Discussion in 'N55' started by Sbrach, Oct 16, 2017.
Time for a 3.5bar TMAP....
I take it the N20 sensor fits as well?
Yeah, same as N54. This was just a first pass at upping the boost with the Commanded WG table. I've already backed peak down to 20-21psi. Tapers down to 14psi at 6k which I think I can get slightly better. I don't know how long I will stay on Commanded WG. It's a daily driver and I don't really want to have to dial in the table every time the weather changes. Need to wrap my head around the stock boost control strategy.
Theoretically, you should just be able to ask for the torque and load you want by moving the various limiters around. Practically, I think the compressor required power (kW) table, or whatever people are calling it, needs adjustment in areas that are hit on a tuned engine and because we don't have all the data it is an empirical adjustment to get it to hit the target boost without significant PID trims. Does this tally with experience? I haven't actually got around to properly tuning it despite my wife having the car for over a year, it is fast enough for her, will never be fast enough for me, and a Cobb OTS map just caused boost oscillation that I never got around to fixing so put it back to stock. I will be soon with MHD, hopefully with realtime tuning, just in time for frosty roads with 19" runflats.
When I went from OTS maps to my own custom bin I started with Commanded WG based on the tuning guide posted by V8Bait and E90post comments from Bahn. I haven't tried tuning with the OEM boost control strategy yet. The OEM bin has WGDC limited to 65% and the diverter valve opening at 80% so once those limits are raised along with tq/load I don't know how drastic the changes to the PID values need to be to prevent oscillations. I know Justin is not using Commanded WG on the OTS maps but Ken is on his custom tunes. Realtime tuning would obviously make PID tuning drastically easier. I'm in sunny Arizona so perfect conditions all winter if you need a tester.
What's the name of the diverter valve opener map? Edit, sorry see it:
Tastverhältnis ab dem das Schubumluftventil öffnet
I believe it is labeled as WGDC % to open Diverter Valve in the XDF. I took it at face value and assume it is an OEM safety measure to protect the turbo.
I will focus on understanding the stock boost control strategy this week and do some testing this weekend. I imagine dialing in the PID will be tedious with 4 minute flashes each revision.
My biggest issues right now are post shift rich AFR (DCT) which I believe is a solved problem I just haven't figured it out on my own yet or found any info on it and the fact that I still see a lot of timing corrections even on E30. Although, after thinking about it a bit I realized that since we only have E54 at the pump in AZ that my E30 mix is significantly lower octane than one made with actual E85 since the gasoline in the flex fuel is likely only 85oct. If my math is right that means my E30 blend is only 96oct whereas if I run straight E54 out of the pump I will be at 100oct. I think I will start running straight E54 from the pump and if I have to lower boost to avoid running out of fuel on stock fuel system it will be worth it to not deal with ignition issues.
Gas station on ValVista and Broadway has E81 at the pump...
I live in a surprise though so after getting home from driving out there to fill up I'd need to fill up again.
Anyone played with the Fuel Start AT (VVT) and Fuel Start MT (VVT) for cold start on ethanol mixes? In the latest repo xdf they are duplicated, but same addresses, and I suspect the(Throttled) versions only are used if valvetronic isn't working, although I did wonder if valvetronic would work if it was very cold. There are other afterstart tables, but hoping just these are necessary.
On N54, Fuel (Start) is used only during cranking. You also need the warm-up enrichment map, as that is what is used while the lambda's heat up until the car can switch over to closed loop.
Yesterday I mixed E40 and ran out of fuel much sooner than I expected lol. WOT was instant misfires. Last night I reverted my changes to the Commanded WG table to get boost back down to around 17 tapering to around 14. So far so good in the lower gears. Can anyone point me in the right direction for resolving the post shift swing rich?
Limiting load below 4K, richening up the spool afr table, reducing max spool mode to 2750, and reducing timing in the 3-4K range at max load a bit because WOT in 6th at 3k results in large timing corrections.
Do you need commanded wastegate blended by ethanol content?
I think for true flex fuel on stock fuel system you would need it. If someone puts in straight E85 you will have to limit boost or they will run out of fuel. I guess you could achieve the same by load ceiling blended with ethanol content.
Load ceiling and modeled torque by gear are already blended. So you do not think commanded wastegate needs blending?
I don't really have the experience or knowledge tuning to answer that question definitively for you.
Reducing load will reduce boost set point so I don't think it's necessary. If you take the time to implement flex fuel I don't know why you wouldn't want to use the PID boost control. It seems silly to have a car that you can change ethanol content on the fly but if the temp changes you need to dial in your WG table again.
Made the changes I mentioned above. Running ok on E40 now at lower boost. My STFT is still way off when WOT in the upper rev range, up to -15%. My scalar values are all around 1.10 in that area. Doesn't that seem low for E40? E40 should be around 15% more fuel, no? I'm thinking this is probably the reason I'm so rich post shift, it seems to go open loop briefly right after the shift and if the scalars are that far off there is nothing to correct it.
Back to E30, car is not reliable on E40. Sometimes it would rip but most times it would break up post shift or at high load. Not worth trying any more.
My one big hang up so far has been the fuel scalar table. My STFTs are still very negative. I keep reducing the table but, for example, at 4700rpm and 170 load my STFT is -14%. The scalar table at that point is 1.10. Does it really need to be .96? on E30? That doesn't make sense to me when the stock table is 1.0 at that point.
I had the same problem with E54. Going past 17-18 psi on my 6266 and it just wasn't a clean pull sometimes.