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Req_fuel & VE just come out in the wash?

June 30 2008 at 8:44 AM

Response to no PITA

Not sure what happened to the L-Jet. I cut the MS away from it and still no fuel. All the more reason to just 'cut bait' and install a dedicated MS harness in my car.

There is an auto tune in MS2 and has the great capability of being able to tune itself without a PC, but there is a kick-butt autotune routine in megalogviewer. It's kind of difficult to describe, but MLV will crunch the datalog and model the AFR as if there were no corrections - it reads the AFR at each point and removes the contribution of the enrichments(or enleanments) so data from each operating point can be crunched. Literally two clicks and it will recalc the VE table, showing each cell changed, the magnitude of the change, and the weighting of each cell's calc. It compares the measured/modeled AFR versus either a standard table of 14.7:1 across the board, or your specific AFR table if you are wideband equipped.

Multiple tables can be neat if you want to tweak things. The default MS2 table is 12x12 (IIRC MS1 is 10x10?). But by having 2 tables, you can have an RPM(or MAP-)activated software switch to flip from one table to the other. This essentially gives you a 24x12 table. With 24 RPM bins, you can really dedicate a few buckets around idle, around peak tq, peak hp, and plenty of smooooth transitions.

From my POV - just getting off the ground here - multi tables are just extra complications at the moment. Of course that may change when I am blasting around and decide to have one table for boost and one for nonboost, or some such silliness. Some guys in the UK are using one table for real driving, and one crippled table for MOT inspection....

I agree that my think my flow rate is too high. Part of that may come from the published tables being rated at 3bar, but the X runs closer to 2.3-2.6bar.

req_fuel - mind if I ask what value you are using ??
By adjusting req_fuel to get idle near 13.5AFR, req_fuel wanted to be near 11.
When I ran my numbers (18# = 191cc/min), req_fuel came out around 15 or 16.
If I use 145cc/min, req fuel goes to 17.4, which makes sense sorta- a smaller injector would have to run a longer pulsewidth.
Running filthy rich would indicate that my injectors are flowing lots more than I expect.

The MS faq says 7-12 is a reasonable req_fuel value, so I think I screwed up somethin' somewhere.

With req_fuel at 15, my VE table was in the 40-70 range. I have to reduce req_fuel to about 4.4 to get the VE table to peak at 98 (peak at 3500RPM, this is kinda what I expected)
I'm auto generating VE tables based on 75ft-lbs at 3500 RPM, and 75HP at 5500 RPM, and naturally aspirated. I figure once I get the NA range working, I can build the boost section in.

But looking at the formulae, it seems to all come out in the wash. req_fuel versus VE. I guess I'll just drive it a bit, hope to err rich, keep an eye on my EGTs, let it autotune, and repeat.

From the glass lined tanks of old Bertone

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