Diy Tuning

[rollex]

Yep.

Read this:

http://injectordynamics.com/articles/ford-injector-characterization/

This is also interesting though not directly related

http://injectordynamics.com/articles/drillbits-and-dipsh*ts/

 

Here is the formula for the slopes:

You can plot the slopes on wolfram alpha or a graphic package, change the breakpoint/offset/high/low slop and see how the curve changes.

IF (fuelmass >= breakpoint) y (fuelmass_lbs) =  highslope_lb_sec * (x (injector_sec) -  (breakpoint* (1/lowslope_lb_s - 1/highslope_lb_s) + offset_sec))

IF (fuelmass < breakpoint) y (fuelmass_lbs) =  lowslope_lb_sec * (x (injector_sec) -  offset_sec)

fuelmass_lbs = airmass_lbs / commanded_AFR

 

Where offset is your injector offset (eg how long it takes for the injector to open and actually start flowing fuel)

Breakpoint is where the two slopes change, usually this is when the injector starts to flow linearly

 

Now the ecu actually feeds in desired fuel mass and then gets injector ms, eg the opposite of how the equation looks. You can rearrange the formula if you wanted to do that.

 

Basically the whole point of the two slopes is to approximate the flow of a non linear injector. With the standard injectors this works pretty well, with large injectors it works not bad however you will have an error as can be seen in pauls graph of injector flow vs approximate flow. This isn't a huge deal but you can see why a nice lookup table would work better, problem is the ford ECU doesn't work that way.

 

edit: Increasing the high slope means a steeper graph, this means you will open the injector for less time for the same requested fuel mass. Bigger injectors flow more fuel, hence you want to open them less for a given air mass. Eg you want to lean the mixture out.

Edited 19/07/16 11:34 PM by rollex

[Ralph Wiggum]

Mike,

The "slope" is the physical property of Fuel Flow vs Injector Pulse Width. 

 

The slope values are fuel mass per time unit (ie pounds per hour/ CC per Hour etc etc)

 

When the injector is operating on the low slope it tends to operate in a less linear manor. This is (partially) because the injector is operating at close to it's min pulse width. Once the injector is flowing fuel on it's high slope factors like injector deadtime (the time it takes for the injector to physically move once energises) come into play and can limit overall fuel mass delivered. 

 

The breakpoint is the change over point from low to high. This is measured in mass of fuel as is usually the point the injector flow become linear

Injector PW minimum is the minimum PW the injector can operate at in a stable manor

 

There are multiple multipliers/adders that effect the final inj pulse width.

IE-

Flow v Pressue (not untilised in our cars)

Offset v Voltage (this is an adder that increases inj pw for lower battery voltage)

Offset v Pressure (as per offset v voltage but not use in our cars)

 

This is a very simplistic explanation but should get you started. BTW im -Luke- on AL and Hiddeous on the HPT Forum. If you've got any questions sing out. Also if you decide to go ahead and want some coaching let me know as I do this quite often

 

Sample of HPT basic injector data screen-

 

 

[rollex]

The ECU actually uses lb/sec however that is a pretty small number so HPT convert it to lb/hr so it is easier to read and see changes.

[Ralph Wiggum]

Yes you are correct. Great write up BTW. I'm working on the KISS principle for Mike since he's new to the way ford does it's thing.

[DarrylC]

In HPT you can cycle through the units to get the display you like.

And as Rolls pointed out you get what most quote as an offset =   (breakpoint* (1/lowslope_lb_s - 1/highslope_lb_s) + offset_sec)).

And if you have Ford data you can calculate all the GM/Chrysler data from these equations for varying voltages and pressures.

[rollex]

As you can see from all of this Mike getting good manufacturer injector data as a base is crucial, without a good starting point it might take a newbie weeks to dial in their injectors with trims that are acceptable. Hell big workshops seem to still get it wrong and ignore manufacturer data (I have absolutely no idea why) and hence end up with sub par results.

 

If you have no injector data and don't have a fuel flow bench (who does??) you can calibrate them with your car and a wideband however it is very tricky and you need to know what you are doing. Basically you can plot trims vs your slopes and back calculate an offset/breakpoint however this is far from trivial as there are so many other things that come into play that will screw with your data, this also assumes your injectors with no data are balanced (they almost certainly won't be). Eg I wasted almost a week due to my plugs being old causing a mild misfire at idle which made my wideband read lean when it was in fact close to stoich. An experienced tuner would not have this happen however if you are starting from scratch you will not have learnt these bits of wisdom yet.

Edited 20/07/16 12:30 AM by rollex

[Mr_Mike]

Cheers for the replies. What Ralph/Luke has posted has cleared up that bit for me, I assumed the injector slope was represented in a tuning program as a 2d graph or a table. Now I realise its a series of date calculated and entered.

Got some more reading to do now.....

[Ralph Wiggum]

Mike,

HPT have a demo version of the software on the website. Maybe grab that and have a play? I've got a couple of FG Turbo files I can send you so you can have a look if you like.

 

 

You can learn a lot from looking at the various models and the changes ford made to the calibrations

 

[rollex]

Does anyone know if there is a demo version of sniper? I emailed to ask but never heard back...

[Mr_Mike]

1 hour ago, Ralph Wiggum said:

Mike,

HPT have a demo version of the software on the website. Maybe grab that and have a play? I've got a couple of FG Turbo files I can send you so you can have a look if you like.

 

 

You can learn a lot from looking at the various models and the changes ford made to the calibrations

 

Awesome I'll D/l that now and have a play. Always makes it easier if I can see what I'm doing in front of me rather than just reading.

Tax return will be in soon so will order VCM Suite then.