i remember MM claimed that the egt would increase on the renesis with the smallest amount of meth introduced. thats just what he would claim. I have no other evidence to introduce about it.

 

Yes sorry. My mistake. Mine was pre TB as the subarus ic pipe work with a front mount was exceptionally long.

 

Yep. Sounds really close to my system. Simple, inexpensive and most of all...reliable. 8 to 12 inches pre-T-body.

lol, FWIW since posting up in this thread I changed out my plugs for the first time since moving to AI. They'd been in for ~ 30k miles and I started to notice a little lumpy idle and slightly harder starting. While the center electrodes were worn down (especially in the leading plugs) and the obvious cause of those issues...there was VERY little carbon. Stock heat ranges.
Not sure about the Renesis, but that's pretty unusual on a 13bREW, especially since I run the OMP and Pre-mix too.

 

Has anyone been having any luck with a small amount of meth or water injection on their boosted renisis? maybe prevailing minds have some new info?

 

I've been running 25% water to fuel and it shows lower amplitude off the knock sensor when the water is running. The difference is ~350 with water running and >500 (where boost locks out) without water. I've seen EGTs go up with water injection during cruise and EGT go down slightly under boost with water injection. Since my setup requires water injection under boost I can't get a back to back with/without.

What I can say for sure is that too much water will raise EGTs. If you have a single stage nozzle then it becomes tricky to have enough water at the top end without flowing too much at the bottom end. I believe this is where people lose power with water injection, and where the claims of higher EGTs come from.

 

all the info you need is on RX7Club ...

 

Here is a good thread on the aquamist forums. It's not rotary specific, but it is helpful.
Tuning for water injection: fuel, ignition, and EGT - Page 2 - waterinjection.info
A lot of the stuff on the rx7club is disjointed you'll have to go through a lot of threads to find useful information and there are a few contradictory opinions. On the safe side you treat water injection as a supplement for safety and assume it doesn't exist for tuning. On the razors edge you treat water injection as important as fuel delivery so any failure could be catastrophic.

 

^^lmao, if you say so ...

edit: it's actually a good thread, but overly technical beyond the basic understanding needed to get a system up and running i.e. for advanced tuners



.

 

Dedicated forum area, just start with the stickies, there are links that will get you to sites that provide you everything you need from sizing to kits known to work well

Auxiliary Injection - RX7Club.com

 

There are lots of kits availible, but sizing the kit/nozles for particular goals is complicated and will require a bit of trial and error since there is not a lot of Rx8 experience. Don't expect a kit/nozzle setup that works great on an Rx7 to be a turn key solution.

EGT has been tested/debated and some people see a rise while others see it fall because it's not that simple a question. There is also no consensus on how to tune with water injection. A few individuals have had a lot of success, but most go through trial and error until the results look good.

The Turbo bricks, or aquamist forums have a lot more consice information on tuning/sizing but nothing rotary specific, but don't take my word for it:
Two Mega AI Info Sources - RX7Club.com

 

Thanks Harlan!!!

 

Been a few years, but Howard Coleman sticky'd a rotary specific formula linked to horsepower and IIRC, boost level. Since displacement is the same on the Renesis, I can't see a reason (off-hand) why that wouldn't work on an RX8...or at least be a good place to start.

 

and some people like to make it infinitely more complicated than it needs to be

Howerton Engineering, LLC ? Calculating Jetting

 

I figured with high compression rotors stuff would be a little different, I would love to see people post what they have done and what kind of improvements they have seen.

I think there is plenty of room on the rx8club to have some info like that.

 

ok, so shoot for the high end of the scale, common sense rules, this is no different than converting an NA car to turbo ...

 

Ok, I guess I wasn't clear. It's easy to determine how much a setup can flow it's hard to determine how much flow you need. So if you size your system to flow 25% water to fuel at 8000RPM/10psi and set it to come on at 3500 RPM/3psi you will be drowning your engine and loosing HP when it initially comes on. If you size it to flow 25% water to fuel at 3500RPM/3psi then when you are at 8000RPM/10psi you will be losing out on most of the benefits because you're flowing too little. The easiest solution here is to run staged injectors, but many people chose a number in the middle and tune out the problems on either end.

