fuel pressure regulator?

[SidWell]

With the MS is there a need to use a fuel pressure regulator? Should I use the stock regulator that sits on a 280Z intake manifold? Should I keep a vacuum line attached to it?

[z-ya]

Yes, like all EFI systems, you need to regulate the fuel in the rail. You also need to keep the vacuum line so that the pressure at the tip of the injector is the same regardless of the manifold pressure/vacuum. The stock regulator will work find for most all applications.

[mario_82_ZXT]

Yes and yes.

In fact you can use any regulator as long as it is for efi. The one that isn't recommended to use are Rising Rate ones as they make tuning very difficult.

 

Mario

[SidWell]

Thanks guys.

[rztmartini]

I was under the impression that the rising-rate FPR was the ideal one to use and would make tuning easier. When manifold pressure rises, it makes the fuel at the same pressure (in the rail) a little harder to come out. So at 15psi boost, wouldnt that mean that the fuel traveling out of the injector was moving at the same speed as base fuel pressure minus 15? if so, then if your base fuel pressure was 35psi and you were pushing 35psi boost, then no fuel would come out of your injectors...so the rising rate (normally 1psi/1lb boost) would keep the pressure differential across the injector tip the same, regardless of boost.

 

I think i have the right idea, but if i am wrong it would be really nice to know now before something goes terribly wrong and i tell someone else . after all, i have not much room to argue because my car has yet to drive fuel-infected at all...

[Matt Cramer]

I was under the impression that the rising-rate FPR was the ideal one to use and would make tuning easier. When manifold pressure rises, it makes the fuel at the same pressure (in the rail) a little harder to come out. So at 15psi boost, wouldnt that mean that the fuel traveling out of the injector was moving at the same speed as base fuel pressure minus 15? if so, then if your base fuel pressure was 35psi and you were pushing 35psi boost, then no fuel would come out of your injectors...so the rising rate (normally 1psi/1lb boost) would keep the pressure differential across the injector tip the same, regardless of boost.

 

I think i have the right idea, but if i am wrong it would be really nice to know now before something goes terribly wrong and i tell someone else . after all, i have not much room to argue because my car has yet to drive fuel-infected at all...

 

The stock regulator on a 280ZX is a 1:1 regulator, as are most aftermarket regulators. That's what you will want for Megasquirt. A rising rate regulator usually isn't 1:1 - they can add anywhere from 2 to 12 psi of fuel for each psi of boost, and this can complicate things. You want a boost referenced regulator, but not a rising rate one.

[z-ya]

I know this has been beat to death, but it is not more complicated to tune with A RR FPR. If you have enough capacity in your injectors, use a stock regulator. If you are on the hairy edge of having enough fuel capacity, a RR FPR can get more fuel out of your fuel system by increasing the fuel pressure beyond a 1:1 ratio. I have tuned a number of cars, (including my own) that have RR FPRs, and there is no difference in tuning. The goal of tuning is to hit your target AFR across all load and map points regardless of fuel pressure. Think of a RR FPR as an automatic FPR that increases fuel pressure when you really need it (under boost). The problem with using a fixed adjustable regulator is that you have a higher pressure all the time. The pressure may be too high at idle to achieve decent idle quality (depending on your ecu).

[rztmartini]

The stock regulator on a 280ZX is a 1:1 regulator, as are most aftermarket regulators. That's what you will want for Megasquirt. A rising rate regulator usually isn't 1:1 - they can add anywhere from 2 to 12 psi of fuel for each psi of boost, and this can complicate things. You want a boost referenced regulator, but not a rising rate one.

 

I didn't know that the stock regulator was a 1:1 boost referenced regulator, which is what I was referring to as a "rising rate" reg. I'm glad I learned that there were some out there that increase fuel pressure by that much. My Aeromotive unit is a 1:1 so I'm all good.

 

My bad Mario