Rotary Water Injection Set Ups

atl93fd · #1 20-02-2004, 02:45 PM

Greetings All,

Is anyone here running the aquamist 2d on their 93-95 RX7 (fd3s)? I'm currently running distilled water which kicks in @ 10 lbs. I'm using solely for anti detonation purposes. The rotary is extremely sensitive to detonation and WI can help me prevent a rebuild or new engine.

My question: Should I notice LOWER intake temps when water is injecting into the intake? Under normal conditions I don't notice anything.

When I circumvented the solenoid, Water Injection ran non-stop and I noticed my intake temps drop as soon as I accelerated from a stop light.

I'm wondering if I need to, turn up the pressure on the pump, have the WI kick in earlier then 10 lbs, or change the nozzle.

Any advice is helpful. If anyone can host them, I'd be happy to post pics.

atl93fd · #2 01-03-2004, 08:24 PM

I didn't get a lot biting on my first post. I'll try again. I have a 1993 RX-7, currently running around 14 lbs of boost. My water injection doesn't kick in until 10 lbs. I believe I'm making about 330-350 rwhp, running 950 cc injectors all around.

I don't notice my intake temps drop when injecting. I also can go 4-5 fill ups conservatively without a noticeable reduction in the amount of water in my resevoir.

I'm running the middle sizednozzle of the 3 coming with the aquamist 2d setup. I'm also running 6bar on the pump itself.

I do have an intercooler and am injecting after the IC, at the intake elbow. My pump is located in the rear hatch, next to the resevoir.

Any input on why I wouldn't notice my intake temps drop or notice the water levels reduce in my resevoir?

robbilau · #3 01-03-2004, 08:45 PM

I'm not familiar with the RX-7 but a few basics:

I assume the air temp sensor is after the water injection?
Have you done a test run just holding the jet out the window so you can confirm flow?
What duty cycle are you running in your injectors at max? Perhaps the duty is too small for significant injection?
The middle jet will be a 0.6 mm jet pushing 250 cc.min at 100% duty. If you're running say 65% duty on your injectors and the 2d matches that duty cycle you're getting a max of 162cc/min of water. That sounds like too little water to me. Richard will need to confirm the 2d behavior though.

I'd start the water below 10 lbs, say at 7lbs and upgrade to the biggest jet you have.

Richard L · #4 01-03-2004, 08:50 PM

My first thought is that you are not injecting enough water.

Need to know your duty cycle of your fuel injectors. The 2d follows the fuel injectors duty cycle so low fuel fuel equals low water flow.

It it possible to measure the voltage that come out of the purple wire ( fuel duty cycle monitor), please let me know what is the peak readings you get. It will be between 0-5V.

I await your reply.

hotrod · #5 02-03-2004, 03:58 AM

Once you confirm you have flow, you may want to log your boost if you can.
At least have a passanger ride along and watch a boost gauge.

You may spend so little time above the 10 psi turn on point that the system never gets a chance to spray a significant amount of water. As mentioned above, you might want to pull back your trigger point to a lower boost.

A 10 psi trigger on a system running 18 - 20 psi boost will be on for a noticiable period of time. In your case, especially if you spend most of you boost time in lower gears you may only be above 10 psi for a second or so in each of the lower gears.

By way of example on a drag strip pass, my WRX red lines low gear in about 1.7 seconds, and 2 second gear only lasts about 3 -4 seconds, 3rd gear is about 4+ seconds and I shift into 4th just a second before I cross the finish line. I probably spend 4 -5 seconds over 10 psi .

There is also the possibility that your boost gauge, boost control system and the boost trigger switch are not in agreement. If you boost control system is actually only giving you 12 psi boost and your trigger switch is a bit high you will have nearly a 0 duty cycle. The second issue is where are you tapping boost. Your sense point may never get above 10 psi even though the boost control system thinks the engine is at 14 psi.

Larry

atl93fd · #6 03-03-2004, 04:20 PM

Awesome replies guys, Thanks.

First off, I'm running the .8 mm nozzle. I belive the kit came with .7, .8, .9 (and I'm missing the .8)

Air temp Sensor is after the WI. I have done a test to confirm flow. At one point, I disconnected the ground and was injecting water 100% of the time for 5 or 6 miles. As stated, when I pulled away from a stop light, I immediately noticed temps dropping. At 7500 RPMS, I reach about 93% of my fuel injector duty cycle. Most of the time (around town and in traffic), I am < 50%. I probably hit 65% duty cycles around 5500 RPMS (again, rough guess but not too far off). Additionally, I notice I spend very little time boosting above 10 lbs. I spool up to 1 bar @ 7500 RPMS and reach 10 lbs of boost VERY quickly. So, under a hard pull, I probably have longer sustained boost then most (quicker spooling sequential systems and higher redline). Having said this, I'm not on the throttle boosting like that as much as I would like.

Richard, I'll get back on the voltage that comes out of the fuel duty cycle monitor. I'm sure I have this info in my PFC, somewhere.

