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General Overlap Questions

EFI Tuning Fundamentals

Discussion and questions related to the course EFI Tuning Fundamentals

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Hey there. Due to this course not going into much detail about overlap, I am still genuinely curious about more details covering the topic of overlap. I do understand from this lesson that the overlap period is when the exhaust and intake valves are both open at the same time, however i would like more of an explanation of how overlap affects a vehicle in general and how different cams affect this overlap period and what benefits or down sides this overlap period can have on your car. My current tuner has just developed a cam design that is supposed to be more efficient than the name brand Brian Crower cams because the specs have a wider range of specs. Can someone shed some light on the topic of overlap vs cam design or point me in the direction of a video that better explains this? Thank you in advance.

I did a webinar that gets into a little more detail that you can find here -

Overlap is a complex topic since it needs to be considered with the rest of the engine in mind. For example if you have a lot of exhaust back pressure then increasing overlap can hurt power since you can end up with contamination of the fresh intake charge by exhaust gasses during the overlap period. It's all about understanding the relationship between the pressure in the intake port compared to the pressure in the exhaust port.