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Hi everybody my name is Johnathan, I've just recently got into tuning and I've completed a lot of the HP Academy courses to get started. I still don't feel that I have a very clear picture of what a general plan of attack should look like when I begin tuning. I understand it will vary by engine and mods, but after repeatedly hearing that tuning is a repeatable science I feel like I should be able to put some kind of tentative process on paper.

The general consensus that I've gathered from HPA and a few other online sources is that it's better to work on Fuel tables before doing too much with ignition timing, specifically getting MAF dialed in and THEN speed density if applicable. But my biggest question then becomes where does Valve Timing come into play? It seems to me like this should come even before ignition timing, am I wrong? I have a GM LFX with a E39 ECU and being that it's a Dual VVT engine I'd assume it's pretty critical to get valve timing dialed in asap so you aren't just undoing all your previous work down the road. I guess my question is, what order should Fuel, Spark, and Valve Timing go in?

For reference my car doesn't have any bolt ons and I'll be largely tuning for more WOT power. If anybody can offer some assistance it would be greatly appreciated!!!

Valve Timing will affect mostly VE, or in other terms, how the engine breathe. So you'll find that when you change the VVT angle, you'll need to correct the fueling. It won't affect the spark as much. The way I do it, adjust fueling, adjust spark, then move VVT, and repeat fueling, spark... easier to do on a standalone with real time adjustment of course.

I asked Andre during the last AMA and here's his answer :

EDIT : A good thing with starting from the OEM maps is that you have a good starting point, and maybe you'll won't have much adjustment to do!

Hope it helps,

Frank

It depends, as Frank said, VVT (in it's various iterations) can have a drastic affect on dynamic compression and cylinder filling. The more efficient the cylinder filling, the less timing that should be required.

I would suggest following Frank's suggestion, especially if they're individually adjustable through a range. Fix the cam'(s) position(s) at one extreme (eg both advanced) and do the fuelling and timing, repeat other extreme (both retarded) and repeat - some systems are just one or the other - possibly try both other options one advanced, one retarded, and vice versa if the system allows it (but double check there's no possible interference, esp' with bigger cam's and/or valves).

If you're lucky, you can then overlay the torque/power curves to see where the cam' timing(s) should be changed for the fullest curves.

If you're unlucky there may be several intermediate positions possible - ah, "continuously variable" - and you may need to spend a bit more time optimising the relative positions - small amounts you could do on the fly, though.

Don't forget, it isn't all about full throttle, getting the light, medium, etc tuning right can make a big difference to driveability, engine life and fuel economy - those last two are often overlooked but can easily pay for the additional tune time, and then some!

Thanks Everybody!!!! That clears it up a lot :)

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