Peak fuel pressure confusion

bluegate

Member
Joined
Oct 8, 2016
I've determined that i am lean at 11.3+ at wot in 3rd with up to 5.0kr. My new gauge, actually 2nd one, shows about 58psi at 17lbs of boost. Is this the fuel pressure the chip allows or total the fuel pump with hotwire, is giving me? If its the chip, how much do i need to add to parameter 1 to get the 2lbs of psi?
 
The chip doesn't control fuel pressure. 58-17=41 psi fuel pressure base. Is that what you have it set to at idle with the line off?
 
The chip doesn't control fuel pressure. 58-17=41 psi fuel pressure base. Is that what you have it set to at idle with the line off?
No, right about 43-45 hose off. I bumped parameter 1 up to 144 and the kr is back to 0, afr was 10.5, but boost is only peaking at 16.5. I know there are a 1000 things to consider, but how does outside temp/humidity play into this. The other weird this is that autometer claims that their recall button on the fp gauge only resets if you reset it, but there are times that it reads 59 and then 40ish without me touching it. This is the 2nd gauge too.

That being said, i dont know if i can count on that gauge even though it wasn't cheap....

Oh i got it, chip control fuel by the injectors, right?
 
Yes chip controls injectors. Are the fuel pressure gauges liquid filled? Those will give different readings depending on if they are hot or cold. They constantly need to be vented when fine tuning fuel pressure.
 
Fuel pressure is controlled by your fuel pressure regulator. The chip setting is used to insure there is a window of correction so your ECM can maintain a target AFR. What chip version do you have? You can raise the fuel pressure to get more fuel or use the chip like you have or both. I normally start with fuel pressure and then change chip setting if necessary for fine tuning.

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Fuel pressure needs to rise 1 to 1 with boost pressure. Set your base fuel pressure as per Erics instructions. There's no magic number in regards to NB or WB...as each engine is different. Ambient air temperature and humidity are large factors that come into play with tuning.
 
Fuel pressure is controlled by your fuel pressure regulator. The chip setting is used to insure there is a window of correction so your ECM can maintain a target AFR. What chip version do you have? You can raise the fuel pressure to get more fuel or use the chip like you have or both. I normally start with fuel pressure and then change chip setting if necessary for fine tuning.

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5.7 chip. I have adjusted acording to tt instructions reduced the kr. I have a regulator on the way also. Fuel pressure rises with boost, it just never makes it to 60 psi at 17lbs of boost. Does that even matter of kr is 0?
 
Gauges are not perfect so either could be off a little bit. Most important thing is no knock. As long as your fuel pressure is rising 1:1 you should be fine. How old is your fuel pump? The FPR can't create pressure the pump can't build and when pumps can't keep up it's also easy to mistake a FPR issue with a pump issue.


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Gauges are not perfect so either could be off a little bit. Most important thing is no knock. As long as your fuel pressure is rising 1:1 you should be fine. How old is your fuel pump? The FPR can't create pressure the pump can't build and when pumps can't keep up it's also easy to mistake a FPR issue with a pump issue.


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Dont know, it came in the bag of other tricks with this car. It sounds healthy, but loses pressure after prime which ive read is not a huge issue. I figured the regulator is the easiest thing to change out, then I'll jack with a new pump. Filter is new. I'll try to attach a log from my phone that shows the most kr it has seen.
 
It costs a lot to rebuild one of these engines so I consider a good fuel pump a good investment. If I wasn't sure what I had or what it was rated for I would replace it. I'm not for throwing parts at it trying to guess what will fix it but the fuel pump is the heart of your engine and running a turbo engine too lean will not end well. There are several good pumps to choose from these days and this is the first thing I do along with a hot wire kit and a 10 gauge ground wire for the pump to the engine block. Sounds like you're focused on knock and as long as you have none you're good.


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Theoretically, if the fuel pressure was not there, be it the regulator or pump, changing my wot setting would not have reduce kr right? Thanks for your help, much appreciated
 
Theoretically you told the computer to open the injectors more to get more fuel out of them instead of asking the pump to increase the fuel pressure to get the same result (more fuel) I see nothing wrong with that but if your pump can't produce 60 psi I would replace it. On one hand you have enough fuel to get the desired result right now on the other hand I like to know exactly what fuel pump I have and what it will support. In my opinion they are too cheap to take a chance not knowing what you have. Fuel supply is the single most important building block for any turbo powered engine.


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Theoretically you told the computer to open the injectors more to get more fuel out of them instead of asking the pump to increase the fuel pressure to get the same result (more fuel) I see nothing wrong with that but if your pump can't produce 60 psi I would replace it. On one hand you have enough fuel to get the desired result right now on the other hand I like to know exactly what fuel pump I have and what it will support. In my opinion they are too cheap to take a chance not knowing what you have. Fuel supply is the single most important building block for any turbo powered engine.


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Done. The most kr i get is 1.2 with a new tt fuel pump. I think my d pipe it touching the cross over pipe a little. Ill fix that and chase the 1.2 a little further.
 
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