Pods. Tuning Option For Those Who Are Still Too Rich!

Ripping a page right out of the NASCAR Tuning Regulations and what Inspectors look for to discourage cheating; I think "Restrictor Plate Racing" can be applied to XJ-Bike Tuning and be beneficial in the endless search for "The Solution" to getting Dialed-in running Air Pods.

I think the "Too much AIR" problem has a solution.

The McKey Perforating Company manufactures sheets of "Perforated Stock Material" with a wide variety of patterns and **Percent of Open Area** that those of you who are experimenting with Pods should investigate.

Not only does the McKey Company have perforated stock in various percentages of open space. They have the capability to PRODUCE a CUSTOM Sheet to specifications needing: More or Less Open Area ...
Patterns to solve percentage issues ... and, choices of Materials the Perforated Product will be made from.

McKey Perforated Products Inc.

http://www.mckey.com/docs/products/perfstock.htm

 

So let me get this straight: Somebody installs pods to increase the intake flow. Then they use restriction of some form (like the material you suggest) to DECREASE said airflow to get the carbs to work right.

You suppose with the right restrictive material choice it will flow the same as the original airbox?

THERE'S an improvement... Darn, Rick I don't know why nobody thought of that sooner.

 

Some people get pods just for looks. (and it's too lean)

I think there could be some gains by switching to the other kind of carb- - the ones that the throttle IS the slider. But that still means adapting, tuning, and experimenting.

 

I also think there's an attraction to the ease of installing-removing the carbs when you have pods as opposed to the stock air box and boots. Personally I don't think their worth the hassle but what do I know? Also when you remove the stock air box you have all that room for a small luggage compartment. What do people put in that space upon removal of the air box anyway?

 

There was an old post on here where someone was talking about experimenting with wads of foam inside the pods until he got the airflow down to the level of a stock airbox setup. It was an older post that I stumbled on to, I don't think the guy ever posted his results though.

 

Maybe that guy is too busy with the chicks he picked up from having a more muscly bike.... or maybe he's stranded somewhere in the desert from them.

 

OK, let's say you came up with a cone shaped piece that Fitz inside the Pod. You make 4 identical cones.
It has exactly 60 holes. You run it, and it's still too lean. You tape over 5 holes and see a slight improvement. You tape over 5 more holes and see black plugs. Now it's easy- - you are tuning in a range of just 4 holes. You could even tape over half a hole, or have 8 holes blocked on one pod, 6 on another.

I see where this would work. But there would be no need for a custom sheet of material, unless you went into high volume production of a finished product. Everybody would still need to fine-tune these screens to their particular exhaust/bike/set-up. The final cone would need more holes than needed for the final tuning.

And it's all just theory until someone gets out in the garage with some tin snips and RTV cement. (and beer).

 

I was debating pods on my XS400 because the stock air filters are hideously expensive... and soon, I imagine, impossible to find.

The question I have is, does this perf material flow the same CFM at all RPMs as the stock airbox? I mean, you might dial it in for idle, but at WOT/redline it might be more restrictive than the stock airbox since for the same total open area, a lot of small holes flow less air than one big hole. I think.

 

its all about harmonics, and a restrictor plate is a narrow rpm range bandage. jet and tune your carbs correctly. its not impossible.

 

I don't think Harmonics is the right word to use to describe what is needed and not provided by Air Pods. Harmonics is frequency.
(But, then ... you will be pulling-off your Carbs with greater frequency!)

The problems to overcome running Pods on Vacuum Carbs are many.

