TPS Question


28 replies to this topic
  • bobpara

Posted June 15, 2015 - 10:29 AM

#1

I have a 2006 WR450F with a carbureator (Not FI)

On the left side of the carb is a throttle position sensor

At steady state throttle going down a road the engine surges up and down

I was told if I unplugged it the 'surging' would stop and it did

 

1) Am I sacraficing any sort of performance by leaving it unplugged?.......it SEEMS less powerful but at the same time more smooth in that the surging is gone

 

2) Since I have Carb and not FI, I assume there is no computer or 'brain' involved in engine control.......why do I have a TPS sensor at all then?

 

3) This is essentially a potentiometer. Their failure mode are the fingers on the wiper of the device rubbing back and fourth in one spot and wearing through the conductive epoxy

     Can I replace this part and my surging problem will go away? (I know there is a bit of calibration involved if I replace it)



  • WRF-Rowdy

Posted June 15, 2015 - 10:42 AM

#2

I have a 2006 WR450F with a carbureator (Not FI)

On the left side of the carb is a throttle position sensor

At steady state throttle going down a road the engine surges up and down

I was told if I unplugged it the 'surging' would stop and it did

 

1) Am I sacraficing any sort of performance by leaving it unplugged?.......it SEEMS less powerful but at the same time more smooth in that the surging is gone

 

Yepp. Snappiness of throttle response, or something like it...

 

 

2) Since I have Carb and not FI, I assume there is no computer or 'brain' involved in engine control.......why do I have a TPS sensor at all then?

There is a CPU that uses TPS + rpm to calculate ignition advance.

 

 

3) This is essentially a potentiometer. Their failure mode are the fingers on the wiper of the device rubbing back and fourth in one spot and wearing through the conductive epoxy

     Can I replace this part and my surging problem will go away? (I know there is a bit of calibration involved if I replace it)

I'd say yes. My '03 did the same thing, I learned to live with it.  Probably the simplest solution short of

using an industrial high quality replacementpotentionmeter would be to add a "dashboard switch"

to disconnect the center wire for road coasting.


Edited by WRF-Rowdy, June 15, 2015 - 10:42 AM.


  • bobpara

Posted June 15, 2015 - 04:46 PM

#3

Let me pose question #3 another way: did anyone have a bike with a TPS from new or very close to new? If so, did it surge like this when it was new or did it happen later as the bike (and the TPS) got older?

In other words is this defect by design or does the TPS get crappy after a while?



  • stevethe

Posted June 15, 2015 - 05:28 PM

#4

Let me pose question #3 another way: did anyone have a bike with a TPS from new or very close to new? If so, did it surge like this when it was new or did it happen later as the bike (and the TPS) got older?
In other words is this defect by design or does the TPS get crappy after a while?


It's not the TPS that causes surging. It's the mapping in the black box. If you want it fixed right see if you can buy a Dynatec ignition for your model. Lots of posts on the Dynatec fix for WR's.

  • Krannie McKranface

Posted June 15, 2015 - 07:53 PM

#5

The ECU has three maps: closed throttle (idle), partial throttle, and WO throttle

The ECU takes info from the TPS postion (resistance) to determine the appropriate map.

The problem is that the ECU's all have a problem in the closed to partial map transition: the ECU can't make up it's mind, so it 'toggles' between the two.

Unplugged the TPS puts you in the closed throttle map at all times, which has the least advance.

You could manually advance the ignition on the flywheel to compensate.

You can also retard the TPS (counterclockwise) to force the system to work at a larger throttle opening, but you still have a sluggish off idle response.

I ran mine unplugged for years, then went to the Dynatek, which eliminates the problem, and makes the bike run MUCH better, especially if you set the TPS at about .60 ohms at closed (no idle) thottle.


Edited by KRANNIE, June 15, 2015 - 07:54 PM.


  • bobpara

Posted June 16, 2015 - 05:24 AM

#6

Awesome.

I can always count on you Karannie for the right answer

So concise and well explained

 

......Any idea if I can get a Dynatec unit for a carbed 'o0 WR450F ?



