¶ VHFI: Volumetric-Hydrodynamic Delivery Pressure Index
A single needle reading says little. The VHFI combines many measuring points.
In our articles and development reports, one figure keeps coming up that you won't find in any textbook: the Volumetric-Hydrodynamic Feed-Pressure Index, or VHFI for short. It is a metric developed by MMHP. This page explains what it is and why we need it.
¶ The problem with simple numbers
A single oil pump can only be described incompletely by individual numbers. The delivery volume tells you how much oil the pump moves, but not how much of it actually reaches the critical points. A pressure reading tells you what resistance exists at one measurement point, but not how the system behaves under load changes, at different temperatures, or at other positions (why position matters so much is explained here).
In practice, single figures get compared constantly anyway: "3 bar at 2,000 rpm" against "2.8 bar at 2,000 rpm." Such comparisons look precise and yet carry almost no information. In our development work, that wasn't good enough for us.
¶ What the VHFI condenses
The VHFI condenses the interplay between delivery volume and hydrodynamic pressure distribution into a single, dynamic index figure. Put simply, it answers the question: how well does this oil system supply the engine across its real operating range, not just at one single operating point?
The index draws on, among other things:
- delivery volume across the rpm range
- pressure distribution across several measurement positions in the engine, from the pump through to the bearing gallery
- dynamic behaviour, i.e. how the system reacts to load changes and how stably it absorbs pressure drops
- defined oil-temperature windows within which measurements are taken
The data basis for this comes from our own measurement technology, which captures these variables simultaneously at millisecond resolution. Without these measurements, the index would not exist; it cannot be calculated from catalogue data.
¶ How the index is derived
We run the measurement passes for the VHFI under controlled conditions: identical temperature windows, defined load profiles, documented boundary conditions, on real engines from our research and teardown work. The weighting of the individual variables within the index is based on our experience from many years of measurement and development work on these engines.
We do not publish the exact composition and calculation method. It is part of our development methodology and therefore a trade secret. What we do publish are the conclusions drawn from it, for example when we compare a standard engine's condition against a converted one.
¶ What the VHFI is not
The VHFI is not a standardised figure, not a manufacturer value, and not something you could measure yourself. It is an internal tool that lets us make our own series of measurements comparable with one another. That is precisely where its value lies: two measurements taken with the same measurement system, the same methodology, and the same boundary conditions can be honestly compared via the index. A single pressure-gauge reading from a workshop cannot make that claim (find out why here).
So if you come across this term in our texts, you now know what it means: not another marketing figure, but an attempt to reduce a complicated system to a single value you can actually work with.
Transparency note: The VHFI is a proprietary metric defined by MMHP. It is not standardised and is not comparable with metrics from other suppliers or manufacturers.