Vacuum Carbs are NOT designed to accommodate Pods.
Pods eliminate the Air Boots which are the racks Velocity Stacks.
The Total Volume of Intake Air is shared by the 4 Carbs,
Cubic Feet per Minute is Precisely Regulated by the Airbox Inlet.
Pods do not regulate Intake Air.
Intake Air is not Velocity Stack Shaped and nor its Velocity Increased.
The element of Turbulence is introduced by the Pods.
Unshaped, turbulent Intake Air fails to sufficiently lower pressure above the Emulsion Tube Outlet causing insufficient amounts of Fuel to enter the Intake Air Stream causing a Lean condition to occur which is not addressed by installation of a Larger Main FUEL Jet.
The Incoming volume of AIR >> remains insufficiently "Shaped", turbulent, and of Insufficient Velocity above the Emulsion Tube opening to provide the dramatic change in pressure above the E-Tube to effectively aspirate the Fuel from the cavity.

Manifold Vacuum causes the Diaphragm Pistons to rise allowing copious amounts of Air with insufficiently Aspirated and Atomized Main Jet Supplied Fuel supplied to allow the Engine to develop power.

For Pods to work ... they are going to need to be integrated.
The Pod needs to Restrict the Volume of Air.
The Air entering the Pod would need to be Shaped and Directed.
A Venturi-type "Insert" needs to direct a condensed flow of the Air across the top of the Emulsion Tube.

It's not Harmonics.
It's Aerodynamics.

 

rick, its the difference between a 1' pipe and a 10' pipe. the stock airbox doesnt restrict flow until the upper revs, if it does at all. it does change the reciprocating velocity (harmonics) of the air coming into the carbs throughout the rpms when compared to an open element design.

an airbox or manifold type intake has harmonics involved. an open element has dead air with no music to change the air charge at the carb inlet.

if your restrictor plate theory is correct, someone could throw dirt on their pods and call it a day. it may bandage a symptom, but its not fixing the problem....incorrect jetting/carb tuning.

 

Wow.

 

You're both right. It's both, as is the exhaust system ("backpressure" is a myth.) 8O

*ding*ding*ding* Bob, tell that man what he's won!

If you switch to good old MANUALLY controlled carbs then tuning for pods is not an issue. It's these damn vacuum-controlled CVs that have to live in such a controlled environment to work; they're only on there because we, mere mortal humans, do not have the ability to control our right wrist in an EPA-satisfying manner.

NOR do a lot of us have the knack for throttle control on a motor with an effective 8000 rpm "working" range. With slide-valve carbs you have to apply throttle as the revs rise, simply slamming it wide open will bog the motor. With a wide-band motor such as the XJ, it would make the bike unrideable for most consumers. With CV carbs, Joe Average can grab a big handful and the bike will respond, because the carbs will take over and apply the proper amount of slide lift AS THE MANIFOLD VACUUM RISES.

The first thing serious racers do is ditch the CVs for slide-valve carbs. But we (mostly) ride on the street.

 

So if manifold vacuum isn't lifting the slides enough, can't we put weaker piston springs in?

 

If you have a spare set of piston springs, you can cut the exact amount of coil off of them so they would be the same, and lift the slider and needle the same added amount. Keep the stock springs just in case.

Zookie400, you would have to throw the exact same amount of dirt on each pod. . . :lol:

So, has anyone with pods added a few inches of "runner" yet?
This added velocity stack may address a couple issues of turbulence and some air volume.
Or maybe nobody wants to complicate the simplicity of pods.

 

I was thinking about doing this for a while before I even read this post. I have a extra set of carbs that I would like to play with for my pods aplication. As far as restrictor plates go I was going to do something a bit different, but it would still restrict the amount of air flow into the carbs but also reduce turbulence.

My idea (and I know most of you are going to laugh or spit at it)
was to fab a cone type sleeve (like a funnel) that would slip on each carb. I would of course have to have each of these cones flow benched until I get the desired amount of cfm's of airflow through them.

First I would need to know what would be ideal flow for these carbs.

In my case I only want to go with pods to clean things up.

 

At that point, it would be easier to just put a rack of standard carbs on it and tune them.

 

What exactly are standard carbs for these bikes? Are there any that bolt right up?

 

Sort of. You would want a Mikuni or Keihin slide-valve carb in the same "size" (intake throat dia.) as your bike; and they would have to be mounted to an adjustable "rack" to fit.

