Propane (LPG) Questions

[STEEVO]

Hi,

I was wondering what you can tell me about manifold types and what is the best for LPG use between dual plane and single plane in V8 engine use.I have heard that LPG takes up more space in the manifold therefore a single plane is most benficial but would a single plane sacrifice torque etc like its equivelant pertol engine does or is LPG fuel not affected by these things.All of that said, If i was to use a carby spacer on my Edelbrock Performer mainifold with an impco 425 and Holley 4 barrel baseplate setup,Which would be best to suit the characteristics of a dedicated LPG fueled performance street engine out of the "Open" type and 4 hole spacers etc and is the insulated "phenolic" spacer of any benefit?

Thanks

 

[franzh]

LPG does indeed take up incoming air volume (from 4 to 8%) which in turn decreases the VE. Logical thinking states that the intake runners should then be larger to accomodate the different air mass, but then the velocity decreases, leading to a poor lower end torque and poor part throttle response.

Generally speaking, use the best available aftermarket intake manifold for the next larger engine size as long as the engine family is the same. The manifold should benefit from the air-gap too, the cooler the intake is, the more dense the air-fuel charge. If the combined air-fuel mass is heated, the LPG expands at a greater rate than the air (its 1.5 times more dense) thus altering the air-fuel mixture.

The spacer simply increases the manifold volume which can increase power slightly, and the phenolic spacer helps keep everything cool too. If you are running the multi-plane manifold, the 4 hole spacer is better, if it is an single plane, the open plenum spacer is better, but dont expect to see a great horsepower increase with either one though.

Dont forget to monitor the LPG temperature as it exits the vaporizer. It should not exceed about 80 deg F (28 deg C) under load. Super heated LPG heats up the air, and ruins the advantages of the cooler manifold.

Franz

 

[egkgoud]

What is the hdro static test pressure for 150 MT capacity above ground LPG Storage Vessel ?

 

[franzh]

In the US, ASME tanks are listed by the hydraulic volume listed as "water capacity", and is listed in gallons.

According to the ASME standard, these tanks are 250 psi, and earlier tanks are tested to 4 times this pressure. Later tanks are tested at 3.5 times.

Either way, its whatever the dataplate states as the working pressure, currently, its 3.5. In the US, NFPA 58 is the code guide here.
Franz

 

[bilgebill]

Franzh, I have recently installed a dual 425 impco setup on my stock 88 454. I am having trouble getting it tuned right. It seems that it can not handle a wide open throttle(too much flow.) Should I go with just a single 425. Also it has no power. Is this due to timing or am I perhaps adjusting the valves incorrectly. I read an earlier thread in which you explained about the larger screw being the max power valve. Is that the center screw or the outer screw. Any advice is appreciated. Thanks.