Stock fuel pressure NA8 -> AFPR
 

Hello!
My question concerning N/A miatas but maybe it's similar to turbo/SC cars

I have some questions about the stock NA 1.8 fuel pressure.
I read that the stock fuel pressure on NA miata was set to 3b (43.5psi) but I would like to know what is the stock pressure at idle? Something around 35psi?

I ask you about that because I need to know the stock pressure at idle and wot before I can put my AFPR and adjust it correctly.
I have an AFR gauge but just want to know that ;)

Thanks a lot!

Ps: It's important to run vacuum line connected on the intake manifold?

Anyone ?

Stock is 43.5 Manifold referenced. If you idle at 30 kpA, that is about -10 psig. So, yes, 43.5 - 10 = 34 psig at idle.

You should run the line to the intake manifold. Otherwise, you negate the benefit of a constant pressure across your injectors.

It seems to me that a better choice, overall, is to increase injector size (but go with ID of FF), rather than increase fuel pressure.

If this is N/A, why an AFPR at all? Is there some reason you want more fuel?

If you only need a little more, get some NB1 injectors.

Rhetorical. I don't really care, just food for thought.

So I should adjust my AFPR to have 35 psi at idle and it will increase to 43 psi in cruise/wot condition to have similar condition as stock. Yes, it's just to have a baseline ;)

Ok ok! A friend of mine suggested me to disconnect the vaccum line during the adjustment of the AFPR and after that, to reconnect this vaccum line.

Yes, I have this AFPR (Malpassi/Sytec) for a long time in my garage and it's the opportunity to use it.
It's also because I will run soon a BP4W head, with 30thou shaved, BP6D square top intake mani and a full exhaust. I just want to be sure that I don't run lean with this setup. If it's the case, I can raised (or also lower the fuel pressure) for the best performance of my car with the possibilty to have a look on the AFR.

Yes I know, MS is the answer but in my case, it's free and should work. Maybe one day, I'll use a MS.

The stock fuel pressure regulator already increases fuel pressure if you go into boost. If you run 10 psi it will run 53.x psi.

If you have a rising rate fuel pressure regulator then it will add multiples of fuel pressure when you go into boost. This is often abbreviated rrfpr.

OP states he has no FI plans.

Yes, like DNMakinson said, no FI plan ;)
Another question, what is the maximum pressure the NA8 injectors can tolerate?

Early morning reading failure by me. Please continue.

The way you adjust it is by pulling the vacuum line off, adjusting to 3bar, then put the vacuum line back on. Don't set it while hooked up because not every engine pulls the same amount of vacuum.

Also, if you plan on switching to a BP4W head and squaretop and other bolt ons you need a standalone ECU anyways.

Thanks guyz for the helps! ;)
Yes MS, one day!

Do you know what is the maximum pressure the NA8 injectors can tolerate? :hs:

Yup ;)

Stop trying to tune your car with a fuel pressure regulator. Buy a standalone ECU and stop bumping this thread.