There is a company that makes them, Hals Speed Shop

Read this thread and if you do a search you will find plenty of different opinions on the stack issue.

On another note, how are you going to monitor the results of your testing?

 

alright thanks

 

Alright, now the factory velocity stacks are tuned to compensate for the different lengths of the factory exhaust pipes correct? Is there a tuneable length velocity stack kit out there? cause anyone with a 2 into 1 pipe or equal lenght duals are technically having the wrong variation in the lengths of there stacks... I have a cfr pipe and am planning on experimenting with different lengths, cause two equal lenght stacks with cause an offset out the other end not?, since the front head pipe in considerably shorter than the rear, wont that be making less backpressure in the front also? If this is right than that would be the only way to smooth out the pressure and such throughout the engine correct? Anyone else's 2cents is appreciated...:notworth:

i have done some dyno testing of velocity stack length.(plan on much more) on a stock motor with v-mods or any kind of slipons i`ve tested the stock length stacks seem to work the best. but on our race motor with an equal length exhaust it seemed to like equal length velocity stacks too with the length being critical. we have lost as much as 9hp with different length stacks. a 1/2 inch difference in length can make a huge difference. if you would like an education of sorts on velocity stack length down load a ten day trial of engine analyzer 3.2 or 3.5 from performancetrends.com. enter all the data for your v-rod and start playing with stack length. the 110 cvo that we ran at bonneville last year we tested every length velocity stack that would work in the stock air filter housing(production class and the air filter housing must appear stock from the outside.) and found that a length change of 1/2 inch could gain or loose 6hp.

 

i have done some dyno testing of velocity stack length.(plan on much more) on a stock motor with v-mods or any kind of slipons i`ve tested the stock length stacks seem to work the best. but on our race motor with an equal length exhaust it seemed to like equal length velocity stacks too with the length being critical. we have lost as much as 9hp with different length stacks. a 1/2 inch difference in length can make a huge difference. if you would like an education of sorts on velocity stack length down load a ten day trial of engine analyzer 3.2 or 3.5 from performancetrends.com. enter all the data for your v-rod and start playing with stack length. the 110 cvo that we ran at bonneville last year we tested every length velocity stack that would work in the stock air filter housing(production class and the air filter housing must appear stock from the outside.) and found that a length change of 1/2 inch could gain or loose 6hp.

Have you done any testing on a stock 1130 with equal length header 2:1, like the rinehart?

 

Have you done any testing on a stock 1130 with equal length header 2:1, like the rinehart?

no we raced the stock motor through 03 and then built an 88 incher. when it was stock we ran a set of bubs that were one of the first pipes available for the 02. we removed the baffles and shortened the front pipe to the same length as the rear. they ended up 20 inches long with a megaphone on them. we did very little velocity stack testing on the stock motor. we ended up making 118hp . the stock 02`s made around 93hp on our dyno we had the throttle bodies bored to 55.5 mm. nobody was boring throttle bodies at the time that we knew of. i was afraid to have them bored any bigger. with a completely stock chassis front pegs and stock wheels we ran 11.09et@119.9mph. the only change to the chassis was chain drive. we geared it for 120mph at 9000 rpm in 5th.

 

Hey Doc....just really curious....I have the SERT, the Rinehart 2-1 pipes, & your MAP for the SERT. I was thinking of running topless with just the K&N cone filters, etc. In your opinion, should I just leave the velocity stack in the OE form, or do you recommend changing it altogether to one from Hal's? I just want to make sure that I run the most optimum performance set-up.

Thanks for your time!

 

Hey Doc....just really curious....I have the SERT, the Rinehart 2-1 pipes, & your MAP for the SERT. I was thinking of running topless with just the K&N cone filters, etc. In your opinion, should I just leave the velocity stack in the OE form, or do you recommend changing it altogether to one from Hal's? I just want to make sure that I run the most optimum performance set-up.

Thanks for your time!

My map is tunned for equal length stacks so the individual filters would work well I guess. How will you filter the intake area for the IAC?

 

Gees, didn't even think of that

 

no we raced the stock motor through 03 and then built an 88 incher. when it was stock we ran a set of bubs that were one of the first pipes available for the 02. we removed the baffles and shortened the front pipe to the same length as the rear. they ended up 20 inches long with a megaphone on them. we did very little velocity stack testing on the stock motor. we ended up making 118hp . the stock 02`s made around 93hp on our dyno we had the throttle bodies bored to 55.5 mm. nobody was boring throttle bodies at the time that we knew of. i was afraid to have them bored any bigger. with a completely stock chassis front pegs and stock wheels we ran 11.09et@119.9mph. the only change to the chassis was chain drive. we geared it for 120mph at 9000 rpm in 5th.

Hmmm...I've got a set of Bubs Jug Huggers. How should I run my stacks since the pipes are not equal length?:ride:

 

Stock configuration, long front short rear.

 

Thank you sir!

 

This is odd. Check this website out, http://www.velocity-of-sound.com/velocity_of_sound/calculator3.htm they have a velocity stack calculator that doesn't take exhaust into account at all. They use intake cam duration, optimum RPM and intake runner diameter along with the "wave number" (recommending to use the "third wave" like NASCAR engineers do because the 1st and 2nd are too long to be practicle). ??????? WTF? Looks like quality hand made stuff, maybe they know what they're doing. Sounds like :blahblah: to me, anyone understand what they're talking about exactly?

Looking at their site does make me wonder what would happen if the stacks we use had a much more pronounced bell on the end of them, they claim it dramatically increases torque throughout the RPM range.

