Rising Rate Fuel Pressure Regulator

[redsunbeam]

At what kind of boost levels does an RRFPR become necessary?
I'm only looking to run low levels 5-7psi on factory ecu and injectors to start with. Will i need an RRFPR?

 

[JustenGT8]

Never. It's a dodgy fix.

 

[redsunbeam]

Never. It's a dodgy fix.

Why? Do tell. I was under the impression it was a common way of getting extra fuel through the injector when injector size was marginal?

 

[JustenGT8]

Dunno about common, but yer that is the didge that was used in the past and also where your ECU cannot cope with boost ie most n/a ECUs.

All a fuel reg should do is maintain the pressure differential across the injector. This theretically means the flow rate thru that sized hole (injector) stays the same and control of fuel can then be accurately managed by the ECU by controlling how long it is open for (duty cycle).

So a normal FPR will just raise or lower fuel pressure the same amount as the pressure in the inlet manifold rises or falls.

If you make that pressure differential variable how can the ECU accurately know what fuel to deliver? virtually no ECU will monitor fuel pressure.

As i said, it is a dodgy fix for other parts of a system (ECU and injectors) that aren't up to the task.

Yes it 'works', jeez boosted carbies 'work'. But it is far from ideal.

As for your situation. There is enough redundancy built into the stock ECU that the flow created by 6ish psi is within the range of the factor AFM and injectors to cope with. Just keep the factory FPR and it will all work. It still won't be great as the ECU won't provide boost appropriate ignition timing, but many folk are getting away with this setup. Start using higher octane fuel though would be my advice.

 

[BigKriss]

I have found that just as a standard fpr sets the base line for fuel pressure to start working from, the rrfpr does the same.
Both will determine the base fuel pressure .
One will require a "fatter" fuel map while the other will probably require a slightly "leaner" map.The ecu does not care what the fuel pressure is, it simply works around that.

I would say that a rrfpr would actually be helpful and beneficial in light boosting of the std engine. Gives the ecu some leeway to work with..

 

[redsunbeam]

Thats one for and one against. Anyone else?

 

[JustenGT8]

I have found that just as a standard fpr sets the base line for fuel pressure to start working from, the rrfpr does the same.
Both will determine the base fuel pressure .
One will require a "fatter" fuel map while the other will probably require a slightly "leaner" map.The ecu does not care what the fuel pressure is, it simply works around that.

I would say that a rrfpr would actually be helpful and beneficial in light boosting of the std engine. Gives the ecu some leeway to work with..

Nah I don't agree, it's not that simple. Variable fuel pressure means an extra thing to consider when tuning. Injector flows are rare linear with duty cycle on a fix pressure differential, imagine the variation with variable fuel pressure....then add atomisation efficiency and I think you have the makings of a tuning nightmare.

No manufacturer uses a rising rate reg, nor do any of the big fuel system brands for performance applications.

All previous comments stand.

 

[markstoys]

I would listen to Justen.

Mark

 

[stevechumo]

Just on a side note that not all 1UZ engines have the same injectors. Some have 215 cc/min injectors and some have 245 cc/min injectors. Please do the search on the Tech articles of this side and you'll see.

Some people may get lucky to get away with complete stock fuel system while boosting low, but that's the risk. If you boost your 1UZ engine using stock injectors that are 215 cc/min, you may run into the risk of not having enough fuel. With those small 215 cc injectors or even bigger 245 cc injectors, some types of fuel enrichment are recommended.

I used the FMU in several low budget boosted cars and they worked great. It's not ideal, but it'll get you through economically. To me, it's like buying car insurance. You leave it there, it doesn't show you it works or not, but it'll keep you going without much worries.

 

[BlackUZZ31]

i run the 245cc in my soarer with a 60psi base pressure and run out of injector duty at redline running 8psi (215rwkw)

 

[ihiryu]

I would say that Justen is right, however, 5-7 psi from what?

Are you running a blower or a turbo, and how big? 5-7 psi from a T25 versus 5-7 psi on a HX40 are going to be vastly different.

Fortunately enough the UZ runs rather rich from the factory, so as Justen stated, most can get away without anything at all.

I currently am running 7 psi through a Vortech V1 and am still running decently rich at WOT

 

[redsunbeam]

I would say that Justen is right, however, 5-7 psi from what?

Are you running a blower or a turbo, and how big? 5-7 psi from a T25 versus 5-7 psi on a HX40 are going to be vastly different.

Fortunately enough the UZ runs rather rich from the factory, so as Justen stated, most can get away without anything at all.

I currently am running 7 psi through a Vortech V1 and am still running decently rich at WOT

Sorry for lack of info, will be running an Eaton M90 blower on an otherwise stock 1990 1UZFE from a soarer, although it is in this.........

 

[JustenGT8]

Loving the look of that, awesome

Tight squeeze much

 

[rdm20fan]

AWESOME!
There are alot of F.M.U.'s that mount after the stock FPR. they allow stock fuel pressure under vaccum, to O they then close the system after the FPR at a rate of 4:1-16:1
you can use these for low amounts of boost. 5psi-7-8psi max maybe. I used one on a 93 1UZ and melted a piston, and head gasket went. at 7-8psi (if i remember correctly) if your planing on anything more then 5psi I would plan on someway of getting more fuel.

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