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Spark plug extra lead wire plug

Posted by rkj 
rkj
December 13, 2010 07:16PM
Hi Guys

On one of the plug wires there is a smaller wire that leads off in to the timing cover and hooks to a snap block on the left side of the motor by (over) the alternator. There are two plugs on the plate together and I think that wire (from one of the plug wire) goes on the inner block but I'm not sure.

Anybody know?

and what does that wire really do ..... confused smiley

will I get better mileage, will it grow hair??

Thanks, Rick
December 13, 2010 09:21PM
Quote
rkj
Hi Guys

On one of the plug wires there is a smaller wire that leads off in to the timing cover and hooks to a snap block on the left side of the motor by (over) the alternator. There are two plugs on the plate together and I think that wire (from one of the plug wire) goes on the inner block but I'm not sure.

Anybody know?

and what does that wire really do ..... confused smiley

will I get better mileage, will it grow hair??

Thanks, Rick

That is the inductive pick up for the #1 plug. It goes back to the Motronic unit and the signal is used to aid in firing the injector banks. If it is not connected, it doesn't seem to affect the operation of the engine at all. Whether it will affect fuel consumption is anybodies guess.
You could leave it unhooked for a couple of tanks of gas and keep track of your mileage; then hook it back up and repeat. Then compare the figures and see if it makes any difference.
rkj
December 13, 2010 09:42PM
Quote
Archeo-peteriX
Quote
rkj
Hi Guys

On one of the plug wires there is a smaller wire that leads off in to the timing cover and hooks to a snap block on the left side of the motor by (over) the alternator. There are two plugs on the plate together and I think that wire (from one of the plug wire) goes on the inner block but I'm not sure.

Anybody know?

and what does that wire really do ..... confused smiley

will I get better mileage, will it grow hair??

Thanks, Rick

That is the inductive pick up for the #1 plug. It goes back to the Motronic unit and the signal is used to aid in firing the injector banks. If it is not connected, it doesn't seem to affect the operation of the engine at all. Whether it will affect fuel consumption is anybodies guess.
You could leave it unhooked for a couple of tanks of gas and keep track of your mileage; then hook it back up and repeat. Then compare the figures and see if it makes any difference.

Thanks Peter, so,if it's disconnected the injectors fire twice as many times as usual?
December 13, 2010 11:51PM
Quote
rkj
Quote
Archeo-peteriX
Quote
rkj
Hi Guys

On one of the plug wires there is a smaller wire that leads off in to the timing cover and hooks to a snap block on the left side of the motor by (over) the alternator. There are two plugs on the plate together and I think that wire (from one of the plug wire) goes on the inner block but I'm not sure.

Anybody know?

and what does that wire really do ..... confused smiley

will I get better mileage, will it grow hair??

Thanks, Rick

That is the inductive pick up for the #1 plug. It goes back to the Motronic unit and the signal is used to aid in firing the injector banks. If it is not connected, it doesn't seem to affect the operation of the engine at all. Whether it will affect fuel consumption is anybodies guess.
You could leave it unhooked for a couple of tanks of gas and keep track of your mileage; then hook it back up and repeat. Then compare the figures and see if it makes any difference.

Thanks Peter, so,if it's disconnected the injectors fire twice as many times as usual?


Rick, that has been my understanding. It has the potential (dependingon engine position) to shorten the crank time. I've never heard a better explanation...I've never heard a different explanation, come to think of it smiling smiley

-----------------------------------------------------------------------------------
1989 - E30 - M20 - Manual. Approximately 270,000 miles
2000 - E46 - M52TUB28 - Manual. Approximately 110,000 miles




Edited 1 time(s). Last edit at 12/13/2010 11:53PM by Earendil.
December 14, 2010 01:35AM
Wow, never heard of that setup. What years was that on? Was it for 4 or 6 cylinder models?

alan
December 14, 2010 01:59AM
Quote
alanrw
Wow, never heard of that setup. What years was that on? Was it for 4 or 6 cylinder models?

alan

It shows up on my 89 6 cylinder. However it should be noted that because these cars do not require it, the majority of people don't know what it does, and some replacement plug sets don't even have it, that many cars that originally came with it no longer have it under the hood. Due to the location that it plugs in, you'd have to get very intimate with your car, and be paying attention, to notice anything was amiss.

-----------------------------------------------------------------------------------
1989 - E30 - M20 - Manual. Approximately 270,000 miles
2000 - E46 - M52TUB28 - Manual. Approximately 110,000 miles

December 14, 2010 11:22AM
Does it show up on BMW OEM?

alan
December 14, 2010 12:25PM
The one on my '91 318i (M40) has been broken off since I got the car, and and in all the years I have had it, I have never had any running problems, I consistantly get 13km/litre or 7.6 litres per 100km, which seems right about the book figure, so, no I doubt it has any adverse effect on fuel consumption.

----------------------------------------------------------------------------------------------------------------------------------
E30'S AREN'T BUILT, THEY'RE CAUGHT IN THE WILD!!!



