Good post and info! Below is some feedback from Shiv@vishnu
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Originally Posted by mad_sb
W00T!
Finally I'm not the only one posting a tuning thread 
Big thanks to the openflash guys and Shiv for the brain dump  I really enjoyed chatting this past week about the findings and comparing notes on the base maps.
I have a few questions and comments after seeing the digest version...
Cam Timing
On stock exhaust, I found a good bit of power on the low rpm and higher rpm sides of the dip by advancing the exhaust cam. I assume you found the same thing? I did not find any difference in the 3,750 range though... I assume the back pressure is just so high there for whatever reason that you can't close the exhaust valve soon enough to avoid reversion?? |
Yes, the dip was reduced in both duration and severity by advancing the exhaust came. Running 40deg of advance down there. Looks like the factory mapping makes some concessions in that respect. Perhaps for fuel economy or emissions.
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Which way did you go with the exhaust cam on the header car to get those gains? My long tube should be hear late this week and I will be hitting the dyno to retune on pump before I move on to E85 again. So I would love to hear what you found. My assumption is less Ex advance with a better flowing header?? I may just roll your cam timing into my starting point tune to save some dyno time.
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I'll be tuning some stock header/stock exhaust cars tonight this week on the dyno. So then I'll be able to quantify the differences in mapping requirements between a stock and fully modified set-up. I agree that the first tuning step would be advancing the exhaust timing (and intake). Seems to pick up great power with no real downsides that we care about.
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AFR
After chatting earlier this week, it really hit home that with 12.5:1 compression (even with DI) you need to treat this a bit like a turbo car and use some extra fuel for cooling so you can get more timing in to get closer to MBT.
I have lots of logs of my car, when stock, running 13.2:1 WOT through the midrange with zero long and short term trims. I struggled for a while with trying to tune it at 12.8 – 13.0. It would make great power for one pull, but the minute you tried to do back to back runs it would start pulling timing. My last pump gas tune I did before going to E85 (The tune I switched back to for base map testing this week) I tuned at 12.5 – 12.6 with a dip towards the rich side of 12 up top... this was by far the most repeatable and knock free tune I have done.
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I'm glad you found the same thing. My first tune attempt was also met with marginal success when I tuned for AFR that was clearly too lean for this engine. It really needs to be rich in the low end/midrange. Especially with the VVT changes. Without enough fuel, the engine will sound hollow and not make max torque.
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GDI Injection Timing
I found a little bit of power around 6,000 on E85 by moving the SOI (Start of Injection) earlier a little lower in the rpm range. I haven't had time to play with it on pump gas. Love to hear more about what you found as I think there can certainly be a sweet-spot where you get the best in cylinder cooling combined with the best charge mixture etc.
Really looking forward to seeing the E85 results soon too. I found that we are not able to get even close to MBT on pump gas above 5,000.... down low we are only off a few degrees once tuned. This is using the same method for timing tuning posted above. Keeping the advance where it makes power, removing it where it does not.
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I'm looking forward to calibrating the E85 map. Thank you for sending me good starting points for injection calibration. It should save a lot of time!
Cheers,
shiv