96Miata!

Hello, I have a 96 turbo miata. I had a question about how the fuel pressure regulator is supposed to work. It is a 3 bar system I know but how is it supposed to act when going into boost? Is the fuel pressure supposed to stay steady at 43 psi or when in boost will it go up by the about of boost pressure? I have searched some and I see it is supposed to be a 1:1 regulator but I wanted to make sure I was right in it meaning in boost it should be 43psi.

If it is supposed to be 43 psi when in boost then mine is going up to about 55psi or so. Does this mean I am overpower the regulator? I have a dw200 fuel pump and flow force 640cc injectors.

Thanks

mjcanton

Your FPR is manifold referenced, so the injectors maintain the same ∆P under various operating scenarios. 55psi under boost sounds about right, assuming you're running ~12psi boost pressure.

96Miata!

Yes It spike to right around 12. I know its manifold referenced I have just heard that its 3 bar which is 43 psi and should stay 43 psi even when in boost but I wasnt sure if that was right.

mjcanton

Pressure across the regulator will be 43PSI because it's manifold referenced. If manifold pressure goes up (boost) the supply pressure also goes up. It's working like it's supposed to.

96Miata!

Okay thank you. I still ltry and search and can't find this info anywhere. Does everyone else agree that the fuel pressure should go up with boost with stock fpr.

96Miata!

Anyone else?

Skamba

Learn to google.

96Miata!

Wow thanks for much. I hadn't already Google before posting.....

Again I just wanted to check that what I was saying was correct. I had someone telling me different so I wanted to confirm.

mjcanton

I think if you do some general searches "how does a manifold referenced fuel pressure regulator work", you would find more than enough information to confirm what I said above. Google is your friend ...

Your fuel supply pressure (what you are measuring) is not static because the FPR is manifold referenced, therefore compensating for vacuum and boost.

Your injector load (i.e. pressure across your injector) is static at 3 bar, because the FPR is manifold referenced.

96Miata!

Okay thank you. I guess I was just getting hung up on the part where you say injectors see static three bar but the pressure obviously goes above 3 bar on the rail when in boost

SpartanSV

The pressure in the rail goes above 3 bar because boost in the manifold is acting against it. 55 psi fuel pressure minus 12 psi manifold pressure equals 43 psi effective fuel pressure. It works the opposite way when you have vacuum in the manifold. If you have 6 psi of manifold vacuum you'll have 37 psi of rail pressure to give you 43 psi effective pressure.

96Miata!

That makes sense now. Than you for your time and explaining it to me.