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Posted by chief
- September 03, 2014, 23:11:50 PMThe ECU is limited in how much it can compensate for modifications of the exhaust and intake.
In the real world pipes make a difference. Different pipes different problems. With most Drifters simply replacing the pipes or the air box will not change things enough to require an additional FI box, like the PCIII or Cobra. BUT, with my pipes I needed the Cobra to stop decel popping etc. I also had to adjust the fast idle.
If you change out the pipes and the air box 99% of the time a FI addon will be needed.
Could be as simple as some previous owner tinkered with the fast idle and its only now a problem because of the pipe change. Also don't know what other mods have been made to the bike.
Posted by Bucko
- September 03, 2014, 22:47:50 PMI don't get the possible lean condition when a better flowing exhaust is added. The ideal fuel mixture calculation performed by the ECU takes into account the intake pressure (as well and ambient pressure). If the exhaust makes the system flow better - that would imply a lower nominal pressure at the intake but the ECU should automatically compensate for the lower pressure the same way the system compensates when one drives up a mountain into lower ambient pressure (even more so since the difference between ambient and intake is even greater if there is an increased flow due to an exhaust change). What am I missing?
In theory this should apply to a better flowing intake as well unless the change is so great it's outside the ability of the system to make the required compensation.
Posted by chief
- September 03, 2014, 19:19:14 PMWhat troll said... the fast idle knob... adjust after the bike is warmed up. And, what PC said... I've had that happen a time or two.
Also check and be sure you don't have the "choke" pulled out. (I know its not really a choke!).Posted by Troll
- September 03, 2014, 19:13:56 PMBy changing the exhaust, you effectively leaned out the mixture a little bit. This will cause the idle to rise. The change in back pressure is the culprit. You will have to readjust the idle after the engine is completely warmed up. As an afterthought...you don't have the "choke" pulled out, do you? Mine idles low when it's cold since I removed the idle speed solenoids, but just fine after it warms up. No big deal. The idle must be set to 1,000 rpm +/- 50 rpm. That little black knob on the cable, down by the water pump is what you use.
Posted by Bucko
- September 03, 2014, 18:53:14 PMI used to have this problem on my old Honda. The problems was that it was so cold blooded that when starting up from cold, the idle had to be turned up in order to keep it running (they're jetted very lean from the factory). Then, of course, once the engine warmed up, it idled to fast. It was that way for years until a buddy clued me in that if I cranked open the idle jets a couple of turns over the factory spec, the cold idle would work much better - which it did and it's been working perfectly ever since. Tweaking idle jets is not an option of course for the Drifter, but maybe your cold idle is set to high to compensate for a similar situation. I've had some cold idle issues lately - still not entirely sure why but I have my suspicions (water temp sensor either faulty or corrosion on the connections to the sensor).
Posted by pcarrell
- September 03, 2014, 17:29:11 PMSounds to me like maybe something is sticking open. If you blip the throttle does it go back down?
Posted by Driftaway
- September 03, 2014, 16:36:39 PMHi just joined VDR and loving the wealth of information. I have a 2001 1500 and I changed out the stock exhaust for the Vance and Hines and converted to the dual mod. It now starts the same. but after 30 minutes of riding it is idling to high. Not sure why it starts and idles the same but only after getting in some miles does it idle high. Any help you can offer this drifter loving newbie would be very appreciated.