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If you're running a Sniper unit that does not contain a built-in regulator and you're also running a returnless system and are having issues with erratic AFRs, please read on. Here's my setup:
Pontiac OHC 6 Sprint, Sniper QuadraJet, Holley Muscle Car In-tank Fuel Module and no return.
The issues: I first noticed that while the engine was running, my fuel gauge (mounted to the inlet of the throttle body) was not steady. By that I mean that it was nearly vibrating back & forth between ~50-65 PSI at a rate of 60-100 Hz making the needle of the gauge a complete blur. This is a liquid filled gauge by the way. I was also having issues with the engine going lean when I would go from idle in park to a drive gear. I thought the system would Learn what to do in this scenario, but it never did. There was also the issue of the engine going lean at a certain RPM and then rich at another certain RPM. Again, I thought the system would Learn what to do, but the RPM sensitive lean/rich condition never solved itself.
So I started doing some research and here is what I found: I was getting a harmonic resonance in the fuel system caused by the injectors opening & closing. Think of a pressurized column of liquid with a valve at the end. When you open that valve, the pressure drops in the column and when you close that valve the pressure rises again. Now, put four valves on the end of that column that open and close many times per second. What you end up with is a column of pressurized liquid that is literally vibrating creating a sine wave. If we apply this theory to the fuel system with injectors as the valves, something interesting starts to happen with the sine waves. We all know that sine waves with the same amplitude, but traveling in opposite directions create a standing wave, or a net-zero effect. When this happens in a fuel system, the opposing sine waves effectively drop the fuel pressure at the injectors to zero momentarily causing them to not fire and creating a lean condition. On the opposite side of the coin, when the sine waves line up in the same direction, the resulting pressure to the injectors is increased to the point that they can no longer hold back the flow of fuel creating a rich condition. These effects are nearly impossible to fix by tuning the ECU. You can get close, but never eliminate it totally.
The solution: Radium Engineering makes a universal inline fuel pulse damper. Its job is to smooth out the pulses generated by the opening and closing of the injectors effectively killing the sine wave in the fuel system. After installing this unit the gauge is now rock-steady! The very first thing I noticed was that the idle was much smoother and the AFR at idle was a lot steadier. After letting the car warm up for a bit I took it on a 20 minute drive and all of the RPM related rich/lean spikes were gone. I also noticed that when the system would go rich or lean it was due to throttle position, not RPM, and it would correct itself very quickly. I'm still running the same fuel map that was in place before installing this unit, but I know that it will Learn and re-map the Base Fuel Table based on what it's seeing now because the fuel pressure is no longer being affected by the sine wave created by the injectors.
Now, if you're running a Sniper unit with the fuel pressure regulator mounted to the inlet of the throttle body, none of this will apply as the regulator will serve dual-duty as a regulator and a damper. However, if you have one that does not have the regulator at the inlet and you're experiencing erratic AFRs and your gauge is a blur, get one of these. Also, if you're running one without the regulator at the inlet, but you've got a regulator under the hood close to the Sniper unit, that may also help dampen the sine wave. My scenario is slightly unique in the sense that I'm running a returnless system with the regulator in the tank which makes a lot of room for the sine waves to build up and be a problem.
I'd like to thank everyone that has helped along the way in my journey and I hope that my research will help someone else in the future. Here's a pic of the installation:
Pontiac OHC 6 Sprint, Sniper QuadraJet, Holley Muscle Car In-tank Fuel Module and no return.
The issues: I first noticed that while the engine was running, my fuel gauge (mounted to the inlet of the throttle body) was not steady. By that I mean that it was nearly vibrating back & forth between ~50-65 PSI at a rate of 60-100 Hz making the needle of the gauge a complete blur. This is a liquid filled gauge by the way. I was also having issues with the engine going lean when I would go from idle in park to a drive gear. I thought the system would Learn what to do in this scenario, but it never did. There was also the issue of the engine going lean at a certain RPM and then rich at another certain RPM. Again, I thought the system would Learn what to do, but the RPM sensitive lean/rich condition never solved itself.
So I started doing some research and here is what I found: I was getting a harmonic resonance in the fuel system caused by the injectors opening & closing. Think of a pressurized column of liquid with a valve at the end. When you open that valve, the pressure drops in the column and when you close that valve the pressure rises again. Now, put four valves on the end of that column that open and close many times per second. What you end up with is a column of pressurized liquid that is literally vibrating creating a sine wave. If we apply this theory to the fuel system with injectors as the valves, something interesting starts to happen with the sine waves. We all know that sine waves with the same amplitude, but traveling in opposite directions create a standing wave, or a net-zero effect. When this happens in a fuel system, the opposing sine waves effectively drop the fuel pressure at the injectors to zero momentarily causing them to not fire and creating a lean condition. On the opposite side of the coin, when the sine waves line up in the same direction, the resulting pressure to the injectors is increased to the point that they can no longer hold back the flow of fuel creating a rich condition. These effects are nearly impossible to fix by tuning the ECU. You can get close, but never eliminate it totally.
The solution: Radium Engineering makes a universal inline fuel pulse damper. Its job is to smooth out the pulses generated by the opening and closing of the injectors effectively killing the sine wave in the fuel system. After installing this unit the gauge is now rock-steady! The very first thing I noticed was that the idle was much smoother and the AFR at idle was a lot steadier. After letting the car warm up for a bit I took it on a 20 minute drive and all of the RPM related rich/lean spikes were gone. I also noticed that when the system would go rich or lean it was due to throttle position, not RPM, and it would correct itself very quickly. I'm still running the same fuel map that was in place before installing this unit, but I know that it will Learn and re-map the Base Fuel Table based on what it's seeing now because the fuel pressure is no longer being affected by the sine wave created by the injectors.
Now, if you're running a Sniper unit with the fuel pressure regulator mounted to the inlet of the throttle body, none of this will apply as the regulator will serve dual-duty as a regulator and a damper. However, if you have one that does not have the regulator at the inlet and you're experiencing erratic AFRs and your gauge is a blur, get one of these. Also, if you're running one without the regulator at the inlet, but you've got a regulator under the hood close to the Sniper unit, that may also help dampen the sine wave. My scenario is slightly unique in the sense that I'm running a returnless system with the regulator in the tank which makes a lot of room for the sine waves to build up and be a problem.
I'd like to thank everyone that has helped along the way in my journey and I hope that my research will help someone else in the future. Here's a pic of the installation:
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