How do you calculate when to turn when using a scooter on OC?

[Dsix36]

I know that turning on thirds (or even sooner if conditions dictate) is the most common approch to OC cave diving but what changes when you scooter. Suddenly you get much further into the cave before you ever hit thirds. There is no way you have enough gas to swim out if the scooter dies. Knowing your SAC rate, swim rate, and gas amounts makes for easy calculation of the distance you can swim with given amounts of gas BUT Y0ou are using gas as you go into the cave (and this can vary from day to day and dive to dive) so how can you truly plan when to turn in a realistic manner that is acceptable,

Very simplified example: swim @ 50fpm, scooter @ 150fpm, SAC @ .5, 160 cf of gas @ 3000psi, 4ATA
Swimming =Thirds is at 2000psi in 20 minutes with 1000' of penetration
Scootering =Thirds is at 2000psi in 20 minutes with 3000' of penetration

Simple logic tell me that is an easy way to die so one must plan according having enough gas to swim out but it can never be a linear plan due to variables of each dive. Turning must be done on thirds of the lowest common denominator. Scootering to 1000' and turning will be way early of 1/3 of my gas supply and at the end of my dive is when I will finally reach thirds. Meaning I turned at sixths. Is there a simple magic formula to calculate proper turn time on the fly?

RB diving is simple since I never touch my OC gas and thus I still have full tanks at only penetration.

OK, let the keyboard warriors attack for asking for online training etc. I have thick skin and really do not care. It will be fun to see how the different replies tally up

 

[flymolo]

also exactly how does one dive stages without a plan? like these are outrageous assumptions people are making in a technical diving forum no less

 

[tbone1004]

it's my opinion that if you want training advice you should get training and not expect others to give said training advice on the internet

so you decided to participate in a thread about this subject why?

 

[Dsix36]

so you decided to participate in a thread about this subject why?

I think flymolo just wanted to call me out for asking the question in the first place since I am am the OP. It does not bother me or I never would have posted in the first place. I just wanted to hear peoples logic for what they do. I have already spoken to several respectable instructors and gotten different answers. I already had a method to plan but wanted to make sure that I was not overlooking anything. I really appreciate and thank those who took the time to explain their planning methods

 

[flymolo]

I think flymolo just wanted to call me out for asking the question in the first place since I am am the OP. It does not bother me or I never would have posted in the first place. I just wanted to hear peoples logic for what they do. I have already spoken to several respectable instructors and gotten different answers. I already had a method to plan but wanted to make sure that I was not overlooking anything. I really appreciate and thank those who took the time to explain their planning methods

That's not true actually I was just saying that i was taught to dive on stage bottles and have a backup scooter. I was responding to someone else who mistook what I said as advocating for doing no math or planning