Ducati Monster Forum

OK, there have been so many threads about this, but I've still not got a definitive answer.

Which is better, Pod Filters or an Open Airbox?

Pods look better everytime.


... and when I say that I'm talking about opening up the frame from a profile view.

open airbox is cheaper, so gets my vote because i'm a tightarse and like having somewhere for my battery to go without too much effort.  pods would be way too much effort for me, even if it does help jetting changes.  because i try to avoid them too.  too much effort.

pods with a box around them may possibly work better, but i'm not convinced of that.  a pod with a good inlet shape might have an advantage, a pod with a bad inlet shape would have a disadvantage.  most people do pods for at least partially visual reasons, so that may have an influence on which is better for you.  visual is not so high on the list for me, as the dents, scratched std mufflers and ventua rack plainly exhibit.  plus there's only one filter to clean with the open lid, but then we're back to effort adn lack of again aren't we.

i think any internet threads with "official" or "definitive" in the title are by nature largely delusional, as the ratio of experienced result to speculation is so low.  but i could be speculating.  well, i am because i haven't tried pods.  see, i've shot my argument down all by myself.  is that self centred or just an inevitable realisation?  serves me right for trying to be a know all.  oh well.

sorry for wrecking your thread howley.

I have Pods on my M900Sie
Pro's  better sound that with airbox
         Less plastic (about 5 lbs)
         More vintage look  ;D
I dyno'd it with K&N /Airbox and after i put the Pod's on and there was 0.5 hp difference

in which direction?

Not up  [laugh]

Where would one buy said pods (01' 750)? DIY anywhere?

Chris at www.ca-cycleworks.com has them...

I have some from TPO on my ride; love them! They sound great and clean things up...

(http://www.applewood.smugmug.com/photos/201531167_PNviJ-M.jpg)

Ok, Ive written about this quite a bit but heres my take on the whole thing:

short answer:  Pods are better, but not through the TPO kit.

Ive run both an open air box and pods and there are a few things that you have to realize about the difference between the two.  Since our bikes don't fire simultaneously, like say a Harley twin, each time one of the cylinders gulps for air, it take in the entire volume of the air box,  by switching to the tiny k&n round filters,  you giving each carb or TB a smaller volume of air to swallow at initial take off.  thereby diminishing low end torque and initial power, which in my opinion is what makes our twins so much fun to drive.  however at higher load and rpms your able to re-fill that smaller volume much faster due to the high surface area of the round filter, yielding more horsepower top end.

With this in mind, I immediately eliminated the TPO kit for two reasons,  one the tiny filter size,  two the uneven flow of air across the two filters.  after some careful measurements I bought the two largest pod filters I could fit under my tank,  to try and maintain that low end power yet keep the high top end advantage of a high flowing filter, not to mention the amazing sound they make.  Ill post up my dyno chart when i get a chance but its a significant improvement over stock with a higher horsepower top end and a steeper curve than just the open air box with a K&N panel filter.  heres a picture of my setup:

(http://img127.imageshack.us/img127/7139/pods1ts2.jpg)

my vote goes for custom setup with pods,  and i swear to god when somebody brings up velocity stacks on the tpo kit im going to smack someone.  Not set of velocity stacks with K&N branded filters is worth 200$.  my setup cost under 100 including a dynojet kit and a few extra jets.

what size filter did you use?

THat doesnt look like theres that much more interal voulme when you compare them to the TPO included pod filters. Although i agree with you 100% those velocity stacks do not make the kit cost such a ridculous amount of money. You can buy velocity stacks in premade sizes for as little was $25 a piece) Its not billet alluminum, but its all the same after you polish the inside with 300grit and hide inside your filters.

I dont want to kill TPO, but i know someone who has a set and im going to ask him to remove his velocity stacks so i can take some measurements.

I've been running no airbox -- no air filters either -- just medium velocity stacks wide open on FCR's for @4+ years.  Admittedly not the ideal situation for most people.  Loud as can be listening to them gulp the fuel while riding.

Im not 100% sure on what the exact part number is but I believe they are these ones: http://www.knfilters.com/search/product.aspx?Prod=RA-0770

When you say "medium" what size do you mean.  AFAIK, they come in 15, 25, 30, 50 and 70mm lengths. (At least they used to.  Apparently, Sudco isn't making them anymore).
I've been contemplating the same, although I'm sure the moment I did I'd hit a friggin dust storm  (which happen all too frequently here in Las Vegas).

I'm in the process of doing some mods, and won't be able to dyno anything probably until I return from a working trip mid-july. But a couple of thoughts occured to me.


The internal volume of one cylinder on my m900 is 450cc.  The volume of the stock airbox is much larger than that.  On top of that, opening the box and replacing the top with a K&N, IMO, completely elimates any restrictions and/or harmonic resonance issues/benefits associated with the closed airbox.  At that point, the only limiting factor is the stock velocity stacks/airbox adaptors that most set-ups use. (including yours, if I'm seeing the photo correctly)


One of the things air likes to do least is turn corners.  That's why I theorize that SOME KIND of velocity stack is beneficial.
(http://upload.wikimedia.org/wikipedia/en/8/8a/Velocity_stack_workings.GIF)
It's also why I feel that any filter that blocks airflow directly into the venturi is,well, blocking air flow.   Especially if it's too close to the opening of the velocity stack.

