ANT
Just ride
- Location
- Sea Isle City, NJ
I've read a lot about the crossover tube in intake manifolds affecting the "signal" in the intake. Can someone give a brief version of what the "signal" is and does?
Can someone explain the whole carb signal thing?
- Thread starter ANT
- Start date
orange flattop freestyler
The Carlsberg ski
- Location
- Essex UK
Briefly,
In short buddy, signal is the amount of air the carb is able to read.
Small carbs have lots of air speed, this is great as lots of air speed creates lots of pressure variations.
Pressure variations is what a carb uses to meter fuel delivery.
This results in a good signal strength.
A carb with a good signal strength will be easier to tune and require less fine tuning due to changing climates and altitudes, this is because it can see such a wide veriety of changes of air pressure.
However they cannot flow massive volumes of air for big power on big displacment motors.
A large carb is quite the opposite.
Due to its large bore size the volume of air it can flow will be much greater but in turn the air speed through the carb is reduced.
This reduction in air speed results in less noticeable pressure changes hence its more difficult for the carb to read whats going, on so is said to have a weak signal.
Due to their weaker signal strength they can be harder to tune and require more frequent adjustments to climate and altitude changes.
Think of it as a viewing angle.
Imagine the carbs have eyes, they need to see airflow in order to meter fuel delivery.
Say a small carb with good signal can see 170 degrees of viewing angle, so sees lots of air and can meter fueling over a wide range of conditions.
A large carb with a weaker signal can only see 90 degrees of viewing angle so therefore they have to be tuned finer to get the same results.
Dont think that big carbs are no good, they are if set up correctly and kept in tune.
I use a pair of 48mm powerbombs on my freestyle boat with no problems.
I hope this clears a few things up, i recomend you read a copy of the Mikuni carb manual, its a good guide and easy to understand for people wanting to know more about how their carbs work.
In short buddy, signal is the amount of air the carb is able to read.
Small carbs have lots of air speed, this is great as lots of air speed creates lots of pressure variations.
Pressure variations is what a carb uses to meter fuel delivery.
This results in a good signal strength.
A carb with a good signal strength will be easier to tune and require less fine tuning due to changing climates and altitudes, this is because it can see such a wide veriety of changes of air pressure.
However they cannot flow massive volumes of air for big power on big displacment motors.
A large carb is quite the opposite.
Due to its large bore size the volume of air it can flow will be much greater but in turn the air speed through the carb is reduced.
This reduction in air speed results in less noticeable pressure changes hence its more difficult for the carb to read whats going, on so is said to have a weak signal.
Due to their weaker signal strength they can be harder to tune and require more frequent adjustments to climate and altitude changes.
Think of it as a viewing angle.
Imagine the carbs have eyes, they need to see airflow in order to meter fuel delivery.
Say a small carb with good signal can see 170 degrees of viewing angle, so sees lots of air and can meter fueling over a wide range of conditions.
A large carb with a weaker signal can only see 90 degrees of viewing angle so therefore they have to be tuned finer to get the same results.
Dont think that big carbs are no good, they are if set up correctly and kept in tune.
I use a pair of 48mm powerbombs on my freestyle boat with no problems.
I hope this clears a few things up, i recomend you read a copy of the Mikuni carb manual, its a good guide and easy to understand for people wanting to know more about how their carbs work.
Last edited:
ANT
Just ride
- Location
- Sea Isle City, NJ
Thanks, I get what signal means now. I have a copy of the mikuni carb thing on my computer. I forgot I had it and never thought to look in it. But thanks I will definetly take a look in there.
waxhead
wannabe backflipper
- Location
- gold coast
think about driving your car with the window down and a chip packet in your hand
at 50mph the chip packet is trying to fly out
at 100mph the packet is really trying to get out
thats the difference the pressure in your car is alot higher than the pressure out side and at 100mph its even moew so
the chip packet is telling you its getting signal and how much
the smaller the carb the faster the air moving and generally the stronger the signal
bear in mind the fuel is not sucked out of the jets its pushed out by fuel pressure
the low airpressure in your carb venturi makes the higher fuel pressure in the fuel want to equalise and it pushes out past the jets
at 50mph the chip packet is trying to fly out
at 100mph the packet is really trying to get out
thats the difference the pressure in your car is alot higher than the pressure out side and at 100mph its even moew so
the chip packet is telling you its getting signal and how much
the smaller the carb the faster the air moving and generally the stronger the signal
bear in mind the fuel is not sucked out of the jets its pushed out by fuel pressure
the low airpressure in your carb venturi makes the higher fuel pressure in the fuel want to equalise and it pushes out past the jets
ANT
Just ride
- Location
- Sea Isle City, NJ
Ok so the reason that i need to block the crossover off with daul 44's is because since the carbs are larger, the crossover needs to be blocked off to increase the air speed which will increase the carb signal?