Karter16's Silbergrau E46 M3 Journal

[Bry5on]

Haha - I would love to compare with your work but at this point agree - sometimes it's good to have separate efforts and then we can compare later. In terms of my process, I'm still figuring that out haha. At the moment all I really have is a tune that transitions from the Euro M3 tune to the CSL tune, with injection timing erring on the side of the CSL tune (which is generally richer) to be safe. I intend to try out a couple of different things from here to see how it goes. I ran a logging session this afternoon with LTFT off and adaptations reset to confirm my assumption that the midrange would be running rich - which it is. Plan from here is to play round with exactly where in the various maps I bring the CSL values in as I suspect I could bring them in at a lower RPM than I currently am in higher RF conditions (we'll see if that's a correct assumption or not ). Really what I'm battling at the moment is my own level of understanding.

One thing I'd love to know (it doesn't relate to any particular issue I'm having, I just was reading the other day and saw it and am super curious). In one of your first posts on the Mullet Tune you said you had to adjust the exhaust cam advance at mid throttle in the high 3k rpm range. How did you work out that was what was needed? From my (admittedly limited) understanding it seems like that would be one of the less consequent things to change and I'm curious as to how you zeroed in on that being what needed to be adjusted?

Good question, honestly hard to think back on that specific moment now that I'm through it. If I can venture to guess, there was probably a lump in the power delivery as you rolled into the throttle. This is one of the tricky things about the tuning in all honesty, throttle application rate changes fueling and can lead you to chase your tail a bit (think, "that just worked last time, what the hell?!").

In the end, doing some homework on cam timing, first intake and then exhaust, would be a smart move if you're still at the basics. You might find that you'll prefer more euro values than CSL in many cases

[karter16]

To Bry5on's point I need to make sure I understand the theory of cam timing well. I understand the individual concepts, but where I've been struggling is putting it all together and visualizing what it means in different scenarios. To this end I decided that some spreadsheets would help (spreadsheets always help).

First up I took the interpolated AVAN and EVAN tables for both the Euro M3 and CSL tunes and calculated the cam overlap for each for each point on the tables:





As you'd expect we have low overlap at idle, high overlap in the midrange, sloping down to high RPM.

So how does that work out as a difference between the two?



The CSL generally runs more overlap everywhere apart from high rpm low load, and particularly in a few different islands in the low and mid ranges.

However - we need to remember that the CSL cams have somewhat greater duration than the standard M3 cams. For the purposes of comparison then we should account for this.




That's cool and all, but what it still doesn't tell us is whether the Euro M3 tune and the CSL tune differ in where the centre of the overlap occurs (e.g. before or after TDC) which is also important information in understanding the differences between the two and why.

So I calculated the centre of the overlap for each of the tunes





And from there we can compare the difference in overlap centre between the two:



Interesting stuff to look through anyway - I feel now with this view I can better visualize and understand the impact of the various tweaks etc. that I'll make. I've only just put these together and haven't worked through them in detail to look at various areas of interest but will update here as I do.

[heinzboehmer]

I've peeked at similar spreadsheets on Bryson's laptop, but the visualizations towards the bottom of the post are awesome. Thanks for sharing.

[karter16]

Ok I think this approach is helping my brain. Here's another interesting view - this is the difference between the Euro M3 tune and CSL as it pertains to the crank degrees at which the intake valve is completely closed.



And correspondingly for when the intake valve opens:



Arguably the point at which the intake valve completely closes is the most important of the 4 (intake close, intake open, exhaust close, exhaust open), so I wanted to isolate that and examine the difference between the two maps. The intake open difference is directly related, plus an offset to account for the extra duration of the CSL cam.

As could be expected we can see that at higher RPM the CSL is configured to to close the intake valve later (by between 5-10 crank degrees) than the Euro M3 tune which will drive more top end power. we can see at low load between 4300 and 6300 RPM that the CSL closes the intake valve earlier than the Euro M3 tune. I presume this is to keep drivability decent with the bigger cams, as presumably is the other island at low RPM thru mid and high load.

[Bry5on]

That last bit is the ticket. Now compare the tune numbers from CSL vs euro and you’ll find that the euro intake cam timing should actually be making more power (and run smoother) above 3k rpm than the CSL values in most cases