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LGT AVCS Tuning Discussion


Infamous1
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would you mind sharing your map for AVCS? I would like to compare mine to someone with stage 2. Thanks!

 

I've always avoided doing this, like almost everyone else... except Mr. LBGT, who has always unselfishly shared whatever he can. Because there is a warning involved with sharing tuning, and especially AVCS tuning... any map is just the one you're running at the moment, and not a definitive answer to anything.

 

However, there ARE some generalities that serve as rough guidelines... but most is scattered here and there in AVCS esoterica. Even seasoned veterans of self tuning often leave well enough alone.

 

Here is the AVCS map I currently have on my car. Evaluating different AVCS profiles takes time, usually, but can be interesting and is not difficult to experiment with. Some non-science that influences me is... does it idle well, does it accelerate smoothly and strongly from a stop, how high a gear can I smoothly and comfortably employ, is the shifting effortless with revs predictably rising or falling, what is the best gas mileage I can get... that kind of stuff. Pouring over logs will bring other evidence, of course, but how the car drives, how well I mesh with it, is my primary concern.

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i will be playing with it tonight, or when I get back from vacation... Thank you.

This is my stock vs stage 2 map.

http://i1133.photobucket.com/albums/m589/dwolson2/avcsstockandstage2.png

 

Any suggestions you think I should try?

My car, 06 5EAT, Stock everything, except , Catless UP, Decatted stock DP, Magnaflow CBE, K&N drop in.

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There is one AVCS thread that, to me, stands above all the others. Everyone probably knows it but here it is:

 

http://forums.nasioc.com/forums/showthread.php?t=1078290&highlight=tuning+avcs

 

Start from the beginning and take your time... it'll take a lot of it. When it is sifted down a pattern will emerge, and AVCS maps will begin to "make sense" to you.

 

We have all, those of us who tune, "been there" with AVCS maps... but the one you have there is ruining your performance in my opinion. Try moving closer to the Cobb stg2 profile I posted, where advance is greater in the spool region. I think I have some maps from my 05 5EAT LGT, I'll see if I can find them... although they were likely for my AVO380 setup.

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Here is a screenshot that may help visualize the "spike." The table shows the values and the 3D graph provides a visual representation. It is the "stock" Stg2 11 WRX AVCS table, and represents a similar map in other cars.

 

The stock 05 LGT map is almost the opposite of that one, in the 'cruise' area. See below.

 

I had no idea the stock tunes varied this much. Does the 11 WRX have exhaust AVCS? If so, would you mind posting up that table as well? I wonder if the difference is related to something they're doing with exhaust cam timing...

 

Stock 05 LGT AVCS table:

 

http://i193.photobucket.com/albums/z151/Legacy_NSFW/Tuning/v000-AVCS.png

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i will be playing with it tonight, or when I get back from vacation... Thank you.

This is my stock vs stage 2 map.

 

 

Any suggestions you think I should try?

My car, 06 5EAT, Stock everything, except , Catless UP, Decatted stock DP, Magnaflow CBE, K&N drop in.

It really depends on what it is you are looking for... there isn't any one 'best' strategy IMO. Some people aim for earliest spool. Some for earliest torque. One owner may wish to maximize fuel economy is cruise while another wants response. One might want the smoothest possible throttle response. There is no 'best AVCS map' just as there is no 'best turbo'.

 

Like hardware choices, it usually goes badly if you mismatch things, like big cams and small turbo for example. In your tune you want to have a direction, a focus, and make all changes toward that end. As it's already been mentioned, making changes to AVCS can and does change volumetric efficiency. Those changes will have consequences to how much air the engine can or will ingest and that will effect your boost tuning, and how much timing you can run.

If there is something you really would like to improve about your tune, and you're sure that AVCS mapping is responsible, a little more information about what it is you want to change would be useful, but then it will help to see more of your tune. I don't know about your tuner, but most don't like to see their work posted on the internet to be second-guessed by the peanut gallery (I include myself in that category). The funny thing is that we amateurs will often approach AVCS tuning last, after boost, timing and fuel are set up (my hand is up, guilty as charged), when it should probably at least have a direction to go in at the beginning of the tuning process. My own tune would have gone much quicker if I'd done more research on AVCS tweaks at the beginning rather than toward the end.

