Anyone played with Velocity Stacks?

[Bleh]

Now I have the bike (seemingly) running right, I can start thinking about my head improvements I'd like to make some time over the next year. Obviously, when improving the head, your main target before cams, shims, performance gasket, valves and springs is to improve the flow of air getting in...

So with that in mind, I was wondering if anyone has messed about with their velocity stacks and what combinations they've found beneficial?!!

As always, thank in advance

[lloydie]

To get them to work you need to do head work .

[Bleh]

They look pretty... nice flared edge a bit of an understatement, did you get them made or buy them?
Would you happen to know how much you increased your flow coefficient by?
Guessing you've had ports polished as a minimum... What else have you done and what sort of gains have you achieved?

[Bleh]

Never mind... just so your post on the other thread

[VTRDark]

So when's the soil going down.

Bleh a fair few of us have taken the cheaper option of replacing the shorter front stack with another standard long stack. This at first gives a noticeable seat of the pants feel in the bottom to mid range. I say at first because as one gets used to things you don't notice them any more

Standard short and long = Average throughout, so an even balance

Two Standard long stacks = low to midrange, so a little more bottom end

Two Standard Short Stacks = Midrange to top, so a little more top end

Two Dr Honda's as in Lloydies pic = Similar to standard long and short, maybe a little more throughout. With some headwork done one could benefit more

I had a go at making some out of fibreglass
http://www.vtr1000.org/phpBB3/viewtopic ... honda+copy

(:-})

[gl_s_r]

Would you happen to know how much you increased your flow coefficient by?

No point in asking questions like this as I don't think anyone on the forum really has the mechanical means of measuring it... Nor do they probably have a nice CFD package and a nice number crunching puter to go with it.

[agentpineapple]

Would you happen to know how much you increased your flow coefficient by?

No point in asking questions like this as I don't think anyone on the forum really has the mechanical means of measuring it... Nor do they probably have a nice CFD package and a nice number crunching puter to go with it.

I have a Casio calculator....

[Bleh]

I had a go at making some out of fibreglass
http://www.vtr1000.org/phpBB3/viewtopic ... honda+copy

(:-})

Did see the post... Looked time consuming. But here's a thought... Take an inner AND outer mould and maybe buy some pre-preg carbon fibre so you can press make some sturdy stacks - could be a nice little earner if you're good with your hands!

As far as flow coefficients go... I can calculate them simply enough. In fact, I have a basic excel model which is in development which can calculate flow coefficient per valve lift IF whoever is flow benching the head is willing to give the readings to the customer.
I could put the simpler part (flow bench testing section) up for anyone interested in having it.

So much can be determined and fairly accurately with flow bench readings but more importantly, increasing your flow coefficient is pretty much guaranteed performance and it's nice to see how much you have improved the head by!

I have a slightly more advanced model, again, still in development, that can establish Cf per cam angle (therefore valve lift per cam angle) which can determine the mean Cf for a whole rotation of the cam and from that you can predict your new max power RPM etc so you can get an idea of improvements before you pay a bean for a dyno test. The downside to this model is you need to know the cam profile/ lift per degree (preferably) so you need to take 360 readings first... Time consuming to say the least!!

The model I am slowly working on is only considering a single cylinder at the moment (which is ok for the VTR I suppose) but hopefully in the next few months, it will incorporate up to four cylinders and be quite extensive with macros and VBA's for ease of use!

[lloydie]

I could put the man dog in the air box and ask

[Tweety]

Would you happen to know how much you increased your flow coefficient by?

No point in asking questions like this as I don't think anyone on the forum really has the mechanical means of measuring it... Nor do they probably have a nice CFD package and a nice number crunching puter to go with it.

I do... I just can't be arsed to do it... I put the bike on the dyno and fiddle... If the bottom line increases, and the torque stays high and smooth, I'm happy... It has worked for a dozen vehicles thus far, so I'm not sure why I have all the other gizmo's really...

[Max]

I've been running 2 short stacks for a few years now, I have lowered the gearing (15/44) and it seems to help it run better near the top of the rev range

[VTRDark]

I could put the man dog in the air box and ask

PMSL
That poor dog takes some abuse.

(:-})

[fabiostar]

so do we have and answer lol... can you just fit two longs or two shorts and get an incease without rejetting?

[gl_s_r]

Would you happen to know how much you increased your flow coefficient by?

No point in asking questions like this as I don't think anyone on the forum really has the mechanical means of measuring it... Nor do they probably have a nice CFD package and a nice number crunching puter to go with it.

I do... I just can't be arsed to do it... I put the bike on the dyno and fiddle... If the bottom line increases, and the torque stays high and smooth, I'm happy... It has worked for a dozen vehicles thus far, so I'm not sure why I have all the other gizmo's really...

This makes perfect sense and I prefer this method as all we are after is a goal and that is more power. The changes we make either move us towards that goal or away from the goal. It doesn't matter if the Cv is faster or slower on a stack but more importantly if the change moves you towards that goal. All the small things can be measured and maybe improved but if it works as a whole package is the question... and that is what you are finding out, the complimentary overlap of parts that improve as a package.

[VTRDark]

Wise words Mark

(:-})