Pod Filters?

Not sure how many people get that reference, but I do. Hilarious.


Also changing to pods does not make the bike louder, and certainly not enough to drown out exhaust noise. I understand what you refer to when you used removing a car aircleaner as an example.

 

The real question is why? I've read many dyno tests on motorcycles and usually they respond better to exhaust tuning than tinkering with the carbs or cams with the stock redline. My 750 has 33 mm valves and 32 mm carbs, the valve stem diameter and other restrictions in the air flow like the curvature of the ports and the valve head also play a part. The carburator venturi works by having a greater restriction between the atmosphere and the cylinder than the the port & valve. If the carburator is less restrictive than the valve & port, vacum will become zero and the airflow will reduce and the bike will slow down or sneeze back through the carbs. The factory airbox work pretty good, just the snorkel and filter element are too restrictive, you'll get more, even, flow by opening up the air inlet to the box and putting a K&N filter inside it. I went farther, it came with a price the 3000-6000 rpm acceleration faded after jetting it rich enough to stop the backrapp (no mufflers) and the mileage decreased as well. Most guys I've talked after switching to pods, never got their bikes to run right. A good set of headers (open or closed) and a k&n filter with the right jets would most likely yield as much or more horsepower and torque than anything else with stock heads, valves, cams, etc. If not I'd suggest getting a bigger engine (or a much lighter bike frame lol)

 

To answer the "why question," looks. With relocating the battery most of the wiring to a box mounted on the rear wheel, I wanted there to be nothing under the seat. Removal of the air box and the installation of pod filters was key to the look. Unfortunately, a bike that looks good but runs like crap isn't of much use to me.

There was a post about going all out and changing to EFI, this is probably a very dumb question, but here goes. Is that actually possible? My 2009 VStar is EFI and I do love that bike... although it loads up because they forgot to tell me that the Cobra pipes I put on did not have an O2 sensor so the computer has no clue how to burn the fuel every once in awhile (looks like I am taking the O2 sensor out of the stock pipes and drilling them into the Cobras this winter as well as working on the XJ).

Thanks for answering my really dumb question.

 

You can get the bike to run fine. Those who say otherwise have probably not tried. It may or may not suffer a minute amount of power on the dyno, but garunteed not enough to notice in the real world. I have 2 bikes excactly the same model year size. One with pods one factory. They both perfom the same throughout the entire power band. It just takes an ability to learn. The main thing I found was adding the stock airbox velocity stacks to the pods. Other than that, jet up, do some shimming, color tune and test ride, repeat. I had it dialed in on one afternoon.

 

MAIN FUEL JET SIZE CHANGES NEEDED PER TYPICAL MODIFICATION:


Typical Exhaust Changes:

+2 main fuel jet size for custom 4-into-2 exhaust

or

+4 main fuel jet sizes for 4-into-1 exhaust

or

+4 main jet sizes for no muffler (open headers)


Typical Intake Changes:

+2 main fuel jet sizes for single K&N filter (inside a stock airbox)

or

+2 main fuel jet size for drilling holes in the airbox with stock filter

or

+4 main fuel jet sizes for individual pod filters (no airbox)


Additional changes:

- Add up all the main fuel jet size increases and subtract 2 sizes.

- Decrease main fuel jet size by 2 sizes per every 2000' above sea level.

- Under a mis-match condition, such as when using pod filters with a 100% stock exhaust, or 4-into-1 header with stock filter and air box, then subtract 2 main fuel jet sizes.



PILOT FUEL JET SIZES CHANGES NEEDED PER TYPICAL MODIFICATION:

Pilot fuel jet size changes are related only to the change in main fuel jet sizes according to the main fuel jet size formula described above. Note that this pilot fuel jet rule is for the main fuel jet size change BEFORE any main fuel jet altitude compensation is factored in:

Increase the pilot fuel jet size +1 for every +3 main fuel jet size increases.

Additional changes:

- Decrease pilot fuel jet size by 1 for every 6000' above sea level. This should be a good place to start. You use the pointie end of the screwdiver right.

 

bobberaha: Thank you! That was a ton of help... Thank you very much!

