Synch vs Balanced

[Mysuzyq]

First off, please understand I'm not trying to be argumentative . But for that rationale to work, there would not be a 'master' un-adjustable reference carb to which the others are matched.....it would suck (no pun intended) if that particular cylinder had a vacuum discrepancy due to poor manufacturing ....ALL of the carbs would be freely adjustable to better match/compensate their respective cylinders. When we adjust 3 carbs to a fixed reference carb, we are seeking uniformity in metering, taking volumetric efficiency of the cylinders as a given.

[TheCafeKid]

First off, please understand I'm not trying to be argumentative . But for that rationale to work, there would not be a 'master' un-adjustable reference carb to which the others are matched.....it would suck (no pun intended) if that particular cylinder had a vacuum discrepancy due to poor manufacturing ....ALL of the carbs would be freely adjustable to better match/compensate their respective cylinders. When we adjust 3 carbs to a fixed reference carb, we are seeking uniformity in metering, taking volumetric efficiency of the cylinders as a given.

And I'm not disputing that. I'm not saying that balancing the carbs is an effort or attempt to make up for a deficiency in one or more cylinders or any such truck. I'm saying that the reason you sync them is to assure that the flow and pull of each cylinder is relatively the same across the board. You have to stop thinking of the carbs as one unit or all the cylinders as one unit. Cylinder 4 doesn't give a rats ass what carb three is feeding cylinder three. But since three is the unadjustale carb you need to more or less meter why cylinder four is allowed to pull so that it matches cylinder three. Yes the volumetric efficiancy is an assumed constant but no two cylinders Are going to pull the same volume of air in the same constraint of time when you take into consideration the fact that one worn valve seat can, albeit minutely, speed up the time in which the cylinder takes in a specific volume of air vs another with a not worn seat. The adjustment you are making not only effects the carburetor but also the cylinder. I am not trying to insinuate anything about making up for any type of defect or slop or anything I'm simply saying that if you were to set the butterflies at exactly the same opening, and then check vaccum levels you'd see that they are in fact not the same. Maybe I'm making it sound more complex than it really needs to be.

[sscott]

Hey TCK,
I didn't want to hijack this thread. I understand what you are explaining in the thread but still confused about the butterflies. In the CV carb rebuild tutorial (page 35 of 53 the carb is totally apart and labeled. I don't see a butterfly anywhere. ( I did just get home from work, 24 hour shift, so perhaps my eyes are messing with my brain LOL) I do see however the rails for the choke for example. Is that the butterly you are referencing?

Thanks for the help!

[koolaid_kid]

Look on page 5. The tutorial calls it a throttle plate, but it is really a butterfly valve. The top pic shows it closed, the bottom pic shows it open.

[sscott]

AAAAAAAAAAAAHhhhhhhhhhhhhhhhhhh

Now that makes much goodlier sense to me!

Thanks!

[cowb0y]

Here's a great explaination of carb theory and it helped me to understand adjustments more clearly.
Have a look. . . http://www.iwt.com.au/mikunicarb.htm

[TheCafeKid]

Here's a great explaination of carb theory and it helped me to understand adjustments more clearly.
Have a look. . . http://www.iwt.com.au/mikunicarb.htm

That also explains plug chops pretty well. That, IMHO is the single most effective test in seeing which way you need to go in any specific carb circuit.
Well.. short of maybe having an AFM meter in your set up, but thats somewhat complicated...

[Mysuzyq]

And I'm not disputing that. I'm not saying that balancing the carbs is an effort or attempt to make up for a deficiency in one or more cylinders or any such truck..

Okay, that is the impression I got from the earlier post. Let's move on.

[koolaid_kid]

That also explains plug chops pretty well. That, IMHO is the single most effective test in seeing which way you need to go in any specific carb circuit.
Well.. short of maybe having an AFM meter in your set up, but thats somewhat complicated...

Actually, that's an AFR (Air to Fuel Ratio) meter, a.k.a. Wideband. At around $300 initial outlay, it is more expensive than it is complicated...but also a lot more accurate.

[TheCafeKid]

Actually, that's an AFR (Air to Fuel Ratio) meter, a.k.a. Wideband. At around $300 initial outlay, it is more expensive than it is complicated...but also a lot more accurate.

Rght you are. I was refering to it as air fuel mixture (afm) meter but you have the proper terminology there. By complicated I simply meant to
measure it acurately per cylinder you'd have to either have a long sniffer you could get up each header from the back or have a bung installed in each header. Otherwise you're only getting AFR readings of the over all exhaust right?

[koolaid_kid]

You are quite correct. If you chose to dial in each individual cylinder, you would need a bung in each pipe. If I were racing and cost (time, effort and parts) were no object, that is what I would do.
However, I am not racing, and cost is an object, so I choose to make all settings in all carbs identical. Therefore, I only need one reading, which can be at the end of the muffler (using a clamp for the O2 sensor) or in the collector pipe using a bung.
I would be interested to see a comparison between the two. I strongly suspect the gain in horsepower and torque would not be worth the effort, since you are basically tuning the engine 4 times, once for each cylinder.
BTW, when I tune a car, I also use the second method, since I cannot adjust each cylinder separately.

[Calvin Blackmore]

still indulgent meanderings and horse****.

what do any of you do for engines that have two port carbs with exhaust dumped into reducxtion non tuned exhausts.


the amount of repeat nonsense for the sake of saying something here for the simple sake of being heard is absurd.

NO NUMBERS NO measures NO nothing
KNOW nothing


to measure is to presume to know

[979roadrunner]

I am speaking of the mass of each piston rod assembly including the mass on each crank lobe

the statistical process control manifest in japanese indusrty would not have allowed a statistically signifigant difference to occur

ballance and blue print is from the days of the model t

Wrong, serious high performance and race engines are balanced and blueprinted.
all that fiddling and hand fitting to get them dimensionality and dynamically 'perfect' is a big part of the $10k+ price of a serious motor.
Model T era engines were not, for the most part, balanced and blueprinted, they were labor intensive to build because at that time they were dimensionally all over the map from being hand built on an individual basis.
The model T, the first mass produced car built on an assembly line, changed all that.
as for production tolerances making that big a difference in anything with tolerances as tight as a motorcycle engine that can live at 9k RPM, I'd agree there probably isn't any significant difference from one cylinder to the next.

[fastpakr]

Carb synching is to balance the individual carbs to each other. It has NOTHING to do with pumping volume of the cylinders. If you balance a carb rack on one motorcycle, it will be perfectly synchronized when pulled and installed on another.

Cafe Kid, you're making this far too complicated. Forget the engine side of the equation entirely.

[Octain]

. If you balance a carb rack on one motorcycle, it will be perfectly synchronized when pulled and installed on another.

.

So once sync'd always sync'd?

Please elaborate on your comment.