Throttle position sensor

[Timan]

I did the search feature and did not come up with a lot of discussion on TPS for the FJR. With my current FZ1 and previous TL100 the TPS was a fairly crucial part of dialing the bike in for best performance. Is it a non-factor with these bikes? As you can tell from post number I'm new and still learning. Thanks for your patience with my learning curve.

 

[madmike2]

There was a recall for some TPS. My '05 was one of the included VINs. You might check with your dealer and have them check your bike's VIN to see if it has or needs to be changed.

Other than that, I don't remember anyone getting the FJR to a state of tune that required adjusting the TPS.

You might try the alternative search method through Google: TPS site:fjrforum.com

 

[ionbeam]

IMO, there are no performance gains to be had through TPS adjustments, though there can be some drivability improvements.

The TPS is locked to the throttle shaft that opens & closes the throttle plates. In side the TPS is a resistor whose value changes with the throttle opening. The ECU supplies a precision +5VDC to one end of the resistor and ground to the other end. As the throttle is turned a ‘wiper’ runs along the resistor and picks up a voltage. When the wiper is near the ground end the voltage it picks up will be very low, when the wiper is near the 5 volt end the voltage it picks up will be near maximum. At idle the throttle plates are slightly cracked so the voltage is somewhat bigger than zero. When the throttle plates are fully open the voltage will be very nearly the full 5 volts. The FSM specifies that at idle the resistance of the TPS should be 650 – 750 Ω and at full throttle it should be 5k Ω.

The ECU takes the wiper DC voltage and runs it through a converter that returns a digital value. The ECU does some simple math on the digital value and converts it into a percentage. At idle the diAG screen should show 15-17, which is 15% to 17% throttle opening. At full throttle the diAG screen should show 97 – 100 which is 97% to 100% of possible throttle opening.

The ECU sees the absolute position of the throttle plates but additionally it can calculate rate of change too. The ECU will know if you are gradually changing throttle position to maintain speed or if you just popped the throttle full open, expecting instant acceleration.

The throttle plates can’t physically be more than 100% open, if the TPS returns a value of 105% I’m sure the ECU recognizes that there is an error and simply substitutes 100%. If you were to set the TPS so that it reached 100% at 7k rpm the ECU would think the throttle plates are fully open and supply FI volume and timing expecting that there is maximum air flow. Since the throttle opening isn’t really totally open, the FI will be excessively rich.

The ‘span’, the amount of travel of the TPS is fixed, all you can do is push the span range lower or higher. If you adjust the TPS to deliver 100% at 7k rpm the idle point will be near 0%, most likely causing the engine to not idle well, if at all.

Hopefully you found something useful in all those words :sleepysmileyanim:

What's in the TPS

 

[madmike2]

Hopefully you found something useful in all those words :sleepysmileyanim:

If he didn't, I did. Thanks for the engineering lesson.

 

[FJRSTAR]

What's in the TPS

I remember thinking at the time that you posted that write-up on the TPS that whatever camera you used is awesome. Very nice close-ups.

And the write-up was awesome as well.

Thanks for the info.

 

[Timan]

Thanks for the replies, and oddly, ionbeam I understand your writeup. What I take away from this goes back to old local saying--let sleeping dogs lie. Somewhat related with the TL1000 I had to jumper out diagnostic connection and then adjust voltages you referenced. The FZ1 is in no way this sophisticated being a gen. 1. I have owned dozens of bikes but this '05 FJR is one of the more pleasant surprises. Imagine being able to flush abs brakes w/o having to reset computers and lube splines in minutes vs. hours. I always thought the FZ1 was the best kept secret, this FJR is close. Thanks again and I will try to keep questions to a minimum.

 

[RTSR1/FJR]

I have messed with it and gained some low speed drivability. I get 44mpg 2 up also. When I set it to 15, parking lot drivability was a little jerky. I set it to the highside of 13 and check it with ohm meter, and it comes out to the lower range of spec, which if I remember was 650 ohm. High side of 15 was 750 ohm. The dash method is just a quick ref. check. Checking it with a meter I believe to be more accurate.

(Admin Note: copyrighted material removed)

Apparently I broke the rules! I forgot, won't happen again and sorry to everyone!

But, for anyone who owns an '03 manual, go to the Electrical section, pg. 8-63 and it describes how to if your so inclined! The dash ref. gets you close and the meter puts you on the mark. If close is close enough, use the dash.

 

[ionbeam]

Timan, glad you understood the write-up, I try to write for the 80% audience (10% could write the book and the other 10%, well, even pictures and arrows may not be enough).

FJRSTAR, my wife and I have several Nikon and Canon digital SLRs as well as several other digicams. But, I keep my old tech, down rev, ratty old 1 mega pixel Nikon 950 for close-up work because it rocks.