cib24

I am preparing to have my car tuned for 0.8-0.85 bar (11.6-12.3 psi for the Americans) with an Apexi Power FC in a quest to have around 300 brake horsepower, but more importantly a car that is a reliable configuration for 10-12 track days per year in the UK (weather never gets hotter than about 80 degrees in peak summer) whilst preserving the 99 spec turbos for as long as possible (hence why I'm choosing to not run more boost).

My car is a 1999 Mazda RX-7 Type RS and the spec when I go for a tune at 0.8-0.85 bar will be:

1. 99 spec twins running sequentially
2. stock airbox with air guide (intercooler sealed off on later models)
3. stock intercooler with stock sealed duct
4. Knight Sports twin tube downpipe
5. 3" high flow catalytic converter
6. Fujitsubo 3" cat-back exhaust
7. NGK 9's spark plugs
8. Koyo N-Flow 48mm radiator
9. Apexi Power FC

I purchased an AEM V2 water injection kit which is on a delivery truck somewhere and my plan is to run the nozzle in the throttle body elbow to help cool the intake charge if the stock intercooler gets overwhelmed at some point during a 15-20 minute track session.

However, all I want is to use the water injection as a safeguard and not to tune with it for extra performance, and thus I don't want it to affect ECU A/F maps or anything like that, because if the water injection were to fail for whatever reason I don't want the car to be too lean when on boost at high RPM.

Now, the AEM kit comes with three nozzles: 250cc/min, 500cc/min and 1000cc/min and recommends each nozzle as follows:



Is the 500cc/min nozzle too large for what I'm looking to do as I think their table is probably geared towards getting a performance increase from the kit itself, when I'm just looking for cooler temps and added safety.

Also, is the location of the nozzle in the throttle body elbow like this ok?

WANKfactor

iTrader: (1)

Check out the sticky on nozzle selection. From what i could glean, for straight water 300 odd cc is heaps but you want twice that for 50/50.

I'm no expert though, but in the same boat as you in that i just want it as a safeguard againt **** fuel and heat stress more than anything else.

Only just set mine up yesterday, goes on the dyno next week.

I'm thinking another way to limit flow (if using the controller) is to set the peak flow to a higher boost level than you are going to go to...?

Im also interested to hear peoples thoughts on different mix ratios - i have four gallons of boost juice but thinking to run straight water so as not affect AFR's unless there is a benefit to adding methanol that someone can point out for me?

Sorry for slight threadjack!

cib24

Yes, I am just going to run straight distilled water.

The AEM kit is progressive with boost and I was thinking of setting it to come on around 8-10 psi to avoid it shooting through on the primary turbo below 4,500 RPM and then have it at max flow by 11-12 psi or so for the rest of the rev range.

If 300cc/min is still quite a bit then it seems to make sense to use the 250cc/min nozzle rather than the 500cc/min nozzle as recommended in the AEM chart.

cib24

Based on the nozzle selection sticky it seems the recommended nozzle size is a minimum of 208cc/min, so hopefully the 250cc/min nozzle provided by AEM is sufficient. It's what I will start with.

Sgtblue

iTrader: (16)

I'm running a M3 nozzle for about the same power. Stock plugs and ignition. But as I think I mentioned previously in another thread, water injection at that location will not really yield significantly lower IATs. It WILL offer knock suppression, carbon control and reduce load on the cooling system.

FWIW (pictures were added back in at the end of the thread)....
https://www.rx7club.com/auxiliary-in...ion-fd-959565/
Not sure if it's mentioned in that thread, but I relocated my IAT sensor upstream of the nozzle. It's visible on the hard pipe just after the intercooler. This was done to for two reasons, to reduce heat-soak from it's stock location under the intake manifold and to avoid the effects of the water.

cib24

Perhaps I have it backwards but I would think that you would want the IAT to come after the WI nozzle, i.e. remain in the factory location.

The reason being the water cools the intake charge and the cooler air requires more fuel, and the CPU can only determine how much fuel to provide based on the IAT reading.

So, if you put the IAT before the WI nozzle then it would be reading hotter air than is going into the combustion chamber which might create a lean condition in the motor since not enough fuel would be provided for the colder air.

Anyway, I just want to keep things simple and as you say suppress knock so I think I will leave the IAT in the stock location. As a matter of fact, I have a fast-acting IAT which I will install at the same time I install the water injection setup.

Sgtblue

iTrader: (16)

As I recall, Howard Coleman who wrote the stickys in this section recommends that for WI, the IAT not be in the stream. I'm not a tuner but believe the logic is...

WATER injection will NOT influence air temp in our application. Water does it's thing in the combustion chamber absorbing heat during it's phase-change from liquid to vapor. It WILL cool things like the interior surfaces of your intercooler if injected in front of it. And the large surface area of the intercooler will, in turn, cool the air. Same is true for the IAT sensor . But injecting water-only into the air stream just ahead of the throttle body and artificially cooling the IAT sensor is just going to screw up your tuning tables.

If IATs are your concern, consider Methanol/Water (AI) mix injected farther upstream. Either pre-turbo or pre-intercooler. Alcohol has great evaporative affects, much better than water, and WILL lower air temps. But know that generally speaking, you will need a more sophisticated management system and higher capacities (bigger tanks).

