All Things Mk5 > Performance Modifications
The ultimate Dyno Graph thread
56OctyVRS:
--- Quote from: Keith@APR on March 23, 2012, 10:44:40 pm ---So if you run out of fuel at 129 bar, how does have a fuel rail limit of 136 bar help anything?
Is the theory that you can run the pressure up to 136 so when it dips, it doesn't dip as far?
--- End quote ---
Reading what others have logged is that some cars dont make the actual 130 bar as the oe valve has opened causing a flat spot. So the rs4 valve doesnt open allowing the fuel rail pressure to stay at the requested pressure. Some have also shown it allows a more stable pressure from the low pressure pump.
Keith@APR:
--- Quote from: 56OctyVRS on March 23, 2012, 10:48:13 pm ---I found that i suffered with the old 5200 rpm hesitation at times. With the rs4 valve fitted that has gone away and the power seems more smoother and more eager to go. Well worth the £36 i paid for it.
--- End quote ---
I'm not saying I'm doubting what you experienced, but I can't quite get my head around what could mechanically could be happening that the valve corrects.
A spike in fuel pressure or continuous over pressure from the HPFP in a healthy fueling system would be created by software as fuel is injected into the rail by an ecu controlled valve in the HPFP.
The job of the FPLV is to open and dump pressure in the fuel rail if it exceeds 130 bar or whatever pressure the FPLV is designed to.
The FPLV is not electronically controlled and is just a manual pop off valve.
If you ask for 129 bar in the ECU the only ways from a parts failure I see fuel pressure going above 129 bar in the fuel rail is if the HPFP solenoid is damaged and the valve is behaving erratically, the return fails (clogged or collapsed or some such) or the injectors turn off unexpectedly or get clogged creating pressure to build as the ecu assumes they are firing and fuel is going into the cylinders, the HPLV itself or the high pressure sensor is bad.
I will see this first hand next week and hopefully I'll be able to see data that helps me understand exactly whats happening.
I'll get a RS4 LPFV and try a swap if all else fails first. I'll report back with what I find out. Hopefully it is a simple as 36 quid.
Keith@APR:
--- Quote from: 56OctyVRS on March 23, 2012, 10:55:01 pm ---
--- Quote from: Keith@APR on March 23, 2012, 10:44:40 pm ---So if you run out of fuel at 129 bar, how does have a fuel rail limit of 136 bar help anything?
Is the theory that you can run the pressure up to 136 so when it dips, it doesn't dip as far?
--- End quote ---
Reading what others have logged is that some cars dont make the actual 130 bar as the oe valve has opened causing a flat spot. So the rs4 valve doesnt open allowing the fuel rail pressure to stay at the requested pressure. Some have also shown it allows a more stable pressure from the low pressure pump.
--- End quote ---
Ok, that makes sense.
The HPLV is not working to spec as fitted standard.
Might as well replace it with the RS4 bit then unless its significantly more expensive than a later revision standard HPLV.
Is this isolated to SEAT's?
We've never had a problem when asking for 129 bar with the HPLV on other 2.0TFSI's.
Thank you!
james:
i put one on my car made the mid range far smoother, then rail was set to 134bar @ wot
bacillus:
--- Quote from: Keith@APR on March 23, 2012, 11:07:02 pm ---I will see this first hand next week and hopefully I'll be able to see data that helps me understand exactly whats happening.
I'll get a RS4 LPFV and try a swap if all else fails first. I'll report back with what I find out. Hopefully it is a simple as 36 quid.
--- End quote ---
This is from a previous posting (no fighting please because it's done using revo software)... :smiley:
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