Tim Murphy

The SFMU operates just like the stock regulator with respect to pressure rise as the manifold comes out of vacuum. I think it is 10-12 psi before manifold goes into boost and takes over from there. Maybe the Corky Bell unit reacts faster? I have disassembled both the Bell unit and the Vortech unit and they are very similar in construction with respect to increasing the fuel pressure with boost pressure. I could not see the lean spot until I added the LM1 and it is definitley there.

GoRideSno

I have always had this impression. They have changed their page now but it used to say that most systems would experience a lean condition between 0-4 psi but not with the 2025. I do know for sure that it reacts much much faster than the boost referenced Aeormotive unit I was using. There was a definate lean spot as you describe. The difference was night and day when I replaced it with the BEGI 2025.

They now make a 2035 which is similar to the SFMU in that it sets baseline pressure too. It's basically the 2025 with an additional regulator.

BEGI Regulators
HTH,
Andy K

Tim Murphy

I just talked to Corky about the 2035 unit and he is not sure if this new unit would be faster or not. The one thing that it does that may help is that you can set the rate of pressure rise to take place before the the manifold comes completely out of vacuum. The only setback for me using/testing this unit is it is not rated above 110-115 psi. Corky thinks that damage may occur in the pilot housing (I think that what is was) if one would excede those pressures. I am way above that fuel pressure under boost.

I am going to install a butterfly plate on the inlet of the sc and open and close it with manifold pressure. This way the sc will go into vacuum when the manifold goes into vacuum and when the manifold get close to atmospheric pressure the butterfly valve will open and the sc will build boost. This is the theory anyway.

BC

Can you email me about the block Tim? Thanks

BC

Do you think this initial-boost lean problem would be solved with a MAP run aftermarket EFI?

Tim Murphy

Yes.

I am checking into the block situation and will let you know.

Gretch

JEEZUS TIM STOPPIT WILLYA................

You ARE the man, buddy, in Soooooo many ways. Now Knock off the wifey pictures before someone says something that is gonna result in denture loss.....

heinrich

I feel strangely compelled to purchase a supercharger of the Vortech variety .... Andy, the gauntlet has been cast ;-)

GoRideSno

LMAO Heinrich
Tim has certainly posted some nice "advertisements". I must admit, it will be hard to compete. Leme see what I can do. I thought only fine beer, cheese and superchargers came from Wisconsin. Seems that the state has some natural resources too.
Oh and Heinrich, be on the look out for a rather hefty box coming from Redondo Beach before the week is out.
Andy

heinrich

YAY!!!! That Cali girl I ordered is FINALLY in stock??!! Nice!

GoRideSno

Fatter rails would be the exact opposite of what needs to be done. Increasing the size of the rails would decrease the pressure within them decreasing flow through the injector. Consider this, the passenger's side rail has about a 15-20% larger voulme than does the drivers side rail. It is longer and has some extra volume inside the hose going to the front damper. It is the last cylinder on that rail too that Tim has blown the gasket in twice. This theory in practice is the Ford Lightning fuel rail. The whole rail is no larger than the line that feeds the fuel from the pump on our cars. So I would say go with a skinnier rail, besides some way of raising pressure faster.
Here's the Lightning rail.

Andy K

Old & New

Andy, I respectfully disagree. A smaller rail will create more line loss / friction to the moving fluid. The amount of "capacitance" would be determined by the volume of the damper.

GoRideSno

O&N,
As much as I would like to take credit for the idea I mentioned above it is actually the suggestion of a fuel injection engineering shop called RC engineering. I actually went to them to get a larger fuel rail made, explained to them Tim's problem and they said that a larger rail would cause more detonation due to a decrease of pressure. Furthermore although the fuel in the lines is under extremely high pressure it does not move quickly at all. Therefore I would have to suppose friction is less of an issue than pressure loss. I was surprised to see that the only fuel rail they offered had an ID of only 1/2" diameter.

Edit, come to think of it, as pressure rises in the rail the fuel even moves slower due to the fact that the regulator is basicly just clamping shut the fuel return line. So at high line pressure friction would be even less of an issue.

Andy K

Jim bailey - 928 International

When dealing with liquids which generally are not very compressible if you have a rigid container and it holds 10 gallons or one cup if the pressure is 50 lbs per square inch and it is full of liquid . If you open a tap the amount of fluid which will spray out before the pressure drops to 5 lbs per square inch is basically the same . Have the same container half full of air and you now have a garden sprayer or accusump and the compressed air will force out a fair bit of fluid . The fuel pressure acumulator used on CIS cars stores 1/2 cup or so of fuel. The pressure damper on the front of the other engines holds very little. Rubber fuel hoses expand and contract a bit . Similar to a garden hose with a closed nozzle on the end when you turn off the spigot at the house then open the nozzle it has one quick burst but a similar hose filled with air at the same pressure "sprays" longer . Open the fuel line on an LH car after it was just running and very little fuel rushes out . Liquids do not compress much which is why we use brake FLUID and try to bleed out all the air.

Tim Murphy

You need to find a different shop because their theory is completely incorrect. I have been involved with fluid power engineering for 18 years and based on what they told you they don't have a clue on what they are talking about.