Jump to content

HOWTO: Ghost Cam and VCT simplification


Recommended Posts

This is a guide to set up a ghost cam on a BF/FG. This involves understanding how the VCT system in the falcon works.

NOTE. This is NOT emissions compliant. This cannot be done on a road car, it must be for vehicles that are used on a racetrack or a powercruise event etc. This is the same as using aftermarket cam shafts. The unburnt fuel will not be cleaned up by the catalytic converter and you will be releasing high levels of carbon monoxide (NOx should be quite low as it is running rich, not lean). Do not leave your car idling in a shed with poor ventilation. E85 is much safer than Petrol however it is still not recommended to breath in the gasses.

Firstly the VCT works by the PCM calculating an intake camshaft position, it then adds the calculated overlap angle to this position to calculate the position of the exhaust cam.

Eg:

VCT_Intake_Cam = Calculated Intake position

VCT_Exhaust_Cam = VCT_Intake_Cam + Overlap_Angle.

Finally to confuse things the PCM then adds/subtracts from the intake and exhaust cam based on boost error. Note this in only in the FGs. This will not affect idle however it will affect your vehicles performance depending on how you have set up the boost control.

image.png.c26dc6288ce83187755edaac02d5f5ad.png

To achieve a ghost cam we need to understand how the overlap angle is calculated. 

There are 3 modes of VCT operation

cam source == 4 is Idle mode

cam source == 99 is VCT  Fault/Not Installed mode

Cam source == 3 is power/full throttle mode

cam source == 2 is part throttle mode.

Now in idle mode the camshaft overlap is capped by the same table that determines the intake camshaft position, so you cannot achieve any overlap, the best you can do is set both the intake and exhaust camshaft to 50 degrees which will give you some lump.

An easy solution to this problem is to force the PCM into cam source == 3 at all times. This means the main VCT tables are used at all times making tuning the vehicle much easier.

To force the camshaft to use the main maps at all times simply set these scalars out of range to -1000 rpm.

auF1079 (VCT Closed throttle disable RPM) set to -1000

auF1035 VCT Closed throttle enable RPM) set to -1000

Now to get a ghost cam the following tables need to be modified

auF0115 (BF/FG)

Maximum allowed overlap angle based on RPM and Oil Temp. Set the lower half of this table to 80 degrees

image.png.4450023c1d582419687b06db8f04e904.png

Now we can change the commanded overlap at idle via auF16492 (BF) auF0116 (FG)

image.png.2e6f724cccbfd45032bddc9f5b0f3cd5.png

Here you can see I have commanded 35 degrees of overlap at a TPS reading of 5, this means as soon as you touch the throttle the cam timing goes back to stock making car parks and low load no problem.

You also need to modify auF16503 (BF) auF0097 (FG) to have similar timing values in the low load/low tps cells. In this example I set 600 rpm to -30 deg to stop the vehicle from stalling, this will also increase the lope when the rpm drops low as the decreased overlap will kick the rpm back up again.

image.png.7c6192d72e3f06c36c303d5e8ba3b69f.png

image.png.2faddbaea004e56e099f7ab6dc22fafa.png

I changed auF0494 (BF) auF16487 (FG) (TPS) axis to 5 in the lowest cell, this means you keep the commanded overlap when hot/cold.

Finally I suggest increasing your idle rpm to 1000 rpm to avoid stalling. 

In the FG there is an overlap adder for speed density auF2260. You will need to put smaller values in the 30 and 60 degree overlap cells. This will clean up the idle fuel trims. BEWARE that some FGs command 30+ deg of overlap when coming onto boost, if you modify this table you may be modifying the WOT fueling as well. If you are using a multi-tune another way to clean up the idle AFRs is to simply add the slope of map table to the tune. auF2928 may be a more suitable table to use for the FGs as it also has an RPM component.

image.png.e92bb854d7951f449840620f678efb7e.png

It is also recommended to disable LTFT when the ghost cam is active by adding this to your ghost cam tune. This will prevent closed loop fueling from maxing out adding fuel (auF0164)

Beware that if you command too much overlap you will foul your plugs and the car will misfire until they clean up. 35 degrees is quite a lot and I would only recommend this as gimmick not in a daily driven car.

Here is a video of what the above settings will sound like.

As you can see low speed reversing etc is not a problem.

Edit: This is possible to do on a BA if you use HAAT3VC or possibly HAAT2xx as these are the late model FPV BAs that had independent cam control.

