factory pro hayabusa stacks

[glenn71]

9.64 @ 145mph.Lowered,stock gearing,pipe, tuned for 91 octane.1.64 60 ft.118.6mph half track.They make lots of torque as a mate who was switching between 2 factory pros and 2 suzuki shorts and 4 factory pros found out.2 very differnt launch rpms required.His best 60 ft so far with them was 1.58,stock gearing.Proof is in the timeslip provided correct shiftpoints are adhered too.They like lean air fuel too.13.1-13.3 is what i,m set at but have seen still more power at 14:1 prior to tuning,perhaps this speeds the burn rate and helps compensate for the higher than required octane rating?

[mike46]

Happy dyno....LOL

You think.....

[gazza414]

MM do you really believe that the shorter stacks will give that much at the top end as indicated by the 2nd run file?????  or are you just throwing this up in the air and seeing where it lands

[mountainmotor]

MM do you really believe that the shorter stacks will give that much at the top end as indicated by the 2nd run file?????  or are you just throwing this up in the air and seeing where it lands

It's kinda like this -  read the first 16 words of the last post of mine .

Now , for your thoughts concerning that first question to me in your post 

[gazza414]

It takes alot more than factory pro stacks to get a top end like that ...all being equal with direct comparions betwwen the 2 run files...I'm sure we're on the same page MM.....even the pretty anodized ones can't work miracles.

[Steve S]

What further complicates this comparison is that Factory Pro offers three, four or five lengths. The most frequently recommended stack is the 45.3-60 which is nominally 60mm in length and bit longer than the Hayabusa short.

[PetriK]

Made an interenet study on this topic some time ago and unfortunately all the "more or less independent" dyno charts I have seen so far indicate that with FP stacks there is more up to 9.5k and less after that. E.g. on the german hayabusa.de forum there is a some dynocharts with factory pros installed and to even one where compared to a similar busa with FP and with short stacks (pipe + yoshi1).
http://img375.imageshack.us/my.php?image=diwoneu1bn9.jpg
Of course one could claim that the k-compensation (SAE correction) is too high on this picture for FP stacks.

After installing the FP stacks I needed to reduce the top end fuel to get the mixture correct - that was good enough indication to me that those are not for me.  After that experience did not bother to dyno with those as I also could see from the log files a change in airbox pressure which was higher with FP - just gave those to someone who is running the engine without an airbox only for a track use. Maybe better suited for that purpose ?