Topic: Pods Thread

[TwoTired]

Being new to the scene, im only just learning what a contentious subject this can be in the spirit of discussion and learning though, how does one modify the airbox for more flow? And does that mean jetting changes to go along with that too?

Why do you think you need more airflow?

The stock induction allows the engine make very good power all the way to red line where maximum engine inlet volume is required. 
Certainly at 3/4 throttle and below that same air induction system provides more than enough volume of air.

If it provides any restriction factor for engine breathing, it is above 3/4 to WOT and near and above normal red line.
You need to flog a 35 year old motor that much?  Such operation is usually reserved for full race applications where frequent engine overhauls are expected.  Is this what you are after?  Is an extra 3-4% gain at red line really worth trashing an engine prematurely?  Or, is it just that it's a cheap bike and you'll just get another when it wears out really fast?

Pods are not about general street performance.  They are usually about looks and perhaps vanity. ...Unless you are making a track bike, of course.

Almost certainly, if you modify the stock air box for the popular and wildly imaginative "more air flow", you will also change the pressure that reaches the fuel jet output/exit ports.  And this will require a re-jet of the carb that simply can't automatically compensate for such a change.  The false assumption that occurs after such meddling is that the larger jets imply more airflow has occurred.  But, this is a false assumption.  The jets must get bigger because there is less pressure differential at each end of the jet fuel supply tubes.

[scottly]

The false assumption that occurs after such meddling is that the larger jets imply more airflow has occurred.  But, this is a false assumption.  The jets must get bigger because there is less pressure differential at each end of the jet fuel supply tubes.

The jets must get bigger because there is less restriction on the atmospheric side of the venturi, which means the motor can ingest more air without the pressure differential required to supply sufficient fuel through the stock jets. An engine is an air pump, after all, and restricting the air input is not conducive to operating efficiency, IMHO.       

[P.abrera]

Being new to the scene, im only just learning what a contentious subject this can be in the spirit of discussion and learning though, how does one modify the airbox for more flow? And does that mean jetting changes to go along with that too?

Why do you think you need more airflow?

The stock induction allows the engine make very good power all the way to red line where maximum engine inlet volume is required. 
Certainly at 3/4 throttle and below that same air induction system provides more than enough volume of air.

If it provides any restriction factor for engine breathing, it is above 3/4 to WOT and near and above normal red line.
You need to flog a 35 year old motor that much?  Such operation is usually reserved for full race applications where frequent engine overhauls are expected.  Is this what you are after?  Is an extra 3-4% gain at red line really worth trashing an engine prematurely?  Or, is it just that it's a cheap bike and you'll just get another when it wears out really fast?

Pods are not about general street performance.  They are usually about looks and perhaps vanity. ...Unless you are making a track bike, of course.

Almost certainly, if you modify the stock air box for the popular and wildly imaginative "more air flow", you will also change the pressure that reaches the fuel jet output/exit ports.  And this will require a re-jet of the carb that simply can't automatically compensate for such a change.  The false assumption that occurs after such meddling is that the larger jets imply more airflow has occurred.  But, this is a false assumption.  The jets must get bigger because there is less pressure differential at each end of the jet fuel supply tubes.

Im not necessarily wanting/needing or planning on more airflow. Just looking to understand and appreciate the concepts being discussed. Thanks for adding to the discussion being new to all this, have to agree though that pods were primarily an aesthetic consideration for me.


Sent from my iPhone using Tapatalk

[Retro Rocket]

Here you go mate, took a while to find it but its a neat solution to a bit more flow, more holes equals more air in...   Look at the whole page..

http://forums.sohc4.net/index.php?topic=103818.msg1464304#msg1464304

[Retro Rocket]

Sorry Retro, I just thought that drewfunk's post was rather helpful as he was passing on his experience with UNI pods and your intentions aside, there is no question your reply was condescending, assuming, and not very helpful. You have over 14,000 posts and I have no doubt that most are very helpful but maybe it's time to step down off your pedestal, throw back a Fosters or two and actually read what you are typing before you click the Post button. Oh, and as far as not caring what I do, you're in good company.

Sorry mate but its an Aussie trait to cut to the chase or as we say, "not beating around the bush", you guys can interpret my comments anyway you choose, they are meant to be informative  not condescending or patronizing,   but i will stick to what i know and that is that most people have no idea just how smoothly these old bikes can run when tuned correctly. I'm not here to stop anyone doing anything, my posts were intended to make a point to the op. As far as whats helpful goes, when comparing pods to pods there are always going to be differences depending on the make up of the pod, thats obvious to me but no so much to the OP, compare ease of tuning a bike using pods and an airbox and it apples and oranges, the airbox wins every time for ease of tuning and thats what this guy was wanting to know...   One thing that should be remembered with pods, basically they were designed for flat out racing, not commuting round town, so thats why its usually easier to tune pods for either one thing or another, not all things all the time, thats the job of the airbox and as another point, ALL modern race bikes use airboxes, there's a very good reason for that too... Oh, and Fosters is a laxative over here...  