  • bobpara

Posted June 16, 2015 - 05:29 AM

#7

I guess I will have to call them

I cannot see an ign module that will fit my bike



  • Krannie McKranface

Posted June 16, 2015 - 12:13 PM

#8

Awesome.

I can always count on you Karannie for the right answer

So concise and well explained

 

......Any idea if I can get a Dynatec unit for a carbed 'o0 WR450F ?

 

'00 WR450? No such thing.

2003 and later.



  • grayracer513

Posted June 16, 2015 - 12:15 PM

#9

The ECU has three maps: closed throttle (idle), partial throttle, and WO throttle

[...]

 

 

Actually...

 

There is only one map, and it uses inputs from the crank position sensor (aka tach sensor, "pickup coil", et al) as a base ignition advance map.  This input is modified by the input from the TPS, which the ECU uses to calculate the appropriate ignition advance based on RPM and engine load state.  This is exactly what the purpose of the vacuum advance on the distributor of your pre-'75 automotive engines was.  Because the engine is using so little throttle at a highway cruise relative to the RPM being spun up, the intake manifold pressure is far lower (higher vacuum) then it is at more throttle, and that means a far less dense air-fuel charge.  That less dense charge requires more ignition advance to be efficiently burned, thus the "3D" map.  The observation that it "seems less powerful" is probably accurate in that mode, but it should make no difference at all to the full throttle performance.

 

Why? Because the system is designed to use lower voltage returned to the ECU to indicate full throttle operation, so when you unplug it, what the ECU sees is low TPS voltage, and it responds by mapping for full throttle.  This is not so much a matter of preserving full throttle performance during a TPS failure, but rather a matter of safety; less advance won't cause the problems that too much would.

 

As Steve says, the complete cure for this is a new, performance oriented ignition map that doesn't aggravate the lean cruise condition and cause the surging.  Some have had some luck fiddling with the adjustment on WR's, but others not so much.  If you connect yours to a VOM and watch the voltage (or disconnect it and watch the resistance), it should change smoothly and progressively as you move from idle to WOT and back down.  If you come to a spot where the readout jumps around, that's a bad TPS, and it won't help matters.



  • Krannie McKranface

Posted June 16, 2015 - 12:19 PM

#10

Actually...

 

There is only one map, and it uses inputs from the crank position sensor (aka tach sensor, "pickup coil", et al) as a base ignition advance map.  This input is modified by the input from the TPS, which the ECU uses to calculate the appropriate ignition advance based on RPM and engine load state.  This is exactly what the purpose of the vacuum advance on the distributor of your pre-'75 automotive engines was.  Because the engine is using so little throttle at a highway cruise relative to the RPM being spun up, the intake manifold pressure is far lower (higher vacuum) then it is at more throttle, and that means a far less dense air-fuel charge.  That less dense charge requires more ignition advance to be efficiently burned, thus the "3D" map.  The observation that it "seems less powerful" is probably accurate in that mode, but it should make no difference at all to the full throttle performance.

 

Why? Because the system is designed to use lower voltage returned to the ECU to indicate full throttle operation, so when you unplug it, what the ECU sees is low TPS voltage, and it responds by mapping for full throttle.  This is not so much a matter of preserving full throttle performance during a TPS failure, but rather a matter of safety; less advance won't cause the problems that too much would.

 

As Steve says, the complete cure for this is a new, performance oriented ignition map that doesn't aggravate the lean cruise condition and cause the surging.  Some have had some luck fiddling with the adjustment on WR's, but others not so much.  If you connect yours to a VOM and watch the voltage (or disconnect it and watch the resistance), it should change smoothly and progressively as you move from idle to WOT and back down.  If you come to a spot where the readout jumps around, that's a bad TPS, and it won't help matters.

 

No, the stock FCR bike ECU has three maps, which cannot be modified, and have fixed igntion advance curves.

It is a 2D mapping system.

The FI models have a 3D mapping system.



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  • grayracer513

Posted June 16, 2015 - 01:11 PM

#11

One map.  Referencing RPM and load is what defines a 3D timing map.

