Spray bar design and size

[dwilfong]

I have had a few conversations on the pipe pressure fitting and line size.

Air moves much easer than fuel thew a line. Making the pressure line the same size as the fuel is not necessary.

I have the block made for the new carb with the slot style needle and the fuel line is only going to be less than 2" to the tank.

Should make for very good reaction to the signal from the carb.

May not even need pressure to run .

 

[Martin Fields]

Just to clarify with you all, when you're talking about increasing the ID of the spray bar are you all running remote needles? If so are they better than using the inflight mixture control?

 

[Martin Fields]

I have bin doing some testing on my make shift flow bench and running on the water in the last few months.

I thought I would share some of the finding I have noticed.

The newest test is with a MAC .550 carb on my EVO .77 eng.

This is a disk eng with a 67 crank and a 80 P/L in it.

I had problems with it taking the plug as it would hit the pipe and rev over.

So I have fitted the carb with a 5/32 OD brass tubing for the spray bar.

This makes a .125 ID spray bar.

I have also started using X-Large fuel line 5/32 thew the whole system and 5/32 tubing in the tanks.

Checking it for mist pattern on my flow box found the sweet spot with it sticking in about 1/4 percent of the boar.

Now this seamed like large size for this size eng but it worked very well.

Can idle and run at very low speed and will pop right off.

The throttle response is very nice and the needle is easy to set with 60% nitro.

No more lean over when it hits the pipe and Rev's.

This is leading me to believe that with high nitro a large spray bar is the best bet.

I can not say that this is the answer to all carbs or nitro % but with a large carb running high nitro it has worked very well for me.

Just some insight on what I have seen.

What is doing by increasing the ID of the spray bar. J

jack on the carb I modified for rick it simply could not flow enough fuel. The vac carb has a very restrictive 90 degree fitting for fuel connection. I drilled out the fitting in both directions and profiled the outlet to a smooth taper. On my homemade flow bench it increased the fuel draw vacuum by 22%.

Hi Greg,

I dont suppose you have any pictures of the mods you've made to a Nova carb? I think that its next on my list of things to do but want to make sure I've got the right idea first!!!

Martn

 

[Martin Fields]

I have bin doing some testing on my make shift flow bench and running on the water in the last few months.

I thought I would share some of the finding I have noticed.

The newest test is with a MAC .550 carb on my EVO .77 eng.

This is a disk eng with a 67 crank and a 80 P/L in it.

I had problems with it taking the plug as it would hit the pipe and rev over.

So I have fitted the carb with a 5/32 OD brass tubing for the spray bar.

This makes a .125 ID spray bar.

I have also started using X-Large fuel line 5/32 thew the whole system and 5/32 tubing in the tanks.

Checking it for mist pattern on my flow box found the sweet spot with it sticking in about 1/4 percent of the boar.

Now this seamed like large size for this size eng but it worked very well.

Can idle and run at very low speed and will pop right off.

The throttle response is very nice and the needle is easy to set with 60% nitro.

No more lean over when it hits the pipe and Rev's.

This is leading me to believe that with high nitro a large spray bar is the best bet.

I can not say that this is the answer to all carbs or nitro % but with a large carb running high nitro it has worked very well for me.

Just some insight on what I have seen.

What is doing by increasing the ID of the spray bar. J

jack on the carb I modified for rick it simply could not flow enough fuel. The vac carb has a very restrictive 90 degree fitting for fuel connection. I drilled out the fitting in both directions and profiled the outlet to a smooth taper. On my homemade flow bench it increased the fuel draw vacuum by 22%.

Hi Greg,

I dont suppose you have any pictures of the mods you've made to a Nova carb? I think that its next on my list of things to do but want to make sure I've got the right idea first!!!

Martn

Martin the carb I was talking about was from a CMB Vac .45 . To be honest I run Zoom or Orlic carbs on all of my nova motors

I see, with both of those carbs do they have a bottom end needle or have they been removed/made without?

