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3Vd In A 4Tx


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#41 fixitsan

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Posted 11 July 2018 - 07:43 am

3VD with a 4TX oil tank it seems then. Black/yellow - blue/yellow are from the clutch micro switch. Provided a 3VD pick up coil will trigger a 4TX ignitor unit why not......TPS should be fine.....not sure about the accuracy of the rev counter..


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That's what it looks like, if there's only one coil it has to have a 3VD crank. Good to know that the 4TX electrics are backwards compatible. The ignition pickup is the same from what i remember.


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#42 MickC

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Posted 11 July 2018 - 09:21 am

So someone has simply put a 3vd into a 4tx with 4tx oil tank and removed 4tx coils and put in one 3vd coil and thats it?

Will it cause a problem the fact that a spark is produced and not used with regards current overload to the cdi.



#43 slipperyox

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Posted 11 July 2018 - 09:51 am

So I assume a 17 42 sprocket combo is not right? change the front to 15?



#44 fixitsan

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Posted 11 July 2018 - 11:29 am

So someone has simply put a 3vd into a 4tx with 4tx oil tank and removed 4tx coils and put in one 3vd coil and thats it?

Will it cause a problem the fact that a spark is produced and not used with regards current overload to the cdi.

Correct in all senses !

 

It shouldn't matter about the load presented by coil to the cdi, because I suspect the resistances of both, and therefore the current flowing,  are very similar....but.....it makes me think that the 4tx must use wasted spark too even though it has 2 coils, because how else could this method method work ?


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#45 MickC

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Posted 11 July 2018 - 12:27 pm

Correct in all senses !

 

It shouldn't matter about the load presented by coil to the cdi, because I suspect the resistances of both, and therefore the current flowing,  are very similar....but.....it makes me think that the 4tx must use wasted spark too even though it has 2 coils, because how else could this method method work ?

Come to think of it I am thinking 270 pulses to a 180 but they are not the pulses will be 180 from the 3vd trigger thingey and the cdi will send a spark when its asked.



#46 Apache

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Posted 11 July 2018 - 01:20 pm

Fixitsan.....it makes me think that the 4tx must use wasted spark too even though it has 2 coils, because how else could this method method work ?[/quote]

Probably right Chris, only one 2 wire pick up on the 4TX and two offset triggers on the rotor.

Mick C. Doubt any harm to the ignitor as there is no second spark produced , coil wiring isolated. No on-board diagnostics so it'll run fine..

So I assume a 17 42 sprocket combo is not right? change the front to 15?


The "4TX" you have was definitely 17/42 from the factory. With a 4TX engine in it would run at 600rpm per 10 mph in 5th...hth.

#47 fixitsan

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Posted 11 July 2018 - 01:58 pm

Come to think of it I am thinking 270 pulses to a 180 but they are not the pulses will be 180 from the 3vd trigger thingey and the cdi will send a spark when its asked.

 

 

Yes probably something to do with the flywheel.

 

But we know for a fact that the magnet position on the flywheel and the pickup coil position never changes, BUT the ignition timing does change with respect to rpm (advances at higher speed). The advance curve is built into the ignitor/cdi. So that makes me wonder if the flywheel needs any more than one single magnet ?

 

The 900 has (I think) about 12 magnets in the flywheel and this gives very much better resolution of crank position. Rather than reading it once per second and guessing where it is at any time by counting the time since the last pulse (relative to rpm) the 900 produces more accurate crank position information, which is important for FI engines

 

Without putting a scope on a 4tx coil to see if it's wasted spark we won't know, unless someone has a 3VD flywheel and confirm the number of magnets


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#48 wicklamulla

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Posted 11 July 2018 - 10:22 pm

oi feel faint and need to lay doon.


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#49 JBX

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Posted 11 July 2018 - 10:51 pm

The 4TX has a 17/42 ratio for years 96-98 and 16/43 for years 99-01.

The gearbox ratios are different too, only the primary ratio is the same.

 

 

 

There is a wasted spark on the 4TX because there is no sensor on the camshaft which could allow the TCI (not a CDI !) to differentiate between TDC compression and TDC exhaust.

 

The crankshaft sensor is a variable reluctance sensor : it detects teeth on the rotor. On the 4TX there is only one tooth that extends to 90° of the rotor : the TCI gets the raising edge of the tooth to send a spark on one cylinder, and the falling edge for the other cylinder, which is ok for a 270° engine : 90 + 270 = 360 = 720 / 2.

 

Btw the rotor teeth are not magnets, they are plain metal. The pickup coil already has a magnet inside its body and detect any metallic part moving within its range which modifies the magnetic field.

 

The 5PS is different, there is a camshaft sensor which allows the ECU to get the exact engine rotation info around the 720° cycle and avoid having a "wasted injection pulse" and also a wasted spark at the same time.

 

The 5PS has 12 teeth on the rotor. Better timing for the ECU, but don't forget an ECU is a complete engine management system with a digital computer and an embedded TCI. That mean among many other thing that the computing power of the 5PS ECU is way above the 4TX simple TCI.


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#50 MickC

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Posted 12 July 2018 - 09:35 am

As far  as I am aware all fourstrokes fire on the compression and exhaust strokes because the firing point comes round every 180,4tx will have two of these 3vd has one.


Edited by MickC, 12 July 2018 - 10:07 pm.


#51 richierex

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Posted 12 July 2018 - 06:53 pm

As far  as I am aware all fourstrokes fire on the compression and exhuast strokes because the firing point comes round every 180,4tx will have two of these 3vd has one.

Not if they have a distrubutor they dont or even a camshaft sensor


Edited by richierex, 12 July 2018 - 07:03 pm.


#52 fixitsan

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Posted 12 July 2018 - 08:04 pm

The 4TX has a 17/42 ratio for years 96-98 and 16/43 for years 99-01.

The gearbox ratios are different too, only the primary ratio is the same.

 

 

 

There is a wasted spark on the 4TX because there is no sensor on the camshaft which could allow the TCI (not a CDI !) to differentiate between TDC compression and TDC exhaust.

 

The crankshaft sensor is a variable reluctance sensor : it detects teeth on the rotor. On the 4TX there is only one tooth that extends to 90° of the rotor : the TCI gets the raising edge of the tooth to send a spark on one cylinder, and the falling edge for the other cylinder, which is ok for a 270° engine : 90 + 270 = 360 = 720 / 2.

 

Btw the rotor teeth are not magnets, they are plain metal. The pickup coil already has a magnet inside its body and detect any metallic part moving within its range which modifies the magnetic field.

 

The 5PS is different, there is a camshaft sensor which allows the ECU to get the exact engine rotation info around the 720° cycle and avoid having a "wasted injection pulse" and also a wasted spark at the same time.

 

The 5PS has 12 teeth on the rotor. Better timing for the ECU, but don't forget an ECU is a complete engine management system with a digital computer and an embedded TCI. That mean among many other thing that the computing power of the 5PS ECU is way above the 4TX simple TCI.

 

 

Thanks for clearing that up, it all makes sense now


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#53 MickC

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Posted 12 July 2018 - 10:05 pm

Not if they have a distrubutor they dont or even a camshaft sensor

I didnt know bikes had distrubutors,I must get out more.



#54 richierex

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Posted 12 July 2018 - 10:46 pm

I didnt know bikes had distrubutors,I must get out more.


Some old Triumphs had points ignition and a distributor and as has been mentioned by JBX. the TDM900 has a camshaft sensor which controls injection and spark. When you said all 4 strokes I didnt realise you meant only bikes but no matter


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