ) the engine is turning 11 RPSecond. And that results in 11 exhaust pulses per second. 5.5 per bank. At least this correlates to my experience.
One thousand one, one thousand two. ffft, ffft, ffft, ffft, ffft, ffft, ffft, ffft, ffft, ffft, ffft. Meh, close to that anyway. l quite likely missed something here. |
Good info in this post. I started a thread yesterday...May buy an 89 XJS Convt V-12. It has no spark and I think/hope it's only the rotor. I will find out tomorrow. I plan to do the "Fix" by cutting off the nub on the shaft, but not until I get it running and/or get it towed to my house.
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Originally Posted by Fla Steve
(Post 1895888)
Good info in this post. I started a thread yesterday...May buy an 89 XJS Convt V-12. It has no spark and I think/hope it's only the rotor. I will find out tomorrow. I plan to do the "Fix" by cutting off the nub on the shaft, but not until I get it running and/or get it towed to my house.
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Originally Posted by baxtor
(Post 1895831)
OK ill join in. 11 revs per second with one firing per 2 revs comes out at 5.5 firings per second ........PER CYLINDER = 66 firings per second or 33 per bank.
l quite likely missed something here. 600 RPM / 60 sec = 10 RPS 10 RPS / 4 cycles = 2.5 bangs per sec 2.5 * 12 cylinders = 30 bangs per second 30 / 2 banks =15 bangs per second per bank |
Originally Posted by JigJag
(Post 1895942)
Dang I swung and missed. Should’ve thought twice before I banged off a post. But I still think we’re off. Lowering the idle a skosh to simplify the math. Hmmmm...
600 RPM / 60 sec = 10 RPS 10 RPS / 4 cycles = 2.5 bangs per sec 2.5 * 12 cylinders = 30 bangs per second 30 / 2 banks =15 bangs per second per bank |
Originally Posted by baxtor
(Post 1895969)
l reckon you swung and missed again JJ. 4 cycles is correct but we get 2 cycles to each rev so 10 revs gives us 5 bangs not 2.5
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Originally Posted by baxtor
(Post 1895901)
Assuming it is Marelli ignition the presence of a spark can be checked before it gets to the rotor(ie. at the coil outputs) The distributor simply distributes the spark to the cylinders and has no bearing on whether or not the spark is being created.
I thought the problem is that the spark runs to ground through the inside the distributor, rather than whether it is generated in the first place? |
Originally Posted by bladerunner919
(Post 1896117)
I thought the problem is that the spark runs to ground through the inside the distributor, rather than whether it is generated in the first place?
1. Grounding inside the dizzy 2. Failure of one of the two coils 3. Failure of one of the two ballasts Anything in pairs on the engine onnthe ignition side, can fail ... |
Originally Posted by bladerunner919
(Post 1896117)
I thought the problem is that the spark runs to ground through the inside the distributor, rather than whether it is generated in the first place?
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Ignition Failure Warning System
What you guys are talking about with having some sort of warning system is discussed in the "XJS_BOOK" listed in the "How To" quick links in this XJS Forum on page 166. It's a bit complicated but a "smart guy" could start making these and we'd all buy it. I strongly suggest you all take a look at this great wealth of information on our complicated V-12s. I plan to do the rotor fix by cutting off the distributor nub...as discussed with the link showing how to...as also mentioned earlier in this thread.
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