Thanks for the help guys. I'm a sales bloke. I'm not a gearhead by any means yet. However, I'm certainly an enthusiast and willing to learn.

rxstephen · #7 12-03-2004, 12:32 AM

Hi,

Here's my experience with my FD3s RX-7 and using a mapped water injection.

I have the injection just after the intercooler, it is currently set to come on at about 6psi and is mapped to run about 30psi (water pressure) at 2000 rpm and 90psi at just over 5000 rpm. I can't remember what nozzel I'm running at the moment though.

I set these values based on winding it up untill I got miss fires and them wound it back a little (nice and scientific).

I have a 1 litre water tank, and go through it about once every 3 weeks with general driving. Typically three or four short WOT runs each day.

When on the race track, I go through 1 litre in approx 12 to 15 minutes full on racing.

Looking at manifold temp, there is little noticable improvement with short WOT runs, this is because the stock sensor is slow reacting and gets heat soak from the plenum chamber. It's pretty usless really and I'm considering moving it to the elbow. On the track if I don't have WI turned on I get heat soak after two laps and the power drops off. With WI turned on I get a constant (about 45 deg C) manifold temp, and repeatable power for every lap.

I'm running an ARC intercooler that is only slightly bigger than stock, plus I'm running stock turbos at 1 to 1.1 bar, so I'm asking a lot of the system and generating a lot of heat. The WI allows me to run at the higher temps while also leaning out (currently between 11.8 to 12:1 AFR, but I plan to lean out some more yet).

My last dyno was 334HP ATW, at 1.1 bar boost, I'm running stock fuel injectors peaking at about 93% duty. With some fine tuning I'll get a little more out of it, but I suspect not much more

Cheers
Stephen

mx5 · #8 12-03-2004, 03:46 AM

Quote:

Originally Posted by atl93fd

Awesome replies guys, Thanks.

First off, I'm running the .8 mm nozzle. I belive the kit came with .7, .8, .9 (and I'm missing the .8)

Air temp Sensor is after the WI. I have done a test to confirm flow. At one point, I disconnected the ground and was injecting water 100% of the time for 5 or 6 miles. As stated, when I pulled away from a stop light, I immediately noticed temps dropping. At 7500 RPMS, I reach about 93% of my fuel injector duty cycle. Most of the time (around town and in traffic), I am < 50%. I probably hit 65% duty cycles around 5500 RPMS (again, rough guess but not too far off). Additionally, I notice I spend very little time boosting above 10 lbs. I spool up to 1 bar @ 7500 RPMS and reach 10 lbs of boost VERY quickly. So, under a hard pull, I probably have longer sustained boost then most (quicker spooling sequential systems and higher redline). Having said this, I'm not on the throttle boosting like that as much as I would like.

Richard, I'll get back on the voltage that comes out of the fuel duty cycle monitor. I'm sure I have this info in my PFC, somewhere.

Thanks for the help guys. I'm a sales bloke. I'm not a gearhead by any means yet. However, I'm certainly an enthusiast and willing to learn.

Which ground did you disconnect? Disconnecting the ground from the air pressure sensor will turn on the W/I all the time but it will still mirror what the fuel injector is doing. The only thing it does at low IDC is to fill your intake with water!!! It doesn't do any mist. So you're not achieving anything with this - what you will do is full the intake manifold with water at cruising and may destroy your engine.

What you want with the 2D is to ground the brown wire (without disconnecting it from the HSV). Then the W/I will activate at full power. This is what you need for your experiment. Also probably it is not a good idea to turn on the W/I at full power when the throttle is closed - so just mount a switch somewhere on the dashboard.

atl93fd · #9 12-03-2004, 04:02 PM

I was doing some looking around and inadvertently pulled the wire out from the female connector (the wrong ground you were referring to).

I called my engine builder (who also installed the aquamist), and he told me it wouldn't hurt to run to home depot and back. Went to home depot, spliced the wire, crimped on the new female connector, and was good as new. So it was somewhat "unintentional".

atl93fd · #10 31-03-2004, 04:52 PM

This thread may be dead, but I thought I'd throw it out there as I'm noticing at least 3 rotorheads here now.

My update: I hit the dyno last week, put down 325 rwhp @ 7200 RPM. The torque curve was nice and flat and I reached my near peak torque very early on. Fuel injector duty cycles were around 93%, I have 4 850 cc injectors. Water Injection came on just after 10 lbs of boost, my peak boost level was .91 or about 13.5 psi. Air Fuel was pig rich all the way through redline. At peak rwhp on my 4th run, A/F was 10.5/1 NO higher than 10.8 to 1. I did have a boost leak at the elbow and the IC. I'm using the stock solenoid and my engine management to control boost.

I still didn't notice any air intake temps drop. I THINK this is because:

I'm running sequential turbos with a 12-8-13.5 pattern, transition occurs around 4200 RPM. Water comes on, goes off, then comes on through redline.
Also I am using the stock sensor which is SLOW and the manifold probably heatsoaks.

Should I notice a dramatic decrease in intake temps while running WI?
A second question, how lean can I SAFELY go without detonation?