MAC Troubleshooting

[Wasted wages]

WW,

I supplied one hint and Charles has provided one half of the equation and Greg just added another little tidbit.

Maybe you need a little more help.

Here it is:

When the engine is running at low speed (rpm) the velocity of the fuel through the lines is low, therefore as Charles stated the resistance due to velocity is low.

When the engine speed is high the fuel velocity becomes high and therefore finds more resistance as the engine speed increases. Basicaly the fuel line is acting like a varible needle vavle that is directly proportional to the velocity of the fuel through the lines.

Our engines are constantly changing in rpm as the boat goes around the lake even though the carb opening may remain at full bore.

This means fuel delivery rate is constantly changing and it is NOT necessarily changing at the same proportion to the engine's needs.

This is just another hint to help you understand the first half of the equation.

WW wrote:

"You can only flow the maximum flow as the smallest fitting in the system will allow. Period. I don't care what size line is connected to it. I'm still waiting for someone here to disprove this,,,,"

WW, You are going on the assumption that the med. fuel line is in fact less restrictive than the needle valve. If the lines are short this is true. However, if the lines are long and a multiple plastic tank system is used as is found in many Scale hulls the resistance of several cross section changes adds up. ( mutiple brass tubes with sharp corners and so on.)

In this situation it is a high probability that the needle is NOT the most restrictive part of the system. Meaning your .015" hole and 1/2" pipe illustration , even though it is in fact true, is irrelavent.

Sweet dreams! B)

Andy wrote,,

Meaning your .015" hole and 1/2" pipe illustration , even though it is in fact true, is irrelavent.

Thank you Andy,,,

I know my illustration is totally irrelivent to this conversation,,it just kinda took that turn somewhere in this post.

I never said that the theory applied to boats,,,only to the principals of fluid flow,you can only fit so much thru a fixed restriction,,regardless of the size of the pipe supplying it,,as long as it can support the max flow of the restriction.

And I know that length, bends, elbows, lift ,velocity, etc all factor into the mix,,,

Believe me,,I totally understand the entire scope of "the fuel line needs to be bigger to support the flow

thing,",I have even been down that road myself,, my purpose here was to wake up a few people to the possibility that bigger is not ALLWAY's better,,or needed.

besides,,being a newbie on the boards is allway's taken with a raised eyebrow or two,, :unsure:

and I just love the friendly wit and banter that everyone interjects into the conversation,,

sorry for waking everybody up :lol: :lol: :lol: :lol:

:lol: :lol: :lol: There you go WW! Just as I predicted earlier......there you go saying I Knew that!

Since you KNOW, go ahead and explain to us the other half of the equation.

I'm all ears,,,,

 

[Charles Perdue]

WW,

I supplied one hint and Charles has provided one half of the equation and Greg just added another little tidbit.

Maybe you need a little more help.

Here it is:

When the engine is running at low speed (rpm) the velocity of the fuel through the lines is low, therefore as Charles stated the resistance due to velocity is low.

When the engine speed is high the fuel velocity becomes high and therefore finds more resistance as the engine speed increases. Basicaly the fuel line is acting like a varible needle vavle that is directly proportional to the velocity of the fuel through the lines.

Our engines are constantly changing in rpm as the boat goes around the lake even though the carb opening may remain at full bore.

This means fuel delivery rate is constantly changing and it is NOT necessarily changing at the same proportion to the engine's needs.

This is just another hint to help you understand the first half of the equation.

WW wrote:

"You can only flow the maximum flow as the smallest fitting in the system will allow. Period. I don't care what size line is connected to it. I'm still waiting for someone here to disprove this,,,,"

WW, You are going on the assumption that the med. fuel line is in fact less restrictive than the needle valve. If the lines are short this is true. However, if the lines are long and a multiple plastic tank system is used as is found in many Scale hulls the resistance of several cross section changes adds up. ( mutiple brass tubes with sharp corners and so on.)

In this situation it is a high probability that the needle is NOT the most restrictive part of the system. Meaning your .015" hole and 1/2" pipe illustration , even though it is in fact true, is irrelavent.

Sweet dreams! B)

Andy wrote,,

Meaning your .015" hole and 1/2" pipe illustration , even though it is in fact true, is irrelavent.

Thank you Andy,,,

I know my illustration is totally irrelivent to this conversation,,it just kinda took that turn somewhere in this post.

I never said that the theory applied to boats,,,only to the principals of fluid flow,you can only fit so much thru a fixed restriction,,regardless of the size of the pipe supplying it,,as long as it can support the max flow of the restriction.

