Questions
Q: How long until larger tables are available in both firmware and MegaTune?
I helped tune the Volvo PV that Emil recently installed VEMS into and we badly need bigger tables. 12x12 is nice, but 16x16 would be much better as the cam and boost on this engine are extreme.
As I understand it, trivial changes are required for MegaTune to use the bigger tables, the firmware I don't know.. Could someone clarify?
Here is a mct/mcd dump from the box: http://www.vems.hu/files/MembersPage/MattiasSandgren/volvo_16v_race_vems.cap
We disabled injopen and injocfuel to see if that would help the situation as it gave us more "power" with the VE-table, but the situation was the same. We are in dire need of more resolution, especially for pressure. 16x8 (rpmxmap, more rpm bins) would not help out much at all, there is so much going on in this engine along the map axis. Can not compare to a standard "high power" engine, this is 100+ hp N/A per litre with forced induction on top.
The owner of the PV is used to Haltech and has mapped 9-10 cars previously, he is really dissapointed and feels that even 16x16 would be on the thin side for his race engine. On his Haltech he had 32 fixed pressure bins, and the engine ran silk smooth. Can you show the maps? It is _very_ likely that it's possible to set with 8x8 configurable bins if interpolation is used (maybe he's not aware of interpolation?)
8x32 (rpmxmap) was much better on his F3, but he has worked with the newer models too and feels the same way.
Something must be _seriously_ wrong there. Either with
- setup (nonlinear, wavy transfer-function MAP sensor output?)
- lack of interpolation
- The first derivative can be any high (although it is limited by nature, except for the variable intake or variable valve actuation point), it just does not require more bins with interpolation. High 2nd derivative value requires bins, but that is absolutely limited.
- lack of multiplication with MAP. If config13 bit2 is set to 1 (which is not sane for speed-density, but often used for AlphaN) than multiplication with MAP is not used, so the VE table will be very steep and harder to tune.
In the RPM direction, for some engines there can be 2..3 small waves in the VE where 9..10 bins can come handy (though 8 configurable bins with interpolation and incredible EGO correction is significantly better than any number of bins without incredible EGO).
In the MAP direction those waves (high 2nd derivative) are simply not possible. The lambda and VE are unbelievably smooth above MAP=60 kPa (upto 512kPa or whatever), and the ideal ignadv just cannot ever have more than 7 significant breaks in the MAP direction.
16x16 will surely be supported in tuningsoftware, mainly for marketing (avoid blaming table-size when the problem is elsewhere; also to make the tuning process somewhat easier by absolutely eliminating the need for moving around bins, ever).
There are things we should sort out before we give up and wait for larger tables, we would like to know what those would be.
Configure MegaTune. The firmware just needs to be recompiled with VE_SIZE_RPM=16 and VE_SIZE_KPA=16 and some testing.
On a happier note, ignition and wide-band lambda is working out great on this motor!
Status log
- Mar 5th, 2005
Another BWM owner needs a Genboard install. Visit MembersPage/MattiasSandgren/PeppesBmw to check it out. We have some trigger issues to work out.
- Feb 12th, 2005
Added a page about a BMW 728 that I'm helping to convert to VEMS/Genboard with help from all of you and MembersPage/EmilLarsson in particular. Visit MembersPage/MattiasSandgren/BmwSevenTwentyEight to check out the wiring issues.
About me
I am the main site administrator of [Sävar Turbo Site] and I have in recent years become more and more interested in combustion engines and cars in general. I have a computer geek background but mechanics always intrigued me - not only electronic gadgets.
I have several cars but my two main projects are :
- BMW E30 325iX (1989) MembersPage/MattiasSandgren/BmwEthirtyIx
- Volvo 142DL (1972) MembersPage/MattiasSandgren/VolvoHundredFortyTwo
The Volvo is long term, my focus is currently on the BMW. I plan to replace the Motronic ECU of the 325iX completely.