Oh, and check this out.......or wrap your brain around it. When the car is in "decel fuel cut", the Maggie growl noise goes away (18.1:1 AFR). Just as soon as the "decel fuel cut" goes away, and AFR returns to 14.7:1, the noise returns. At light loads and at idle, the noise is there.........hell if I know what it is
Well, the growl is fixed!! I am so happy, and so is my wife, as now the Magnacharged G8 is almost whisper quiet, besides the "cool guy blower whine" when you get into it.
Here is what I found............I came home from work one day and grabbed my mechanics stethoscope and started poking around under the hood. I checked all the points on the blower where I though the noise could eminate from, like the bearings on the rear pulleys, or blower case, etc etc. I then stuck the stethoscope on the fuel rail........BINGO.........there's the noise. I followed the fuel rail over the fuel block, and then from the fuel block to the OEM fuel. The OEM fuel line was resonating as well (I could actually feel it with my hand!), and I was like, "I'll be damned". The OEM fuel line between the fuel block and the fire wall consists of a quick coupler-to plastic line - to quick coupler, and then a steel line that snakes down behind the firewall banket. Originally I thought to split a piece of hose, and push it over the OEM steel fuel line, and attempt to snake that down behind the blanket. The idea here was to use the rubber hose to isolate, or dampen the pulses / resonance that I was hearing / feeling. Well, that didn't work, as it was impossible to push the rubber hose over the OEM line that resides behind the blanket.
I shared my findings with Magnacharger, and we came to the conclusion that I was experiencing a "water hammer effect". When the injectors are opening and closing, the constant pressure drop / refill / pressure drop refill causes a frequency to generate within the rails. On some applications, a "dynamic fuel pulse dampener" is recommended to "zero out" the potentially harmful frequency. Being the cool guys that they are, the boys at Magnacharger had something for me to try. Basically I was going to use a C5 fuel block that utilized the OEM "fuel pulse dampener", and attempt to graft that onto to my G8 fuel supply components. There were a few fitment issues, but since this was more of a proof of concept, or validation, I was up for the challenge. I had to make a few mods, but the results are worth the effort. The fuel rails, fuel block, and fuel line are now very stable, I can no longer feel the nasty pulse / resonance, and more importantly, there's no "GROWL" in the cab. My wife is now happy......and so am I!
Here is what the dampener looks like:
http://www.whipplesuperchargers.com/product.asp?ProdID=1196
Apparently GM, and many others, use this when the fuel system requires it. Quite frankly, I'm surprised this device is not required on ALL mechanical returnless fuel systems.
Here are some shots of the fuel block with pulse dampener: