Originally Posted by Gump 159
I was pulling out from a stop the other day, slipped the clutch and holding the front brake a bit (cuz the DB in front of me couldn't decide to turn or go straight) when I noticed I really liked the tone of my pipes. More of a deep rumble than the usual thump thumpa. My idle speed was down to about 900/920 RPMs from the factory 1050 or so. My question is...Can the idle speed be adjusted down on an EFI? and if so how?
You will need a SERT (Screamin Eagle Race/Super Tuner) to tune the idle RPM. From the SE training video, many examples from the SE team showing idle RPMs set at 900 (at normal temperature 180 and up). I tuned my bike to 800 RPM and it sounds awesome (SE exhaust) with crisp deep exhaust notes. If at low RPM, your bike produces uneven sound levels, your AFR (Air Fuel Ratio) is either too rich or too lean for idle. You cannot just simply lower the RPM, you will need to tune the idle RPM. I spoke to a mechanic at Harley, he said he hasn't seen any official document regarding engine harm at lower RPMs. In fact, by design, the ECM lowers the RPM at higher temperature at idle to help reduce the engine heat. Also, for a bike with EFI, there is a low oil pressure warning light that warns you on low oil pressure. Typically, at idle oil pressure is 7psi to 12psi. Oil pressure lower than 5psi will trigger the warning light. At 800RPM, oil pressure is around 9psi. So as long as you don't get your warning light on, your RPM is good. I have been at many Harley events. About 20% of Harley bikers tune their bikes for performance and sound (more difficult and the fun of a Harley ownership), about 50% tune their bikes only for performance (easier) and the remain 30% ride their bikes as is, any upgrade is for the look only (this is not tuning). Below is a section about Idle RPM tuning from official Harley Davidson SE manual (version 2011). The idle RPM can be set to the lowest value (the SE Super Tuner allows 800 RPM as the lowest value for EFI, you cannot set lower) or as slow as the engine is not dying. Below is the "Idle RPM" section from the manual:
Use this Tuning Table to set idle RPM to desired setting and to correct idle-related problems.
• If engine idle speed seems too low or engine occasionally dies, increase Idle RPM cells in appropriate engine temperature to correct.
• If engine idle speed seems too high, decrease Idle RPM cells in appropriate engine temperature to correct.