 

[Charles Perdue]

Hello Mr. Martin, I build the Zoom carbs and they do not have a low speed needle. The Zoom carbs vary the fuel draw on the spray bar by rotating the carb barrel around the holes in the spray bar. Different angles of the airflow over the holes in the spray bar vary the draw and the corresponding amount of fuel that the carb delivers to the engine at different throttle positions. This is also in conjunction with the velocity of the airflow through the carb and both of these together determines the different amounts of draw, this meters the fuel and maps it to the demand of the engine. Charles

 

[Martin Fields]

Hello Mr. Martin, I build the Zoom carbs and they do not have a low speed needle. The Zoom carbs vary the fuel draw on the spray bar by rotating the carb barrel around the holes in the spray bar. Different angles of the airflow over the holes in the spray bar vary the draw and the corresponding amount of fuel that the carb delivers to the engine at different throttle positions. This is also in conjunction with the velocity of the airflow through the carb and both of these together determines the different amounts of draw, this meters the fuel and maps it to the demand of the engine. Charles

Thanks for the info Charles, are you still making carbs?

 

[RodneyPierce]

Hello Mr. Martin, I build the Zoom carbs and they do not have a low speed needle. The Zoom carbs vary the fuel draw on the spray bar by rotating the carb barrel around the holes in the spray bar. Different angles of the airflow over the holes in the spray bar vary the draw and the corresponding amount of fuel that the carb delivers to the engine at different throttle positions. This is also in conjunction with the velocity of the airflow through the carb and both of these together determines the different amounts of draw, this meters the fuel and maps it to the demand of the engine. Charles

holy smokes!!! He is alive!!!

 

[anthony_marquart]

OK,.. I need some of those carbs.,..

I start to petition for more ZOOM carbs,..

 

[dwilfong]

Hello Mr. Martin, I build the Zoom carbs and they do not have a low speed needle. The Zoom carbs vary the fuel draw on the spray bar by rotating the carb barrel around the holes in the spray bar. Different angles of the airflow over the holes in the spray bar vary the draw and the corresponding amount of fuel that the carb delivers to the engine at different throttle positions. This is also in conjunction with the velocity of the airflow through the carb and both of these together determines the different amounts of draw, this meters the fuel and maps it to the demand of the engine. Charles

Charles great to here from you again.

I was hoping this would bring you out of the wood work.

Thanks for sharing this insight with us all.

Don't be a stranger boating needs people like you involved in the hobby.

 

[Charles Perdue]

Thanks guys and hello Mr. Martin,

Currently I am not making any Zoom carbs. However, the mind never stops. Myself, with a lot of help from from NASA, in the form of aerodynamic and hydrodynamic test charts, has come up with a different spray bar and hole configuration that is showing a lot of promise in testing. As with anything different on our toy boats, the on-water testing is the proof-of-the-pudding. I am still in the tweaking stage but it is showing to be better than anything that I have came up with or have tested so far.

I am still catching up with many of my other projects that I had neglected while producing the Carbs. We will just have to see what the future brings.

Thanks again,

Charles

 

[RodneyPierce]

Keep in touch you old codger!!!

 

[Jack ODonnell]

Thanks guys and hello Mr. Martin,

Currently I am not making any Zoom carbs. However, the mind never stops. Myself, with a lot of help from from NASA, in the form of aerodynamic and hydrodynamic test charts, has come up with a different spray bar and hole configuration that is showing a lot of promise in testing. As with anything different on our toy boats, the on-water testing is the proof-of-the-pudding. I am still in the tweaking stage but it is showing to be better than anything that I have came up with or have tested so far.

I am still catching up with many of my other projects that I had neglected while producing the Carbs. We will just have to see what the future brings.

Thanks again,

Charles

That tweaking that Charles is talking about is working for sure !!! J.O'Donnell

 

[Charles Perdue]

Oh, I stop by here ever so often just to see what you younguns are up to....

Charles