That's why I opted for UNI foam filters rather than K&N ones with a top.
(http://www.unifilter.com/home%20page/pods_copy.jpg)

When I get a chance to run the dyno tests with several combinations of pods/stacks I'll post the results.  I'm not holding my breath for any huge gains.  I thinking .5-2 hp like supertjeduc reports are going to be about it.  Like he said, it's more about losing the 5 lbs of plastic.

Airbox lid was open?

i think all the k&n have a velocity stack incorporated in them.

No but air/fuel was with airbox and Pods about 13 to 13.5

OK.
I think opening the lid is one of the most substantial changes you can do.
OEM compared to open lid w KN & Dj kit, what a difference!

I'm still not convinced when it comes to velocity stacks,  mostly because every carburetor out there uses the venturi effect to create vacume to add fuel, basically if you look at your carb, the tapered shape entering the carburetor is a velocity stack,  my filters are attached directly onto the carbs, I don't see the point of adding another stack above the one already cast into the carbs.  The only way I could see the velocity stack principal working significantly more than stock would be to continue the taper of the outer edge of the carb to create a bigger inlet into the carb itself.

And my "fresh from the Dyno" data bears that out.  Unfortunately, I don't have a strictly "apples vs. apples" comparison, as I've added FCR's and DynaCoils as well but here's the results. 

Pre-FCR/DynaCoil  71.8 hp and 57.8 ft/lbs of torque.


FCR's+Dynacoils with UNI pods with OEM velocity stacks inside: 70.4 hp and 54.4 ft/lbs.

FCR's + Dynacoils with UNI pods only 73.2 hp. and 56.9 ft/lbs

All these are with the Gallaseti 2-1 exhaust.  I had better torque, and less hp with the RoadRacing exhaust, which I'm going to put back on and re-test.


(http://crs-america.smugmug.com/photos/224645274_vzfEp-L-1.jpg)
OEM carbs with Dynajet kit, open box/K&N, RoadRacing exhaust.



On an FCR, that radius is machined into the airbox adaptor.  It is replaced by a velocity stack.  You don't have both, one on top of another.  And you're right, of course that wouldn't work. (Which is why, I think, the pod with the OEM velocity stack on top of the airbox adaptor, pardon the pun, sucked.)

Machined my own -- 85mm with a very radius'd shape on the end.  Didn't dyno test as of yet as I will do a few more exhaust modifications first.  Seat of the pants testing tells me the shorter ones I had machined before made more power.  Again -- not validated on the dyno as of yet.

I talked with Alex O. awhile back in regard to trumpets after my experience.  He has run the Sudco ones before -- but got better #'s using the FCR very short ones.  The engine had Guy's MBP heads and a bunch of work on it and is not a normal engine. 

I've known of quite a few others that have done what we do.  Some use a pre-filter airsock ONLY to keep the big things out of the stacks.

I've got REALLY BIG K&N's on my 620. I doubt they improve the performance of the machine in any way, but they are inexpensive, look really cool, and are louder than my cored exhaust when you wank the throttle. Makes just ridin' around a lot more fun...


(http://jdude.brinkster.net/ru1420.jpg)

ok, I really want to see a picture of your bike from the side,  right now, Im almost sure that the top cylinder pod filter would look like a penis for you motorcycle  [evil] 

if you were going to play with velocity stacks on a carb bike i think you'd need to mke some that go into the std carb opening, as the transition from carb mouth to the larger diameter will all but kill the effect of the stacks.  anytime you get a big change in cross section you get big flow speed changes and wave reflection.  you don't want any steps if you can help it.

the carbed 2v motors have a long inlet system downstream of the throttle, but most of the injected bikes have trumpets upstream of the throttle that would make the overall system nearly as long.  ST2 are one model that doesn't.

removing the trumpets from the throttle bodies and running pods will shorten the inlet tract on nearly every model.  usually shortening an inlet tract reduces the peak torque value, but widens the spread of torque across the rpm range.  so that might be part of the issue as far as dyno tests go, and they're not getting revved high enough to make an obvious difference.

Well, if it does, at least its a healthy-sized penis:

(http://jdude.brinkster.net/chop.jpg)

eh must have just been the angle,  killer looking bike btw, love the solo seat  with the shorty pipe and headlight,  thats a winning combo right there.

Brad, I don't know who you're addressing, but here's where I'm at.

The FCRs come with this type of airbox adaptor:

(http://www.allensperformance.co.uk/images/fa-fcr2-68.jpg)

Using it with the rubber bit that apapts the OEM MIkuni's to the airbox (in the shape of a velocity stack) didn't work well, as you suggest.

Where I'm looking to go is replacing that entire set-up with velocity stacks, which replace the radius of the adpator with an entirely different one, in a variety of lengths.

(http://www.allensperformance.co.uk/images/groups/fcr2.jpg)

what yourself and psychochild were saying about carbs pretty much.  wonder what a small diameter trumpet inside a filter that ran from the 38mm carb entry out would do?  like those fcr ones you show - they're a true extension of the carb itself, not another bellmouth twice as big as the carb entry which has its own bellmouth.

That's what I'm looking to find out, as soon as I can find a source for them.  According to Chris, Sudco no longer carries them.  I'm hoping another dealer, like the one I lifted the pics from, still has some in stock.
In the meantime, I'm trying to decide which length to go with.  They're kind of expensive to be doing some trial and error dyno tuning.

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

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?