And I know that length, bends, elbows, lift ,velocity, etc all factor into the mix,,,

Believe me,,I totally understand the entire scope of "the fuel line needs to be bigger to support the flow

thing,",I have even been down that road myself,, my purpose here was to wake up a few people to the possibility that bigger is not ALLWAY's better,,or needed.

besides,,being a newbie on the boards is allway's taken with a raised eyebrow or two,, :unsure:

and I just love the friendly wit and banter that everyone interjects into the conversation,,

sorry for waking everybody up :lol: :lol: :lol: :lol:

:lol: :lol: :lol: There you go WW! Just as I predicted earlier......there you go saying I Knew that!

Since you KNOW, go ahead and explain to us the other half of the equation.

I'm all ears,,,,

Me too. Just like a corn patch in july.

 

[Brent Wyble]

Come on Andy, I want to be one to say I knew that to.

 

[AndyBrown]

Well....right now I've got to keep my mind on A/A Pro's, A Cube's and MAC USA's so some of you will have engines to race with, so........ we'll get back to this a little later. B)

 

[Scott Norris]

Is that what you call a Commercial Break? :lol:

 

[Marc Pagé]

Well....right now I've got to keep my mind on A/A Pro's, A Cube's and MAC USA's so some of you will have engines to race with, so........ we'll get back to this a little later. B)

Thank you Andy to make it your priority I'm in a hurry so much to try all those physical laws with my MAC USA

 

[Russell Bear]

Andy, tell Megan thanks for shipping the bushings so fast. Got them today and the .430 one is installed with the pipe set at 12-1/8". Will give it a try soon and let everyone know how it went.

Thanks everyone for the tips.

 

[Dan_Cousin]

Andy, tell Megan thanks for shipping the bushings so fast. Got them today and the .430 one is installed with the pipe set at 12-1/8". Will give it a try soon and let everyone know how it went.

Thanks everyone for the tips.

Russell, I could have reduced that stinger with my channel-locks. We'll give that a try if the bushing doesn't work. :lol: I'll guarantee it will make tank pressure when I'm done :lol:

 

[Russell Bear]

Andy, tell Megan thanks for shipping the bushings so fast. Got them today and the .430 one is installed with the pipe set at 12-1/8". Will give it a try soon and let everyone know how it went.

Thanks everyone for the tips.

Russell, I could have reduced that stinger with my channel-locks. We'll give that a try if the bushing doesn't work. :lol: I'll guarantee it will make tank pressure when I'm done :lol:

Yea I know, but it wouldn't have looked as purdy

 

[Wasted wages]

Maybe ole Bernoulli can help you out,,,

http://www.eng.fsu.edu/~schreiber/uol/exp100/

 

[ALLAN YUEN]

Well....right now I've got to keep my mind on A/A Pro's, A Cube's and MAC USA's so some of you will have engines to race with, so........ we'll get back to this a little later. B)

Hey Andy h34r: What's New" A Cube's engine????? Size? Is built by Jim Allen???

 

[Don Ferrette]

Maybe ole Bernoulli can help you out,,,

http://www.eng.fsu.edu/~schreiber/uol/exp100/

Only if he can tell us who you are.

 

[John Finch]

You don't need a degree to know that as the flow in any diameter of tube increases, the friction of the fluid againt the inside of the tube increases. The smaller the diameter of the tube for the same volume means more friction, less total flow with everything else being the same. Increasing the diameter of the tube will slow the speed of the flow causing less friction for the same volume thus increasing the amount of fluid that will pass through the tube. A tube too large will be affected more by the acceleration, deacceleration and the G forces in the turns as it has more fuel weight inside of the tube at any given time. Just my $1.02 worth. (Inflation don't you know)

100% true,,,,BUT--If the friction of the fuel moving thru the line is high enough to cause a problem then the line it self has become the restriction not the needle.

All of this means nothing to the needle valve,,,

THE WHOLE POINT I HAVE SAID FROM THE START IS:

IF the line size from the tank to the valve is big enough to handle the MAXIMUM flow of the needle setting

then a LARGER line size will do nothing to improve flow at static pressue.lets leave all pipe pressure out of the mix for now,,and compare apples to apples,,

Lets look at it another way,,,,if you took a piece of brass round stock and drilled a .015 hole thru it and connected it to a 1/8 inch fuel line and a gallon of fuel,,,it would drain out at the rate of the .015 hole,,,,if you connected it to a 1/2 garden hose and repeated the process it is still going to drain out at the rate of the .015 hole.

The size of the hose supplying the fuel does not matter as long as all other test elements remain equal.

it would be the same as if you poked a .015 hole in the jug,,

Andy ,I did agree that the test of attaching the fuel line straight to the carb proves that the pickup and lines were to small. because the motor still went lean ,,with no restrictions in the line. I just don't buy that once you have established that the line supplying fuel to the valve is OK then a LARGER line will do anything,,down stream of the valve,,yeah it can make a big difference due to volume change.

