"In In a normal V8, the two banks don’t fire at the same time, a V12, the two banks DO fire at the same time",
I read this else ware, they are talking about the jag v12

I don’t think the statement is correct, or am I wrong

Has anyone got an opinion on this

 

Our V12 is really a Double Six.

Firing order is standard 6 cyl 1 5 3 6 2 4.

Siamesed on ours as 1a 6b 5a 2b 3a 4b 6a 1b 2a 5b 4a 3b.

So, its fires across bank to bank in turn.

 

As the engine has 12 cylinders, and each cylinder fires once per TWO revolutions of the crankshaft, I have always assumed that a cylinder fires once per 360x2 /12 = 60 degrees of rotation (of course in the order that Grant mentions). So no, two cylinders in our Jaguar V12s do not fire at the same point of crankshaft rotation.

 

Somewhere on here is an excellent animation showing the firing.

 

Just look at the rotor, its a normal rotor. There is no way for two plugs to fire at the same time.

 

The Jag V12 fires alternate sides of the engine , so it fires Right Front, Left Rear, Right Rear Left Front.

Cross plane crank V8's (this is most V8's) fire 2 cylinders on the same side consecutively, this is what gives the V8 its traditional burble.

No engine I know of fires 2 cylinders at the same time.

 

Thanks guys for your replies, you confirm my thoughts.

Now can I ask, how dose the injectors fire.As I see it, there is only four wires going to each bank (left and right)If three are active and one is neutral, how do they activate six injectors independently

 

The injectors are "batch fired" all at once

From the ROM:

"The injectors are operated by the ECU in two groups of six. Each if further broken down into two sub-groups of three, although each pair or subgroup is operated simultaneously to make up the two groups of six twice per engine cycle."

Cheers
DD

 

Well that is correct for most engines. But I had a Hyundai Sonata, with the 4 cylinder engine. It had 2 coils for four cylinders. It fired one cylinder on the compression stroke, and the other one on the exhaust stroke. Motorcycles have used this setup for years, a four cylinder with 2 coils, and four leads, 2 from each coil. So they technically fire 2 cylinders at the same time, only one makes any power. There was a claim, it also helped on emission reduction. I don't know that I believe that.

 

That technically isn't firing as there is no compressed air-fuel mix to fire. It is simply the wasted spark ignition. The Citroen 2CV did that.

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As Daim said that is wasted spark and was used by almost every car manufacturer with coil packs (GM DIS and Ford EDIS are 2 examples) before COP and sequential.

 

Yeah thats pretty much what I said, only in a slightly different way.

Jack

 

Thanks Doug, I have been wondering for some time how they worked

 

Velocette did that, but it didnt work on my AJS
sparked every rev

 

In theory, the EFI is basically a sequential 4 cylinder setup. Just instead of triggering one cylinder it triggers via a common wire 3 instead. Jaguar just didn't want to highlight they were using a 4 cylinder setup on a V12

And as the Digital P is very well/closely related to some Bosch management systems, you could probably get away using a Bosch 4 cylinder ECU if you somehow found a way to adapt the pressure/vacume sensor to it... But then again, a vacume sensor in the intake manifold would do the job as well...