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Ecky · 06-28-2019, 11:04 PM

Finished cleaning up my low speed fuel maps and built my cam angle tables for low speed (subject to change).

Angles marked in red are for throttle response and power, chosen for their ability to stuff the maximum amount of air into the cylinder.

Black are transition cells, or those basically unused.

Those marked in green are where the majority of steady state driving happens. High cam advance in those areas drastically reduces power output - in some areas 33% or more - because (I believe) the intake cam opens early enough that it prevents some of the exhaust gasses from going out through the exhaust. In other words, a lot of EGR. This should raise cylinder pressure with gasses that don't contain oxygen and pull gasses back in which have heat (usable energy) which hasn't been extracted yet. It should also reduce vacuum in the intake, raising load and moving the engine closer to optimal BSFC. The downside to a lot of EGR is that in more extreme cases I might have to pull timing to avoid detonation from the extra heat, which could negatively affect economy.

Soon the area marked in green will become my lean burn window, which may mean I might have to get rid of the crazy cam advance there. Lean burn requires significantly more ignition advance because the flame front is slower, and the leaner you go, the sooner you have to start combustion, otherwise the piston will race down the cylinder ahead of the slower explosion with no energy extracted at all.

My plan is to lean out to maybe 18.5:1 or 19:1, put a small load on the engine (maybe run the A/C), hold the throttle very still at a specific RPM (let's say 2250RPM), and in real-time advance the ignition timing 0.5 degrees at a time. Every time I advance timing, if power increases (meaning more energy is getting extracted from the combustion event) I should see a small increase in RPM. I'll keep doing this until I stop seeing improvement from adding timing, then back off a few degrees, and that should be close to optimal ignition timing in that rough area of the map for that air-fuel ratio.

06-28-2019, 11:04 PM	#333 (permalink)
Ecky Master EcoModder Join Date: Dec 2011 Location: New Zealand Posts: 5,077 ND Miata - '15 Mazda MX-5 Special Package 90 day: 39.72 mpg (US) Oxygen Blue - '00 Honda Insight 90 day: 54.69 mpg (US) Thanks: 2,904 Thanked 2,560 Times in 1,586 Posts	Finished cleaning up my low speed fuel maps and built my cam angle tables for low speed (subject to change). Angles marked in red are for throttle response and power, chosen for their ability to stuff the maximum amount of air into the cylinder. Black are transition cells, or those basically unused. Those marked in green are where the majority of steady state driving happens. High cam advance in those areas drastically reduces power output - in some areas 33% or more - because (I believe) the intake cam opens early enough that it prevents some of the exhaust gasses from going out through the exhaust. In other words, a lot of EGR. This should raise cylinder pressure with gasses that don't contain oxygen and pull gasses back in which have heat (usable energy) which hasn't been extracted yet. It should also reduce vacuum in the intake, raising load and moving the engine closer to optimal BSFC. The downside to a lot of EGR is that in more extreme cases I might have to pull timing to avoid detonation from the extra heat, which could negatively affect economy. Soon the area marked in green will become my lean burn window, which may mean I might have to get rid of the crazy cam advance there. Lean burn requires significantly more ignition advance because the flame front is slower, and the leaner you go, the sooner you have to start combustion, otherwise the piston will race down the cylinder ahead of the slower explosion with no energy extracted at all. My plan is to lean out to maybe 18.5:1 or 19:1, put a small load on the engine (maybe run the A/C), hold the throttle very still at a specific RPM (let's say 2250RPM), and in real-time advance the ignition timing 0.5 degrees at a time. Every time I advance timing, if power increases (meaning more energy is getting extracted from the combustion event) I should see a small increase in RPM. I'll keep doing this until I stop seeing improvement from adding timing, then back off a few degrees, and that should be close to optimal ignition timing in that rough area of the map for that air-fuel ratio. Attached Thumbnails __________________ Ecomodding 2015 MX-5 Miata Honda Insight w/Acura TSX engine 2000 Insight TLC & Build Thread Last edited by Ecky; 06-28-2019 at 11:11 PM..