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Variable Cam Control Tuning: Ford’s HDFX Strategy

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Ford’s HDFX Strategy

04.34

00:00 - For those who are reflashing a late model Ford engine control module, you're going to need an understanding of how the Ford HDFX or high degree of freedom executive works.
00:10 This is a relatively complex control strategy that has far reaching effects over every aspect of engine operation and on face value it can be challenging to understand how the cam targets and mapped point tables relate.
00:24 This module is not designed to be an all encompassing break down on tuning a late model Ford ECM and we'll be looking at a quick overview of the strategy only.
00:34 This starts with the fact that Ford does not present us with a conventional VE table for their speed density operation.
00:41 Instead a range of coefficients that are used in a complex quadratic equation in order to calculate airflow for a given operating condition are provided.
00:50 These are confusingly referred to as offset, quadratic term, slope and blow through slope which aren't overly helpful to us.
00:59 To make matters worse there are 16 tables for each of these parameters labelled map point 0-14 and optimum power.
01:07 It's worth noting that depending on the specific Ford vehicle you're tuning, not all of these MAP points may be active.
01:14 You could liken this to Honda's approach with the K series engine with tables for each cam angle.
01:19 There's a lot more to it than the Ford ECU but for now we're only conventrating on the cam control.
01:25 Fortunately all the popular tuning platforms for the Ford application understand that the tuning community can't work directly from these coefficients and instead build tools into their software to convert the mapped point coefficient into a more conventional VE table.
01:41 To be accurate, it isn't quite a VE table since Ford kind of skipped past volume and moved directly to air mass which after all is the part that's important.
01:51 This is why the tables look relatively flat compared to a conventional VE table which we may be more familiar with.
01:57 Without getting deeper into this, we can manipulate the tables in the editor and then generate new coefficients for the mapped point we're manipulating to achieve the result we're looking for in the same way as manipulating a normal VE table.
02:11 That's all well and good but the next obvious questions are how does the map point relate to cam angle and how do we know or define which map point the ECU should use? To start with, there are 2 tables that define the cam angle for the intake and the exhaust cam where applicable based on the mapped point.
02:30 For our example file from a 2014 Ford Mustang V8, we can see the intake valve opening and exhaust valve closing targets for each of the mapped points.
02:39 Now we know what the cam angle targets are for a given map point we also need to know or define what map point the ECU is accessing.
02:47 We can log this by logging the parameters known as mapped point weighting for each of the relevant mapped points.
02:54 The way this works is that the mapped point weighting tells us which mapped point it being referenced at any time.
03:01 To make this just a little more complex however the ECU can interpolate between mapped points.
03:07 For example we could possibly see that the mapped point weighting may be 50% on map point 7 and 50% on map point 8.
03:14 Going back to our intake valve opening table we can see that the target for map point 7 is -30° and for map point 8 it's -50°.
03:23 In this example the ECU would be interpolating halfway between the 2 targets which would be -40°.
03:30 The next question is how to we define which mapped point the ECU will use for a given combination of load and RPM.
03:37 In this case the Ford engine control module uses a variety of different operating modes such as best drivability, best fuel economy and emissions reduction.
03:47 For each of these modes there's what Ford refers to as a distance table.
03:51 This is an oddly named table but if we look at the distance table for best drivability from our sample file, we can see the target mapped point vs load and RPM.
04:01 This defines which mapped point the ECU will use which in turn then defines the cam targets which we've just covered.
04:09 When we see a number in the distance table of 7.5 for example, this means the ECU will interpolate between mapped point 7 and 8.