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

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.