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Discussion Starter · #1 ·
I've installed a high performance exhaust and K&N filtercharger set up on my '82 280ZX turbo. I've been told by many mechanics that these cars run very lean. There are a few tricks, such as adjusting the AFM spring tension, but it seems that increasing the fuel pressure is one way of getting a little more fuel into a car that is breathing freely.

The fuel regulator maintains a difference between manifold vacuum and and fuel pressure at a constant 36psi. This explains why you don't read 36psi at idle when you hook up a fuel pressure gauge. At idle, manifold vacuum is about 15 - 20, so the fuel pressure would read about 25psi. At open throttle where manifold vacuum falls to 0, fuel pressure guage would read about 36psi.

You could increase fuel pressure by installing an adjustable fuel pressure regulator, but these are expensive >$150 and would require some bracket fabrication. Or you can simply do what the pressure regulator does, restrict the flow of fuel to maintain a set pressure limit. I've taken a small fuel injection band style clamp and attached it to the fuel return line. I can increase the fuel pressure by restricting the return flow. Instead of an idle pressure of 25psi and full boost of 36psi, I can now get a range of 30psi to >40psi. Just enough to match the free flow exhaust and K&N filtercharger. Car seems to run a little smoother and respond better.

So Z-experts, does this seem reasonable? Before I would recommend this technique to anyone, I'd like to hear what the Z-experts think.

Regards,

Chuck

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Discussion Starter · #2 ·
Chuck, altering fuel pressure is not worthwhile, on your car until you start making about 15 to 20 more bhp. First the fuel rails are too small to deal with increased fuel pressure. There are a couple of guys out there that are now making fuel rails that are high flow and capacity($200) but unless you were to go with a massive increase in turbo boost, there is no performance benefit. Second, the injectors that are on your car are of the old style Bosch pintle and seat, and these injectors cannot not take any kind of overpressure or they fail in the open position. The injectors can be replaced with newer style ones, and these injectors can run at a higher pressure without danger, yet that won't add to your performance the way you want. In order to take advantage of the performance upgrades that you've done, talk to the guys over at Jim Wolf Technologies, and they can custom program a zxt computer for you. Not only would that be your best power gain for the dollar, but also the safest on your engine without blowing out your components.
 
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