Trial and error will be required because each setup is different. Injecting Pre turbo vs post, or injecting pre intercooler vs post will change how much water you need for whatever your desired results are. Also what percentage methanol/ethanol you run will change the the amount of flow needed.

 

Again, you go too far too quick and thus over-complicate the beginning of the process by jumping right into advanced situations. Plus WITH would you fire it off at at only 3 psig? With the right system most of that is readily resolvable. Again, it's not much different than converting NA to a turbo. You don't just slap one on, crank up the boost, and then go zoom zoom zoom all the way home.

 

nope it's all about the zoom zoom boom

 

I don't disagree with your reasoning here, except for the "drowning" bit. But you're assumptions seem to be based on tuning with WI. Not everyone values power over longevity, so not everyone tunes with WI. My personal experience is admittedly anecdotal and purely from butt dyno...but I've experienced no discernible power loss with a boost activated system turned on at low psi/low rpm with a properly sized nozzle on stock twins with stock ignition and stock fuel. No break-up anywhere. And I've halved knock values while virtually eliminating coolant temp spikes after periods of high boost/high load periods. Based on spark plug conditions, I also believe I'm controlling carbon really well...despite pre-mixing and a working OMP.
It depends on what you're looking for out of WI. Since water isn't a fuel, it doesn't lower IATs much and since I'm not looking to increase boost levels dramatically, personally I don't see much need to tune with it. This also allows me to keep the system simple, reliable and inexpensive. AI is a different story.

 

Using <5gph (start with 1gph) for some safety margin is pretty easy if that's all you want. Trigger it high enough that at wont cause problems and keep the flow low enough so that it won't affect tuning or power.

The problem is that people want a straight answer without asking a straight question. Can WI lower EGTs? Sure. But it may not depending on how much you inject and where.

Can WI lower IATs? Sure, but how effective that is will be dramatically effected by application.

Can WI raise HP without tuning? Yes, but only in certain applications.

I don't want someone to read this thread or one of the one's on rx7club then buy a kit based on a different setup and complain about results.

Also the side exhaust port causes problems if you inject too much water at low engine loads which I have personally seen. The setup that caused me problems was a 1gph nozzle at 150psi that kept spraying in cruse/idle and caused a lot of missfiring/higher EGTs/power loss. It took several minutes of cruising for the water to clear out after I had stopped it from injecting.

 

What you post suggests you're using AI/WI on a normally aspirated engine....which makes NO sense IMO. And ANY WI that continues at idle is the result of dumb application, bad installation or malfunction.

 

It was due to a malfunction not design, but the point is that 1gph is almost nothing and can still cause problems if injected too early.

Here is an older thread:
https://www.rx8club.com/series-i-maj...k-dyno-212447/

I don't really believe the dyno numbers from that thread, but I have seen a few other threads where people tested back to back water injection and complained about having either no benefit or a power loss. If you are losing significant power you are injecting too much, or at the wrong place in the intake.

 

No. The point is that your system failed. So I'm not sure what your point was. And I inject over 3 times more water than 1 gph at 1.5 psi and as previously stated, have no problems and no discernible power loss.
Or using WI on an normally aspirated engine.

 

There is no magic that happens when the engine transitions from NA to Boost, just a change in pressures and mass flows. You can inject NA but the flow required is pretty damn low and there is no benefit (other than cooling) without tuning.

Also I never said anything against your setup, nor suggested it couldn't work, quite the contrary:
I'm happy with my setup, and I'm running non intercooled. IAT's have never been a problem (<145F) up to 8psi and knock stays low.

I'll post more info as I get it. Right now I'm overhauling everything so I can go for more power.

Edit: To add some more info without complicating things too much here is a quick rundown of injection points

Pre-turbo: Shows efficiency gains and can cause a turbo to flow more at the high end. Too much to early and that seems to have an opposite effect.

Pre intercooler: Bad idea. Water does not flow smoothly through an intercooler and IATs will be slightly lower from the water but the drop in intercooler efficiency will counter a lot of the gains.

Post intercooler: Lowers IATs after the intercooler has done it's job, may add some power.

Any place you inject will be beneficial to knock.

 

for my particular application I just want it for slight cooling effect, clean engine, and anti knock. I don't want to tune for it, so if I run out to big deal. I was thinking like a 340cc or so starting at 5-7psi.

just thinking throttle body area.

thats where I am at with my research and my desire results.