Velocity Stacks....probably again

[turbo_billy]

Gentlemen (and Ladies), a question for those more knowledgable on the subject than myself.
I understand the effect of playing around with the lengths of the stacks (midrange/topend) but my question is:
Are these changes performed whilst still using the standard airbox.......with or without air filters.......doing away with the airbox completely and just running open stacks........?
If someone could fill in the blanks I would be extremely grateful. I appreciate that some rejetting (or remapping) would be involved but would like to know a little more on the subject.
Thanks in advance.
Regards
Tim

[AMCQ46]

With the standard honda ones, The longer length optimises the harmonics in the air pulses to be most efficient at mid rpm, and the short ones do the same for high rpm.
The billet ones that muppet imported are fitted in std air box using in my case a BMC street filter (higher flow than standard, but lower than K&N). These billet ones are a copy of the HRC race parts and as well as being close to the longer one in lenth, they are shaped with serious aerodynamic curves and clearly flow more at all rpm.
I already had a dyno jet kit fitted for the filter and pipes and it doesn't feel like it needs much more than a tweak on the airscrew to optimise for the new velocity stacks.

Does that help?

[lloydie]

You keep the air box


Sorry officer
The voices made me do it

[agentpineapple]

everything stays the same, you just change the velocity stack/trumpets to whatever you want, i would recomend a more free flowing air filter.....k&n or bmc or pipercross...... but then you would probably need some rejetting and lighter more free flowing exhaust cans. where will it all end

[lloydie]

everything stays the same, you just change the velocity stack/trumpets to whatever you want, i would recomend a more free flowing air filter.....k&n or bmc or pipercross...... but then you would probably need some rejetting and lighter more free flowing exhaust cans. where will it all end

it don't end I'm already thinking about. +1 pistons and porting&polishing


Sorry officer
The voices made me do it

[tony.mon]

everything stays the same, you just change the velocity stack/trumpets to whatever you want, i would recomend a more free flowing air filter.....k&n or bmc or pipercross...... but then you would probably need some rejetting and lighter more free flowing exhaust cans. where will it all end

it don't end I'm already thinking about. +1 pistons and porting&polishing

Been there, done that, back to playing with airboxes and filters.

Next games are about crankcase porting, possibly pressure reduction in the cases, but definitely exhaust port rerouting.
By which I mean that the actual exhaust port needs moving sideways; as standard they are offset to one side, and only one of the two valves is directly in line with the port, but the other is hidden.

Simply moving the port to a more central position should liberate some power.That's what the SP1 and 2 have, and they develop a fair bit more power with much the same engine architecture.
But it's a lot of work......

[edds11]

tony, how far over can you move/elongate the exhaust port before you hit the water jacket.......nervous time on the dremmel me thinks

[tony.mon]

Nowhere near far enough, so you will end up removing a section of the outer waterjacket and fabbing up a section to replace it, which will need welding in place.
But that new section can contain a replacement ex clamp stud position, as you'll lose the old one by chopping the section of head out.

No idea if it'll work, but it looks like a good game to play, doesn't it?

By work, I mean liberate more power...
Should do, though.
Looking at the big bore race exhausts, the narrowest part, and so the bit that limits gas flow most, is the exhaust port.

Although on the SP1 they had a round port, (a bit larger diameter than the Storm, but centrally placed between the two ex valves)and the SP2 had a smaller, oval one- not sure I understand the theory behind that, but it seems to work.