WANKfactor

iTrader: (1)

The devil's own site doesn't seem to have an opinion on the affect on the AIT sensor, which is interesting; https://www.google.com.au/url?sa=t&r...12064104,d.dGo

Also from other reading i've done the last few days, water alone has a much higher cooling ability, whereas Meth has an effect on flame-speed, the effects of which i wont pretend to understand.

Ive decided to dillute Boost juice with 50% water by volume (im not sure what %meth that gives me as they perhaps mix it by weight??) just because i have it, through a 300cc and thinking the water alone might build up some funky oily slime in the intake tract over time?
Not very scientific, but its just a safegard against a bad batch of fuel, and heat management of combustion surface in my expensive fresh engine.

Sgtblue

iTrader: (16)

Well maybe I'm only pretending to understand, but if you put some water on one arm and alcohol on the other, which one will feel cooler quicker? Alcohol has greater evaporative cooling. That's why it's good at effecting IATs. Water's evaporative qualities aren't as good. It takes a lot more heat to phase-change water to vapor. But that means it also absorbs more. And why it's more effective in the combustion chamber.
I am NOT a big brain, but there are some here that are. If they see this I'm happy to stand corrected, but this is how I understand the differing properties and applications.
As to positioning the IAT sensor before or after the nozzle, make your own call or follow your tuners advice. I've had mine (also a fast-acting version) placed before the nozzle for some years now without issue.

cib24

There is a difference between meth and alcohol. Yes, alcohol cools better than water and meth, but water cools better than meth right?

WANKfactor

iTrader: (1)

Yeah i know what you mean, alcohol evaporates much faster, but from what ive been reading the same amount of water pulls twice the amount of BTU or (whatever the correct terminology is).
Yeah theres some big brains but a lot of conflicting theories and ideas on the subject.

Im not a tuner's ****, just trying to set this up properly before it goes on the dyno this week!

As to the AIT sensor, how far back from the TB can it be placed without problems?

Iv got my WI nozzle about 6-8"
back from the tb. Can i put the ait sensor another 3-4" back from that?

Sgtblue

iTrader: (16)

Methanol is a type of alcohol.

Sgtblue

iTrader: (16)

Yes. I think what you're referring to is "specific heat". Water's 'specific heat' is greater than alcohol. And how I understand this is that it takes more energy/heat to cause water to phase-change to vapor than it does alcohol. That's why alcohol's evaporative cooling is better, but water's capacity to carry heat is better. And why AI and WI applications differ.
Again, my profile will confirm I have no scientific background...just what I've been able to glean.
Sounds fine to me. You'd probably want it somewhere shortly after the IC so it's reading post-intercooler temps. But not seeing an inch or two either way being really critical.

WANKfactor

iTrader: (1)

Yeah, moving it from the snout, about 10" upstream. Should be ok.

"specific heat" thats the one! https://www.google.com.au/url?sa=t&r...xXdxWQDv2adBbg

CREEPENJEEPEN

iTrader: (7)

Back from the dead, I see your last activity was yesterday. (Stalking, lol)

You are doing the exact setup as what I'm about to do, which is only doing water injection to maintain a "healthier" temp for my engine so I get more life out of it. Therefore, I have a few questions.
Also, our cars are similar with the same mods, 99 spec turbo sequential, power FC, KS downpipe.

1. What size cc nozzle did you go with?
2. How is it working out?

(The last question is a bonus question for anyone that can answer it)

3. Can a Power FC have an input for an "AEM water injection fail safe" if I want to use water injection/meth injection to handle more power? (It would be nice to cut boost or retard timing if the tank ever runs low or a leak happens, seeing if the power FC can even do that. This doesn't apply to me now but will in the future if I want use meth to get more power)


Also, I'll share some knowledge about water injection vs. meth injection. This information comes from the famous book, "Street Rotary," written by an engineer, Mark Warner. To sum up, he says water can carry heat away faster than meth (Better BTU's), but it "virtually" makes your engine displacement smaller since the water molecules take up space in the combustion chamber. It doesn't matter if meth takes up space in the combustion chamber because it's a fuel; water is not. So this is why people do 50/50, to get the best of both worlds. With the OP and me, I would be OK with doing 100% water and losing some HP for better reliability.

Also what is up Sgt Blue, it's been awhile!

Sgtblue

iTrader: (16)

Just gettin’ older Corey, but not much wiser…since I’m still playing with this car.

Street Rotary’s a great book. And IIRC while water is not a fuel and you would intuitively see some power loss, by taking up space in the combustible chamber it also increases dynamic compression just a bit too.

CREEPENJEEPEN

iTrader: (7)

Lol, same here. I ended moving to Orlando after I got out the military. I have only seen one FD in the wild here, I'm very surprised.

Yeah, I forgot about that, you make a good point so that will help.
Also I just learned water injection helps with MPG by a huge margin, I should of done this a long time ago. Pretty soon I can daily my FD without worrying about it breaking down.

Sgtblue

iTrader: (16)

To (try) to answer one of your questions…

There’s a formula that Howard Coleman put in one of the stickies in this section for determining nozzle size by horsepower. I used that and never had issues no any loss of power that registered on my butt-dyno. Pretty sure it’s still there.