How much do the length of the intake "tubes" from the filter (pod filters) to the throttle bodies matter? Do they need to be equal?
I ask because I have to move the horizontal filter, and to do so would need to make a 90 degree elbow. This would make it significantly longer.
Equal is ideal and should be attained as often as possible. Unless they are equal lengths, you cant synchronize your throttle bodies by balancing the negative static pressure of each cylinder (carb stick tool or manometer)
That being said, its not required but preferred. Unless you have a drastic difference in the intake lengths, you may not notice that much of a difference.
My personal suggestion is to get a TPO Beast Kit if you can. They come with machined aluminum velicity stacks that have worked great for my pod setup.
I basically have 3 options.
1. Run unequal lengths
2. Run equal lengths (but add unnecessary length on one, thus adding weight)
3. Run open venturies
Check out ITG air filters. They have a full range of air horns and spinnings and flanges and should have something that will work for you.
http://www.itgairfilters.com/downloads/ITG2009Catalogue.pdf (http://www.itgairfilters.com/downloads/ITG2009Catalogue.pdf)
Don't forget that you are going to shift the HP and TQ curves depending on how much you lengthen /shorten
Preferance is "equal length" but the equalizer is the air filter assembly itself.
I usually just run my own custom machined velocity stacks with a pre-filter screen at most. Never a problem for myself for many years. But plan on tweaking with your fuel adjustments to make work.
Quote from: TiAvenger on April 15, 2009, 03:05:58 PM
I basically have 3 options.
1. Run unequal lengths
2. Run equal lengths (but add unnecessary length on one, thus adding weight)
3. Run open venturies
My 2 cents worth (also, we have organized resistance and aren't going to answer any more questions 'til you post pictures. :) This is your own doing, since you voluntarily posted the epic life-changing docu-drama of the lathe work and we need more of this).
Any additional weight gain by adding length to one is going to be so insignificant that it won't make any measurable difference in your bike's performance. A difference in length may make a slight difference in engine performance, so you should focus on engine performance and do the best you can to make them equal length.
I think running just open venturi's will sacrifice some performance since it helps if the air enters in a smooth path provided by the intake tubes and also you get some amount of tuned ram effect from the stacks. I like MotoCreations suggestion of old school straight velocity stacks with just pre-filter screens. Sounds like you will wear the motor out in short order but you won't unless you're riding in sand or dirt all the time.
If you can't find anything suitable in the catalog link that gage posted, if you wanted to bad enough you could probably turn or spin a set of aluminum velocity stacks on the lathe. I've never tried metal spinning but always wanted to. But then you probably want to finish this project bike while you're still young enough to ride it...
the only thing it will impact is dynamic tuning, and how it will impact that you'll need to test to detirmine. it will make no difference at idle, the air flow volume is way too low. having them different lengths might spread the torque band a bit at the expense of peak torque - could be a good idea. run the cam timing different too to match, more advanced on the long runner cylinder.
it'll really need individual cylinder tuning to make the best of it, or to reduce the negative impact as it may turn out. personally i wouldn't be too worried about it. if your doing it for a certain look or whatever then that's the priority and anything else is to be worked around or minimised in terms of negative impact. given you're modifying an existing design there's always compromise, and the reality is in the end you're just going to make it work.
velocity stacks would be the simplest answer, I'm a bit hesitant though, how will the engine hold up to wet environments?
QuoteMy 2 cents worth (also, we have organized resistance and aren't going to answer any more questions 'til you post pictures. Smiley This is your own doing, since you voluntarily posted the epic life-changing docu-drama of the lathe work and we need more of this).
Not much to show except for a huge chunk of styrofoam that Im shaving down. You' ll get your preciousessss when I have something to show. [laugh]
My old Triumph has open air filters sticking out each side, right in wind and rain slipstream. Not open velocity stacks, but K&N filters. Any rain water hitting the filters gets sucked right into the engine. I've ridden it through some major rain (always amazed that nothing shorted out and went up in smoke) with no known ill effects. A little moisture in the air makes for better running and I think it'd take a lot of water to do real harm.
But I don't know for absolute sure that your Duc would be OK. Also, I think MotoCreations said his specials use open stacks. Maybe he can comment on the water.
Quotehaving them different lengths might spread the torque band a bit at the expense of peak torque - could be a good idea. run the cam timing different too to match, more advanced on the long runner cylinder.
I don't know if it ever got built but I remember hearing of an idea to build a twin with one cylinder having short stroke and large bore, the other with longer stroke and smaller bore, with corresponding valve timing.
my vote: machined Velocity Stacks
if only we knew someone with a lathe - then we could make them ourselves [cheeky]
*fine print: this is not my bike, nor would i do that to my own street bike. I just think machined velocity stacks are badass!
Quote from: MrFry - Cycles on April 16, 2009, 12:07:22 PM
my vote: machined Velocity Stacks
*fine print: this is not my bike, nor would i do that to my own street bike. I just think machined velocity stacks are badass!
