TPS Effect on Mixture

[Kiwi_Roy]

I thought I'd better not hijack the other TPS thread.

 

A while back I made myself a little black box so I could +/- the sensor signal by up to 300 mV thinking this would allow me to change the mixture map on the fly.

 

I thought I would be able to notice a significant change in acceleration however it seemed to have almost no effect leaving me disappointed and puzzled.

 

Perhaps at speed the throttle position has less effect than other inputs such as engine revs.

 

Is there some sort of math formula showing the relationship between TPS mV, RPM, Air/Oil temperature and the resulting mixture.

 

 

I had thought of strapping my osciliscope to the tank to monitor the injector opening time but that might be a bit distracting

[motoguzznix]

Roy

 

There is no math relation between TP and rpm.

There is a map with 16 TP lines and 16 Rpm rows which means there are 256 points to be defined. Every point can get an individual value that is equivalent to injection time. The values are defined in the course of the engine tuning on the dyno in the factory.

A similar offset map exists for the tunning of the second cylinder and a third map aplies to the ignition timing.

 

The TP adjustment assures that the engine works in the correkt area of the map for every running condition. Fooling the TP therefore is no good idea and will show downsides in some areas of the map.

[Kiwi_Roy]

Roy

 

There is no math relation between TP and rpm.

There is a map with 16 TP lines and 16 Rpm rows which means there are 256 points to be defined. Every point can get an individual value that is equivalent to injection time. The values are defined in the course of the engine tuning on the dyno in the factory.

A similar offset map exists for the tunning of the second cylinder and a third map aplies to the ignition timing.

 

The TP adjustment assures that the engine works in the correkt area of the map for every running condition. Fooling the TP therefore is no good idea and will show downsides in some areas of the map.

Sorry, I should have been a bit clearer, I have no intention of using this as a permanent fix. You are right of course, I simply thought by moving up or down the TP rows I would be making the mixture more or less rich.

 

When I gave up on that I bought a MyECU, it's magic.

[Cliff]

Without knowing the specifics of your circuit or riding test...

 

300mV should make quite a difference at low/no throttle where the input is around 1/2 volt. I'm not sure what the typical cruising voltage is but if around 2V or more, then 300mV is not that big a change.

 

Other complications

The throttle also affects spark advance so increasing the TPS voltage would richen and retard.

If the ECU is running closed loop most changes to the inputs would be ignored as the ECU trace the gas sensor.

[Buzzard]

I don't have the answer to the original question, but I do have something to say about this. I live at 6000' alt., and have a 2002 LeMans with the Ti pipes and race ECU. It would not run cleanly at lower RPMs, bucking and snorting in traffic. I did set the TPS per recommendations on this site, using a volt meter and such. No help. I then carefully marked the position of the TPS, and moved it just a hair one way a bit, a bit more, the other way a bit, and a bit more, taking careful note of any changes in running characteristics. I did find a sweet spot where my bike runs near perfect. The sweet spot was just a hair advanced of the "text book" setting. My Guzzi runs quite well now.

[Kiwi_Roy]

I don't have the answer to the original question, but I do have something to say about this. I live at 6000' alt., and have a 2002 LeMans with the Ti pipes and race ECU. It would not run cleanly at lower RPMs, bucking and snorting in traffic. I did set the TPS per recommendations on this site, using a volt meter and such. No help. I then carefully marked the position of the TPS, and moved it just a hair one way a bit, a bit more, the other way a bit, and a bit more, taking careful note of any changes in running characteristics. I did find a sweet spot where my bike runs near perfect. The sweet spot was just a hair advanced of the "text book" setting. My Guzzi runs quite well now.

 

I guess that's the kind of thing I was trying to do only instead of moving the TPS I just added or subtracted a few mV.

Here's the circuit I used

Throttle position Trim Pot.pdf

The idea was to find the sweet spot, measure the offset mV then move the TPS to get the same offset.

However once I assembled Cliff's ECU I soon forgot about that.

Thanks Cliff, my bike now runs like a Swiss watch