Here is a procedure to upgrade a BA to use the F6 operating system

Edit 2: You can increase the lope quite dramatically by modifying this table (auF11706). This is the proportional gain of the idle spark feedback algorithm. By increasing it to 5000 it will toggle between min spark (-7) and max spark (MBT ~25 deg) causing even more lope. This table is only available in workshop edition. 

image.png.285ca8aae93967acba3f81251a284226.png

In the 5.0 Coyote v8s we have found the figures below tend to give quite a good result without even touching the cam timing. There can be a hesitation when transitioning from idle to throttle, so you may need to add timing to the low load main spark map to help the transition. In the 6 cylinders the numbers don't seem to affect drivability much so you can put silly figures like above without issue.

image.png.a884cc7c3d9a5b380aab1465a57e3c0b.png

If you are using the multi tune to do ghost cam you can add the following table to the ghost cam tune to increase your idle rpm, this means the non ghost cam tunes can retain a completely stock idle rpm.

image.png.a69e36d71b636e64799743651dcd1b40.png

Here is an example of the required tables in a BF to add ghost cam to to tune 4 only if utilising the multi tune functionality.

image.png.1b85fea0115ea891d2026ed6185d4af8.png

Value files now available for FG and BF

 

  • Like 3
Link to comment
Share on other sites

If you have stock cams providing you don't you don't touch the tables such as "Expected position of cam hardstop" you will be fine. If you change these tables you run the risk of hitting the physical interlocks to stop the cams from causing valve piston interference.

If you run aftermarket cams and extend the overlap even further again (no one would do this) via the VCT system there is a possibility of valves making love to the pistons depending on the cam design.

The only other risk is fouling your plugs if you leave it idling lumpy for a long time without your air fuel/spark being correct. However that is no different to running actual cams

Link to comment
Share on other sites

1 hour ago, Roland@pcmtec said:

Send us an email with your file and the specific scalars you can't find, or if you are happy to share publicly you can post it here as an attachment.

actually it's the tables mentioned above that i can't find. Does it matter that the tune is a Herrod/Sct tune?

cheers

Link to comment
Share on other sites

On ‎8‎/‎6‎/‎2018 at 5:19 PM, fordsrule said:

ok, it looks like there might have been a setting in the Views list that was stopping it, i can find the tables now

thankyou so much

Hi, the image below is from my tune, as you can see it differs from the example you posted in your guide. My query is which line do I change to match your example as I have more lines?

Thanks, Steve

my auf16487.PNG

Link to comment
Share on other sites

On 8/25/2018 at 5:49 PM, Roland@pcmtec said:

You can do whatever you want there. Experiment and see what works best. 

I have no idea what to do with that table as mine had been tuned with SCT. It has more rows than what you showed from your BF table. Can you give me a little more details please?

Just want a little "tiny" rattle from ghost cam ? Very tiny bit

Link to comment
Share on other sites

  • 4 weeks later...
On 7/31/2018 at 2:23 PM, Roland@pcmtec said:

 

Now in idle mode the camshaft overlap is capped by the same table that determines the intake camshaft position, so you cannot achieve any overlap, the best you can do is set both the intake and exhaust camshaft to 50 degrees which will give you some lump.

 

What tables/ scalers need to be changed to achieve this method?

Link to comment
Share on other sites

  • 2 weeks later...

Got all the fueling sorted. Sounds good in park/ neutral but driving still has the issue of overshooting below idle rpm, sometimes stalling. Ive tried gradually reducing the cam angle so its not as sudden, which doesnt make too much difference. Is there more parameters that nees to be adjusted such as idle airflow or spark timing at idle to help it not overshoot? 

Link to comment
Share on other sites

13 minutes ago, richardpalinkas said:

Got all the fueling sorted. Sounds good in park/ neutral but driving still has the issue of overshooting below idle rpm, sometimes stalling. Ive tried gradually reducing the cam angle so its not as sudden, which doesnt make too much difference. Is there more parameters that nees to be adjusted such as idle airflow or spark timing at idle to help it not overshoot? 

Definitely recommend setting the idle rpm higher and also more airflow at idle. If you raise the airflow to get the idle timing lower (eg 5 degrees ish) then you have more timing reserve to catch the fall. If you are already idling at 20 degrees the PCM can't respond quick enough to catch it. Timing cause the idle to jump almost immediately, more idle air has a small lag delay and can oscillate.

I also recommend leaving the oil temp table fairly standard, that way when the car is cold it won't have the lumpy idle.

Link to comment
Share on other sites

1 hour ago, Roland@pcmtec said:

Sounds like it is misfiring. How much overlap is that?

As per auF2260, but i have read it again and you say to reduce the values there so there is no misfire, i will have to make that adjustment.

But the idle did change to more of a lump just after the end of that video

Cheers

 

Link to comment
Share on other sites

  • 2 weeks later...

Hi Team,

New member to PCMTECH & tuning of such ECU's.

I took the time to read through the ghost cam scenrio, got to work, great..after the 1st run got over it, sounds good though..lol...one thing i didnt find as a scalar is auF2260 i dont seem to find this. Car is a 2013 FG XR6 MK2 turbo following strategy  HAEK4MF.HEX / BBMF

Is this missing on such stargey?

running PCMtech version 0.74.

regards

Abs

FG-MK2-XR6-TRBO-GhostCam&Overboost-16-12-18.tec

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Unfortunately, your content contains terms that we do not allow. Please edit your content to remove the highlighted words below.
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...