The biggest drawback (and why this isn't a commonly discussed solution) is the high COST (up to $800/ea new) for such carbs. That's why more of us aren't running slide-valve carbs. I had looked for a set for my 550 (since they were often raced) and they're out there but I didn't want to spend upwards of $2K for a used set, and still have a tuning challenge ahead.

 

Could adjusting the Air/Fuel mix screw compensate for any rich/lean conditions?...

I have a LM1 wideband 02 sensor I use to tune cars with, and I thought of taking off the muffler/mid pipe to expose the header collector so I can put the wideband 02 sensor inside each exhaust runner to read the true air/fuel mixture from each cylinder. Then using the air/fuel mix screw to adjust a little? if the fuel mix is way off I have dynojet stage 1&3 jets to play with, 120, 124, 132, 136 main jets.

I ride a 82 XJ750 Maxim, 4-1 header/exhaust, K&N box air filter and stage 1 dynojet kit 124 main jets.

Is the wideband idea worth trying?

 

Hey, Welcome Zero Boost !!

You seem to have alot of equipment at your disposal.
If you pull your exhaust system apart and stuff the O2 sensor in the header pipe, you ruin the dynamics of the full exhaust system.

But we appreciate your efforts and inputs!!
You need to put your wide band sensor in the muffler and then tune the bike in increments. Very tiny changes.
You will need a seat of the pants confirmation also.
Keep at it !!
TIME

 

There are Exhaust Sensor Bungs at the bottom of each Head Pipe.
They are the Ports formerly used by Yamaha to read Exhaust Gas Analysis.
The vast majority of Dealerships abandoned Yamaha EGA due to inaccurate results and repeated Test Equipment failure.

 

Zero, the problem is not a rich or lean condition at any one RPM, it's getting the CV carbs to perform correctly through the entire rev range.

CV carbs need a finite controlled amount & velocity of intake air flow; pods allow unrestricted (infinite) air flow. As a result, it's nearly impossible to tune the carbs to behave correctly at all RPM. They simply weren't designed to work with unlimited intake airflow, hence this discussion.

 

It's 9,500 / 2 X 45 cubic inches / 12 / 12 / 12 = 123.7 CFM / 4 =

30.9 CFM for each carb. Max. But at what pressure drop??
You would only want less than a tenth of a PSI of pressure drop.
Maybe only a couple hundreths.

 

Bigfitz52: I see... then the whole idea about the pod restriction plates makes sense as long as the plate opens when the throttle opens, right? this could benefit anyone running rich air/fuel mix, with or with out air pods.

I could fab some kind of restriction plates for the inside of the air box that would open more as I give it more throttle.

 

Thanks for that info, I have a friend who has access to a flowbench, I just ned to find the time to get my machinist friend to make a few of these cones with different sized orifices and size of the pitch in the cone as well. I know I only have the size of the pod to work with butI should be able to shape the flow and control the cfm's by the pitch of the cone and also by the size of the orifice.

Can you elaborate on the whole pressure drop needed and how that works? Specially in a stock set up ?


Eddie

 

Can we, at some point, change the title of this thread to "too lean"??

Both the Carter AFB and Rochester Q-Jet carbs have a spring loaded air door to help control the large secondaries. I can imagine it would take many hours to engineer something comparable.

Xulf13. . . If you still have a completely stock bike, here's what you do to see how much pressure difference there is between outside air and the air inside, just before the intakes, while driving the bike.
Get some clear 1/4 inch tube, maybe 8 feet?
tape a water filled loop near your gauges,
one end goes into the breather vent hole in the airbox,(sealed)
the other goes under the seat, with a rag wrapped around it to prevent any effects of wind on it.
If you see an inch of water level change at WOT, that is 1/27 of a PSI.
I'm betting you'd see a half inch, which is about 0.02 PSI

 

The idea of the Perforated Insert is solely to reduce Volume.
The Rack operates on a shared Volume ÷ by 4.
(X ÷ 4) = V1 Where X is the Max Volume allowed in CFM by the Airbox Inlet Port.

