It is to set the TPS to the desired voltage output at idle which on your typical Keihin setup is .5v at idle with safe range of .4-.6v. Tweaking the TPS a tad is the easiest way to richen or lean the whole map. Making the ECM think the throttle plate is open a bit more than it really is, will cause richer delivery. IE setting it at .6vdc at idle will be richer than setting it at .4Vdc. Of course it is rare that a machine needs linear change across the board to make it run better esp when adding pipes etc. That is where the fuel tuners are usefull that separate the map into many pieces or at least low, mid, high.
Thanks Marc for taking the time to share your EFI knowledge, I liked the thread on Altitude Adjustment......now I can really screw up my machine Does adjusting the pressure sensor offset the fuel map linearly also? My bike won't run for more than about 1 sec on the first cold start. I have a JD tuner and have the idle adjustment (blue/green) leaned all the way out to get to it running on the 2nd cold start (used to take 4 starts). Is this normal? Does the JD tuner change the resistance at different points (Idle, low, mid, high, etc)? So, do I need to unplug the tuner and measure Vdc at sensors? Also, my bike has 2 TPS's. Why is that? I have a 2007 yamaha raptor quad (with much simplier looking Mikuni FI) that has tons more hours on it and has always run on the first start (also has never had flame outs or any other engine issues).
Can I lean the Mikuni map by adjusting the TPS and if so, how is it done, I am rich across the board.
Again I have not owned an EFI husky, mikuni or keihin. I do spend much of my 50hr workweek working on EFI of all kinds in many brands, though. If the TPS has slotted mounting points you would loosen the screws and move it one way or the other. The goal is to LOWER the output voltage at a given throttle position, making the ECM think the throttle is several percent more closed than it really is. I would hate for anything I post to result in someone's bike running WORSE and without it in front of me, or a service manual with wire diagram to look at, I simply cannot give you a precise answer. The short answer is , yes, tweaking the TPS can make it run leaner. Doing it wrong could make it worse, and even putting marks on the body, it can be difficult to return to where you just were. If you are at wits end with the bike, place some marks on the TPS and Throttle body to mark roughly where it is and to use as a movement gauge. The tps is in line with the throttleplate shaft. Tweak the tps A LITTLE in the SAME direction that the throttle shaft moves when you open the throttle. Does that make sense? Ride it, decide if it improved it, and go from there.
Awesome Marc! What your saying makes total sense to me after reading about (what I think) are very slight differences in fueling between peoples bikes...... Apparently the TE has 2 TPS's according to the shop manual. I accidently/on-purpose removed "Throttle Sensor #2" which appeared to fit over the end of a shaft that moved kind of freely. I thought it odd that the shaft moved independant of twisting the throttle, but now makes sense with your info. My first attempt at reinstall obviously was not right and the bike idled real high and would not come down. After my 2nd attempt the bike ran fine. So it sounds like if you wanted to tweak your fuel delivery across the board (linearly), tweak the 1st Throttle Sensor on the main butterfly? All the sensors have a painted mark from the factory that makes it easy to get back to the factory setting (maybe put there for idiots like me). It also apparently has a MAP sensor. I'm thinking it is heavily guarded in the front of the throttle body, with a different style adjustor. Shop manual didn't show a picture, but it was called out in the wiring diagram........Note to self: DONT TOUCH. For my cold starting issue, I'm going to try an Iridium plug first before I pull the sledge hammer out to fine tune now that I'm dangerous with more knowledge!
Awesome stuff Marc, no problems on your responsibility, it's my bike, all on me, I appreciate the tip and am going out to start tweaking now!
Awesome guys hope the info helps, feel free to ask questions or PM as needed. I'm certainly not the end-all on EFI but I have learned a lot over the years and at various OEM training classes (Honda's was amazing....) and am always willing to share knowledge!
My TE511 with uncorked exhaust and JD tuner always take three tries when cold in the morning. Did it when completely stock too. Does not bother me as i let it idle a good 2-4 minutes before riding off anyway. Many people say with EFI let it start and run for a good minute or two before touching the throttle at all. this lets the TPS and learning part start clean.
Mine (smr 511) is fuel injected and it takes between 2-4 starts cold in the morning I just always thought it was normal
http://www.cafehusky.com/threads/2011-te449-running-well-with-factory-efi-system-finally.41069/ The Factory setting for the TE449 TPS is 0.7v. Most are much less than that, closer to the high 0.5v range. Mine runs quite well at 0.8v, it stopped the flameouts and stalling without the need for a PCV or Jd tuner box. I've linked to the thread above.
2012 511 - correcting the TPS voltage made a huge difference on my bike. Just runs smoother all around.
Hi, Sorry for replying that old topic. First, thank you all for sharing your knowledge and experience! Am I correct: to tweak the TPS sensor enrichens the injection, since the ECU believes that the throttle is more open? Second point: There is a TPS reset, where the ECU learns the min (and max) value of the TPS sensor. What happens now when you perform a TPS reset after the TPS sensor tweak? If I understood everything correct, it would be like without the tweak and the reset? Is this correct? PS: the voltage on my TE449 is 0,71 V originally. If you do not have the mentioned adapter, it is quite easy to put some small rigid cables into the connector of the ECU from outside after removing the cap there. BR Florian
As mentioned, changing the TPS position does alter the AFR across the board but it's not linear from a percentage standpoint. Think about it, altering the TPS to tell the system that the throttle is at x% (degrees) open instead of the actual physical y% open (say a difference of +\-5 degrees) makes a huge difference at lower throttle positions and less at more open positions. For example, at the actual physical opening of say 10 degrees, a 5 degree difference is 50 %! and the system will enrich or lean the mixture accordingly. At 95% actual position the same 5 degree difference is only about 5%! Actual air flow vs throttle opening is not linear as well, being biased towards lower openings (the % change in flow is greater at lower openings), but not nearly enough to change the relationship as described. Conclusion, changes in TPS significantly affect lower throttle openings the most and taper off as the throttle is opened based on the percent change. Of course, I'm assuming a system where TP and RPM are the main variables for the fuel map. Some systems use the MAP sensor for load along with RPM to define the fuel map and the TPS mainly for accel fuel and fuel trim under certain conditions.
Hi, Thanks a lot for your answer and for highlighting the drawbacks/specialties of tweaking the TPSensor. Maybe my questions was not clear: what happens if you perform a TPS reset (intended or unintended) of the tweaked system? Will it become untweaked by the reset process, because it learns the initial positions again? BR Florian
Tweeting the TPS position followed by a reset of the closed and full open positions should essentially recalibrate the system to the stock settings. If you want to bias the the fuel ratio, resetting after altering the TPS position will cancel any desired affects as it'll normalize any voltage offsets. On other non adjustable TPS systems, the only means to create a delta offset is through a software change (reset) along with changes in the mechanical closed throttle stop screw.
Hi, thanks for confirming my guess. Then I wonder why some of us chase absolute values (stock 0,7; running well at 0,8; some bikes down to 0,5) and - if I understand correctly - do TPS reset more of less regularly. Then the absolute value should not be important. In other threads people report that they need a TPS reset every few weeks to keep the bike running properly. Does anybody know why? I guess possibilities are -drift of 5V reference of ECU (unlikely) -GND shift (may be, if I remember correctly, the TPS ground was not same as battery ground in my measurement) -changing resistance in connectors (hopefully not) -change/drift of the TPS sensor itself (does anybody know what's inside? Simple potentiometer or magnetical/optical encoder?) @Dangermouse: please do not get me wrong. I appreciate your pioneer work on easy tweaking the system. I just want to understand the whole thing. Sorry, I'm engineer ;-) BR Florian
