What's the maximum fuel pressure you should ever see? I'm looking at using an oil PSI electronic guage to monitor fuel pressure and I'm trying to make sure I'm under the guage's limits.

 

well in my 88tII I see 55psi under boost, I don't know if it goes past that ever but thats the highest I've seen it at.

 

I think it's around 60. What's the gauge good up to?

 

95psi I think...

 

In the top-feed ND fuel injectors, we don't see any gain after going past 70psi of fuel rail pressure.
So, keep the maximum under 70psi.


-Ted

 

42psi + your maximum boost if you are running a stock FPR will be your maximum fuel pressure.
95 psi is plenty.

 

wow good info! So you could basically use your fuel pressure guage like a boost gauge??? so I'm seeing 55psi witch is 13psi away from 42 so I'm running 13psi of boost???

 

Depends what your base fuel pressure is... factory specs are 39-42 psi. You could be running 16 psi.
A boost gauge is still a FAR better idea, but this does work. It does all depend, though, on a properly working and referenced FPR.

 

why would a boost guage work better?

 

probably be cause you wouldn't be guessing on how much boost your running because like scathcart said the factory specs are from 39-42. unless now you knew that it would be 39, 40, 41, or 42 every time before boost.

 

What does boost have to do with fuel pressure?

 

because the fuel pressure rises under boost 1psi for every psi of boost.

 

so what the hell would I use a boost guage for? I don't care about boost I want to know fuel psi...

 

Oh gawd...


-Ted

 

 

well ****...

 

From the FSM, regulated (static) fuel pressure should be 36-37psi for S4's and 34-40psi for S5's.

For NA's that's the highest you'll ever see. For turbo's you add your max boost to get max fuel pressure.