[scottly]

i bought some UNI filters since i've had good luck on my XS650 with them and they've been recommended quite a bit. Well hot damn, the difference was immediately noticeable. It revs out to redline much smoother and quicker, and idles much more consistently. I highly recommend the UNIs.

The UNI foam filters have more resistance to air flow than gauze filters, so don't require as much re-jetting.

[Stoli]

Sorry mate but its an Aussie trait...

I saw all the Crocodile Dundee movies and he wasn't like that at all.

... and Fosters is a laxative over here...  

Like I said, maybe you would benefit by taking a few Fosters.

[Retro Rocket]

Sorry mate but its an Aussie trait...

I saw all the Crocodile Dundee movies and he wasn't like that at all.

... and Fosters is a laxative over here...  

Like I said, maybe you would benefit by taking a few Fosters.

So you found the need to try and correct me by doing the same things you apparently don't like {why doesn't that surprise me..!}, none of your business either,  a well thought out reply based on ....ummmm.....Nothing.  You obviously have no clue and don't know any Aussies, which may possibly be a good thing, I can only think of one more reply for you this fine morning......F--- O--.... you're clever, you can fill in the rest...

Sorry mate but its an Aussie trait to cut to the chase..

That's one thing I really like about you, Retro, call it like you see it. Yep, sometimes seems "harsh" by our wussy, American decorum, but not to me. Once I calibrated to your style, I've grown very fond of it. Often much like your taking the words out of my mouth. Besides, posts are tone deaf and if people want to feel good, perhaps technical discussions are not the place to find that. These threads should be focused entirely upon technically proven data, not anecdotal seat of the pants dyno riding.

Having said all that, which pods should I run on my 550 please, Retro? K&N cones or ovals? I don't like the look of the uni- foam units.    If I want something that runs great, I'll plop down $18k on a new BMW or KTM and leave the tinkering to the check book!

Seriously though- Over here, one thing is for certain, more and more bikes being put back on the road here in the states, aren't accompanied by stock induction parts. So it is getting much harder to locate these parts and restore them to their factory tuning. Despite it being better, it's becoming a real necessity to develop a tuning model for pods as an alternative. And yes, lots of that is driven by the aesthetic choices some owners/builders make (myself included).

Of all the aftermarket products made for these bikes, you'd think someone would make a replacement air box from ABS or carbon. Think of the market appeal for that! Especially if it came with the enhancements in the inlets and filter units.

Morning Cal, looks like i need to supply some  tissues and cement for the sooks mate, this touchy feely stuff is not my thing, hypocrites just get me going too ..

The carbon airbox is an idea i've been flirting with for a while but i would like more volume for my use so i've been trying to see where i can squeeze in some more size, it would have to open differently to the stock version but thats the easy part...

The best aftermarket attempt at an solution to pods was Brians {tintop} anti pod set up....But it used logic and engineering like Honda did so it wouldn't work for these guys either... { i can hear the whining already}...

[Killer Canary]

Unfortunately, logic doesn't get much use over here. Come for a visit and see what the ratio of soup bowls to full face helmets is.

[scottly]

These threads should be focused entirely upon technically proven data, not anecdotal seat of the pants dyno riding.


Seriously though- Over here, one thing is for certain, more and more bikes being put back on the road here in the states, aren't accompanied by stock induction parts. So it is getting much harder to locate these parts and restore them to their factory tuning. Despite it being better, it's becoming a real necessity to develop a tuning model for pods as an alternative.

While seat of the pants dyno riding is not as accurate as a real dyno, it still provides some useful information. Cal, if you bring your bike to AZ, I'll put it on the dyno for free! (You'll have to do your own jet changes....)

[Terry in Australia]

Ah, popcorn time, this thread never gets old..........

[goldarrow]

Ah, popcorn time, this thread never gets old..........

Long live the PODS!

[Retro Rocket]

One thing the OP needs to take into account is that where he lives has huge annual rainfall, very high humidity and salty air, an airbox would be a better all round bet in these conditions....

[Terry in Australia]

Ah, popcorn time, this thread never gets old..........

Long live the PODS!

And may the pods thread never die!

[dave500]

like pods of whales?

[Bailgang]

You obviously have no clue and don't know any Aussies, which may possibly be a good thing,

Are you kidding? You Aussies scare the hell out of me. I can envision having a few drinks with you guys in a bar is similar to being at some red neck bar here with someone yelling "YEEE HAAA" at the top of their lungs. It might be fun though provided I'm the designated driver. 

[dave500]

we don't have red necks here,we have #$%* heads though?

[Stev-o]

Did someone order popcorn?

[goldarrow]

Did someone order popcorn?

Hottest popcorn yet!

[Stoli]

Sorry to disappoint guys but you can put the refreshments away. That last response from RR summed up his character much better than I ever could.

