Penny Tech - TPS Adjustment Tool

[cedric]

I was noticing some hard starting when cold issues with my bike (a Husaberg FE350) and I figured a good first step would be to check the TPS setting for the FI. There are several commercial products available to help accomplish this, the simplest and cheapest one is the TPSTool.com pigtail that plugs in between the wiring harness and the TPS and allows you to connect your multi-meter and get a reading. I didn’t want to order one and then have to wait for it to arrive, so I searched around a bit and learned that basically the TPS is potentiometer that receives 5V DC input from the bike’s wiring harness and limits the voltage returned depending on the throttle position. The more the throttle is opened, the higher the voltage returned from the TPS. I found several guys on various forums that were building devices that used a 9V battery with a small regulator that limits the input to 5V and connecting that to the TPS to get a reading. I soon realized that all around my house are transformers that convert 110V AC to 5V DC for charging various electronic junk. With that in mind I set about building a device to test my TPS setting.

I took an old Blackberry charger that lists its output as 5V DC and then clipped its mini USB cable and teased out the 4 wires inside. The black and red wires are the power +/- and the only ones needed. I clipped off the green and white data wires and tested the voltage coming out with my meter, 5.00V exactly. Perfect.

I connected the red/black wires to some small wire pieces I had laying around and put some bullet connectors on the ends. These wires will provide the 5V into the TPS and the ground. The black wire (ground) I added a female blade connector in the middle so I could tap in with my meter. Then I made up another wire with a bullet connector on one end and an alligator clamp on the other end. For each wire I covered up as much of the bullet connector as I could with heat shrink tube to prevent shorting out when I plug the wires into the tps. The bullet connectors have just enough of an opening in the end to slide over the pins on the TPS connector. If they are too tight, you can pry them open a bit with a micro flat blade screw driver.

Then, to test the TPS setting, connect the three wires to the TPS, the black wire (ground) is the top-most pin, then the 5V input in the middle, and the variable voltage output is on the bottom. Connect the black lead from your meter to the blade connector in the ground wire, and connect the red lead from your meter to the wire coming off the bottom connector. Set your meter to 20V DC, then plug in the phone charger and check your setting. In my case I was reading 0.57V. I turned the TPS until my setting was 0.64V, plugged the TPS back into the bike and immediately noticed a significant improvement in the cold starting. To set the TPS properly, the idle should be adjusted to the factory spec, and then the TPS set to whatever number is the factory spec for your bike. I don’t have a tachometer on my bike but may pick up one of the small aftermarket units for this purpose. It’s my understanding that a larger setting number is a richer setting and vice-versa. In any case, I now have some baseline numbers to work with and can make relative adjustments either way and see how the bike responds. This cost me nothing, as I had all of the materials lying around in my garage. I hope this helps others diagnose and tune their FI bikes.

P.S. I realize that my throttle body is filthy. It's not something I look at very often. Which is a nice perk of fuel injection!

[boland]

Impressive! You and axel99 should start your own dirt bike electronics side business!

[cedric]

I got a little ride in on Saturday and the bike started perfectly and ran better than ever. I think I'll leave it alone for now

[RJHenry]

Cedric:

Thank you for the great education on TPS. I gave the penny tech a go - though I used a long USB cable and then tried a few distinct charging plugs to nail the 5.0 V. The adjustment went OK, but it was tough to keep the bullets on the TPS pins while adjusting it - I needed more hands! Unfortunately, I was not as careful as appropriate... and managed to bend the center pin and not notice. When I reassembled, I REALLY bent it. I was VERY lucky, however, and managed to straighten it without breaking it.

My follow up research led me to a "dime-tech" solution that is a little more idiot proof - a plug in extension harness with taps for the meter. http://www.tpstool.com This "plug-in" solution lets you start, run, and adjust with the meter connected. A very nice aspect is that they ship WORLDWIDE for the same $36.95 as within the USA!

In my research I also discovered a comment that the Euro map (which I have) requires an idle TPS setting of 0.61V. When I checked mine tonight it was 0.59V and it started VERY POORLY. Much cranking, seemed lean, have to throttle to start.

After setting it to 0.61V, I was DUMBFOUNDED - it starts cold in HALF a revolution. I then set MrsHenry's FE250 to 0.61V (she also has the euro map) and the same result. INSTANT starting. INCREDIBLE

I am happy to pass on my good fortune - if anyone wants to tune, happy to share the jumper harness.

Again, many thanks!
RJH

[downunder366]

Great info.
Thanks guys.

[axel99]

You can build the TPSTool knockoff yourself for about $11us with the proper connectors and 15min to build. I have sourced the connectors for the model 3 (2016 250,350 and 450XC-F) and have leads on the other 2 models. If you are only ordering a single M/F connector its not economical. Need to do a bulk buy. It also would not be hard to build a idiot proof meter that basicaly lights a led when a preset resistance is detetcted. The preset resistance threshold could be user configurable using a potimeter and multimeter. I think its just as easy to fiqure out how to use a cheap multimeter directly.

If you are interested in a group buy send me a PM, if there is enough intrest I can look into doing a limited production run of a TPS Tool knockoff and figure out firm pricing, would estimate it to be in the $20cdn range

[trailguy]

PM sent.