I'm now testing with the catless headers.
- worse fuel economy
- little bit more power from 1500rpm to limiter, most difference is on the midrange; peak torque and after 6000rpm. Also more sharper throttle response while driving
- quiet, but only because the catalytic converter header was cracked, or actually in 2 pieces.
Why the worse fuel economy: probably because egr effect is not present the same way.
More power is not really a good deal for fuel economy, but I have an idea that I'm going to try if I can recover the fuel economy.
About 2 months ago I tried different, mostly intake cam timing at part throttle.
When I went way more advanced, at some point the engine started missfiring badly and had to retard ignition timing quite a lot.
It may have been because of too much egr effect, and did not like more ignition timing at all.
Before missfiring it was able to keep the speed as low as 6L/100km reading, when usually it's 8L or more when driving straight road (I use same road for testing) at 100km/h.
That _might_ work better with the better flowing catless headers. Don't know untill trying and testing.
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problem with stratified charge is that the leaner areas don't burn well and the fuel there is sort of wasted. A higher energy ignition system, preferably that ignites the cylinder at multiple points, that can ignite a more homogeneous lean mixture is optimal.
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Maybe sort of "controlled" pre-ignition could solve this problem?
Something like spark-assisted compression ignition.
Ethanol could work better than gasoline.
Atleast with gasoline the engine would probably melt spark plug quickly.