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Old 04-16-2021, 04:04 AM   #18 (permalink)
Master EcoModder
Join Date: Jan 2012
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spyder2 - '00 Toyota MR2 Spyder
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2006 AM V8 Vantage

Gonna continue using this thread to keep notes on my tuning efforts. Unfortunately, I still have not been able to figure out the DFCO parameters, which is costing me some fuel.

Idle: I think it'll idle okay at 680 instead of 750, dropping my hot idle gph from 0.42 ish to 0.37 ish. I haven't been able to find the idle speed control table though.

VVT: I made some really rough estimates, assuming around 30% iEGR dilution at idle based on observing that a small change in vacuum produced a big change in load, comparing hot vs. cold idle. I think I can bring down the iEGR amount in the low load, low speed cells to improve combustion stability for mpg, and then feed more EGR in at higher speed with later intake valve closure to reduce overall vacuum by around 0.5-1psi, by targeting ~20% total EGR (compared to 100% undiluted cold air, this has around 60% oxygen concentration, a good improvement!).

I think I can push that retarded cam position to medium load as well AND feed more external EGR in, giving me higher pulse efficiency for P&G.

0.5psi at cruising speed is a respectable ~600 watts, 1psi is around ~1200 watts (compare to the ~15-22 kW it takes to go down the freeway), and improved combustion stability hopefully has a noticeable effect. If I can get 50mph cruise from 26 to 29mpg, the numbers would start to look a little more like a normal car, and if I can crack 30mpg at 45mph, that would be amazing. Otherwise, I'll continue to P&G diligently.
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