Rising Fuel Regulator

[kid nismo]

Will it be possible to use a non-rasing adjustable fuel reg on our ET?

my understanding of rasing fuel regs are that, they are more for non standard turbo engine.

since i'm running a microtech, the comp will be determining the fuel level under boost rather than the adjustable fuel regulator itself.


Is this right?


cheers

[Callumgw]

The computer does not set fuel pressure.

The regulator sets the fuel pressure based on the manifold pressure.

For a fixed rate unit the fuel pressure is a constant amount above the manifold pressure. This is how the standard ET/Exa one works. So for example the fuel pressure will always be 36psi higher than the manifold pressure

For a rising rate regulator the pressure difference increases as the manifold pressure increases. Here the fuel pressure may be 36psi higher at 0 vac and increase to 64psi at 10 vac. The amount of change is what sets the "rate" of the rising rate.

C

[Kimmo]

I could be mistaken, but I was under the impression the point of a rising-rate regulator is to compensate for the standard ECU's shortcomings by increasing the amount of fuel to pass through the injectors while they're open as boost rises, second-guessing the ECU...

Not exactly an elegant solution, and I gather it's pretty tricky to set up right. With a decent aftermarket ECU with enough sensors plugged in and big enough injectors, the ECU should be able to deliver the correct amount of fuel by opening the injectors for the appropriate amount of time, rendering a rising-rate regulator superfluous.

[kid nismo]

so any adjustable regulator will do, as long as the ECU is tuned and the adjustment on the regulator are to factory spec???

[Kimmo]

Why would you use the stock fuel pressure if you have an adjustable regulator and an aftermarket ECU?

You could prolly do stuff like telling the ECU it's using bigger injectors but bumping the pressure instead... yeah guys? Or am I just tripping.

[Callumgw]

adjusting the fuel pressure differnce will change the amount the injectors flow and may effect the spray pattern. So tune hte ECU to the base pressure you choose. Aftermarket adjustable ones look swanky, add a gauge to the fuel system and make the fitment universal, becasue you cn dial in the required pressure for different cars. There isn't mauch sense in changing unless your stock one is bust or you want a pretty thing under the bonnet or you want to change the base pressure.

C

[Damo]

Why would you use the stock fuel pressure if you have an adjustable regulator and an aftermarket ECU?

You could prolly do stuff like telling the ECU it's using bigger injectors but bumping the pressure instead... yeah guys? Or am I just tripping.

Literaly 99.9% of multi point petrol injected cars use between 2.5-3 bar of fuel pressure. Basicly an industry standard. 'They' probably adopted this as there was no reason to push any harder as the gains wern't worth the cost.
The pros to using higher pressure would be a better fuel atomisation, higher flow potential through an injector and more accurate fueling. Cons, shorter life span of pumps, pump flow potential drops markedly, more likley hose rupture, sticking injectors and a harder life for the injectors.

If you are just upping pressure to get more out of the stocko injector, note that the % increase in flow is equal to the square root of the % increase in pressure.

eg to get 10% more out of injectors you must increase pressure by 21%.

1.1 squared = 1.21 so 36psi + 21% = 43psi makes 250cc - 275cc

1.3 squared = 1.69 so 36psi + 69% = 61psi makes 250cc - 355cc



Damo

[kid nismo]

......would be a better fuel atomisation, higher flow potential through an injector and more accurate fueling......


Damo

damn thats creepy Damo. Exactly what my brother said, except he didnt mention the CONS to me lol.

thanks guys for the feed back.

[Kimmo]

note that the % increase in flow is equal to the square root of the % increase in pressure.

Nice point