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HOWTO: Custom OS Speed Density via MAP - VE Tuning model for locked camshafts


Roland@pcmtec
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Problem: You have large camshafts with locked VCT (or a 5.4 V8) and are having trouble tuning the low rpm/low load portions of the map due to the non linear airflow characteristics (due to reversion and overlap) with the standard linear speed density model.

Solution: Utilise our custom operating system and the "Speed Density via MAP" speed density model. This replaces the speed density map (Inlet camshaft position vs RPM ) with MAP Pressure vs RPM like a traditional GM style VE model meaning you can now have a non linear airflow model.

To enable this feature you require the workshop edition and a 5 credit "Standard Custom OS". This is an extra 2 credits on top of a standard license.

First open the custom operating system wizard, select "Standard Custom OS" and press Next.

image.png.b70429da2cfa6326030b97520b4711b0.png

You will then see a "Custom OS Options" page. Leave these items standard.

image.thumb.png.c1e27008183b940bf3f79ec92df4d104.png

Press "Check License and Proceed" which will then ask you to license the file, this will charge you an extra 2 credits (total of 5 for the vehicle). This will only be charged once.

You will now see a second set of Custom OS options (these can be changed as many times as you like). Select "Speed Density via MAP Sensor" for the "Speed Density Configuration" 

image.png.53fbd5c1937ad5f5c224769989f1d3f3.png

Press Next then "Finish" and the file will automatically save and re-open.

Now navigate to the slope of map table within the speed density section where you can see the Y-Axis is now MAP Pressure (kPag)

image.png.916e6b05531e8ad26f995e39d1ab8f80.png

The next step to work out the home position of the camshaft and find the row which is close as possible with the new locked cams. If we look at the standard VCT configuration and assume the -10 row is the closest to where the new cams are installed we will copy this row to the entire map.

image.png.81ce494e9c2a2885e46d7c4122e8b1ea.png

 

You can see the first row (-10 VCT inlet cam angle) has been copied to the entire map. The speed density model will now operate as if the VCT system has been locked at the -10 position.

image.png.48005d57259e5dcdc43632dc41c42211.png

 

If the airflow model was completely linear with no oscillations, overlap or reversion, eg we were still using the standard camshafts locked at -10 we would find that the AFR should now be perfect and flat across the entire rev range with the above table and no changes required.

As large camshafts have overlap and reversion at low rpm/load you will now find that the airflow model is no longer linear and you will be likely running rich at low rpm and map pressures. You can now simply tune this map like you would any traditional GM VE model vehicle. Eg to make it leaner at low rpm/load. Simply increase the speed density slope values at the cells you require. Remember that 101 kPa is approximate 1.0 load and anything above is boost.

This tuning style ONLY works with locked VCT or not VCT (eg 5.4 V8). If you try and use this model with VCT you will likely find yourself chasing your tail, especially if the VCT fails or operates differently in different conditions (eg when cold the VCT does not operate the same). This is because for a given MAP pressure your VCT position is not constant, therefore your model will be wrong and you must use the standard model which has a different row per VCT camshaft angle.

Lots of our customers have had a lot of success with this tuning model on large camshaft vehicles and we highly recommend it for large cammed cars which have rich/lean issues at low load/rpm.

 

 

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  • 5 weeks later...
  • 1 month later...

Hi I'm looking to use this method with locked vct, large cams and up to 40psi of boost.

Given that there are only 6 rows for the Y axis, am I to scale the Y axis in 10psi increments ie; 0 to 50psi ? I noticed that there are 8 cells when you go to change the axis values.

Also wondering which tables will reference the off boost driving etc.

Any help is appreciated 😁

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  • 9 months later...

Hi guys can you tell me if you need to increase resolution on the y axis as like puff am going over 40psi with a compound arrangement i am asking as i am not sure what other tables this will have an affect on if i do rescale to suit boost and rpm i am going to target  i have done the 4 bar map update swap over to boost sensor and will run small cam set up no overlap but will be solid lifter 

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Speed density tables are only for cam angle and rpm, they are load independent so there would be no need to change any scaling.

If you are running 40psi and 20psi on the same tune, then I would definitely advise rescaling the spark tables to ensure you are getting max ignition timing at both load levels. Don't peg the tune at 2.0 load like some people do, as you'll be missing out on part throttle and part boost torque.