A Perforated Insert that Regulates Flow from 100% -to- [25%] ... or, some other "Known Volume Restriction" >might< reduce the Unrestricted Volume of Air to within a parameter that would make Adjusting the Air-Fuel Ratio easier ...

IF ... and, only if ...

The Restricted Volume causes a corrected Venturi Effect and the subsequent Lowered Pressure Differential is strong enough to BOTH aspirate FUEL from the Emulsion Tube Opening and cause the Diaphragm Piston to Lift due to lower pressures acting upon the Vacuum Cavity.

To achieve the Effect ... It will likely be necessary to introduce MORE
Main AIR to surround the Emulsion Tube.
A Factor that might be impossible due to the FIXED Diameter of the Main AIR Passage.

 

I think it would be better to change the thread to "Hopeless Case"

 

Yamaha came up with a really elegant solution to the problem.

It's called an AIRBOX. Seems to work quite well.

 

Tell me about it, what a headache. I think I will end up opting out for a smaller battery or relocating it in my case to clear things up a bit.

It's like the more you read about this, the more questions one has and the more hopeless it becomes. So to get this straight, people who only up size the main jets have good response only at certain RPM's but not thru the full range?

I see a lot of people mentioning that their bike is running with pods, and stock jets. But never comment or post photos of their plugs or mention any quirks the bike may have.

Others with larger jets after installing pods and opening the exhaust say they are running fine, but idle poorly, and some say it runs great, but determining what great is can be dificult in some cases. Everyone has an opinion, some think that what some will consider decent is great for them.

I know these bikes will run lean, oh yeah they will scoot, but you know the valves are about to burn up at any moment.


I don't know,

I really like the way pods look, it seems some have made it work for them.

Maybe we should start a thread of GOT PODS? SPECIFY AND HOW DOES IT RUN, PROOF NEEDED

 

I think that the main air passage is capable of passing quite a bit more air than is needed, which is why restrictive air jets of different sizes are used in different models.

 

Precisely. The whole game is REGULATING the airflow to a CONSTANT value. That's why they're called Constant Velocity carbs.

My whole point about the airbox is those ten engineers and millions of development dollars are what came up with the original system as fitted.

Yes, it was tweaked a tad lean to satisfy the EPA and a little "fine tuning" (as in drill out the protective caps and crank on those mixture screws) can cure that. An XJ in "corrected" stock tune (factory leanness fixed) will run like a sexually molested large primate. The airbox (and exhaust collector box) were not bad things, all that you need to do is richen the bike up a bit. I've seen a factory tech bulletin that told the dealers to go ahead and give the mixture screws an extra HALF a turn out if the customer was bitching about stumbly throttle response and cold-bloodedness, but to warn said customer that his fuel economy might suffer. All the motorcycle magazines of the day would pop a .0010" shim under the needle seats too.

OK, pods look cool. But bring on any pod-equipped 550 and we'll see how it runs against a properly maintained and tuned stock bike. Both of my 550s will pull from 2500rpm to 9500rpm without so much as a blubber or stumble, and run to redline in all 6 gears almost as quickly as you can shift.

 

But pods do look cool!

There was a thread a while back on someone using PVC tubing and clamps to join all 4 carb inlets and putting ONE pod on it to restrict airflow. Looked cool, seemed to get the job done well, too. That would be the best way to go in my opinion.

I wish I could find that thread.

 

restricting air flow to fix a low end jetting issue, will hurt your top end power and jetting.

the air box doesnt restrict, it creates a larger volume of air with velocity. pods eliminate that volume of pulsing intake air. with 14 psi of ambient pressure, the air pressure is there to operate the cv slide whether you have the pods or airbox.

jet the carbs properly, whether you have an airbox or pods or nothing. it will run great.

 

"Restricting air flow to fix a low end issue, will hurt your top end power and jetting"
The ... Carbs ... Are ... NOT ... Designed ... To ... Operate ... Without ... A ... REGULATED ... Air ... Flow.