Im thinking that or carbon fiber ones. [evil]
The sooner I bomb the 750 motor, the sooner I can put a 800 in. [evil] [evil] [evil]
Quote from: TiAvenger on April 16, 2009, 12:10:33 PM
Im thinking that or carbon fiber ones. [evil]
The sooner I bomb the 750 motor, the sooner I can put a 800 in. [evil] [evil] [evil]
(http://www.cyrilhuzeblog.com/wp-content/uploads/carbon.jpg)
http://www.cyrilhuzeblog.com/2007/07/08/carbon-fiber-velocity-stack/ (http://www.cyrilhuzeblog.com/2007/07/08/carbon-fiber-velocity-stack/)
originally made for harley - i'm sure it could be adapted
Adapted?
Hell no, Im going to start making the plugs this weekend.
I'm machined and made a few in carbonfiber (via mold) as well over the years for myself and customers. Main thing that I've seen via the dyno on my own bikes is that the larger radius'd upper lip always generates better max rpm power. Anything with a sharp lip on it -- not as good. But as soon as you put an air filter on it, you need a proper edge for attachment for sealing purposes.
Thus why I usually use the sock-style pre-filter assembly with a skeleton wire support beneath to keep from sucking it down the intake. Never a problem with dust or water. Essentially the pre-filter is to keep out big things that might muck up jets, block slides/butterflies open or rocks that might hit the valve/piston itself.
With my personal DesmoDevil, I'm running velocity stacks only with no sock pre-filter or anything. The intakes are more protected by the wiring harness/tank enclosre then on a Monster, etc. Never a problem in riding in dusty Arizona or elsewhere for the past five years. A bunch of my customers run theirs the same way with EFI, FCR's or regular carbs. Everyone else uses a pre-filter sock due to the low clearance it requires.
note: we regularly run the F1 vintage racecars, vintage Ferrari's/etc for racing / road use without filters most of the time. I honestly can't remember in 20+ years of getting anything stuck in the carbs/EFI/mechanical FI'ers.
One cavaet -- intake "honk" is really loud with velocity stacks only. (or with a pre-filter only) Too much for some folks. You are forwarned.
Second cavaet -- if your engine "burps" when cold (ala FCR's etc), the air/fuel get spit back out the velocity stacks and can cover things or light smoke out from beneath the tank. With air filters, you almost never notice this happening. You will without air filters!
As mentioned before, you do need to correctly adjust the air/fuel ratio via tuning. Don't just slap on a set of open velocity stacks and assume your bike will run with the correct air/fuel ratio -- it won't.
QuoteSecond cavaet -- if your engine "burps" when cold (ala FCR's etc), the air/fuel get spit back out the velocity stacks and can cover things or light smoke out from beneath the tank. With air filters, you almost never notice this happening. You will without air filters!
Even on an injected engine?
Quote from: TiAvenger on April 16, 2009, 12:48:31 PM
Even on an injected engine?
Proper tuning applies to carbs and efi. You'll need to get whatever you build/buy/decide upon properly tuned man.
I meant the burping [laugh]
You should know that I should know better than that. [cheeky]
how are you controlling fuel/air?
megasquirt micro?
Quote from: MrFry - Cycles on April 16, 2009, 01:10:22 PM
how are you controlling fuel/air?
megasquirt micro?
1.5 ecu with a flightcycles motocard.
I'm really not at that point yet. [laugh]
Quote from: MotoCreations on April 16, 2009, 12:45:28 PM
Anything with a sharp lip on it -- not as good. But as soon as you put an air filter on it, you need a proper edge for attachment for sealing purposes.
ITG has filters with a proper velocity stack incorporated into the base. I bought a couple over the winter to do a pod setup on my 02 S4. It is going to wait until next winter when the engine gets rebuilt.
It would be the best of both worlds - Flitration and improved airflow/looks
ya know... now i'm thinking a set of aluminum stacks on the CB might be the way to go
Quote from: MrFry - Cycles on April 16, 2009, 01:29:00 PM
ya know... now i'm thinking a set of aluminum stacks on the CB might be the way to go
should I buy more metal? [evil]
Quote from: TiAvenger on April 16, 2009, 01:30:55 PM
should I buy more metal? [evil]
seeing as i can't find anyone selling any...
lets hold off until the project can start again ;D
Quote from: MrFry - Cycles on April 16, 2009, 02:08:21 PM
seeing as i can't find anyone selling any...
lets hold off until the project can start again ;D
Hurry up and move then. [cheeky]
Quote from: TiAvenger on April 16, 2009, 02:13:17 PM
Hurry up and move then. [cheeky]
i'm tryin' i'm tryin'!
Quotemegasquirt micro?
Excellent idea. We need to add it to his list ;D Do you know anyone running one on a Duc?