Throttle Position Sensor
Posted September 19, 2010 - 06:33 AM
Can anybody here shed some light on the subject.
Posted September 19, 2010 - 06:53 AM
Why do some people run with this disconnected? Don't know.
Why does the bike continue to run? This is a function of the map that the computer reads to calculate ignition timing and injector duration based on all the feedback from all the sensors. A well design system will realize that the sensor is not functioning and have an alternate map of values (via open loop) to use to calculate ignition timing and injector duration (It may also be the throttle position sensor does not have much weight when figuring the overall equation). I've worked on a number of cars and trucks with fuel injection, but never had a bike that had this type fuel system. Fuel injection is great, but still I like a simple carb for my bike. Of course, I'm still the type of guy that prefers to have a kick start on my dirt bike.
Edited by t_bois, September 19, 2010 - 07:28 AM.
Posted September 19, 2010 - 08:55 AM
There is another system that uses a carb and a computer, which I hate. It was used for a short time in the auto industry. Hopefully this is not a system that is being deployed in dirt bikes as it is junk. It's like taking the worst of 2 worlds to create one!
With this system, a carb will be outfitted with a number of solenoids that get modulated with an on/off pulse generated by a computer. The computer (via the solenoids) will allow the fuel mixture to be modified by changing the open/close duty cycle of the solenoid, which will allow for a more quicker change in fuel mixture when demands require.
The reason I hate this system is that adds another point of failure with little or no gain in performance.
But to get back to your question, the throttle position sensor serves the same purpose here as what was stated about. It gives input to the computer to help determine when the mixture needs to be a bit more rich or lean by detecting how fast the throttle is being opened or closed. Some compare it's function to that of an accelerator pump.
Edited by t_bois, September 19, 2010 - 08:58 AM.
Posted September 19, 2010 - 09:41 AM
The reason people disconnect it is to quick test it.Disconnected, the bike reverts to a RPM based map and ignores TPS signal. In this 'limp mode' if the bike runs better, that typically confirms something is wrong with the TPS. Next step is to get a meter and the manual and go through the tests to see if it is defective or simply out of adjustment. Left disconnected, perfiormance drops off severly.
Most motorcycles have few sensors, the weight gain and increased electrical draw outweigh their benefits. Typically, the TPS, a MAP and and RPM, some do have temp sensors and that is about it. Big bikes tend to have a few more as well as lamda A/F sensors.
Posted September 19, 2010 - 11:53 AM
Is the YZ fuel system similar to port injection or thottle body?
Posted September 19, 2010 - 12:44 PM
On a 2010 YZ450FI (fuel injected) , the bike will still run with the MAP unplugged (albeit real poorly), it will not run with the TPS disconnected. It will idle but that is all.
Similar to port injection though the injector is right near the butterfly, which is right next to the port.
TPS on a carb'd bike only adds data. It is not critical, it meely enables the CDI to fine tune the ignition timing. TPS is critical on a FI machine as the machine has no way to know how wide open the throttle is otherwise, it could only guess based on RPM. If the bike were idling and you opened the throttle, the bike would stall as there is not enough fuel at idle mode to enable higher RPM. Theoretically, if you could get the RPMs up, the system could guess the fuel needed, but a stall is the typical result.
Posted September 20, 2010 - 05:51 AM
I don't really understand a whole lot about what it does. I get the basic idea ...
Posted September 20, 2010 - 07:42 AM
Posted September 20, 2010 - 02:05 PM
Posted September 20, 2010 - 03:57 PM
Posted September 20, 2010 - 04:07 PM
Posted September 20, 2010 - 04:16 PM
If you pull it, the bike will in fact run, however it will default to a "limp" mode with a reduced snap and general peppyness feel to it.
When I bought my bike I went dual sport road riding with my dad on his DRZ and I noticed the pulsing. So we pulled over, I unplugged the TPS and the surging went away but with a less "lively" feel to the bike. Plugged it back in and the bike felt better power-wise but still surged. All is in spec with the sensor so I just live with it surging a little.
Posted September 20, 2010 - 04:39 PM
From what I'm reading, this must be a common problem and obviously the manufacturer has overlook this as a problem. Do all WRs have this issue?
Posted September 22, 2010 - 02:29 PM