After a mild build this last spring (details listed below), I finally had time and enough break-in miles on the bike for a dyno tune. The bike tuned just fine hitting the 13:1 target AFR until right around 4000 rpms, then the AFR raised to 14+. The tech tried every trick that he knew to force the AFR to 13 above 4000 rpms including making the ECU thinking it is a 120R motor and reducing the cells in the far right bottom corner of the AFR table to 11. Nothing worked. The tech confirmed twice that there is no intake leak. We ran out of time so he didn’t have time to test the fuel pump for pressure. Since the bike was nicely tuned in the normal riding rpm range, I rode it home. The plan is for the tech to discuss this tune with the other techs and schedule me up later to finish the tune.

Several possible reasons for this issue the tech and I kicked around are:
1. Fuel pump delivery issue at and above 4000 rpms. Might need a new fuel pump? I’m no expert, but seems to me the fuel pump delivery pressure is constant throughout the rpm range and if there was an issue with the fuel pump, the issue would exists at all rpms?

2. Injectors are limiting fuel delivery at and above 4000 rpms, thus bigger injectors might fix the issue. This seems to me to be the most likely reason?

3. Might need a larger throttle body. Again, I’m no expert, but Dan Baisley’s opinion when I asked him if I would benefit from a larger TB, said no, not until you get to 103”.

So I’m curious what the tuners and more experienced motor builders on this board think what the solution(s) might be to fix my tuning issue?

I attached a link to the final dyno chart. The lower red line garbage was the break-in map I used, I know, bad choice for a map, but the bike ran well, plugs looked fine, didn’t ping and didn’t have decel pop. But looking at the AFR graph, you’ll see the blue line increases above 13:1 to 14+ above 4000 rpms maxing out at about 14.8:1 AFR.

JPG: http://priceamp.home.comcast.net/~pr...ey/95Build.jpg
PDF: http://priceamp.home.comcast.net/~pr...ey/95Build.pdf


Here’s the bike specifics:
2006 FXSTi
SERT
25 degree Injectors
95” big bore
SE 9.25 flat top
Baisley Super Stock heads
Andrew’s 26N
SE adjustable PR and lifters
SE AC with K&N element
SE clutch plates, SE spring diaphragm, VP70T
Rinehart 2-2 flush cuts

 

Check fuel pressure I have seen clogged fuel filters rob top end

 

They has 2 types of injectors in 06. The had 8 degree injectors and 25 degree. You have to know which ones you have and use a MAP specifically for that injector. Did you do this? The 8 degree injectors have only 3 small pin holes in them to deliver fuel, the 25 have 8 or so. big difference.

 

The changes were to the spray pattern not the flow characteristics, they are still pretty close and shouldn't cause an issue as lean as that was.

 

For this issue, I should have listed in the specifics that the bike has 25 degree injectors.

 

Had a similiar problem when my bike was getting tuned ....was the fuel pump at high rpm not putting out enough

 

Did you just replace the fuel pump with a new stock unit and then the tuning issue was fixed?

 

I didn't say the flow was differn't, just that each injector is MAP specific, That's why there is 2 sets of MAPs for '06 bikes. 8 degree MAPs and 25 degree MAPs

 

Sorry for the confusion I was just saying that if you load a 8 degree map in a 25 degree bike the difference at WOT will not be as dramatic as what is pictured in the graph, a fuel filter is cheaper than a pump and a maintenance item that should be replaced every 20k

 

Run it with a pressure gauge inline before replacing parts.