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hi mate no prob with the spark or boost control i was just not sure if i changed the axis value if it was going to change any other table i might not be looking at i have done similar set up on another engine just never with a oe pcm   ps thanks for all the work you have done with pcmtec hp was starting to do my head in 

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I understand. With the axis when you open them you can see a list of shared tables at the bottom. All the tables that share an axis will need rescaling to suit eg spark has blk and MBT off the same axis. 

In 2.10 (available on the website) when you modify and axis it will prompt you to auto rescale the referenced tables. We highly recommend utilising this function. 

Alternatively there is a manual rescale option available here 

 

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47 minutes ago, Roland@pcmtec said:

If you are running 40psi and 20psi on the same tune, then I would definitely advise rescaling the spark tables to ensure you are getting max ignition timing at both load levels. Don't peg the tune at 2.0 load like some people do, as you'll be missing out on part throttle and part boost torque.

After testing this with E85 on the dyno, the timing is pretty much the same at 20psi as it is at 40psi. Obviously when you are knock limited this would change, but you can't efficiently go much higher than 2.0 load with 98 anyway.

Max power is about 20 degrees of timing but you only make a small gain after 18 degrees of timing so that's where I tend to leave it.

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Just rescaled a map for s&g. From 1.0 load I made it jump in 0.5 increments up to 4.5 load. After the rescale it actually removed several degrees of timing.

Of course you could go through and add it back in, but just rescaling from 2.0 to 4.5 load would make the car slower.

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Hey mate car is on 25psi now and on e85 now with 1650 injector(will swap to id2700) and good fuel set up and i have the load opened up to suit were i am now i was just after some feed back on weather or not it would change alot of other things i might not know about if i changed the numbers  Yes the timing numbers seam to be the same with most of the engines with this bore size and chamber shape and comp I have been playing with one on meth and it only wants the same numbers it can take more but for very little gain I have done a lot of work with another 6cyl high boost engine i hope to take what i have learnt from that and move it over to the barra I hope to see around 60psi from the compound setup running meth  I have a built engine ready to go in the car now and am just waiting on a turbo 400 and to finish off some pipe work for the compound 

 

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4 minutes ago, dynotunz said:

i have the load opened up to suit were i am now i was just after some feed back on weather or not it would change alot of other things i might not know about if i changed the numbers 

This is definitely a question for @Roland@pcmtec or another developer, as they can see the math in the code and which other tables are affected by a simple borderline knock timing change.

I know that a lambda change in the base fuel table can affect final timing, due to the spark lambda correction table. I don't know if anything else in the tune is affected by direct changes in the borderline knock table. Physically some things change such as afr, egt, cht etc and some of these physical factors can affect the tune in regard to temp related corrections, eg fuel related O2 temp, flange temp etc or timing related cht, iat temp etc.

The only thing I can think of right now is that if you put high numbers in the borderline knock table it will revert to the MBT timing table for that particular cell, in which case you would need to modify the MBT values to get a final timing change. I have seen this firsthand while tuning and while the timing updated as expected, the overall power (this was on the spool up) didn't change at all.

As far as rescaling goes, the pcm measures the load (within the map/boost sensor capabilities) regardless of the max load on the Y axis. Even when I run 4.0 load or so with the table showing a max of 2.6 load, the timing still reacts to changes to the bottom line of the borderline knock table. If you've updated your spark Y axis you will have more accurate timing control in the updated areas, rather than it following the bottom line or pegging the table.

 

Hopefully something useful there and looking forward to some more technical info and/or correction from the developers.

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Basically what puffwagon said. 

 

The load will always be the actual load, even if you peg the table at 2.0 and it has enough boost for 4.0 load it will simply peg and run along the bottom of the 2.0 row. 

If you rescale the axis it only affects the tables that axis references. As per the rescale guide it will show you a list at the bottom and suggest to auto rescale for you (since 2.0).

This is the only thing it will affect. The axis is not used by anything other than those (2 I think) spark tables that you can see listed at the bottom of the axis view page. 

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When you are done feel free to post up a new thread and ask for people to review what you've done. There are quite a few people who will be happy to help out. We can also refer you to paid training via phone/teamviewer where they can assist with the whole tuning process (base files, mechanical review, dyno set up, datalogging assistance). If you are interested in this send us a contact ticket and we can refer you on www.pcmtec.com/contactus

Good luck and have fun!

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  • 9 months later...

Hi folks, I've use this method with Kelford 218-C cams and locked VCT and it works great, the fuel does what it's told. The downside is locked VCT sucks balls on a barra with large cams.

