327_TPI_77_Maro

iTrader: (8)

I have a good running stealth rammed, self-tuned 350 chevy that I just installed an electronic 0-100 psi fuel pressure sender and gauge on the other day. If I set the fuel pressure such that it reads 43 psi on the gauge with the vac line to the adjustable holley fuel pressure reg disconnected and plugged and the engine idling, then plug the vac line to the reg back in and go for a drive, I see 34 psi at cruise, 32 psi at very high vac conditions (decel from high speed w/ closed throttle) and 39 psi at WOT. I made a video of a zero to very high speed full throttle run where I never let off, and the fuel pressure stays at 39 the whole time. My wideband AFR stays rock solid around 12.2 for the whole run (yeah I know its rich, still roughin in the tune)

My question is, for anyone who has an in-car fuel pressure gauge for an EFI vehicle, is it normal for the pressure to never hit the zero-vacuum set point of ~43 PSI or should I take this to mean I have an intake restriction and my engine vac is not dropping to near zero like it should? Or should I suspect the Holley reg has a problem? I remember hearing a lot of people complaining about these regulators years ago when I first got the Stealth Ram.

I don't know what my engine vac is @ WOT, I will hook a gauge up and check it this weekend and report back. I have a cheap chinese cotton gauze 6"x5" cone filter on an aftermarket 3" intake duct w/ stock MAF in it. I did a quick calc and the surface area of the filter looks sufficient for my CID and RPM but that assumes the filter media was made properly...I have a K&N cone twice the size on order tonight to check out if the filter is causing a restriction.

Thanks for any ideas or input.

Steve

327_TPI_77_Maro

iTrader: (8)

It was the air filter...WOW. Those chinese no name cone filters are THAT bad. Changing it to a K&N cone leaned out the WOT AFR by a full point and I had to re tune. My fuel pressure now comes within 1 psi of the 43 psi set point at WOT. The chinese cone filter was that restrictive that it was leaving a significant amount of manifold vacuum @ WOT due to the huge restriction it caused.

The_Punisher454

Which type of Chinese filter do you have? I have been looking at some of the long cone Spectre filters and wondering how well they work, this may give me second thoughts.

327_TPI_77_Maro

iTrader: (8)

I don't remember what brand it was, it looks exactly like the Spectre ones though. Just get a K&N, it's not worth saving a few bucks on these things.