MPI Fuel Pressure regulator

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On the L200 MPI inlet manifolds, what fuel pressure regulator do people run? The thingy that sits on the fuel rail to keep the injector tips at a cosntant pressure.

Is the original L200 one OK for running boost into it? Or do the Starion/some other turbo mitsubishi ones fit?

[ProZac]

You need a rising rate regulator to increase the fuel pressure at the same rate as the manifold pressure, this keeps the pressure differential across the injector the same under positive manifold pressure.

The L200 unit isnt suitable, as it's not a rising rate regulator.

Most of the setups I've seen use an aftermarket fuel rail adaptor that converts the two bolt flange on the end of the rail to an AN fitting, or a simple barb. They then use an aftermarket fuel pressure regulator mounted on the firewall or inner fender.

Don't get a cheap fuel pressure regulator, they're really unreliable. Go for an Aeromotive, or SARD unit.

[thrash]

Sorry Zac, but a little correction - you need a regulator from a turbo car, not a rising rate one.

Regulators from N/A cars are not designed to see boost, and so do not work properly on a turbo motor. If you get one from a turbo car, as Zac said, is designed to match fuel pressure with manifold pressure so that the pressure differential stays the same.

A rising rate regulator is a different beast. It does not increase fuel pressure proportionally (up to a limit) with manifold pressure, it raises the fuel pressure exponentially when compared to manifold pressure. Most aftermarket ones are usually adjustable so you can actually use one as a standard turbo regulator by setting the pressure ratio to 1:1. I think this is what Zac is referring to when he says use a rising rate regulator.

That's not to say you can't use a rising rate one with the ratio adjusted differently, you'd just have to tune with the fuel pressure (and hence flow at any injector opening) increase in mind.

From what I gather, some professional tuners prefer to not use them at any other ratio as it adds another variable to the equation.

[ProZac]

A fuel pressure reg that increases fuel pressure 1:1 with manifold pressure has always been known to me as a rising rate regulator. There are most definitely RR regs out there that aren't a 1:1 ratio, but best to stay away from those.

[Bitza]

What do you guys think of the Malpassi turbo regulator?

Fully adjustable and has basically 1:1 ratio for boost.

I currently run 25 psi on idle (as the Rochester injectors are 800cc) and 25 psi boost which sees injector fuel pressure at 50 psi total.

If I wind the base fuel pressure up (say to 40 psi) then I have no room to drop injection timing and the air/fuel ratio is still RICH, 25 psi was close to 14.7:1 at idle conditions.

[fugazi]

The Malpassi is good. The copy's not so very...

[1320ft]

Malpassi regs are good, used to use them on everything.

But I can supply you one of our Proflow Compact EFI regs with a gauge for the same price as just the Malpassi Reg

http://www.vpw.com.au/Category/Index/357684

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I always called the non linear FPR's as "rising rate". I asked as it seems like some of the Mitsubishi FPR were used in both N/A and turbo applications.

Anyway I probably don't need adjustable at this stage so I'll look at getting an Evo one to fit the rail. I'm hoping the o-ring and bolt centres will be the same :?

[fugazi]

Proflow Compact EFI regs with a gauge for the same price...

Resistant to alcohol (E85)?

[1320ft]

Resistant to alcohol (E85)?

Yeah, they have an e85 resistant diaphragm.

[JA83]

the stock non turbo fuel pressure reg will be fine but not ideal. When the engine is creating a low pressure in the intake (vacuum) the fuel pressure will be lower, then when the throttle is wide open it will go to full regulated pressure.. say 35-40 psi. as long as the fuel pump can maintain enough flow under boost with a non turbo reg there is no issue, it wont lean out as long as the tuner has the a/f ratios correct under full load!

In my eyes rising rate fuel pressure regs are for cars on stock ecu's that have more boost/timing put into them and to push more fuel through an stock injector during its duty cycle to compensate roughly.

[ProZac]

the stock non turbo fuel pressure reg will be fine but not ideal. When the engine is creating a low pressure in the intake (vacuum) the fuel pressure will be lower, then when the throttle is wide open it will go to full regulated pressure.. say 35-40 psi. as long as the fuel pump can maintain enough flow under boost with a non turbo reg there is no issue, it wont lean out as long as the tuner has the a/f ratios correct under full load!

In my eyes rising rate fuel pressure regs are for cars on stock ecu's that have more boost/timing put into them and to push more fuel through an stock injector during its duty cycle to compensate roughly.

Almost all turbo cars have a fuel pressure reg that increases fuel pressure in response to positive manifold pressure.

Say your turbo is generating 7 psi of boost, if your standard fuel pressure of 40psi is maintained constant by the regulator, then the injector only has a pressure difference of 33psi across it. You could increase the duty cycle to give it some more fuel, but you'll strike atomisation problems as the injector will effectively be working at a lower supply pressure than it is designed for.

If you use a regulator which increases the fuel pressure pound for pound with manifold pressure, the pressure difference across the injector remains constant. Easier to tune and keeps the injectors working in its specified pressure range.

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I managed to get an EVO4 one for next to nothing so will wait until that arrives, see if it fits and report back here!