I've just swapped back to the VCT phasers, however I have restricted the available movement in them so I don't end up with valve/piston clearance issues. I've also swapped back to cam angle style SD maps and have done a couple of hours road tuning. I have the WOT stuff sorted, normal driving acceleration sorted and 80/100/110kph cruise sorted, however I still have a bit to do on the super light load stuff such as 50kph cruise and decel.

Can anyone comment on whether I am wasting time adjusting the low load stuff as it seems to act like alpha-n tuning down there?! Perhaps I can adjust the cam timing enough at each rpm point under 2500rpm to create extra resolution for the fuel in the low load/rpm part of the SD map.

I'll continue persevering anyhow, I haven't put a lot of time into it yet but noticed it acting funny so thought I'd make a post about it. Any and all ideas/comments are welcome 😊

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Is the tuning correction table worth exploring in that area? The axes would suggest so TPS vs RPM.

I presume you have no overlap commanded running at the light load so reversion should be ruled out?

How's your injector DC  PW down there? Bloody big injectors love running on low slope lol. 

 

Edited by hjtrbo
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0.01%injdc, 0.55ms at idle.

There is 0 commanded overlap up to and including 150 ad count, it idles at 144 ad count...with 30 degrees overlap.

My tuning correction tables are load vs rpm so might not be that helpful.

I did notice that my interior light was flickering a bit and affecting the afr. I tried the headlights and it leaned out so there is probably some injector voltage values not correct.

There might also be something happening with the fuel heating up after a while cos I know that it gets farken hot with the 2 pumps going full bore all the time.

I've been sitting in the driveway working on it, looks like it just needed some more tuning for the most part but will see how it goes.

Anyhow the missus is sick of hearing about it so it's another reason I'm posting here and thinking out aloud.

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Also, I remember Roland saying a while back somewhere about the tuning correction table being inferred load or something like that and that it acted more like tps input. If I can dig up that post I'll link it back here. 

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3 minutes ago, hjtrbo said:

Yeah, that's right in a shit spot. Most injectors won't go properly linear till 2-3ms. Can you lower fuel pressure and still have enough up top?

 

Haha yeah true that, here I was thinking I'm retarded and can't tune lol.

I'm at 4 bar now but my fpr gauge unscrewed the face inside it so I can't adjust it until I get a new one.

I'll get a new gauge and adjust after I crack the shits from tuning it.

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Maybe try 3.5bar base??? Still should spray alright at that pressure.  

I guess if your cruising up the road at 50km/h and fuelling is everywhere no matter what you do, then I'd put money on that being injector all day long. Conversely, if it is stable and trims are good at 50kPa 1500rpm but trims way off at 70kPa 1500rpm then perhaps the tuning correction table will help. 

Tuning correction table explained here. There is quite a bit to it if you go into how it's derived. Ideally you'd find the PID and log it :)  

https://forum.pcmtec.com/topic/218-speed-density-tuning/?do=findComment&comment=1364

 

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I've got it in open loop override at the moment, I'm sure it would be great in closed loop.

The fuel is stable when cruising slow but the act of closing and opening the throttle affects it massively while the cam timing doesn't really change.

I'll have a proper look at the thread tomorrow, it's been a long day.

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On 10/23/2022 at 5:59 PM, Puffwagon said:

Can anyone comment on whether I am wasting time adjusting the low load stuff as it seems to act like alpha-n tuning down there?! Perhaps I can adjust the cam timing enough at each rpm point under 2500rpm to create extra resolution for the fuel in the low load/rpm part of the SD map.

I'll continue persevering anyhow, I haven't put a lot of time into it yet but noticed it acting funny so thought I'd make a post about it. Any and all ideas/comments are welcome 😊

You can use the tuning correction table for alpha-n style corrections. This uses estimated load which is derived from the failed MAF table. You can also make the speed density tables bigger via the wizard if you need more resolution.

Inferred Load is derived from this table.

image.png.29c64f849f0068f6eb569e917a1b1d12.png

 

You can datalog inferred load via MID66768 as shown in the DMRY for the table

image.png.55656756bcce3476eeb45822750d36cf.png

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I've made my tables larger and have the cam timing in 5 degree increments from -20 up to +25, although it only goes up to about +15 when driving.

I spent a lot more time today fine tuning it and it's mostly good now. It still goes rich between 1000 and 1300rpm on decel, but re enabling closed loop O2 seems to be able to grab it before it gets crazy. Normal driving and cruise trims are 1 to 2% but it pulls up to 7% at low rpm decel.