To all on the board,,I have worked in the refrigeration field for over 30 years,,and I'm not talkin' domestic refrigerators,,I'm talkin large commercial refrigeration racks and large industrial stuff with 600 hp Frick screws. I have seen my share of BAD piping and problems caused by poor design. I have been involed with solving flow isssues due to undersized lines , lift (head ), oversized lines, lines with to long of a run for the size of the pipe and on and on and on.

I've solved flow issues on refrigerant and water alike,,,and one thing has alway's remained a constant,,,

You can only flow the maximum flow as the smallest fitting in the system will allow. Period. I don't care what size line is connected to it. I'm still waiting for someone here to disprove this,,,,

Flame away,,,

WW,I have a co-worker that says he is going to connect four chillers in parrallel using the same supply and return piping (very large main line he says) for a distributed chill water system. He thinks that he can run two chillers at the same time when one is designed for 600 gpm flow and the other is designed for 1000 gpm flow. He doesn't even plan to isolate the chillers with valves. He is adament it will work. I doubt it very seriously even if each un-used chiller could be valved off. What is your opinion?

 

[Charles Perdue]

You don't need a degree to know that as the flow in any diameter of tube increases, the friction of the fluid againt the inside of the tube increases. The smaller the diameter of the tube for the same volume means more friction, less total flow with everything else being the same. Increasing the diameter of the tube will slow the speed of the flow causing less friction for the same volume thus increasing the amount of fluid that will pass through the tube. A tube too large will be affected more by the acceleration, deacceleration and the G forces in the turns as it has more fuel weight inside of the tube at any given time. Just my $1.02 worth. (Inflation don't you know)

100% true,,,,BUT--If the friction of the fuel moving thru the line is high enough to cause a problem then the line it self has become the restriction not the needle.

All of this means nothing to the needle valve,,,

THE WHOLE POINT I HAVE SAID FROM THE START IS:

IF the line size from the tank to the valve is big enough to handle the MAXIMUM flow of the needle setting

then a LARGER line size will do nothing to improve flow at static pressue.lets leave all pipe pressure out of the mix for now,,and compare apples to apples,,

Lets look at it another way,,,,if you took a piece of brass round stock and drilled a .015 hole thru it and connected it to a 1/8 inch fuel line and a gallon of fuel,,,it would drain out at the rate of the .015 hole,,,,if you connected it to a 1/2 garden hose and repeated the process it is still going to drain out at the rate of the .015 hole.

The size of the hose supplying the fuel does not matter as long as all other test elements remain equal.

it would be the same as if you poked a .015 hole in the jug,,

Andy ,I did agree that the test of attaching the fuel line straight to the carb proves that the pickup and lines were to small. because the motor still went lean ,,with no restrictions in the line. I just don't buy that once you have established that the line supplying fuel to the valve is OK then a LARGER line will do anything,,down stream of the valve,,yeah it can make a big difference due to volume change.

To all on the board,,I have worked in the refrigeration field for over 30 years,,and I'm not talkin' domestic refrigerators,,I'm talkin large commercial refrigeration racks and large industrial stuff with 600 hp Frick screws. I have seen my share of BAD piping and problems caused by poor design. I have been involed with solving flow isssues due to undersized lines , lift (head ), oversized lines, lines with to long of a run for the size of the pipe and on and on and on.

I've solved flow issues on refrigerant and water alike,,,and one thing has alway's remained a constant,,,

You can only flow the maximum flow as the smallest fitting in the system will allow. Period. I don't care what size line is connected to it. I'm still waiting for someone here to disprove this,,,,

Flame away,,,

WW,I have a co-worker that says he is going to connect four chillers in parrallel using the same supply and return piping (very large main line he says) for a distributed chill water system. He thinks that he can run two chillers at the same time when one is designed for 600 gpm flow and the other is designed for 1000 gpm flow. He doesn't even plan to isolate the chillers with valves. He is adament it will work. I doubt it very seriously even if each un-used chiller could be valved off. What is your opinion?

OK you guys, ease up on Andy so he can get back to work on his new AA PRO's. I am anxiously awaiting delivery of my 2 21's to run in my Generation II BOSS Hydro. Spring is just around the corner.

 

[Jack ODonnell]

Boss hydro. Boy that rings a sweet bell

 

[AndyBrown]

Jack ODonnell ! Welcome aboard Jack !

WW, I've spent many years with our friend Bernoulli.

