Safely turn off engine (not by key)
 

Long story short: we've got an 1994 1.8 NA8 on the dyno for tuning.
The engine is wired to car via long wires.
At today, we "switch off" the engine by switch off directly the battery... Not Ideal. The engine as not installed the alternator, so no power spike during battery detachment, however we're concerned about other kind of damage.

What is the fastest way to turn an engine off whilst not kill off power entirely?
We tought to ground coils like the motorbikes "killswitch" , however this is a NA1.8 with 4 wires coils so i'm not so well informed (usually, like my 1990 1.6, i've 3 wires).

unplug the fuel pump

No, i dont like that. Mostly because the fuel pump in on board and i am working in dyno chamber. I truly prefer to put a switch on crankshaft sensor or ground the coil... What is to prefer?

If you prefer to put a switch on the crank sensor or ground the coil(s), then what does it matter what we prefer?

There are many ways to turn off a running engine. I prefer sealing off the dyno chamber, evacuating the air, and filling the cell with argon.

Maybe my bad english prevent me for being undestandable. I was asking if someone knows a realible way to turn off an engine runnin without any power surge or spike, i.e. preserving any damage to ecu and or and other system.

At this point, after some researches i think if i understand this diagram correctly, i can put a switch on the W/R cable, just prior the 4 injectors (intersection X12) and actually turn them off. There is any problem doing this? Maybe some kind of Voltage surge or electrical noise can damage them?
https://cimg1.ibsrv.net/gimg/www.mia...db4f0bbd6d.jpg

Skip the key and just put the ignition on a switch. Seems like a no brainer.

My RX-7 has a tired engine that floods on hot restarts. To combat this, I wired in a fuel pump cut-off switch to turn off the car.

I think it breaks ground on the pump relay under the dash - slowly starves the engine of fuel and shuts off.

Simple and effective - just don't accidentally hit the switch in boost :)

I dont see why this is so complex.

You want a way to turn off the car quickly, and without damage.

The car started off with an ignition switch designed for exactly that.

Why not either:
put it back
wire up a new switch into the ignition wires (which you can then put anywhere you want)