 

Of course there are many features that were put into the map by Subaru for reasons that someone who has a tuned car might not care very much about, like emissions or fuel consumption. The 'tree-hugger' spike is one of those. I prefer early torque to early spool and won't tolerate vibration or a lumpy drive if the performance benefit isn't huge. Personally I did not like having any more than 10* under 0.80 load at any rpm as for me it decreased VE and response. I found it best to see max advance reached around 1.40 load and between 1,600rpm and 2,400rpm for a good compromise between torque and spool in that area. Care has to be taken that advance doesn't ramp up too high in cruise conditions. I never saw any good in having any advance at all in that bottom left corner.

 

TBH the table you have now looks broadly similar to my current non-cruise one. I use a bit more advance in the 1.20 and 1.40 load columns, ramp down to zero steeper and earlier in the up-to 0.80 load range, and don't have that ridge of 15* through the 2,000rpm row like that. Of course I have no reason to believe my table is any 'better' than yours.

 

The problem is that applying changes now will effect the rest of the tune. Your boost control may need adjustment to remain as smooth as possible. You may see knock in places you didn't before. You may be able to add more timing in certain areas over the map you have now. Since load will change differently through a pull your timing curve may no longer be smooth and base timing maps will need to be tweaked further. By the time you've made all the compensations the gains you might have made from improved VE may have been lost. For sure it will be hard to figure out what change made what difference. You cannot just paste someone else's tables into your map and call it an A/B test, it's just not that simple.

This I think is why not too many talk about AVCS tuning, and why it takes so long to properly develop the map to meet your goals.

 

Hope this helps.

Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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It really depends on what it is you are looking for... there isn't any one 'best' strategy IMO. Some people aim for earliest spool. Some for earliest torque. One owner may wish to maximize fuel economy is cruise while another wants response. One might want the smoothest possible throttle response. There is no 'best AVCS map' just as there is no 'best turbo'.

 

Like hardware choices, it usually goes badly if you mismatch things, like big cams and small turbo for example. In your tune you want to have a direction, a focus, and make all changes toward that end. As it's already been mentioned, making changes to AVCS can and does change volumetric efficiency. Those changes will have consequences to how much air the engine can or will ingest and that will effect your boost tuning, and how much timing you can run.

If there is something you really would like to improve about your tune, and you're sure that AVCS mapping is responsible, a little more information about what it is you want to change would be useful, but then it will help to see more of your tune. I don't know about your tuner, but most don't like to see their work posted on the internet to be second-guessed by the peanut gallery (I include myself in that category). The funny thing is that we amateurs will often approach AVCS tuning last, after boost, timing and fuel are set up (my hand is up, guilty as charged), when it should probably at least have a direction to go in at the beginning of the tuning process. My own tune would have gone much quicker if I'd done more research on AVCS tweaks at the beginning rather than toward the end.

 

Of course there are many features that were put into the map by Subaru for reasons that someone who has a tuned car might not care very much about, like emissions or fuel consumption. The 'tree-hugger' spike is one of those. I prefer early torque to early spool and won't tolerate vibration or a lumpy drive if the performance benefit isn't huge. Personally I did not like having any more than 10* under 0.80 load at any rpm as for me it decreased VE and response. I found it best to see max advance reached around 1.40 load and between 1,600rpm and 2,400rpm for a good compromise between torque and spool in that area. Care has to be taken that advance doesn't ramp up too high in cruise conditions. I never saw any good in having any advance at all in that bottom left corner.

 

TBH the table you have now looks broadly similar to my current non-cruise one. I use a bit more advance in the 1.20 and 1.40 load columns, ramp down to zero steeper and earlier in the up-to 0.80 load range, and don't have that ridge of 15* through the 2,000rpm row like that. Of course I have no reason to believe my table is any 'better' than yours.

 

The problem is that applying changes now will effect the rest of the tune. Your boost control may need adjustment to remain as smooth as possible. You may see knock in places you didn't before. You may be able to add more timing in certain areas over the map you have now. Since load will change differently through a pull your timing curve may no longer be smooth and base timing maps will need to be tweaked further. By the time you've made all the compensations the gains you might have made from improved VE may have been lost. For sure it will be hard to figure out what change made what difference. You cannot just paste someone else's tables into your map and call it an A/B test, it's just not that simple.

