Honda CBR 600RR Forum banner

05 06 cbr600rr oem velocity stacks

2K views 7 replies 3 participants last post by  Arjay67 
#1 ·

Attachments

See less See more
2
#2 ·
I also read that shortening the stacks will cause loss of power under 14krpm but inscrease peak power? Can anyone confirm that for me? Kinda turning me off from changing them to the shorter ones...is it a noticeable loss for low end and midrange? I have a full akra and will be getting it tuned next summer.
 
#4 ·
There's no loss of power changing from 2long/2short to 4short stacks, been dyno proven by some members here including me, if you feel a bit experimentive i'd suggest you dyno the engine with your full system with the 2L/2S stacks then install the 4S stacks then dyno it again with no changes to the mapping. Afterwards you can further tune the fuel map & gain more power with the 4S stacks.
 
#3 ·
That is indeed odd, i thought the 05-06 stacks were also the same as the 03-04 stacks in terms of length, never knew that they're even shorter than the 58mm stacks on cylinders 2 & 3, i might try & get a set of those stacks, did you get them from ebay?
 
#8 · (Edited)
Induction tract length is a well-known science and what it really comes down to is what RPM you typically run your engine at.

It's a linear curve and this makes it really easy to pick the ideal length for your RPM range. There is a formula one company in the UK (forget their name right now) and they posted up the math to figure it out but it's dead simple - assuming you know what RPM you want the most efficiency at.

I made an Excel spreadsheet covering all the bases but I can't seem to find it....

Because the curve is perfectly linear, the ideal solution, when it comes to induction tract length, is a variable length tract. I believe Yamaha came up with a cheesy solution along those lines as their intake tract length changes between two positions depending on RPM. I say cheesy because the ideal solution would be a stepper motor arrangement where the tract length changes in 255 steps according to engine RPM :smile2:

The problem with a design like that is room.

But it's a well-proven science, it's been known for years, and it's linear. Aha - found the link;

Jenvey Dynamics

"A guide figure, from the face of the trumpet to the centre of the valve head is 350mm for a 9,000 RPM engine. Other RPM are proportional i.e. for 18,000 RPM the figure is approximately 175mm."

So as you can see, the higher the RPM the shorter you want the tract length to be, and the lower the RPM the longer you want the tract length to be.

So in a perfect world, you would want the tract length to vary in steps in keeping with the RPM of the engine or in the practical world, aim for the typical desired RPM range and make 'em that length 0:)

Honda engineers are not stupid. I went after power in this respect with a different Honda and measured the induction tract length to the intake valve center. They were off by 5mm........this led me to believe their engineers were aiming for a slightly different RPM range then what I had in mind but 5mm is nothing.

Like I said, it's very simple math and when Honda engineers design an engine they will run the math and then choose the best length according to their desired RPM range.

I found the file too. I'll see if I can attach it....
 

Attachments

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top