Post by 358t on Jan 18, 2011 21:18:17 GMT -6
There are FIVE BASIC COMPONENTS to a mechanical fuel injection system.
1. FUEL PUMP
The first and most important component of these systems is the fuel pump. These mechanical pumps are capable of very high pressures and are typically driven off of the crankshaft at half of the engines speed by a belt drive. The fuel pump is sized to output over twice the amount of fuel that the engine requires. Due to this, the system needs to be always be thought of in terms of "bypassing fuel."
2. FUEL CELL
The fuel cell is more important in a mechanical fuel injection system than any other system. This is due to the fact that over half of the fuel is bypassed from the engine back to the tank. It is imperative that the location, size, orientation of the fuel cell and the sizing of the lines is correct. Please keep the below items in regards to the fuel cell.
Fuel Cell Location - Place in front of the engine if at all possibe. If you cannot mount the fuel cell in front of the engine in a door car application due to space limitations we have a surge tank option you can read about on this page. Distance away makes no difference to it is OK for the fuel cell to be in the nose of a dragster.
Fuel Cell Capacity - KillerRONS.COM recommends that the fuel cell capacity be twice that of usage per pass. The typical injected alcohol engine uses 1.5 to 2.0 gallons per pass from "trailer to trailer" so a 3 gallon minimum fuel cell is required.
Fuel Cell Orientation - The pick-up of the fuel cell needs to face towards the rear of the vehicle so that upon acceleration it is covered by fuel. It is not acceptable for the pick-up to be towards the front or side of the vehicle as this could lead to cavitation of the fuel pump and a "lean" condition at launch.
Fuel Cell Vent - Due to the large amount of fuel bypassed back to the tank it is important that fuel cell be allowed to "breathe" with an appropriate vent. An OPEN #6 or 3/8" line is the minimum with NO roll-over valves, one-way valves or filters utilized.
Return Line - All return lines that carry bypassed fuel should dump onto the top of the fuel as far away from the pick-up as possible. No anti-aeration tubes submerged into the fuel should be used.
3. THROTTLE BODY
The third component is the throttle body that sits atop the intake manifold. The throttle body is typically made up of one (Flying Toilet) or multiple (Terminator) throttle blades. The function of the throttle body and throttle blades is nothing more controlling air flow to the engine from idle all of the way through wide open throttle.
4. BARREL VALVE
The fourth component of the system is the barrel valve. In simple terms the barrel valve's primary responsibility is to set the idle mixture by bypassing un-needed fuel back to the fuel cell. Thus, producing an idle mixture that is just rich enough to prevent a "lean" stumble or hesitation when the large throttle body is opened quickly to partial and wide open throttle.
An incorrect idle mixture (excessively rich) along with improper use of the fuel shutoff cable can result in excessive fuel consumption and diluted oil which is the single-most form of user error in these systems. You can read more about how to PROPERLY use the shutoff cable in the second bulletpoint on this page.
Making adjustments to the idle mixture is done with the BARREL VALVE TURNBUCKLE. To adjust the idle mixture, the user should loosen the two jam nuts to allow the tie rod to be adjusted easily. To lean the mixture the turnbuckle would be lengthened which rotates the spool clockwise toward straight up vertical or 12:00. To richen the mixture, the turnbuckle needs to shortened which rotates the spool counterclockwise.
THE "SNAP TEST"
To perform this test you will need to bring the engine to temperature using the shutoff cable with the car in Park and on jack stands. Once at temperature, move the shutoff cable inro the fully "ON" position and give the engine a quick "snap" of the throttle. If the engine response is "crisp" lean the idle mixture by lengthening the turnbuckle 1/2 turn. Repeat this process quickly until the engine stumbles or hesitates. At this point your idle mixture is bypassing too much fuel and is slightly lean. Now it is time to make your final adjustment by shortening the barrel valve turnbuckle one complete turn. You should give the engine one more quick "snap" of the throttle to make sure the hesitation or bog is gone and the engine is "crisp". This is the correct idle mixture as the engine is slightly rich.