This I think is why not too many talk about AVCS tuning, and why it takes so long to properly develop the map to meet your goals.

 

Hope this helps.

 

Well said.

 

fahr_side provided the necessary fine print.

 

Sharing one's self-tuned maps is like sharing one's poetry... or going to a nude beach. It's best done among friends. :lol:

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Here on the left is the 08 Spec B stock setup for cruise/non cruise. On the right is currently what I'm running right now. They were done by MickeyD2005 and in the case of this map, the only tweak I've made is to reduce all cells at 40 in the low load to 30. That alone helped drivability and significantly reduced low load knock.

 

I've tried a bunch of other setups including 0 in the under 1 load and the "Tuned by STi" style acvs mapping from the 07 Australian Wrx. Pretty much every setup has run better with less AVCS under 1 load than more.

1806959177_specbavcs.thumb.jpg.aa967d691730a3c66b03b09e4ca529fe.jpg

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Here on the left is the 08 Spec B stock setup for cruise/non cruise. On the right is currently what I'm running right now. They were done by MickeyD2005 and in the case of this map, the only tweak I've made is to reduce all cells at 40 in the low load to 30. That alone helped drivability and significantly reduced low load knock.

 

I've tried a bunch of other setups including 0 in the under 1 load and the "Tuned by STi" style acvs mapping from the 07 Australian Wrx. Pretty much every setup has run better with less AVCS under 1 load than more.

 

My knock sum immediately halved, for example.

 

Good stuff. This thread does something more established ones don't... examine developed maps, oriented around personal preferences, rather than adherence to some engineering whp ideal.

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Thanks for reviving this thread. I had noticed a stumble in acceleration at light load during everyday driving in this exact low RPM/load region, most noticeable after I went to a LWFW. I've tried knocking down timing with little affect. I've tried fiddling with CL fuelling (yes it happens in CL), again with little affect. I too experience load load knock, it would really make me happy if this helps on both fronts. This at least gives me another area of my map to investigate.
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Thanks to all that replied, I am trying to figure out 1. what would drive the best, but 2. Why the hell is my around town mileage so bad? ITs kind of annoying that the only time I get good mileage is driving 80 down the freeway. its weird too, I can drive like an @$$, and get 15/17 or drive like an angel and get 17/18. It doesn't add up... I was thinking this might have something to do with it. I will try applying and editing my timing when I get back thursday or friday and see if I can get some improvements. That spec B map will give me at least a side by side, and I will also try fahr sides suggestions. Are you thinking it will help my cruising? Thanks!
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  • 2 weeks later...

Needless to say, I'm not using the AVCS map I posted... although it isn't too far off from there.:) But I'm posting because of something that has changed a LOT since modifying the AVCS map that came with my AP Stg2+AEM tune. My knock sum has dropped incredibly.

 

It's one of the things I use the AP to check, pretty much constantly when I drive. For months I became accustomed to knock sum in #4 in the two hundreds, and about half that in #2. WOT logs are free of FLKC now, through tuning. But the knock sum numbers bothered me. Because they would increment just lightly revving the motor, or driving as gently as I could, I didn't worry about it, but I wasn't happy either.

 

Ever since the last map the knock sums are, relatively speaking, gone. Yes I can increment it by revving the engine. Yes a few counts are almost always there... but SMALL numbers, and occasionally NO knock sum. Also, the huge disparity between cyl 4 and 2 is gone, with no correlating balance between counts and cylinder. In fact, sometimes cyl #2 is a tad higher, sometimes #4. Both, however, have counts ten times less than I got with the stock AVCS map, i.e., where it once might have been 200 it is now 20, etc.

 

It's fun to play with the theory, and conjecture the reasons. All I'm saying is what I see, and that I like it. Combined with the overall smoothness and driveability the changes I made to my AVCS have provided, the huge reduction in knock sum counts is an unexpected bonus. I don't know exactly WHY so it only provokes more thought, and another means by which to judge the AVCS tuning.

 

Anyone else note this?

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Are there 4 knock sensors or does the ECU use some other method to narrow it down to 1 cylinder?

 

Good question!! Like NSFW said, it is a funciton of my AP, and I've just taken it for granted. When I was looking where things were and saw my knock sensor in its usual place I didn't think to look for two... though nothing until now has led me to this question. How, indeed, does the ECU get that data??