Just wondering, if I stage a pump using the imrc switch point will that affect this table or use that table? My load is currently around 5.4 at WOT so having it go down to 1.3 might not be good.

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That's exactly what I need to do. I was making it lean enough down low for part throttle driving and then I would do a WOT pull in 6th gear from 1500rpm to 2250rpm to check it and it would be miles too lean. Conversely I would adjust the fuel to be good at WOT and at the cam angle it used, then it would be pig rich at part throttle with the same cam angle. Even after the extra tuning today there was still a similar discrepancy happening when I would use medium to full throttle at low rpm.

I'll put it back into open loop and finish the fuel tuning off with that table and hopefully can nail it in a short amount of time. Haha now I just need a long hill to drive up 😂

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3 hours ago, Puffwagon said:

I'll put it back into open loop and finish the fuel tuning off with that table and hopefully can nail it in a short amount of time. Haha now I just need a long hill to drive up 😂

Just pump that left foot up bro and get that calf muscle working.

#Old_school_road_dyno_steady_state 

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17 hours ago, Puffwagon said:

That's exactly what I need to do. I was making it lean enough down low for part throttle driving and then I would do a WOT pull in 6th gear from 1500rpm to 2250rpm to check it and it would be miles too lean. Conversely I would adjust the fuel to be good at WOT and at the cam angle it used, then it would be pig rich at part throttle with the same cam angle. Even after the extra tuning today there was still a similar discrepancy happening when I would use medium to full throttle at low rpm.

I'll put it back into open loop and finish the fuel tuning off with that table and hopefully can nail it in a short amount of time. Haha now I just need a long hill to drive up 😂

Firstly are your aftermarket cams degreed the same as stock? Eg 0 deg overlap actually equals 0 deg overlap? If not you'll be chasing your tail.

Make sure you are tuning the map offset AND the map slope. At low map values the offset becomes more and more important. As this is the value at 0 kPa.

The other problem with large camshafts is the equation for airmass becomes non linear at low rpm/airspeeds due to reversion and overlap (problem is the Falcon uses a linear model). If you have VCT still there is a VCT overlap adder which will assist, make sure you multiply this out with larger camshafts as you are going to be getting more blowthrough. Eg the stock cams suggest 30% of airflow is lost out the exhaust at 4000 rpm if you run 30 degrees of overlap. I bet your larger camshafts are going to do more again. This multiplier is for the slope table.

This is the tables used in a BF. In an FG they use an adder for the slope table (basically the same thing).

image.png.f37703c8bcf0bfa59ebd9fd84a41216e.png

There is also this table which is applied to the final aircharge (eg post slope/offset and everything). It is simpler to just multiply this table out to account for the different overlap than the one above. This of course assumes that 30 deg overlap in the datalogger actually == 30 deg overlap with your cam shafts, if they are degree'd with overlap at the home position, then ALL of these tables will be out of wack and making a mess of the speed density calculation (I'm going to bet this is the case, otherwise people wouldn't get their lumpy idle with "stage 4" cams that everyone buys). If this is the case, then see if you can use an offset pin to re-degree the cams to have the same home position as the stock cams and everything will work much nicer.

image.png.6894ae6abed101cff36af01e261b062e.png

The next thing to consider is the air speed/reversion issue. Big cams with reversion tend to happen at low air speeds, eg part/closed throttle. The only way to correct for this issue is via the tuning correction alpha-N map at low throttle angles.

Edit: Interesting facts

For those that are interested the Falcon speed density model is linear (eg y=mx+c where c is the map at 0 and m is the slope of map), mustang uses a quadratic so it can account for non linear airflow models without needing alpha-N as badly. They also have a "Blow through" equation to account for overlap as well. The whole model makes for much better airflow modelling (and hence emissions controls) but it is horrific to re-calibrate.

image.png.c2d844b63d3e593fb0da2b13ce11055f.png

So Falcon is y=mx+c eg

air_mass = slope_of_map * map + map_at_zero;

For Mustang

y = c + mx + mx² 

if (map > blowthrough pressure)

     air_mass = slope_of_map * map + quad_of_map * map² 

else

     air_mass = slope_of_map_blowthorough * map + quad_of_map * map² 

 

With the Falcon linear model you can datalog your AFR error to fix the linear model reasonably easily, or at least fudge it. With the Mustang you are up shit creek however you can just rely on the awesome built in wideband STFT closed loop fueling to get you out of trouble.