 

You'll notice they mention the 'Desired Optimum RPM'. Well, the exhaust system is also tuned for the same 'Optimum RPM'. This is what links the two even though they are tuned independantly. Matching the intake and exhaust Optimum RPM will give you the most volumetric efficiency (total amount of air/fuel mixture sucked in during the intake stroke devided by the volume of the cylinder).

If it's done right you get a supercharging effect (more than one cc of air/fuel mixture per one cc of displacement). This make more power!

 

This is odd. Check this website out, http://www.velocity-of-sound.com/velocity_of_sound/calculator3.htm they have a velocity stack calculator that doesn't take exhaust into account at all. They use intake cam duration, optimum RPM and intake runner diameter along with the "wave number" (recommending to use the "third wave" like NASCAR engineers do because the 1st and 2nd are too long to be practicle). ??????? WTF? Looks like quality hand made stuff, maybe they know what they're doing. Sounds like :blahblah: to me, anyone understand what they're talking about exactly?

Looking at their site does make me wonder what would happen if the stacks we use had a much more pronounced bell on the end of them, they claim it dramatically increases torque throughout the RPM range.

just tried it and got the same number as i got from my engine analyzer program. go figure. by the way performance trends have free 10 day trials of engine analyzer you can download. you need to have all your engine data to use the program. so far most of the things the program told us have worked but not every thing has. and a few things that didn`t jive exactly was the fault of my data entry. at least it is more fun than a video game. the hp numbers generated are crankshaft hp. multiply by .85 and get rear wheel aproximately. the 110 cu in dyna we ran at bonneville made exactly what the program said it would and we designed a lot of the set up from the program. our v-rod also makes the hp predicted by the program .but the program led us to change the cam on the bonnevile motor but it didn`t respond like the program predicted.we are still trying to figure out why.

 

So if there were some way to auto-adjusting velocity stacks that changed lengths according to throttle/rpm it would be like running a super-charger and we could potentially be getting 100+ VE at all points!

K someone with some mechanical know-how, get to work! That would still be technically naturally aspirated too!

 

So if there were some way to auto-adjusting velocity stacks that changed lengths according to throttle/rpm it would be like running a super-charger and we could potentially be getting 100+ VE at all points!

K someone with some mechanical know-how, get to work! That would still be technically naturally aspirated too!

Hey again,

It wouldn't supercharge at all the RPMs but it would help maximize the VE.
The intake runners (manifolds) and exhaust (head pipes) could not be variable length unfortunately.

Your idea is a good one though. If there were a way to adjust the height of the velocity stacks that would expand when there's intake vacuum and shrink when there's intake pressure we would have what you are talking about. I think something like this exists on some Jap super sport bikes.

I've been thinking of this for a while. It would be really cool...

 

I just realized, the Kuryakyn Hyperchargers work the same way - on vacuume.
When there is intake vacuum the flaps are closed and they open as the vaccume decreases. Based on this, I'm sure it could be done.

I'd think you need some kind of spring loaded vacuume actuated device that would lift an outer stack as the vacuume decreases. The inner stack could stay fixed and the outer stack can rise. If both stacks are 2.5 inches the min height would be 2.5 inches and the max height could be 5 inches. The problem is calibrating it to know what height you should have for the right vacuume.

I wish we could get the HD guys to adopt this idea. Well, more likely Buell would do it first!!!

 

So if there were some way to auto-adjusting velocity stacks that changed lengths according to throttle/rpm it would be like running a super-charger and we could potentially be getting 100+ VE at all points!

K someone with some mechanical know-how, get to work! That would still be technically naturally aspirated too!

formula one cars have used in the past velocity stacks that changed length and diameter with rpm. how the hell the did the diameter thing i have no idea.i don`t know if they still do that or not. at one time they also used a pnuematic system to open and close valves controlled by the ecm. no camshaft. they could change valve lift and timing to optimize ve at all rpm`s. i believe that was outlawed as being too expensive. must been very expensive to do if it was too expensive for formula one.your idea would work but would be tough to do. you could do an adjustable length stack with an electric solenoid and an rpm switch. a long length for lower rpm`s and short for high rpm and set the rpm switch to switch lengths at the rpm were hp curves would cross.to find the crossover point overlay the dyno sheets of the short stacks and the long stacks. if you wanted to get totally carried away you could use some type of butterfly in the collector like some of the modern sport bikes to increase back pressure for more torque at low rpm`s and open it at higher rpm`s for more hp. sounds like a lot of work but you sure could have some kind of bragging rights if you make it work.

 

i have done some dyno testing of velocity stack length.(plan on much more) on a stock motor with v-mods or any kind of slipons i`ve tested the stock length stacks seem to work the best. but on our race motor with an equal length exhaust it seemed to like equal length velocity stacks too with the length being critical. we have lost as much as 9hp with different length stacks. a 1/2 inch difference in length can make a huge difference. if you would like an education of sorts on velocity stack length down load a ten day trial of engine analyzer 3.2 or 3.5 from performancetrends.com. enter all the data for your v-rod and start playing with stack length. the 110 cvo that we ran at bonneville last year we tested every length velocity stack that would work in the stock air filter housing(production class and the air filter housing must appear stock from the outside.) and found that a length change of 1/2 inch could gain or loose 6hp.

i have said this before and the more i read your threads the more i will say it.......:notworth::notworth:

 

http://www.1130cc.com/forums/showthread.php?t=11765

Check out this thread from 2004.