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Talk me into a link


Wildt267

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I’m looking into switching to a link plugin for my 06 Sti. Features all look great. The one problem is it looks like I’d loose a chunk of resolution from my current 32x32 fuel and ignition maps. I was hoping the Link engineers could make me feel a little better about it. Or maybe I’m missing something altogether. I don’t mind being wrong.

thanks in advance.

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On 1/9/2021 at 2:24 AM, Vaughan said:

How much variation do you actually have in your 32x32 maps? if possible could you attach images of them?

Some areas have 2-5 tenths of milisecs in the fuel map and 1-3 degrees of timing in the ignition maps.  My main goal for the car is smooth drivability and this particular car has always been a pain about that.  If you have ever looked at the factory load compensation maps in a Subaru ecu you'll probably know what im talking about.  I'm not using the factory ecu, but an obscure aftermarket unit.  Does most all the things the newer ones do , just not to my liking.  Seems like it's a slow outdated processor or something.  The car is currently set up with aggressive cams, runs up to 34 psi of boost and has a redline of 8500.  That's a fair amount of ground to cover right?  I was watching a spa vid regarding table resolution on the link.  He had trace enabled and it looked like the Link was interpolating many steps between cells. Not just doing a simple average.  I was hoping someone could enlighten me a little on that.  I had sent the Link sales team an email inquiring on that but they didn't get back to me.  I noticed the aem infinity also employs a fast processor with smaller fuel and ignition tables.

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All tables have interpolation between the cells both horizontally and vertically, the output value from the table proportionally takes into account the values in the (up to) 4 cells surrounding the current operating position. An example of this that we used to do was run a 1uz engine reasonably well with a fuel table that was 2x2 cells.

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Further, the breakpoints on Link table axis are not fixed to equal increments like many older ecu's.  Many older ECU's you had fixed say 500 or 250RPM breakpoints.  With Link you can have largely spaced increments where the VE is linear or has little change and then space them closer only where it is needed such as where you have some effect that can not be taken care of with linear interpolation.  

Also, compared to an old mS based ECU even the most basic Link traditional fuel model is quite a bit more advanced, the Link fuel equation takes into account lambda target, MAP or baro and approximated charge temp if enabled.  This makes the fuel table much flatter.  The Modeled fuel equation mode (VE based) is even more advanced, taking into account fuel charge cooling effects, fuel properties, etc. 

Most engines I tune I start with evenly spaced 1000RPM and 20-40kpa break points and only add extras where needed.  Another advantage over many of the older ECU's is you can add a row or column after tuning without messing up any of the existing table.

This is an old low res video and hard to see now, but one I remember as a good example of how a decent fuel model needs less table resolution.  This is an old Autronic SMC ECU running a NA honda race engine, first a pull with a normal fuel table, then Ben deletes all except one cell from the fuel table and does another pull.  AFR changes by about 0.5 in some places and power barely changes.  The Autronic has a fuel model roughly halfway between our traditional and modelled modes in terms of completeness.   

https://www.youtube.com/watch?v=vZQvB0KD5NA

 

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I myself came from 17+ years of tuning Hydra with 32x32 tables to the Link.  There have only been a couple of occasions that I was not able to address what I needed or felt I needed resolution wise with the number of break points provided by link.  In one such instance I ended up using the 4D fuel table to provide finer adjustment in the region required by setting different and many break points right where I was having the issue.  This worked great for me. 

Even when I was using Hydra more, I would sometimes find that there were more columns or rows than necessary which did generate some "busy work".  One thing that should also be possible to do is copy and paste your current ecu into excel then determine what percentage different from perfectly linear each value is between the two adjacent columns.  I would do this at times and then just eliminate unnecessary columns or rows to have a more concise fuel table.

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On 1/10/2021 at 10:29 AM, Wildt267 said:

Some areas have 2-5 tenths of milisecs in the fuel map and 1-3 degrees of timing in the ignition maps.  My main goal for the car is smooth drivability and this particular car has always been a pain about that.  If you have ever looked at the factory load compensation maps in a Subaru ecu you'll probably know what im talking about.  I'm not using the factory ecu, but an obscure aftermarket unit.  Does most all the things the newer ones do , just not to my liking.  Seems like it's a slow outdated processor or something.  The car is currently set up with aggressive cams, runs up to 34 psi of boost and has a redline of 8500.  That's a fair amount of ground to cover right?  I was watching a spa vid regarding table resolution on the link.  He had trace enabled and it looked like the Link was interpolating many steps between cells. Not just doing a simple average.  I was hoping someone could enlighten me a little on that.  I had sent the Link sales team an email inquiring on that but they didn't get back to me.  I noticed the aem infinity also employs a fast processor with smaller fuel and ignition tables.

I have some customer with subaru EJ257 (4 avcs) with more than 500whp and run as smoth as a stock car (big cams, 8000rpm redline, etc like your car). There is some work to get there, but is just time. I would say that you dont need more resolution that what link provide, you should be available to get where you want without problems with Linkecu. 

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