SnowmobileGuy
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- Jul 15, 2010
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I have a 2006 FJR1300A. Like many of you, I don't appreciate the abrupt throttle response when rolling on the throttle after coasting in gear with the throttle off. There are a bunch of fixes out there that mitigate the issue to varying degrees - Barbarian mod/CO, throttle spring removal, throttle body sync, G2 throttle tube, removing throttle cable free play, PCIII/PCV, etc. They all seem to help some, but there are some folks out there that can't get the issue resolved to their satisfaction with those fixes (either singly or in combination). I contacted Dynojet and they indicated that there Power Commander can not completely eliminate the issue because the Power Commander doesn't stop the fuel from shutting off. You can smooth out the response once the ECU tells the injectors to open, but the fuel will still be cut off when coasting in gear with the throttle off. That got me thinking along a different track.
There are only a few ways the ECU can sense that you are coasting while in gear. The maintenance manual does not have an FI system flowchart - it just focuses on trouble shooting tables and wire diagrams. One must infer the system logic. It knows what gear you are in, it knows your speed, it knows throttle position, manifold pressure, air temperature, etc. It also knows when the clutch is pulled in, but the FI system doesn't show that as an input (it's used in the starting circuit). My thought is this: How about tricking the ECU into thinking you never close the throttle. It seems this could be accomplished by advancing the TPS adjustment just a bit above spec. There might be a risk of running a bit rich if the ECU relies heavily on the TPS reading for injector timing and thinks the butterflies are more open than they actually are. If it primarily relies on engine speed, manifold pressure and temperature, and air mass flow, it might not be a big deal. Perhaps there is a proper median there somewhere - that is, just a few degrees of TPS advance above spec might be tolerable as far is stoichiometry is concerned, but still fool the ECU into thinking the throttle is not shut off. If this were to work, you would have to drop the idle speed a bit (with the idle adjustment knob or the air screws). Is my logic flawed? Has anyone tried this? I'm planning on trying it, but wont be able to get to it for at least three weeks.
There are only a few ways the ECU can sense that you are coasting while in gear. The maintenance manual does not have an FI system flowchart - it just focuses on trouble shooting tables and wire diagrams. One must infer the system logic. It knows what gear you are in, it knows your speed, it knows throttle position, manifold pressure, air temperature, etc. It also knows when the clutch is pulled in, but the FI system doesn't show that as an input (it's used in the starting circuit). My thought is this: How about tricking the ECU into thinking you never close the throttle. It seems this could be accomplished by advancing the TPS adjustment just a bit above spec. There might be a risk of running a bit rich if the ECU relies heavily on the TPS reading for injector timing and thinks the butterflies are more open than they actually are. If it primarily relies on engine speed, manifold pressure and temperature, and air mass flow, it might not be a big deal. Perhaps there is a proper median there somewhere - that is, just a few degrees of TPS advance above spec might be tolerable as far is stoichiometry is concerned, but still fool the ECU into thinking the throttle is not shut off. If this were to work, you would have to drop the idle speed a bit (with the idle adjustment knob or the air screws). Is my logic flawed? Has anyone tried this? I'm planning on trying it, but wont be able to get to it for at least three weeks.
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