Injection while cruising and general setup questions

[b4tn]

I have a custom turbo on my Mazda MX6 2.5L 6 cyl. I was monitoring my intake temps and have noticed that the temps get around 100 degrees C at pre boost levels, At 10 inches of vacuum and a 4krpm and up cruise. It is non intercooled because of space issues so I wanted to go the water injection route. I currently am running a Megasquirt Stand alone fuel computer and it has a water injection controller option. It can be activated based on map, rpm, and intake temp and then when activated pulses with the injectors.

What I need to know is, will it be ok to start injecting water before the boost during instances of Vacuum? If so how do I size the nozzle? I currently have between 220-250 hp (guessing) at 7 psi once my intake is cooled enough I am going to turn up the boost to 10psi. My ultimate goal is 300 hp.

I was thinking of having the water injection to start spraying at 10in/hg, 4k rpm, when intake temps are above 65 degrees C.


And my last question is about nozzle placement. Due to my fast spooling turbo it is very common for me to make boost at partial throttle. So if I put the nozzle 6 inches before the throttle body is there going to be problems with water distribution? the throttle plate is partially closed.

[Richard L]

Th temperature is quite high but it is quite normal for a non-intercooled and small turbo.

The placement of the jet for general cooling should be as far away from the throttle plate as possible. Cooling all the metal in the inlet tract along the way is a good thing especially you injection at vacuum.

Since you have a programmable system, you can set the spray at a very small duty cycle during vacuum- possibly at 5-10% opening, it will have the same effect as a cool day. As soon as you are on boost, you can ramp up the duty cycle immediate (compensate for the delay on fast spool up turbos). As soon as you arrive at medium boost, make a steady increase from then onwards high boost.

It is just an idea. If you go for the aquamist 2c system, you should be using a 0.7mm, approcikte allow you to spray between 10-20% w/f ratio (rough estimate).

[b4tn]

That should work then. I did some experimenting on my home from work just now and my duty cycle at 10hg and 4k rpms was around 14% as boost climbs of course so doesnt the duty cycle up to 65% so if I use a fast acting solenoid it should keep the water just about right then. On another not my temps for just some quick passing and country road cruising never went above 140 degrees F. Its the autobahn that kills me. So it will just activate above say 150 F and I should be fine and not even use to much water.

About the nozzle sizing. How many CC does the .7mm nozzle flow at 100 psi? The pump i was gonna use is a 100psi pump. I'm not certain but if I calculated this right I should need a nozle that flows around 200 cc. I have 6 220 cc injectors for a total of 1320cc combined fuel flow take 15% of that and I need a nozzle that will flow 198 cc. Does that sound right?

Thanks for the help

[Richard L]

The 0.7mm nozzle will flow approximately 250cc/min at 7 bar (approx.20%). Since you have a controller, it is better to have bigger jet for future use in case you need it.

You need to test the 0.7mm jet manually by using your 100psi pump for one minute into a measuring glass. Allow some reduction in flow when you are injecting against boost pressure.