When in doubt, use full throttle,
it may not improve the situation, but it will end the suspence.
rkj
December 14, 2010 05:08PM
Quote
Flyboy
The one on my '91 318i (M40) has been broken off since I got the car, and and in all the years I have had it, I have never had any running problems, I consistantly get 13km/litre or 7.6 litres per 100km, which seems right about the book figure, so, no I doubt it has any adverse effect on fuel consumption.

From 1987, 325i's, in the USA, had this extra lead wire from the plug wire. The four bangers (later models, not M10's) I don't know about, but from what I've heard here, this wire might save a fraction on MPG but it times the injector bank firings. So. if it's disconnected (I'm pretty sure) the injectors fire twice as much as they would if it was connected. I'm pretty sure I remember a few other minor plus' you get if it's hooked up. In my case I'm going to route the wire (temporarily, until I do a timing belt) over the top of the valve cover in front and tie in to the block under the thermostat housing, the wire should reach. The Eta's don't have this set-up at all.

Rick
December 14, 2010 07:09PM
Quote
rkj
Quote
Flyboy
The one on my '91 318i (M40) has been broken off since I got the car, and and in all the years I have had it, I have never had any running problems, I consistantly get 13km/litre or 7.6 litres per 100km, which seems right about the book figure, so, no I doubt it has any adverse effect on fuel consumption.

From 1987, 325i's, in the USA, had this extra lead wire from the plug wire. The four bangers (later models, not M10's) I don't know about, but from what I've heard here, this wire might save a fraction on MPG but it times the injector bank firings. So. if it's disconnected (I'm pretty sure) the injectors fire twice as much as they would if it was connected. I'm pretty sure I remember a few other minor plus' you get if it's hooked up. In my case I'm going to route the wire (temporarily, until I do a timing belt) over the top of the valve cover in front and tie in to the block under the thermostat housing, the wire should reach. The Eta's don't have this set-up at all.

Rick

If the wire is missing, the ECU doesn't fire the injectors twice as often, it just fires the banks from a default. That means that the bank that has #1 plug and # 1,3 and 5 injectors would fire at the optimum time. But since only one of those cylinders is on the intake stroke at a time, The fuel charge on the other two simply sits in the intake plenum until the intake valve opens and sucks it in. Since only one of the six cylinders is on the intake stroke at a given time, it really little difference which bank of injectors fires when. The same amount of fuel will be available to each cylinder; just that the charge may not be as freshly atomised as it could be.
December 14, 2010 08:00PM
Doesn't the ECU modify injector pulse depending on O2 sensor (like a data feedback system)?

alan



Edited 1 time(s). Last edit at 12/14/2010 08:01PM by alanrw.
rkj
December 14, 2010 11:09PM
Quote
Archeo-peteriX
Quote
rkj
Quote
Flyboy
The one on my '91 318i (M40) has been broken off since I got the car, and and in all the years I have had it, I have never had any running problems, I consistantly get 13km/litre or 7.6 litres per 100km, which seems right about the book figure, so, no I doubt it has any adverse effect on fuel consumption.

From 1987, 325i's, in the USA, had this extra lead wire from the plug wire. The four bangers (later models, not M10's) I don't know about, but from what I've heard here, this wire might save a fraction on MPG but it times the injector bank firings. So. if it's disconnected (I'm pretty sure) the injectors fire twice as much as they would if it was connected. I'm pretty sure I remember a few other minor plus' you get if it's hooked up. In my case I'm going to route the wire (temporarily, until I do a timing belt) over the top of the valve cover in front and tie in to the block under the thermostat housing, the wire should reach. The Eta's don't have this set-up at all.

Rick

If the wire is missing, the ECU doesn't fire the injectors twice as often, it just fires the banks from a default. That means that the bank that has #1 plug and # 1,3 and 5 injectors would fire at the optimum time. But since only one of those cylinders is on the intake stroke at a time, The fuel charge on the other two simply sits in the intake plenum until the intake valve opens and sucks it in. Since only one of the six cylinders is on the intake stroke at a given time, it really little difference which bank of injectors fires when. The same amount of fuel will be available to each cylinder; just that the charge may not be as freshly atomised as it could be.

So, we're talking about fuel injector pulse timing, as in degrees, yes?

It's weird, I'm a car guy and I'm having trouble seeing this in my head Peter.
December 15, 2010 12:37PM
Injection duration is controlled by throttle opening, air flow and O2 data, timing will be determined by the wire.
rkj
December 15, 2010 04:33PM
Quote
Michiel 318iS
Injection duration is controlled by throttle opening, air flow and O2 data, timing will be determined by the wire.

Thanks Michiel, I understand. Today I got decent time in on the car, there was plenty of wire to run over the top of the motor and through the water hoses down to the mounting plate, that firing wire plugs in to the inside hole in the metal holder plate. I cleaned all the connections and got everything together (well, I'm still at it actually) and will finish tonight.

While the car is in here I have a few other things on my list, my goal is to, someday, fix my damp weather starting issues eye rolling smiley
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