 

From an '06 YZ450F manual:

 

 

Attached Thumbnails

  • 3D.png


  • Chas_M

Posted June 16, 2015 - 02:14 PM

#12

In KTM's at least, the FCR TPS carb does supply '3 D' mapping.  The TPS advance curve is superimposed over the built-in factory advance default curve and acts much like the vacuum advance in older cars like gray racer mentioned.  The TPS functions primarily by adding advance under partial throttle and lower RPM conditions.  As the throttle opens up and RPM increases the added advance is gradually reduced to zero and at full throttle the advance follows the factory default curve.  I have actually added an on/off TPS switch on several of my bikes and could not detect any 'seat of the pants' difference.


Edited by Chas_M, June 16, 2015 - 02:16 PM.


  • Krannie McKranface

Posted June 16, 2015 - 03:29 PM

#13

One map.  Referencing RPM and load is what defines a 3D timing map.

 

From an '06 YZ450F manual:

 

That's a 2d map, that adds the ignition curve as an input variable, which it isn't. 

The ignition curve is the result, not a variable.

 

A 3D map would be  RPM, TPS, and Temp, or MAP, or anything else, to put you on the curve of ignition. 



  • WRF-Rowdy

Posted June 16, 2015 - 04:16 PM

#14

That's a 2d map, that adds the ignition curve as an input variable, which it isn't. 

The ignition curve is the result, not a variable.

 

A 3D map would be  RPM, TPS, and Temp, or MAP, or anything else, to put you on the curve of ignition. 

Maybe you guys simply got different words for the same thing.

I'd say ignition advance can be calculated using

A )  0 parameters,  e.g. a fixed value of "degrees before TDC", like old breaker contact ignition w/o vacuum advance, (XT500A)

B ) 1 parameter, advance is a function of rpm (early CDIs like the XT600),   graphically a line (x = input y = output)

C ) 2 parameters, advance calculated for each combination of two input values, like rpm + TPS, (or rpm + MAP, or ..)

       (non EFI WRs), graphically a "3D mountain surface" ( x,y coord are input,  z coord is output)

D ) 3 parameters,  input could be for instance rpm + TPS + MAP

E ) 4 parameters,....

F ) 5 parameters: ignition is calculated using rpm + TPS + MAP + coolant temp + air temp  (EFI WR450F)

 

everything using more than 2 input values to calculate ignition advance cannot be represented graphically.

 

B ) and later won't kick back during starting

C ) and later knows about load

anything reading coolant temp doesn't need a cold start circuitry (if the user manages to hold the throttle open at 3%-ish)

 

You two are just fighting about what to call case C), the old WR400F CDI

reading just rpm + TPS to calculate ignition advance.

That is a 2 parameter function, which can be depicted as 3D graphics.

 

It would be really interesting to see the instruction flow of the EFI WR's ECU. My guess would be:

 

Fuel:

They use an 2D array of rpm + MAP to calculate a base fuel amount.

That amount  would be multiplied by a correction factor calculated from rpm + coolant temp (choke)

Finally they'd lineraly compensate for air temp (=density)

 

Ignition:

2D array using rpm + fuel (represents load) should be sufficient

 

Lastly both raw values are modified by our beloved PowerTuner mapping.

 

 

If the MAP sensor delivers an absolute pressure reading they'd have altitude covered as well!

The TPS is unnecessary and too coarse (not sensing host-start knob position) and

would only be used when the software deems MAP values to be unplausible as a "limp home" catch all.


Edited by WRF-Rowdy, June 16, 2015 - 04:45 PM.


  • Krannie McKranface

Posted June 16, 2015 - 04:36 PM

#15

Maybe you guys simply got different words for the same thing.

I'd say ignition advance can be calculated using

A )  0 parameters,  e.g. a fixed value of "degrees before TDC", like old breaker contact ignition w/o vacuum advance, (XT500A)

B ) 1 parameter, advance is a function of rpm (early CDIs like the XT600),   graphically a line (x = input y = output)

C ) 2 parameters, advance calculated for each combination of two input values, like rpm + TPS, (or rpm + MAP, or ..)

       (non EFI WRs), graphically a "3D mountain surface" ( x,y coord are input,  z coord is output)

D ) 3 parameters,  input could be for instance rpm + TPS + MAP

E ) 4 parameters,....

