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# engine cycle?

### Tech Articles

Discussion and questions related to the course EFI Tuning Fundamentals

on the power cycle graph, where does pos. 5 to pos. 6 fit as far as intake/ compression/ power/ exhaust? is it when the cycle passes that cylinder and moves to the next?

Hi Joshua,

Position 5 to 6 represents the exhaust stroke. The point where the exhaust valve opens, pressure drops to 0 then the piston returns to TDC and evacuates the cylinder of exhaust gases.

Those are both the same diagram?

Assuming it is a standard pressure/displacement OTTO cycle graph, Chris is correct.

The diagram isn't clear because the two loops aren't actually separate, but form a figure 8.

This may make it clearer for you - Vc is TDC and RvVc is BDC, and the engine is rotated twice.

https://i.pinimg.com/originals/9a/0d/dc/9a0ddca7e16384a51b4c21a1e0ef797e.png

Gord -- That is a much better diagram!

OK thank you... can you tell me what vC and RvVc mean? thank you for taking the time to help me

Gord posted it above. VC is TDC (Top Dead Center) RvVc is BDC (Bottom Dead Center).

ohhhhh okay lol... not to keep dragging the conversation on but can you possibly tell me the correlation between said position and the letters? I wouldbmve never figured out RvVc meant bdc. thanks gor your input!!!

I wouldn't mind knowing myself - I used that illustration because it was the clearest one that showed the process, not sure it is even in english! :-)

I knew WHAT they were because I learned it in high school, MANY years ago - IIRC, the class was Applied Mechanics, later Engineering Science ;-)

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