Quote from: brad black on June 23, 2008, 06:47:16 AM
welcome to my world.  expect there to be a lot of error in your trial.

you could make up a base section and a top bellmouth and use exhaust tubing for the stacks.  cut a diagonal slit section out of one side, then push it together and weld up the seam - cheap tapered tube.

or just run straight tubing and have multiple lengths on hand so you can do consecutive dyno runs, just swapping the middle bits.  don't stop to look at the results and it won't take too much time to get the results.  possibly a good way to get a feel for what length does.

I'm hoping a good book and an old-timer can get me half the way there.  I'm sure someone somehwere has done this before. 

i wouldn't waste any time on books or previous experience, unless it's from ducati 900 with fcr carbs.  even then it depends on how well the bike was set up and how good the testing procedure was.  going back thru old dyno runs these days i often pick more annoyance over poor procedure or things i should have done than useful information.

make up a quick change trumpet system of some sort and do runs one after the other, then finish with where you started, just in case engine heat, etc has moved the info somewhat.  don't worry about tuning for each set up - that can come later.  and with carbs it won't matter too much anyway, unless you get really bad resonance, etc in an rpm band.  there won't be any magic length, just a best compromise based on what you want.  test as long and short as you can too - alway go to the end points, even if they're somewhat illogical.

once you get a length then you can work on taper, etc, from there.

As Brad mentioned, I'd just take a base as it will be pretty much standard.  Use straightwall tubing -- ixnay on taper as the result isn't worth the experimentation as I discovered.  Then the bell/mouth opening -- a nice wide radius actually helps here. (based upon my IMSA GTP days when we varied and had the budget to experiment with) 

Basic premise is thus:  short trumpets make more horsepower -- longer ones make more torque.  Ideal world of course.  In the IMSA day (as well as playing with old CanAM cars), trumpets varied in length to trick the engine into a wider powerband.  A v-twin only had two intakes and no gain.

I'll machine up two new ones for mine in a few weeks for my DesmoDevil.  I'll document the process when I make them on the mill/lathe.

ok,  Pods look cool, preformance is debatable... I still want pod filters but here is my question.


What has everyone that removed there airbox done with the return hose from the crank case vacuum thingy (the big black box with a hose entering it from the crank case and another feeding back into the airbox)  I thought that was there to help with the whole PCV issue and that removing that is bad.  If I go to pods, I lose a connection for a hose.

BTW, not much different but I am currently on an 01 900ss. 

Thanks

Tim

Quote from: vampireduc on August 24, 2008, 03:32:12 PM
ok,  Pods look cool, preformance is debatable... I still want pod filters but here is my question.


What has everyone that removed there airbox done with the return hose from the crank case vacuum thingy (the big black box with a hose entering it from the crank case and another feeding back into the airbox)  I thought that was there to help with the whole PCV issue and that removing that is bad.  If I go to pods, I lose a connection for a hose.

BTW, not much different but I am currently on an 01 900ss. 

Thanks

Tim

Thats pretty much it. If you go pods, you HAVE to get the crank case breather, unless you can build your own contraption.

I've never dyno'd the difference, but whenever I've switched to pods I've had to richen the mixture. Most of my experience is with 900 style motors and FCRs and foam filters - the larger the better. I'm doing some experimenting with intakes, velocity stacks, and ram air, but won't have anything definative (assuming there is such a thing) for quite awhile. If you're going to Daytona in March, I should have some pretty good data to share.

Does anyone know the required flange ID I would need for an '03 620?  I want to go with the UNIs like dlearl, but I'd rather not take the airbox off until I'm ready to throw the pods on.

I'm curious about the noise value. I'm currently running an open airbox and find it uncomfortably loud.
With an open airbox the sound appears to be directed upwards straight at the rider, with pods is it any less loud for the rider?

Depends on ECU activity, e.g. How will ECU respond?