Hey guys,

I'm thinking about finally installing the AEM water/ meth kit and euro spec water tank that have been gathering dust in my garage for the last few years, but I'm not sure about the best way to go about this or even if it is a good idea. Would appreciate some thoughts from the community.

First, my setup is stock 1995 ECU, stock twin turbo sequential. Air temp sensor is also in the stock location and is the stock sensor. I would not be running any alcohol, strictly DI water, and would install the supply line in the intake elbow.

So, considering the above is a water injection system even a good idea? I have read through some posts and there is some discussion about the need to relocate the IAT sensor to be upstream of the water injection. If that is needed then this is a no go. Any thoughts on that part?

Then assuming I do the install, I believe I will need a constant 12v and an ignition on/trigger 12v source. Is there a good source for these feeds within the interior fuse box or should I connect at the battery main under the hood?

Thanks in advance for any help with this!

 

Theres no gain to be had with the stock ecu. Its more likely to cause issues. No need to worry about anything install related until you upgrade the ecu and even then, it won't do much for you. Stock is stock and is perfectly fine as is. Leave it alone until you decide to mod it for real.

 

Like Cr-rex said. Stock ECU it may cause more harm than good. Wait for an ecu upgrade.

With that said. I have a PFC and never changed my iat sensor. At this rate I do not plan on it. I am running "lower boost" at 13.5-14psi and believe it greatly helps even with the smallest nozzle. My logs look great. I had a few slightly lean issues that I am sure the water helped keep everything cool. If you plan on upgrading I would keep it around u till your ready.

 

No personal experience with WI on a stock ecu, but with a properly sized nozzle no idea why it couldn’t be added on the stock ecu and be beneficial. You’re not tuning with it and WI function is for increased engine cooling, knock suppression and carbon control...all of which happens internally regardless of engine management. IMO, the killer for you is if you’re unwilling to relocate the IAT sensor up-stream from the nozzle. If you don’t want to do that, especially on the stock ecu, then I wouldn’t add WI.

 

Thanks for the advice guys. I guess I’ll hold off installing the setup for now.

 

Well, I guess he could always try. I experimented a lot with mine. Turning on at 6psi was too low. 7 was borderline. 8psi is about as low as I can go without affecting performance too much. . This is with varying arc from min to max with the smallest nozzle. Maybe this is where "every car is different" kind if thing comes into play. If I was to do a low rpm pull in a low gear it would even stumble a tad. This is with a very healthy ignition system and a twin power. Maybe a passenger wouldn't notice, but I could. I am still unsure of the pre or post iat. I still see pos and negs to both. I did lean it out in those "stumble" areas to see the difference and it was no where near as bad, but I never wanted to "tune" for inj so I set the afr back to where I wanted it to be and just raised the turn on boost. 8-10 is still 2psi. OP could always try.
I would like to say I can attest a bit too the benifits as I had a few leaning sessions at higher boost and high rpm and there were no noticeable increase in knock readings at all. I am sure the water helped... when I say lean I am speaking into the 12s at 13.5-14psi for a second.

OP there is a huge water/meth section on this forum with some incredible reads. I would check that out and decided for yourself if you want to add now or wait. I think it is under "alternate fuels".

"Rotary performance"
Alternative Fuels

 

Water-only with a Pfc, m3 nozzle pre-TB BUT with IAT relocated upstream and post IC. Boost switch set to ~ 1.5 psi (not progressive) on absolutely stock ignition including 9’s and 7’s. No stumble, no noticeable breakup anywhere. While I wouldn’t argue there wasn’t some power loss, it’s not discernible to me. Also no break-up that I can hear or feel right up to 7k. And it’s been this way for about 14 years with no changes or problems...other than replacing a $20 Hobbs switch out once.
​​​​​​Maybe Howard Coleman, who wrote the AI section stickys can chime in, but IIRC from his posts on the subject, he didn’t want to leave the stock IAT downstream of the water due to a concern that it would mess with tuning tables. And I would guess it would also screw with the stock ECU.

 

i do think that some sort of AI is beneficial on FDs from stock to maxxed out.

in your case water will cool the combustion chamber, which is closer to the edge than you might think even in stock power output, AND clean your internals which is quite valuable. i have rebuilt in excess of 150 BREWs and they all arrive with rotors coated with carbon. i have also received motors running AI and the rotors look clean. clean rotors are a big deal. AI keeps carbon out of the grooves that house the sideseals, corner seals and oil seals. carbon can stick seals and also contribute to autoignition.

so really a double win here... just like pre-mixing... kind of a pain but the right thing to do in the long run.

as to loss of power... not much.

if you are just doing300/500 CCs of water it is easy to calculate.

water has negative BTUs. air and fuel create positive BTUs.

if we use an OE power output:

255 X .85 = 217 rw rotary hp.

217 requires 55,142 BTUs per minute (11 AFR)

flow rates from the typical nozzel often have an "M" preceding a number. an M10 flows 630 cc/minute at 100 psi.
the numbers are linear so an M5 flows half of an M10.

you should do around 300 to 500.

if you did 500... 500 CC is .132 of a gallon.

so .132 X 8087 (neg BTUs/gallon) = 1067 neg BTUs

1067/55142 = 2% (rounded)

.02 X 217 = 4 rw rotary hp.

no biggie

as far as damage to the IAT/thermistor... i haven't seen a problem. should you wish you could easily relocate it to the upstream side of the throttle body... the elbow, the silicone coupler or...

 

Stock engines have detonated many times just do to carbon buildup.
These is caused by two factors: (1) engine runs filthy rich to reduced detonation but this causes carbon buildup. Mazda's fault for design errors like an inadequate IC.
(2) Owners not running high power enough to burn off the carbon.
I know a person who rarely go on the power with a totally stock FD. One of the turbo hoses split and I replaced it for him. He went out to test it, got on power, and BOOM!!!
Stock to wild, water injection is a positive.

 

I see no harm in adding it. Especially the AEM kit which is a very straight forward kit.

Also I would run plain blue washer fluid. Has a little methanol in it but it's not super corrosive and also won't freeze on you like straight water.

Buddy of mine said it best - a water injection setup can make your FD run like it's a cold day all the time. Anything you can do to reduce heat in these cars is a win win.

Dale

 

For me most noticeable was the elimination of temp spikes from periods of hard boost. I can repeatedly row thru the gears under wot and the temperature reading on the commander doesn’t move much more than a degree C. And I think that’s gotta be helpful to the coolant seals.
My plugs stay cleaner longer too, which I take as an indication carbon is being controlled...despite premixing at half-rate on top of a working OMP.
It’s been too long and I honestly don’t remember the before and after on knock readings.