A diesel has to have a mechanical pump, which is almost always actuated when the engine is turning. So, if you coast in gear, you can restore your vacuum, but you lose some momentum (energy) in the process. If the 2-4 brake pumps' worth of vacuum in the system isn't enough for you, then I can see three options:
- Make a reservoir out of a PVC pipe, increasing your vacuum system's volume by 1-3 liters.
- Add a small electrical pump to replenish vacuum while EOC.
- Replace your mechanical pump with an electrical one, like from an EV. This will reduce the load on your engine since the electrical pump will turn on only when needed.
BTW: Make an engine kill switch, it should be much better and safer than keying off. In my turbodiesel's case the engine kill switch keeps the power steering on and doesn't reset the computer. It may also keep the airbags and other important stuff on.
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e·co·mod·ding: the art of turning vehicles into what they should be
What matters is
where you're going, not
how fast.
"... we humans tend to screw up everything that's good enough as it is...or everything that we're attracted to, we love to go and defile it." - Chris Cornell
[Old] Piwoslaw's Peugeot 307sw modding thread