VP 37 Pump Tuning: Tools & Guide

Hello everyone,

So far, my attempts at pump tuning without using electronic 10c modifications (only adjusting the upper part and the HDK sensor) have yielded little real progress. While I've noticed a slight increase in power, the occasional hesitation at low speeds, which is a known issue with the stock configuration, has also increased, particularly at higher RPMs.
If I completely eliminated the stuttering (which wasn't inherently a problem), the original performance was almost impossible to maintain.

After I had finally had enough of these shenanigans yesterday, I took a closer look at the HDK ignition coil and determined the short-circuit ring positions at idle, under partial load, and under full load.
Then I "stretched" the characteristic curve of the sensor slightly, which is roughly equivalent to a minor 10c diode adjustment. To achieve this, I thinned the magnetic plates in the area where the short-circuit ring is located at the beginning of the full load range, and continuously monitored the effect using an LCR meter. A slight downward bending of the plates further reduced the µH measurement value in the relevant sensor range.

Because these changes unfortunately also reduce the maximum sensor value, it was subsequently necessary to recalibrate the HDK sensor to account for the electrical tolerance range of the engine control unit.
Subsequently, the position of the pump control system was also incorrect and had to be readjusted.

But the effort was worth it: Previously, the time for driving at 2000-4000 RPM in 3rd gear, with absolutely no jerking, was 6.5 seconds, but now a time of 6.0 seconds is achievable.
If you push the engine to its limits, right up to the edge of its tolerance range, and even until it starts to stutter, then times of 5.8 seconds are also possible. And all of this with 195/60 14 tires; with the original 185 tires, the times would be about 0.2 seconds faster.

It is therefore possible to achieve noticeable pump tuning without any jerking or a flashing preheating lamp .
However, this would require quite a bit of effort .

Hi,
I'm not quite sure what you're referring to. Are you talking about this copper sheet that's bent into a shape? Or something else?

Hi.

Quote:

I don't quite understand what you're talking about.

Are you referring to this copper sheet that's bent like that? }

Instead of copper, it's the flat, round iron discs that the moving arm travels over, approximately halfway between the zero and end positions.