fuel pressure

[AlCorr]

How much fuel pressure is too much?

 

[jfluffy2]

I think it is over 80 psi

 

[Ozymandias]

12-15psi would be nice for the CP3.
More isn't needed and could possibly hurt the seals of the low pressure side of the pump.

 

[cerberusiam]

Too much pressure is not a real concern in most scenarios, unless youare building some kind of monster LP. As a rule, 1/4 to 1/3 of output pressure at the CP-3 inlet is adequate for flow and operation. Stock case pressure is 75 psi so 15-20 psi is a good range to shoot for.

 

[AlCorr]

If I can keep the fuel pressure up around 20-24psi would I get better MPG?
Thank you all for the advise.

 

[Ozymandias]

No, it's only feed pressure, the CP3 has an internal Gearpump for the low pressure feed to the high pressure rail pump.

 

[cerberusiam]

If I can keep the fuel pressure up around 20-24psi would I get better MPG?

That is pretty subjective. There have been instances of slight increases in efficiency with adequate fuel pressure. Whether it is the adequate pressure or the old system not being adequate is hard to determine. When you start talking about efficiency then it goes into other areas like fuel temp, entrained water, and entrained air, etc.

It will depend greatly on what you have for pressure and flow now, what year of truck, mods, general usage, etc. Stock fuel pressure is adequate for a stock engine and normal usage, add 1 mod and it may not be adequate. Fuel is a funny thing when it actually gets injected, what happens to the fuel before it gets injected can make a difference.

 

[Ozymandias]

Like magnets on the feed line...

 

[p-Bar]

Cerb how come the Duratrashes don't need a fuel pump? since using the same CP3? I have heard we can nurse our rigs home with bad pump.

 

[cerberusiam]

The lack of LP on the Duramx's causes issues, they just won't admit it. As a geenral rule on a stock Duramax, an LP adds 40 hp to available power. They don't make full power without an LP, they just run decent with what they can draw. Was chatting with a friend last night and he just had a DMax in his shop with a complaint of low power and low mpg. All he did was add an LP and the customer was ecstatic. Power came back and mileage was up.

The CP-3 is not exactly the same. The Gear rotor pump is a different design that is aimed more towards pulling fuel, the lines are larger from the tank to the CP-3, and the tank location is higher in relationship to the CP-3 than in the Dodge application. It all makes a difference.

The Dodge trucks will run home if you are careful as long as the pump doesn't seize and block the fuel inlet, kinda depends on what exactly fails. If the LP ever dies and you have to break the system, they will likely never prime again. The CP-3 simply cannot pull fuel that far.

 

[p-Bar]

Cerb poor design by Gm . I read somewhere if you use a tuner on the Dura you starve the CP3 which causes metal on metal on the gears and sending that mess downstream to the injectors.

 

[cerberusiam]

The dmax pump typical fial point is beating the gear rotor pump to death. That is really any gear rotor pump that is forced to draw its fuel, the cavitation beats it to death hence then need to provide adequate head pressure to negate that.