Drill your HPFP to 4-5mm
If your hpfp is banjo conection, drill the IN gas tube

See this post:

https://www.golfmkv.com/forums/index.php?threads/drilling-the-hpfp-bamboo-fitting-to-5mm.382982/

Hi,
I have a very odd problem with the autotech upgrade kit:

Although all paramters in mapping are changed according to the data found here in the forums (and some more) the railpressure keeps spiking up to 170-180bar in rmp range above ~5800_min under WOT and part throttle.

Since a few weeks I've done nothing else than logging (With vehical logger) and testing different mapping changes, but no luck so far.

I logged a lot of HPFP PID parameters, and from the point where the railpressure exceeds the requested pressure, the delta angle of the MSV (Quantity regulator valve) drops to 0 and the "I" part of the PID controller freezes. So basically, with 0 duty cycle the for the MSV, the bypass inside the pump should be fully open to "bleed" the excessive fuel into the low pressure side.

So far, I would say this is a "correct" behavior, as the ECU tries to lower the exceeding railpressure, but for some reason the hardware does not respond accordingly.

Fo testing purposes, and to go sure the pump itself is not at fault, I bought a genuine new Hitachi HPFP, and installed it "as is" in stock form.

Immediately the railpressure is regulated correctly. Then I installed the autotech kit in the new pump, and the problems are back immediately.

A new RS4 pressure limiting valve is also part of the setup plus a upgrade intank fuel pump.

For some reason I cant wrap my head around how it is even possible to have (at max) 180bar railpressure with a 130bar pressure limiting valve except for one thing:

What if the 1.5mm restriction in the "T" piece which redirects the overflow from the PLV to the low pressure fuel supply is causing this issue?

But then, there would be heaps of others having this same problem as soon as the autotech kit is installed...?

Maybe someone has a bright idea for a solution, or even first hand experience with this situation?

BR
Alex

Hi Adrian,

I have now heard several times, that this is kind of normal, and most common "fix" is, just to eliminate the error code detection for exceeding railpressure.

I find this to be a lumpy solution, so its not an option for me at all.

The same effect is occuring also at part throttle, starting at an rpm range of about 5500-5800rpm. In fact, in part throttle the effect is even worse, as less fuel is requested and used by the injectors.

For me there are 2 possible sources for the issue:

1. The above mentioned 1.5mm restricor in the "T" or "Y" piece from the pressure relief valve to the low pressure pump inlet - assuming it is there....it is mentioned in the self study programs, but there seem to be more versions of this fuel line. Some WITH restrictor, some WITHOUT.
The restrictor in the barb fitting from the pump feed is already drilled out to 5mm in my case...

2. The Quantity Control valve on top of the pump is not fast enough to accuratly operate the bypass in higher rpm ranges with the added fuel quantity from the autotech pump, resulting in very short delta-angles...

You can see this in the logsdata, even when the requested deltaangle is 0, due to the delay parameter data in the ECU mapping the REAL deltaangle is still somewhere around 50 degrees....
So my second guess is, that the inertia of the coil/magnetic system is to high to meet the requested railpressure.

(Working on a solution....)

BR
Alex