SETTING THE IDLE SPEED
Once the idle mixture has been established it is time to set the idle speed (RPM) by adjusting the amount of air shown to the engine at idle. This is accomplished with the IDLE ADJUSTMENT SCREW. Newer systems have an Idle Adjustment Screw on each side of the throttle body. For initial adjustments, it is best to adjust on the barrel valve side only. KillerRONS.COM recommends setting the idle speed no lower than 1000 RPM with the car in gear.
5. BYPASS PILLS AND NOZZLE JETS
The Main Bypass Pill controls the amount of fuel bypassed at partial and wide open throttle. Larger orifice pills lean the mixture by allowing more fuel to be bypassed back to the fuel tank ultimately decreasing the system pressure. On the other hand, smaller orifice pills richen the mixture by not allowing as much fuel to be bypassed back to the fuel tank therefore increasing system pressure. These pills can be changed in a matter of seconds with no gaskets or draining of fuel required.
The final metering in the system takes place at the eight Nozzle Jets that are installed in the injector bodies in each individual runner. The nozzle jets are the only components in the fuel system that do not work in a bypass condition. Larger nozzle jets allow more fuel to pass through to the engine and lower the system pressure. Smaller nozzle jets allow less fuel to pass through to the engine and increase system pressure.
The relationship between the orifice sizing of the Main Bypass Pill along with the eight Nozzle Jets determines the amount of fuel that is delivered to the engine at a specific pressure. New systems are shipped with a baseline setting for the engine's horsepower rating along with analyzing specific information about the engine and vehicle. KillerRONS.COM can also offer free baseline Main Bypass Pill and Nozzle Jet tune-up recommendations by filling out the questionnaire here.
In a small number of engine or fuel system configurations an extra bit of bypassed fuel is required at various RPM's. In these instances a Mechanical or Electronic Hi-Speed Bypass is utilized with a Hi-Speed Bypass Pill. These pills work the same as above in that larger orifice pills lean the mixture and smaller orifice pills lean the mixture.
In summary, these systems are quite simple if you think of them in terms of bypassing the excess fuel back to the fuel cell with the barrel valve bypasses.
For a fully illustrated version of this article including using a leakdown tester to check/set the idle mixture goto www.killerrons.com/why.cfm
1. FUEL PUMP
The first and most important component of these systems is the fuel pump. These mechanical pumps are capable of very high pressures and are typically driven off of the crankshaft at half of the engines speed by a belt drive. The fuel pump is sized to output over twice the amount of fuel that the engine requires. Due to this, the system needs to be always be thought of in terms of "bypassing fuel."
2. FUEL CELL
The fuel cell is more important in a mechanical fuel injection system than any other system. This is due to the fact that over half of the fuel is bypassed from the engine back to the tank. It is imperative that the location, size, orientation of the fuel cell and the sizing of the lines is correct. Please keep the below items in regards to the fuel cell.
Fuel Cell Location - Place in front of the engine if at all possibe. If you cannot mount the fuel cell in front of the engine in a door car application due to space limitations we have a surge tank option you can read about on this page. Distance away makes no difference to it is OK for the fuel cell to be in the nose of a dragster.
Fuel Cell Capacity - KillerRONS.COM recommends that the fuel cell capacity be twice that of usage per pass. The typical injected alcohol engine uses 1.5 to 2.0 gallons per pass from "trailer to trailer" so a 3 gallon minimum fuel cell is required.
Fuel Cell Orientation - The pick-up of the fuel cell needs to face towards the rear of the vehicle so that upon acceleration it is covered by fuel. It is not acceptable for the pick-up to be towards the front or side of the vehicle as this could lead to cavitation of the fuel pump and a "lean" condition at launch.
Fuel Cell Vent - Due to the large amount of fuel bypassed back to the tank it is important that fuel cell be allowed to "breathe" with an appropriate vent. An OPEN #6 or 3/8" line is the minimum with NO roll-over valves, one-way valves or filters utilized.
Return Line - All return lines that carry bypassed fuel should dump onto the top of the fuel as far away from the pick-up as possible. No anti-aeration tubes submerged into the fuel should be used.
