Quote:
Originally Posted by Nissan370
Ok as I prepare to get deep into the 500 and 600 hp range
What are the reasons to go return style on my fuel system
And why would just staying return less be a bad idea
ATM I am using 340lph automotive fuel pump and 750cc injectors
I will be jumping up to a 950cc injector
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Generally we tell people that the stock fuel system is adequate for 500-550rwhp (turbocharged). Thats not saying you couldnt squeeze more out of it with perfect or even less-than-perfect circumstances... but its not the best idea to consistently run a fuel system at its maximum capacity unless you are heavy into your vehicle tuning and logging and give it above average attention and monitoring.
But our power estimates are assuming all things in the engine are stock. Once you reduce your volumetric efficiency with lower compression.. you are reducing the efficiency of your fuel system as well.
For two reasons. The most obvious is the common sense that a lower compression ratio makes less output of the provided air/fuel mixture. So it will take more air and more fuel to get the job done. The less obvious reason is a side effect of the higher boost pressure it will take to get to the same power. Since you need to add more air to make the same power with lower compression, you will end up at a higher boost pressure to achieve the power. The higher boost pressure will reduce the fuel pressure differential.
The fuel pressure differential is the difference in pressure from your intake manifold to your fuel rail. Your factory fuel pressure is around 52 psi at the regulator (in the tank). Imagine your intake manifold operating at 52psi of boost... the injectors would merely drip fuel into the manifold when they open. That is just an extreme example to convey how intake manifold pressure has an effect on the delivery of fuel from the injectors. There are also effects on injector spray pattern, or fuel atomization, from operating at a lower fuel pressure differential.
These reasons and more have to do with why we are generally more comfortable pushing the stock 370z fuel system further than say the 350z DE fuel system, as the VHR motor is so much more efficient.
So while we say 500-550 for a stock engine turbocharged... it will be lower for built engines, and also lower for supercharged cars (superchargers consume power from the crankshaft before it makes it to the wheels). I wont say that people cant go further... they can and they will. Recommendations are just about when things are clearly safe. Running outside safety boundaries can mean inconsistency.. from car to car, or from day to day in the same car.