 

[Wasted wages]

You don't need a degree to know that as the flow in any diameter of tube increases, the friction of the fluid againt the inside of the tube increases. The smaller the diameter of the tube for the same volume means more friction, less total flow with everything else being the same. Increasing the diameter of the tube will slow the speed of the flow causing less friction for the same volume thus increasing the amount of fluid that will pass through the tube. A tube too large will be affected more by the acceleration, deacceleration and the G forces in the turns as it has more fuel weight inside of the tube at any given time. Just my $1.02 worth. (Inflation don't you know)

100% true,,,,BUT--If the friction of the fuel moving thru the line is high enough to cause a problem then the line it self has become the restriction not the needle.

All of this means nothing to the needle valve,,,

THE WHOLE POINT I HAVE SAID FROM THE START IS:

IF the line size from the tank to the valve is big enough to handle the MAXIMUM flow of the needle setting

then a LARGER line size will do nothing to improve flow at static pressue.lets leave all pipe pressure out of the mix for now,,and compare apples to apples,,

Lets look at it another way,,,,if you took a piece of brass round stock and drilled a .015 hole thru it and connected it to a 1/8 inch fuel line and a gallon of fuel,,,it would drain out at the rate of the .015 hole,,,,if you connected it to a 1/2 garden hose and repeated the process it is still going to drain out at the rate of the .015 hole.

The size of the hose supplying the fuel does not matter as long as all other test elements remain equal.

it would be the same as if you poked a .015 hole in the jug,,

Andy ,I did agree that the test of attaching the fuel line straight to the carb proves that the pickup and lines were to small. because the motor still went lean ,,with no restrictions in the line. I just don't buy that once you have established that the line supplying fuel to the valve is OK then a LARGER line will do anything,,down stream of the valve,,yeah it can make a big difference due to volume change.

To all on the board,,I have worked in the refrigeration field for over 30 years,,and I'm not talkin' domestic refrigerators,,I'm talkin large commercial refrigeration racks and large industrial stuff with 600 hp Frick screws. I have seen my share of BAD piping and problems caused by poor design. I have been involed with solving flow isssues due to undersized lines , lift (head ), oversized lines, lines with to long of a run for the size of the pipe and on and on and on.

I've solved flow issues on refrigerant and water alike,,,and one thing has alway's remained a constant,,,

You can only flow the maximum flow as the smallest fitting in the system will allow. Period. I don't care what size line is connected to it. I'm still waiting for someone here to disprove this,,,,

Flame away,,,

WW,I have a co-worker that says he is going to connect four chillers in parrallel using the same supply and return piping (very large main line he says) for a distributed chill water system. He thinks that he can run two chillers at the same time when one is designed for 600 gpm flow and the other is designed for 1000 gpm flow. He doesn't even plan to isolate the chillers with valves. He is adament it will work. I doubt it very seriously even if each un-used chiller could be valved off. What is your opinion?

I also doubt that it would work very well, the 600 gpm chiller would more than likely run at full capacity while the 1000 gpm chiller may not be loaded enough,I'm assuming that the inlet and outlets for each machine are different sizes,,this will create some flow difference,, but butterfly valves on the outlet of each chiller would be the cleanest way to do it,, as each valve could be ballanced to the proper flow for each machine.

Not to say that it won't work at all,, but if your installing "as new" or refurbing a system why not install the valves?

If your seriously doubting if it will work at all,,PM me and I will give you my number and we can discuss it further,,WW

 

[John Finch]

Thanks WW. I may get in touch before the project starts.

 

[Tom Foley]

Ok , just to add to the curiosities of fuel line size , etc , I have run a myriad of boats using the same old flow meter as some sort of bench mark for adjustment in the event of having a new rig , clogged whatever , etc . Well just for comparison , i run my twin mac 84 Roadrunner at a setting that started out at 8.0 @ 40 on the meter as a start . Then after cautious leaning and plug reading over the last 3 years I am now at a slightly fat and happy setting of 7.2 @ 40 on the same meter with frosty pulled glow plug elements that look textbook and are good for about five runs which I think is very good . The motors run sweet !! Well my SG 45 with mac 45 is beyond the scale of the meter to run good . When you put the flow meter on it it is off the scale and immeasurable . I run Webra needles ( isolated ) on the twin and the 45 is equipped with a Bob Violett adjustable needle . I think it is an anomalie that a 45 can flow more than a 90 to run good . Obviously the system components and their associated flow drag are to blame for this situation . I feel if I set the 45 up with a webra or similar needle it would flow in the 5.5 - 6.0 range on the meter which by the way is only a comparison tool to go by . Each motor combination has it's own happy area on the meter . With that said I only go by performance and plug reading to tune the setup and use the meter as a gauge or benchmark for readjustment if nescessary . Tom .I use 5/32 feed and pressure on the twin and 5/32 feed and 1/8 pressure on the 45 .

 

[Charles Perdue]

Boss hydro. Boy that rings a sweet bell

Hello old friend. Welcome to the site of many opinions and do you know what is strange? All of them are correct.