Hi all;

Have an '07 Fat Boy and have upgraded to Python Staggereds, V&H Fuel Pak and a Doherty Power Pacc intake. All is well and what a difference; well worth the green and effort. My question is this: the idle (even when all stock) was always too "busy". I know that the Fuel Pak does not allow for idle adjustment, but I was looking at the back of the throttle body and I noticed a set/stop screw that the throttle cam rests against. I looked at the screw/stop and it appears to be "locked" in position with gorilla snot. Has anyone filed down the back of this screw/stop to bring the idle down a hair? I'm only looking for about a 50-100 rpm drop.

Thanks,

T

 

Yeah, you probably could adjust that screw a bit. But then the IAC stepper motor would just open up its passageway to bring the idle back up again, and it would throw off your throttle position sensor calibration in the ECU which would have detrimental effect everywhere.

The short explanation is that screw sets the closed-throttle position (I believe it's something like 4% open) so the computer stuff can do its thing. So, no, you can't adjust that screw to drop your idle. What you need to do is get into the computer and do it there. That calls for the SERT, which would relegate your Fuelpak to on-the-shelf status, plus another almost $400 for the SERT itself, and if it doesn't come with a map for your breathing components and you can't find one that's close-enough to just use, you'll be looking at a few hundred more bux for a dyno session.

That, or the DTT or TMAX aftermarket ECUs...

 

Glen is correct, if you back out the screw the IAC will open more to maintain the desired idle speed set in the ECM. I adjusted mine a couple weeks ago on some advice from another forum. The advice was that TPS voltage should be ~0.4and IAC steps should be ~40 at 0 throttle. My TPS voltage was 0.55 and IAC steps were 15, soI adjusted the stop screw out until I got 0.41v and the IAC stepper went to 36 ( used SE Race Tuner data mode to do this ). The ECM learned the new TPS voltage as 0% throttle...I believe, but don't know for sure, that the ECM reads the TPS voltage when you turn on the ignition and calls that 0% throttle.
Making this adjustment resulted in the VE New numbers being lower than they had been, especially at lower throttle openings, and themotor responding a little better. I also had to tweak the cranking fuel some to regain instant starts.

 

It has to be adjusted by the dealer with the digital tech or using a SERT or it will return to where the ECM is programmed like mentioned above.

 

I thought the goal was to have "VE New" be equal to "VE" (AFV=100%)?

 

That is the goal.What I found after Iadjusted the throttle stop screwto actually close thethrottle platefurther was; the VE New values were typically less for a given cell than they had been before the adjustment. I had adjusted the VEvalues to = VE New values from data mode before I messed with the throttle stop. Then, after I changed the throttle stop, I resetboth VE tables to reference values and did another datarun.
One example from my datafiles at 5% throttle and 2000 rpm:
TPS voltage 0.55 (before) VE Front=89.5 ref, VE New=89.0; VE Rear=93.5 ref, VE New=95.0
TPS voltage 0.41 (after) VE Front=89.5 ref, VE New=87.5; VE Rear=93.5 ref, VE New=91.5

After the second datarun, Iagain changed the VE tables to = VE New values.
I'm not sure this was worth all the work involved; readjust throttle and idle cables, redo VE tables and cranking fuel table, but I've convinced myself that the bike feels better than it did before.

 

Thanks for the additional info!

The ability to do that's a pretty good mechanism we've got, isn't it?