Fuel Pressure Regulators

[SeriesIIGTST]

Hi all,

Was wondering, people state that when you start modifying your engine, you should get a rising rate fuel pressure regulator or something like that. How does this help? Is this something only moderate/heavy modified engines should have or will it give gains on any engine regardless of state of tune?

Cheers!

[macka]

The skylines run really rich right.

Say 10 parts air to 1 part fuel

On a mildly modified engine u can use this adjustable reg to wind the overall pressure down when on boost so that your mixtures can come back to say 12:1 more power more fuel economy

On a higher modified car u can use it to bump up the pressure to make your injectors squirt more so u can delay having to buy bigger units..Also a bigger fuelpump sometimes requires u to use a reg.

cheers

[blind_elk]

I may be wrong here, but I understood that a rising rate reg did the opposite.

A factory reg runs a 1:1 ratio between boost and fuel pressure, so for each psi of boost, the regulator increases the fuel pressure by 1 psi.

A rising rate reg runs 1:1-and-a-bit boost:fuel pressure, so for each psi of boost, the regulator increases the fuel pressure by say 1.1 psi. At higher fuel pressures, more fuel is injected at a given injector duty cycle. This is to stop the A/F leaning off at high boost levels.

The advantage of rising rate reg is that they can be adjusted to give a different-from-factory base fuel pressure, say 45 psi at idle instead of 40psi at idle. This is a cheaper way than fitting a set of higher capacity injectors.

[macka]

Yep your right as youve taken that from somewhere iv read before Thats for rising reg.

Some regs u can go down as well and lean your settings out

[blind_elk]

I actually realised that after I posted. Because you can adjust the pressure, you can reduce as well as increase the base pressure. Therefore you could effectively lean off the mixtures a bit (on a dyno of course!) by reducing the base pressure.

[SLY33]

Originally posted by SeriesIIGTST

Hi all,

How does this help? Is this something only moderate/heavy modified engines should have or will it give gains on any engine regardless of state of tune?

Cheers!

I'll give you a straight answer to your question.

You will need a rising rate regulator if your car is producing over 215kw at the wheels.

- this is when your injectors Duty Cycle are maxed out, ie cannot supply any more fuel.

Also note that the standard fuel 'pumps' are only good for about 200 at the wheels max, and are not known for their reliability.

All you need to know about the regulator is that it can raise the fuel pressure so that when your injectors are OPEN, more fuel will come out due to the higher pressure.

You wont get any gains on a standard engine. Gains will only be realised if your injectors are too small to supply the required amount of fuel (which is around the 215rwkw mark).

just beautiful!

[rev210]

One very large point worth considering if you intend to push the stock injectors with high base pressure:

* As you increase pressure your fuel pump's maximum flow decreases.

This means if you want to wring every last bit out of the stock injectors with a rising rate you had better have the big ass 044 bosch or something similar. Some of the 900 series bosch intank pumps would be pushed very hard to supply the necessay fuel at the high pressures you need for stock injectors to get 230+rwkw.

This is an example of pressure Vs flow for the big bosch.

kgf/cm2 Flow (L/hr)

2 ------------------249

3 ----------------- 236

4 ---------------- 224

5 -------------- 206

6 ----------- 195

[Clint32]

Do you think the stock regulator will be ok to use with 550cc injectors and a 044 pump. The injectors will have plent of spare duty cycle so it should be ok im thinking, wanting about 240rwkw.

[rev210]

Originally posted by Clint32

Do you think the stock regulator will be ok to use with 550cc injectors and a 044 pump.  The injectors will have plent of spare duty cycle so it should be ok im thinking, wanting about 240rwkw.

That should be fine, 550's (6 of) are roughly 550hp worth at the same pressure. you can get a reg later if you need to.