 

This should give you an ideal of where to start just remember to use the pointie end of the screwdriver.

 

I have to ask this question... There have been many references to the correct way to use a screwdriver, what are you all talking about? I feel like the kid in middle school sitting alone at the lunch table on this one!

 

If you click on the xjforever on top of the screen and go to the information overload hour and scroll down to the carb section there is alot more info on jetting from Chacal.

 

Thanks, there is so much information on this site it is often hard to find exactly what I am looking for... much appreciated.

 

What do the velocity stacks do? I have pods on mine. Has a rough spot right at 5000-5500 rpm. No clue why.

 

Velocity stacks effectively lengthen the total intake track ( from filter to intake valve) which increases the weight of this air and the dynamics of how the cylinder would be filled, possibly moving a torque curve and hopefully raising peak HP.

It also gives a little headroom, because carbs spit gas back upstream when the flow reverses, and they also straighten and shape the airflow, and impress your friends that don't have them.

 

Well impressing my friends was not really in my mind when searching to clear up the flat spot through my rev range. If you have the stock airbox boots throw them on the pods and try it. Please tell me if it doesn't help and I will shut up about it.

Link in my signature of reference to boot size.

 

TimetoRide that is what Streetbrawler has done by putting the stock airbox boots on the pods he increased the length of the boots back to stock length. It gave the air time to stream just like it does coming out of the stock air box only at a higher volume.that is why he was able to tune his bike to run through all ranges of throttle. the short boots on the pods are what causes the turbulance the air does not have time to stream. there is another post where a tube was inserted into the center of the pod still using the pod boots. yes he did restrict the airflow but more importantly he increased the length of the intake tube giving the air room to stream.

 

where did this myth come from about airbox airflow being smooth and pods having turbulence?

not for the xj but on my suzuki i made a "wind tunnel" type of thing where i cut 3 different intakes in half including the filters and mated them to a piece of glass. i used a fine tip on a bee hive smoker and watched the air stream coming through the filter and down the tract. the airbox, similar in design to that of an xj, was the worst, the intake air eddies around after the sharp cornered exit from the box, with no bell to smooth things out.

as for the clamp on filters, they were smooth as a babies behind.

 

awesome zookie, way to shut 'em up

 

I'm sure you realize that the airflow only "flows" a little more than 25% of the time due to valve timing - - that the airflow is more like a jackhammer than a garden hose, and that smoke tests and shop vac tests are never going to display the true characteristics.

Considering this, would any vortex continue to spin when the air stops and reverses, or would the turbulence itself need to also reverse, or , would the reversal create NEW turbulence on the lee side of any obstructions ??

I would agree that longer, straighter, smoother runners are better.

 

Yes anything that impedes or changes the direction of airflow will cause turbulence. By adding pod filters with longer intake runners you reduce the reversal in flow due to the fact you are not pulling air from a common source. I.E a stock airbox has a common plenum when intake valve #1 is open and pulling in air it is pulling it from the common area therefore it will reverse the air flow from all other intakes in that plenum causing turbulence. I will agree that installing pod filters on our bikes is a huge pain in the ass but if you are willing to put the effort and time in it takes to jet and tune to the pods there is no reason these bike cant run as good if not better than the stock set up.

 

^ what he said.

 

i thought of the exact same problem when i built the makeshift wind tunnel, so instead of a shop vac i used an air compressor intake (coincidentally close in displacement to my suzuki) to suck the air through and as a bonus i could vary the rpms because its gas powered with adjustable throttle.

admittedly, the reversion, valve opening, and max rpms are nothing like the real engine, but certainly gave a better example than a solid flow.

what i saw with the minimal reversion the compressor had, was that any vorex would actually "back up" with any real amount of reversion. it was minimal and again, my test was nothing like the real thing when it comes to the true pulses and reversion of a cam/valve engine.

my test was aimed more at watching the velocity of the intake charge and to check for any turbulence, and i used the stock airbox just for "control". as a side observation, i can say that pod filters do NOT create turbulence.


FWIW- it was very easy to build the quasi-wind tunnel, anybody with spare time should try it out, its pretty cool.