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I don't know how the cams are degreed compared to stock cams, Kelford would have the answer to that tho.

In regard to how lumpy the cams are, they were lumpy when they were locked at 00 but now that the vct is on there they don't sound any different to stock.

I appreciate you taking the time to post up this info, I'm sure I'll be able to put it to good use. Haha my matrix goggles are pretty good lol

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Just now, Puffwagon said:

I don't know how the cams are degreed compared to stock cams, Kelford would have the answer to that tho.

In regard to how lumpy the cams are, they were lumpy when they were locked at 00 but now that the vct is on there they don't sound any different to stock.

I appreciate you taking the time to post up this info, I'm sure I'll be able to put it to good use. Haha my matrix goggles are pretty good lol

Find out and adjust them if you can via an offset pin (I'm not a mechanic so I don't really know how exactly this is done, but apparently it can be done). If not, go and find all the tables that use CAM_OVERLAP as an input (MID04821) and shift them to account for the offset and I bet your speed density will magically get much closer with stock values. Here are all the tables I can find that use CAM Overlap as an input. I would offset all of these to make your cam overlap actually correct.

auF2260

auF11811

auF11440

auF3174

auF16657

auF2928

auF0063

auF0064

auF0065

auF0066

image.png

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You may be able to get around the cam offset by adjusting these values. As a test datalog the camshaft values, modify these, then datalog again. If it shifts it would effectively shift an offset of your camshaft home position

First column is intake, second is exhaust.

auF12259 Cam Offset with engine off

auF11468 Cam Offset with engine off high range (not sure what high range means)

 

Or possible these ones:

auF11173 CAM STOP

auF12525 CAM STOP (For a V8 maybe?)

 

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There's a total of 5 holes in the front of the cams, one is used for the pin to locate the cam and the others to allow oil through the phaser. Likewise there are 5 holes in the vct phaser, one for the pin and the others for transfer of oil.

You could weld the vct pin locating hole shut and redrill it where you want it to change the base cam angle.

I probably won't do that unless I have no other options. I've made great progress with just the SD map and hopefully can do the rest with the other tables.

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My car was idling at -30 overlap.

auF12259 made no change.

I changed auF11468 from -70 to -60 and the overlap changed from -30 to -20. I then changed it to -45 and the overlap was around 0 give or take.

It now idles very lumpy and also changed the idle trims in neutral from 1 to 0.87 and the drive idle trims are 0.98 with a medium choppy idle.

I had it going to -20 cam angle at wot before and now it goes to +15.

Interestingly enough the overlap has changed back to -30 at idle after about 300 seconds but still had the adjusted overlap at wot. Both wot tests were done in the driveway on the brake. It has leaned out quite a bit at wot.

I then put it back to stock, the idle stayed at -30, smooth idle, wot went to -20 and fuel returned.

I'll upload a log for shits and giggles.

I haven't tried the other parameters.

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To explain the log, the first part is me setting up the equations for the fuel temp and ethanol percentage. Then the weird up and down bit is what the car has started doing the past couple of days as it warms up. I probably changed something but I'll check another day. After that you'll see the cam timing doing stuff, every time you see the wideband reset is obviously when I reflash it. The last two wot spikes in the log are everything back to normal, the previous spikes are with the cam offset changed.

Anyhow it's past beer o clock so yerp 🍻

cam offset test.teclog

Edited by Puffwagon
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  • 4 weeks later...

Slight follow up, the intake cam seems to be 11 degrees advanced according to some logs that I've compared. I'm pretty sure that was the number I measured when I assembled the engine with locked VCT. I'll see if I can get it to run the extra cam retard it needs up top with the VCT angle table when I get a chance. Haha otherwise it looks like I might have to use the offset parameter mentioned earlier and do the SD map from scratch....again

 

Edit: I added 10 degrees to the cam timing table and the timing still stayed where it was. It is showing the intake cam error that matches what the table is asking for.

Edit edit: There's 42 teeth per phaser which works out to be about 8.5 degrees per tooth. I'm gonna move both cams one tooth and see what happens.

Edited by Puffwagon
Tried and failed
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Moved both cams 1 tooth and the cam timing looks the same as a previous high power dyno run. It also has stuff all cam error at wot now.

Worth a mention, the cam timing was installed correctly with the various marks etc. Both cams are visibly on the retarded side now but the car seems happy with it.

Will see how the graph looks on Thursday after a dyno run, I won't be convinced everything is working right until after the dyno.

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