F ) 5 parameters: ignition is calculated using rpm + TPS + MAP + coolant temp + air temp  (EFI WR450F)

 

everything using more than 2 input values to calculate ignition advance cannot be represented graphically.

 

B ) and later won't kick back during starting

C ) and later knows about load

anything reading coolant temp doesn't need a cold start circuitry (if the user manages to hold the throttle open at 3%-ish)

 

You two are just fighting about what to call case C), the old WR400F CDI

reading just rpm + TPS to calculate ignition advance.

That is a 2 parameter function, which can be depicted as 3D graphics.

 

No one is fighting

You are spinning crazy with your discussion



  • WRF-Rowdy

Posted June 16, 2015 - 04:56 PM

#16

That's a 2d map, that adds the ignition curve as an input variable, which it isn't. 

There is no ignition curve, just a three dimensional ignition surface.

You didn't bother to read the small print yamaha has added to the grapic grayracer513 posted, correct?

 

Personally I'd call a flat road map on a table a 2D map,

a three dimensional map like you see sometimes in the visitor centers of national parks I'd call a 3D map,

but hey, that's just me, and yamaha marketing :rolleyes:


Edited by WRF-Rowdy, June 16, 2015 - 04:56 PM.


  • Krannie McKranface

Posted June 16, 2015 - 05:00 PM

#17

Right, that 'image' has nothing to do with the mapping. 

It's a 3d rendering for explanation purposes.

RPM and TPS determine the map. That's two axis.

 

Not OEM, but still the same method. Unforetunately this graph only shows the WOT curves.

 

 

DYNAFSWR450F.jpg


Edited by KRANNIE, June 16, 2015 - 05:05 PM.


  • WRF-Rowdy

Posted June 16, 2015 - 05:10 PM

#18

That is another, albeit less visually appaling, way of drawing a 3D landscape.

Dynatek took all lines of a yamaha style 3D cube that run from the low rpm edge to the high rpm edge and layed them upon each other.

As if you look at the yamaha cube parallel to the throttle axis.

 

Much better to actually see the exact advancement values (great for reverse engineering :devil: )

but almost impossible to see/feel what dynatek is doing when one opens the trottle at constant rpm.

(And it would get very cluttered were there two or three TPS values, that would have identical advance

from say 5000 to 6000 rpms, but a different "sequence" below 5000 and above 6000.)

 

Alternatively, they could have drawn many rpm lines on a 2D throttle vs. advance graphic.

 

Or they could create the 3D representation like yamaha marketing did.

 

 

As I said, same thing (2 parameters produce one output)  just different names or representations for it.


Edited by WRF-Rowdy, June 16, 2015 - 05:23 PM.


  • WRF-Rowdy

Posted June 16, 2015 - 05:17 PM

#19

btw. interesting to see that they don't use 0° advance for idle. 

Good to know, never hand kick a Dynatek yammie.



  • grayracer513

Posted June 16, 2015 - 06:44 PM

#20

You guys are a crackup, actually. 

 

 

That's a 2d map, that adds the ignition curve as an input variable, which it isn't. 

The ignition curve is the result, not a variable.

 

A 3D map would be  RPM, TPS, and Temp, or MAP, or anything else, to put you on the curve of ignition. 

 

Funny that Yamaha even explained the principal right on that page, and you don't get it.  It's not a question of a "3 input" map, it's "3D".  Since none of the factors in the equation are dimensions, it's obviously a figure of speech.  Neither does anything say that the three elements of a 3D map have to be of the same class.  RPM and TPS are variables that are considered by the "map", which is in fact nothing more than a variously sophisticated software program. The ignition curve is the output.   Three "dimensions".

 


RPM and TPS determine the map. That's two axis, ...

 

Then a simple RPM based ignition advance would be one axis right?  Graph that out for me on one axis.

 

Throttle position provides the third element of the algorithm.

 

 

 interesting to see that they don't use 0° advance for idle. 

Good to know, never hand kick a Dynatek yammie.

 

You know those three marks on your stock flywheel that are separated by 5 degrees each?  ;)






 
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