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I am curious as to why the guys at riverena changed the bowel design they removed the lip. One thing I did think about was injection timing.If you can retain the lip it's very beneficial to keep the flame front away from the cylinder walls and head . Without it the flame front cools as it hits cold surfaces and you get more soot and less power . Those lips are also designed to increase bowl tumble to improve Aur fuel mixing . I'm so interested in bowl geometry and improving combustion but holy cow that is a major trial and error game .Even when you read articles in improving it you get 70% chance of reducing effeciency. Very slight chance of improving it with the most subtle changes in bowl geometry. It would be incredibly easy to get it wrong.
I noticed that with stock 1HDT injection timing the spray pattern on the piston top is almost all in the bowl with only a very small wash pattern on piston top.
When you advance the timing the injector cracks earlier in the piston stroke before TDC and sprays fuel on the piston top or squish face. I suspect some of this fuel on the crown doesnt burn because of quenching with the cooler head and piston. Or it burns at the wrong time producing soot and wasted fuel.
Is Riverena making the bowl opening larger to allow for advanced pump timing so all the fuel sprays in the bowel?????
The first pic is stock timing the second poor pic is advanced timing. Notice the spray pattern on the advanced pic. It is way outside of the bowl washing carbon off.
Stock the pattern is capured in the bowl.
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