Effect of Water/Meth injection on spark plugs

FlyingGrape · #1 11-10-2011, 03:16 PM

Currently working on a turbo charged petrol engine. We are running 50/50 mix water/meth and at the moment just under 20 pounds of boost. We have a 4 port water injection system (4 cylinder engine). AFR's are between 12.2-12.6:1 (On a low boost setup these engine seem to work well with AFR's around 12.2:1 range and dont need a lot of combustion cooling).

We have noticed that the spark plug strap, ceramic core and electrode are come out very clean but down in between the thread body and base of the electrode it is quite sooty.

Is this likely that water/meth is cleaning the top of the plug? Any suggestion on why we are seeing this heavy soot inbetween thread and electrode. Is plug perhaps too cold given cooling of combustion from water /meth?

Richard L · #2 17-10-2011, 09:03 AM

If you see white ceramic core, you are running lean with good combustion timing. Sooting electros is the result of too cold a grade, perhaps 1 to 2 grades hotter may improve the situation.

RICE RACING · #3 10-12-2011, 12:01 AM

This is totally normal, variations to what you are describing happen with different combustion chambers and plug positions, but typically will come out as you have described. Mine are the same.

FlyingGrape · #4 12-12-2011, 02:46 PM

Thanks for that. Appreciate the follow up reply.

Richard L · #5 07-01-2012, 11:18 AM

Here is a set of images showing the speed of combustion, greatly affected by the position of the spark plug.

It is not always good to have fast combustion duration. You will loose some low end torque at low RPM. Central spark is great for medium to high RPM. I believe carefull mapping a water injection system will extend burnt rate and improve low end torque.

Ideally, having two spark plugs firing separately based on RPM is a possible solution. You can see how fast the flame rate advanaces on the bottom image.