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Originally Posted By: A_Harman
There's a lot to like about the dual-squish, dual-plug Chrysler Hemi combustion chamber, and I don't get hung up on worrying about whether the surface of the combustion chamber is really a section of a sphere or a collection of conic sections, revolved surfaces, planes, and fillets. It is the squish pads, dual plugs, and the direction of air flow out of the intake ports that contributes to fast combustion. That is the ultimate goal that makes possible complete combustion, low emissions, and high power output.
Yes, agreed, though as I mentioned, I think camshaft profile may be more of a compromise with this design than it is with a wedge. I may be wrong, but that's based on historical development behaviours with the design, so it is more of an "educated guess" than anything
Originally Posted By: A_Harman
I think the GM LS3 has a larger intake valve than the 6.4 Hemi. 2.165 vs 2.13, the last time I checked. But GM has a smaller exhaust valve, which they compensate for by putting longer duration on the exhaust lobes. When GM designed the DI Gen V LT1, they actually decreased the intake valve size to 2.125. The Gen V head also has canted valves, whereas the Gen III and IV don't. GM had to make more room in the chamber to put in the injector, and move the spark plug closer to the center of the chamber to get into the spray zone of the injector. The LS3 head actually flows better than the Gen V LT1, and the LT1 only makes more power because it has a longer duration cam, and higher compression ratio.
If it came down to an ultimate HP contest, I think the Hemi could be built to beat the LSx.
Great info about the newer gen LSx stuff
You are right, the LS3 heads have 2.165 intake valves and 1.59 exhaust, the 6.1L had 2.08/1.65's and the 6.4L has 2.14/1.65's (for the big bore HEMI's).
I believe you are likely correct, that a full-out HEMI could best an LSx, probably awful anecdote but look at Mountain Motor and what dominates there.
There's a lot to like about the dual-squish, dual-plug Chrysler Hemi combustion chamber, and I don't get hung up on worrying about whether the surface of the combustion chamber is really a section of a sphere or a collection of conic sections, revolved surfaces, planes, and fillets. It is the squish pads, dual plugs, and the direction of air flow out of the intake ports that contributes to fast combustion. That is the ultimate goal that makes possible complete combustion, low emissions, and high power output.
Yes, agreed, though as I mentioned, I think camshaft profile may be more of a compromise with this design than it is with a wedge. I may be wrong, but that's based on historical development behaviours with the design, so it is more of an "educated guess" than anything
Originally Posted By: A_Harman
I think the GM LS3 has a larger intake valve than the 6.4 Hemi. 2.165 vs 2.13, the last time I checked. But GM has a smaller exhaust valve, which they compensate for by putting longer duration on the exhaust lobes. When GM designed the DI Gen V LT1, they actually decreased the intake valve size to 2.125. The Gen V head also has canted valves, whereas the Gen III and IV don't. GM had to make more room in the chamber to put in the injector, and move the spark plug closer to the center of the chamber to get into the spray zone of the injector. The LS3 head actually flows better than the Gen V LT1, and the LT1 only makes more power because it has a longer duration cam, and higher compression ratio.
If it came down to an ultimate HP contest, I think the Hemi could be built to beat the LSx.
Great info about the newer gen LSx stuff
I believe you are likely correct, that a full-out HEMI could best an LSx, probably awful anecdote but look at Mountain Motor and what dominates there.
