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Continuously Variable Cam Questions

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Just watched this video. REALLY cool how all of this works.

My question is on the order of events in the tuning process.

Here is how I think it goes:

1) Set variable cam table to a static percentage. Such as 20.

2) Tune VE and get desired A/F locked like normal.

3) Adjust Ignition timing throughout the entire RPM range based on dyno feedback / MBT / lack of detonation like normal.

4) At this point go back to the cam control map and make sure its got the same table as A/F. Then start adding advancement and see if the A/F goes rich or lean. If lean it means that the engines VE has increased and you can keep adding advancement until more increase in advancement doesn’t equal an increase in VE.

5) Then go back to the same cell from step 4 that you just adjusted the CAM advancement in and readjust A/F ratios to the VE map based on the cam changes to get it back in line with the VE map.

6) Keep repeating all the way through the RPM / Load range.

Is this correct?

Where / when in this process do you adjust ignition timing?

Thanks!

My own technique goes like this:

1. Configure the cam control system and make sure the cam offsets are correct and the ECU can advance/retard the cams accurately.

2. Start with the cam map set to zero

3. Roughly tune the fuel and ignition timing - There isn't much point being 100% accurate now

4. Make a change to the cam timing of 10 degrees and assess the result (this really needs to be done on the dyno while watching torque). If you are moving the right way then the AFR will generally move lean as you mention however you couldn't accurately map the VVT just on the basis of AFR alone. It's really the torque that you want to watch/optimise.

5. If the change is positive, keep going until the torque plateaus. As you make these changes you may need to adjust the fuel delivery to keep the AFR on track, or adjust the timing to suit.

6. Once you have the cam timing optimised, you can then do a final tune to both fuel and ignition.

7. Rinse and repeat. What you will find though is that you will quite quickly get an idea of the shape of the map. This means you don't need a cam control map with super tight axis break points, or alternatively you don't need to optimise every zone. It all comes down to how much time you have on your hands.

If you have variable intake and exhaust, the tuning gets a little more complex as the optimal intake cam position will also depend on the intake cam position. It's an iterative process of going back and forth until you don't see any more improvement.

Hopefully that will help you :)

Perfect...thank you!

Andre,

Great webinar btw - I have a much better understanding of the system as a whole.

I am running a 350z with the DE engine and the Haltech Platinum Plug & Play (not the sexy standalone like you guys have). I don't have exhaust cam control on the car but within the haltech software I have a 'Exhaust Target' under my Variable Cam Timing tab within my ECU Navigator.

My question is - how should this table be set as to not negatively impact the rest of the maps? Can I delete all but the required 2x2 cells? Can I zero them all out? Should I not even worry about it?

Thanks,

James

Hey @bealljk, our car only has the variable intake cam too - It's only the later HR engines from memory that have 4 cam variable adjustment.

I've only dealt with our Platinum Pro system on the Z so can't speak exactly for the system you're using. I wouldn't imagine it having any result though regardless what you do to the exhaust cam timing map. I personally would leave the map zeroed.

Hello, what load axis do you recommend on an double vanos m3 s54 itb turbo engine w Link G4+ ecu? Thanks!

If you're running itb's you'll need to use TPS as the load axis for both your fuel table and your VVT tables.