 

Also, I guess I just assumed :) that RR would have the Knock Sum parameters already and that the AP was a johnny come lately as usual. No?

 

Even if my car didn't drive better I'd be happy with my AVCS tweaks for the reduced knock sum by itself. When I get more opportunity I will investigate what exact changes primarily contribute to the reduction in KS. However, it must be mostly from eliminating the so-called "spike."

 

I can post my current :) AVCS map should anyone care.

 

edit: just read sumfoo 1's post, makes sense.

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Here is what I am actually running on my car. The higher load is similar to what MickeyD2005 normally runs but the low load area which was mostly stock is completely different. My car runs considerably better with this setup and currently both my cruise and non cruise are set this way. My knock sum is very minor compared to the stock avcs mapping in the low load.

244853185_currentavcs.thumb.jpg.2c0c87f497da5fe9020d7f14ed5e8dcc.jpg

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This is my current table. I see no improvements running more than 30* at any rpm/load site. I see only less torque if I run over 0* past 5,200rpm. Running more than 10* before 0.80 load does me no favors for torque.. fuel economy is increased but so is vibration and bucking / hesitation.

 

As Smiles said: "We learn wisdom from failure much more than from success. We often discover what will do, by finding out what will not do."

 

I mentioned in another thread that you can see timing pulled from 'knock' when in fact it's just that you have -ve boost error... boost is higher than targeted for the revs/requested torque. Timing is pulled before knock is even seen, as a preventative measure.

If you reduce VE with sub-optimal AVCS mapping then boost can often be increased as a side-effect. Improving VE means it's harder to hit your boost targets with the WGDC currently set.

avcs_noncruise.png.26b05160e8d9852479bea58c2f30d1a4.png

Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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^^ I'm going to have to try that mapping on mine. As it is I'm very different from that... not quite like the one in my post, but similar in essence.

 

To evaluate I have four or so maps on the AP that are identical except for the AVCS table. They all "work," of course, but after driving one for a while, then switching, a good subjective comparison can be made.

 

To me, the table is more about driveability and highway manners than power. After all, when we are WOT we are likely at maximum load and the only relevant column is the last one. Even a map such as the above fahr_side table, which is waaay different in advance balance, has a final load column not vastly removed from mine.

 

After rebuilding my base map using the newest v300 Cobb map, which is a far more refined product by the way, including most if not all the 'tweaks' we here have learned to make over time, I'm starting some things over. That said, I've already changed the AVCS map twice and am currently very happy, especially with the reduced knock sum. I'll post that table asap... meaning when I find a convenient way to take a screenshot without multiple programs and editors :( (anyone?). You will see then the distinct difference I mention. But who knows, I may try fahr_side's map and like it better. :) Playing with AVCS is both fun and easy... as well as largely an exercise in tuning that doesn't involve high speeds and danger, not to mention the wear and tear on the engine.

 

An excellent thread.

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This is my current table. I see no improvements running more than 30* at any rpm/load site. I see only less torque if I run over 0* past 5,200rpm. Running more than 10* before 0.80 load does me no favors for torque.. fuel economy is increased but so is vibration and bucking / hesitation.

 

As Smiles said: "We learn wisdom from failure much more than from success. We often discover what will do, by finding out what will not do."

 

I mentioned in another thread that you can see timing pulled from 'knock' when in fact it's just that you have -ve boost error... boost is higher than targeted for the revs/requested torque. Timing is pulled before knock is even seen, as a preventative measure.

If you reduce VE with sub-optimal AVCS mapping then boost can often be increased as a side-effect. Improving VE means it's harder to hit your boost targets with the WGDC currently set.

That is for a wrx, anyone put it on a lgt?

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I'll post that table asap... meaning when I find a convenient way to take a screenshot without multiple programs and editors :( (anyone?). You will see then the distinct difference I mention. But who knows, I may try fahr_side's map and like it better. :) Playing with AVCS is both fun and easy... as well as largely an exercise in tuning that doesn't involve high speeds and danger, not to mention the wear and tear on the engine.

 

An excellent thread.

Take a regular screenshot(with the button on your keyboard) then open up MS paint, ctrl V, and select the table and ctrl c, then, ctrl v into a new MS paint document. Sounds like a PITA, but its really easy

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