Regarding my Dundee comment, that was intended as humor but apparently it struck a nerve. If I offended any of the other Australians in the house, I sincerely apologize.

Hey Stoli,

Id be interested to know what pod/jet combo youre running...just to have some starting points.

P.abrera - You can find jetting info in my first build thread but I wouldn't recommend you use it as a baseline for your '76 550K since that bike is a '78 750K with PD carbs. Two very different animals when your talking jet sizes. If you still want to try to get pods to work, you might want to start here:

http://forums.sohc4.net/index.php?topic=103861.0

About 5 posts into the thread is a ballpark formula. Emphasis on the word "ballpark". First figure out what the stock jets were on your bike then apply the formula based on your current configuration then do a timing check, balance your carbs and adjust the idle and then go out and do some plug chops. There is also some good info over at HondaChopper.com. I found this page very informative and helpful as it describes the role of the different jets and needles throught the throttle range.



http://www.salocal.com/sohc/tech/carb/asmpg_mgs/jetgraph.htm


Good luck. Can't recommend it if you want a daily rider as soon as possible, but if you are just having some fun with the build, like I was, then you get real good at pulling the carbs off as well as pulling and replacing spark plugs.

[Stev-o]

Here are some Pods for sale, if anyone is interested...

Feel Lucky?


http://forums.sohc4.net/index.php?topic=139443.msg1330989#new

[TwoTired]

The false assumption that occurs after such meddling is that the larger jets imply more airflow has occurred.  But, this is a false assumption.  The jets must get bigger because there is less pressure differential at each end of the jet fuel supply tubes.

The jets must get bigger because there is less restriction on the atmospheric side of the venturi, which means the motor can ingest more air without the pressure differential required to supply sufficient fuel through the stock jets. An engine is an air pump, after all, and restricting the air input is not conducive to operating efficiency, IMHO.     

Good lord, we are at the brink of agreement.  Whooda thunk?

If you consider that the very largest source of restriction in the SOHC4 induction system is the slide in the carburetor, any other restrictive element or membrane is of secondary concern to the position of the slides.  It is only when the slide is nearly totally raised that changing restrictive elements has some affect on power production.

Understand that while the engine is running and displacing air, there is a constant battle to equalize pressure between outside atmospheric and the lower pressure caused by the falling pistons on the intake stroke (pulsed).  This pressure difference between source and supply drives the air flow, and is why the carbs don't continue to provide fuel when the engine is stopped.   Filter membranes, induction duct lengths, and duct walls all impede or delay that equalization pressure action due to the drag they impose and the density/viscosity of the material (air/fuel).   But, these effects regarding power are secondary to the slide's position.

I agree, if you are focusing on operation where the slide no longer dominates the air restriction (at or near WOT), then some designs of pod filters can get you a 3-4% power increase (at WOT) due to a little more oxygen reaching into the piston chambers.  Still, most of the jet orifice size increases are due to atmospheric pressure reaching into the carb throat easier/faster.  And when the pressure differential across the jet metering tube becomes less, fuel flow is reduced, requiring a larger orifice to restore the fuel volume/ratio to that needed by the engine's displacement and ingestion characteristics.
The repercussions of altering pressure equalization action at WOT with PODs is that the new pressure equalization effects also occur at slide positions other than WOT, leading to every other fuel metering path needing alteration to restore proper fuel mixtures for NO gain in power factors.





 

[scottly]

If you consider that the very largest source of restriction in the SOHC4 induction system is the slide in the carburetor, any other restrictive element or membrane is of secondary concern to the position of the slides.  It is only when the slide is nearly totally raised that changing restrictive elements has some affect on power production.

Correct, and therefore the main jet is no longer the dominate jet at lower throttle openings. The main jet selection is the primary change required when switching to a lower restriction intake. Power production at less than full throttle is a moot point; the concern at part throttle operation is drive, er, ride-ability: how the bike performs when ridden at normal street speeds. 

[TwoTired]

Power production at less than full throttle is a moot point;

Sorry, I can't agree it is a moot point, unless you are making a pure race track only bike.  The vacuum loss from pod installation will lean both the pilot circuit and slide needle metering.  These have to get larger orifices/adjustments to keep the engine temps down, make correct cruise power mixtures at part throttle, allow proper throttle response off idle, and compensate for throttle position drop outs in some portions of slide needle operation.  I don't understand why you'd think this is without concern.

[scottly]

Power production at less than full throttle is a moot point;

Sorry, I can't agree it is a moot point, unless you are making a pure race track only bike. 

It's simple Lloyd: if you need more power for the riding conditions at hand, you open the throttle more, but that doesn't mean WFO. I have over 60 dyno runs on an FT500 after changing the stock airbox for a large K&N POD, and increasing the main jet alone was responsible for 90% of the tuning required to produce a well behaved bike under all conditions, and netted 58MPG in a combined 82 mile loop consisting of slow off-road as well as highway speeds up to 75 MPH.