3. THROTTLE BODY
The third component is the throttle body that sits atop the intake manifold. The throttle body is typically made up of one (Flying Toilet) or multiple (Terminator) throttle blades. The function of the throttle body and throttle blades is nothing more controlling air flow to the engine from idle all of the way through wide open throttle.
4. BARREL VALVE
The fourth component of the system is the barrel valve. In simple terms the barrel valve's primary responsibility is to set the idle mixture by bypassing un-needed fuel back to the fuel cell. Thus, producing an idle mixture that is just rich enough to prevent a "lean" stumble or hesitation when the large throttle body is opened quickly to partial and wide open throttle.
An incorrect idle mixture (excessively rich) along with improper use of the fuel shutoff cable can result in excessive fuel consumption and diluted oil which is the single-most form of user error in these systems. You can read more about how to PROPERLY use the shutoff cable in the second bulletpoint on this page.
Making adjustments to the idle mixture is done with the BARREL VALVE TURNBUCKLE. To adjust the idle mixture, the user should loosen the two jam nuts to allow the tie rod to be adjusted easily. To lean the mixture the turnbuckle would be lengthened which rotates the spool clockwise toward straight up vertical or 12:00. To richen the mixture, the turnbuckle needs to shortened which rotates the spool counterclockwise.
THE "SNAP TEST"
To perform this test you will need to bring the engine to temperature using the shutoff cable with the car in Park and on jack stands. Once at temperature, move the shutoff cable inro the fully "ON" position and give the engine a quick "snap" of the throttle. If the engine response is "crisp" lean the idle mixture by lengthening the turnbuckle 1/2 turn. Repeat this process quickly until the engine stumbles or hesitates. At this point your idle mixture is bypassing too much fuel and is slightly lean. Now it is time to make your final adjustment by shortening the barrel valve turnbuckle one complete turn. You should give the engine one more quick "snap" of the throttle to make sure the hesitation or bog is gone and the engine is "crisp". This is the correct idle mixture as the engine is slightly rich.
SETTING THE IDLE SPEED
Once the idle mixture has been established it is time to set the idle speed (RPM) by adjusting the amount of air shown to the engine at idle. This is accomplished with the IDLE ADJUSTMENT SCREW. Newer systems have an Idle Adjustment Screw on each side of the throttle body. For initial adjustments, it is best to adjust on the barrel valve side only. KillerRONS.COM recommends setting the idle speed no lower than 1000 RPM with the car in gear.
5. BYPASS PILLS AND NOZZLE JETS
The Main Bypass Pill controls the amount of fuel bypassed at partial and wide open throttle. Larger orifice pills lean the mixture by allowing more fuel to be bypassed back to the fuel tank ultimately decreasing the system pressure. On the other hand, smaller orifice pills richen the mixture by not allowing as much fuel to be bypassed back to the fuel tank therefore increasing system pressure. These pills can be changed in a matter of seconds with no gaskets or draining of fuel required.
The final metering in the system takes place at the eight Nozzle Jets that are installed in the injector bodies in each individual runner. The nozzle jets are the only components in the fuel system that do not work in a bypass condition. Larger nozzle jets allow more fuel to pass through to the engine and lower the system pressure. Smaller nozzle jets allow less fuel to pass through to the engine and increase system pressure.
The relationship between the orifice sizing of the Main Bypass Pill along with the eight Nozzle Jets determines the amount of fuel that is delivered to the engine at a specific pressure. New systems are shipped with a baseline setting for the engine's horsepower rating along with analyzing specific information about the engine and vehicle. KillerRONS.COM can also offer free baseline Main Bypass Pill and Nozzle Jet tune-up recommendations by filling out the questionnaire here.
In a small number of engine or fuel system configurations an extra bit of bypassed fuel is required at various RPM's. In these instances a Mechanical or Electronic Hi-Speed Bypass is utilized with a Hi-Speed Bypass Pill. These pills work the same as above in that larger orifice pills lean the mixture and smaller orifice pills lean the mixture.
In summary, these systems are quite simple if you think of them in terms of bypassing the excess fuel back to the fuel cell with the barrel valve bypasses.
For a fully illustrated version of this article including using a leakdown tester to check/set the idle mixture goto www.killerrons.com/why.cfm
