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HybridZ

Under pressure


John Scott

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The information from the fuel injection posts is pretty amazing. Also got me thinking..actually worrying about my fuel pressure. My budget Z has never had a visible fuel gauge to see whats really happening under boost. I have no question that my Mallory 140 can supply enough fuel, but I've been reminded now that I'm seeing some pretty high boost #s, the importance of having 7# over your boost psi. There is no way the Mallory can deliver 23 psi! This is an issue of line pressure overcoming boost, not flow rating. So now I need to shell out another $300 for a pump that can push mid 20 psi, or is there a cheaper alternative? Anyone know what the Mallory maxes out at? At ANY boost level my wimpy 15 psi gauge is pegged.

JS

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quote:

Originally posted by John Scott:

<snip>I have no question that my Mallory 140 can supply enough fuel, but I've been reminded now that I'm seeing some pretty high boost #s, the importance of having 7# over your boost psi. There is no way the Mallory can deliver 23 psi! This is an issue of line pressure overcoming boost, not flow rating. So now I need to shell out another $300 for a pump that can push mid 20 psi, or is there a cheaper alternative? Anyone know what the Mallory maxes out at?

JS


 

Well... you're not going to like the answer...

 

m140_g.jpg

 

 

As you can see, the 140's output decreases dramatically above 12psi. Looks to me like if you want to run 15psi of boost, you probably ought to be looking for a different pump - sorry. (this would make a great pump for feeding a surge tank, though smile.gif)

 

Actually, I'd be willing to bet that the stock zx turbo's pump would flow plenty at 20psi (remember, flow capacity goes up with decreasing pressure). The stock n/a EFI pump might even work. Unfortunately, though, I've never flow tested one to know for sure. How much horsepower are you planning on?

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