1 fuel pressure fluctuations Sun Mar 07, 2010 8:18 am
Ned
Life time member
Hi brick pilots.
For some time I have been looking at the vacuum fluctuations generated at the throttle bodies vacuum ports. Because the vacuum port is close to the butterfly edge the fluctuations are pretty wild. Has anyone looked at this
The vacuum port is connected to the fuel regulator to compensate for engine load. However, if you connect a pressure gauge to the fuel line, the vacuum fluctuations translate to pressure fluctuations. I am sure that BMW have taken this into account, but I thought to see if I can reduce the this and see how it affects the performance.
I've installed a restriction into the line close to the throttle body and thus reduced the pressure fluctuation by 90%+. The restrictor is a tube with a inside diameter of 1mm or less which is about 2-2.5cm long and plugs into the existing vacuum line. Something like Carbtune restrictors.
The effect? the bike seems to be smoother with less vibration on idle and midrange. The pressure is steady and does vary with the vacuum change as it should.
I though that I was kidding myself until I got home from a longish ride to find that the idle has gone up by a few hundred rpm. I assume that I am getting more fuel into the cylinders because of reduced pulsing of the pressure regulator. I need to investigate this, but unfortunately, I will be away next week for the most of it.
Any ideas, comments?
For some time I have been looking at the vacuum fluctuations generated at the throttle bodies vacuum ports. Because the vacuum port is close to the butterfly edge the fluctuations are pretty wild. Has anyone looked at this
The vacuum port is connected to the fuel regulator to compensate for engine load. However, if you connect a pressure gauge to the fuel line, the vacuum fluctuations translate to pressure fluctuations. I am sure that BMW have taken this into account, but I thought to see if I can reduce the this and see how it affects the performance.
I've installed a restriction into the line close to the throttle body and thus reduced the pressure fluctuation by 90%+. The restrictor is a tube with a inside diameter of 1mm or less which is about 2-2.5cm long and plugs into the existing vacuum line. Something like Carbtune restrictors.
The effect? the bike seems to be smoother with less vibration on idle and midrange. The pressure is steady and does vary with the vacuum change as it should.
I though that I was kidding myself until I got home from a longish ride to find that the idle has gone up by a few hundred rpm. I assume that I am getting more fuel into the cylinders because of reduced pulsing of the pressure regulator. I need to investigate this, but unfortunately, I will be away next week for the most of it.
Any ideas, comments?