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Mini Me Fuel Pressure?

1571 Views 6 Replies 4 Participants Last post by  PTSUPERD
I have been reading everything being posted regarding fuel pressure/pumps/injector compatibility thanks to my SX pump crapping out at the track. Apparently turning the pressure up to 80 lbs was not making the pump happy. Before the pump failure, 80lbs would make it smoke a lot more than the previous 60lbs, and the truck was running 1/10 faster in the ¼ mile. It smoked out the lights for the first time using this pressure. This is contradictory to what I have been reading and have been told.

I now have the FASS system installed which might add another small wrinkle to the equation. It has a return line going to the tank directly from the FASS for the extracted air. I used a ball valve on this line to further regulate the amount of fuel returning to the tank. I can’t say for sure but this may help move more volume of fuel to the heads. I am currently running 62lbs at the regulator.

Now a few questions:
• Why would the truck smoke more with the pressure set too high? Doesn’t more smoke mean more fuel?

• If the fuel pressure was too high, why was the truck running faster?

• Could there be a weak component that would be helped by excess fuel pressure?

• Will higher pressure kill the FASS pump?

• Most importantly, what are your findings regarding MM’s and the best fuel pressure to use for performance and fuel mileage? I have been told that 55lbs nets a few more HP than higher pressures. Seems low to me and it nets less smoke than higher pressures.

BTW, I do have the regulated return sump feed fuel system.

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Smoke doesn't always mean more fuel....

Take your charge air tubes off (no boost) apply a boost signal to the map sensor and see what kind of smoke you get. Did you get more fuel? Or did you just stop burning what you had?

Running faster I have no idea. That's hard to say, especially considering how many variables there are that could have changed also.

Fuel pressure IMO should be adjusted on a truck by truck basis (if you care, it's not the big a deal anyway) until the throttle is the crispest, and the smoke is the lowest.

Mine smokes the absolute least at the 60lbs it's running now.

FWIW, my truck now makes an additonal 60rwhp with the compound turbocharging.......I did absolutely nothing to the fueling at all. Guess if the smoke went up or down. Either way you'd guess wrong, because it didn't even go down, it's just gone. That is 60hp that was trailing me out the tailpipe before that I am now burning and using.

All else equal, more smoke usually just means more smoke.
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"Common Sense" might also tell you that more ICP will move more fuel with better atomization. However I have personally watched injector flow rates cut in HALF by pushing ICP too far. People will crank the ICP, actually observe that the truck stops smoking, and not ever once think it is simply not injecting as much fuel. It can still make more power considering just how hanusly overfueled most trucks are in general. Dropping fuel quantity and increasing fuel quality (atomization, injection pressure) can make more power on a truck that was simply overfueling before.

"Common Sense" would tell you that advancing the timing more and more will lead to cylinder pressure curves getting farther and farther to the left, but after a point, they move back RIGHT again.

"Common Sense" might tell some that more boost equals more airflow.

"Common Sense" might lead you to believe that when the crank was at 90* that the piston was at half stroke.

"Common Sense" might tell you a lot of stupid things. That's why it is always much, much better to test things rather than being led around by "common sense".

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