now thats confusing....Originally Posted by Jermoslin
LSA is not overlap
the only reason people think that LSA=overlap is because LSA has a direct effect on overlap...the lower the LSA the higher the overlap will be...assuming all other cam specs are the same....does that make any sense?
Negative overlap is generally a smaller duration cam shaft with a wider lobe separation, which I'm sure we've figured out by comparing the two cams examples. It's used in factory applications that are more focused on lower rpm and part throttle efficiency... Or in boosted application with the same constraints.
Most forced induction cams can be smaller on the duration and wider on the lobe separation, which gives you less overlap, due to the fact the engine isn't relying on the scavenging from cam timing and pressure from the good ol atmosphere to fill it.
You can obviously take advantage of scavenging effects on a boosted motor to bump up the efficiency at higher rpm but on a street motor why? Just turn up the boost. Inevitably the best results come from stabbin cam after cam in a particular combo on the dyno to get the perfect one.
Gen I Viper
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