"The Airbox doesn't restrict, ..." Incorrect.
"It creates a larger volume of air with velocity." No. It don't!

"Pods eliminate that volume of pulsing intake air." Wrong.
The Pods actually create turbulence at the Horns.

"14 psi of ambient air pressure etc."
Ambient air pressure is not a factor. The decrease in pressure caused by the Intake Air as it gains velocity passing through the Venturi over the Emulsion Tube opening and below the opening at the bottom of the Slide Piston causes a depression which Main AIR and the Volume within the Diaphragm Piston move toward to correct (A Vacuum being an unnatural state).

"Jet the Carbs properly, whether you have an airbox or pods. It will run great."

It will run great.
Airbox. Yes.
Pods. No.

Don't sell "Run Great" to somebody on the fence needing to make an intelligent and informed decision about whether they ought to scrap the Airbox and run Pods.

You DON'T get "Great"
You ONLY get close.

And, close is "NO Cigar"

 

they ARE the regulator of airflow. they are designed to have unlimited air supplied to them at ambient air pressure. they may NOT be jetted to handle that situation, but they can be. with your stock airbox, tap in a pressure guage at the inlet of the carb, and please post up your findings. i have done it before on other machines.

and a restrictor plate doesnt?! why restrict airflow to fix a turbulence problem, why not make a free flowing louver to direct and control the wild air?

:lol: right. totally insignificant. rejetting for high/low altitude is just for fun.

as for the run great debate.....maybe you should stop pushing your uber-lean jetting techniques. lean is close, and close is no cigar.

 

OK now i am completely,totally,undecisively NOT going to attempt the pods. after reading all the experts have to say i got me a king sized headache and need to go for a ride. Yikes if only we the stupid had known the only issue was CONSTANT VELOCITY then buying pods and carb jet kits is a COMPLETE waste o time and money. sigh. about the slide carbs though i have heard of one or 2 guys doin this. My question is market research i guess cause the PODS LOOK COOL MAN and i wanna be able to use em so i guess i need to search out this option and weigh all the factors.
WHAT would be the biggest challenge for adapting slider carbs versus CV carbs other than an adjustable rack? ANY IDEAS?

 

MONEY. Cubic dollars. Slide-valve carbs, even used ones, ain't cheap. Plus then all of the jetting would be experimental until you got in the ballpark; again money is a factor: Complete jet sets X4 can get real expensive real quick. The expense is what stopped me, I couldn't see spending more for a (used) set of carbs than I did for the bike to begin with.

I would say find someone who raced XJ750s and talk to them but it's doubful you will; it's a shaft drive bike. Most club racers use chain-drive bikes for track bikes; hence the dominance of certain models in each class over the years.

 

yea just my thoughts exactly. i know a few racers but NO ONE has raced a shaft drive bike.

 

In all of my Posts having to do with Tuning and Mixtures, I have consistently and emphatically warned everyone about the danger of running too Lean.

Not a casual reference.
An aside.
Separate text.
Like this!
With DANGER and WARNING and the reasons clearly stated.

 

thanks bigfitz and rick you are always there to keep us in line as well. thanks again. lean is bad really really bad and needs correction but rich isnt good either. maybe a little rich and one or 2 sizes up in hottness like maybe a bp6 or a bp5? any thoughts?

 

You do.

I'm not sure where
"maybe you should stop pushing your uber-lean jetting techniques" came from.

YOU started this thread, as far as I can tell, to try to warn folks, new owners especially, about what they would be getting into before casually chopping up their airboxes in favor of pods. And to point up the folly of then attempting to restrict said pods. At least I thought that was your intent.

The point is well taken; however you will always run into "don't confuse me with facts when I've already made up my mind."

Don't lose any sleep over it. You tried. (WE tried.)

 

Too Rich has a way of regulating itself. The Plugs foul and draw your attention to the problem right away.
Also, with no Fuel Gauge, you get frustrated at the more frequent need to Gas up.