After I ran full exhaust on my S5, my boost levels top out around the 10-11 psi range. For a lot of reasons, I want to keep the stock TMIC. So I'm looking into a water meth kit for added protection. However, I don't have the option (nor do I want to) to tune the engine for it. So basically all I'm looking to do is add efficiency to the TMIC, and a fail safe towards detonation.

Does that seem silly?

 

Just use water only then, no need to retune, in conjunction with an ambient air intake intake temps should be low enough in the cool temps now at those boost levels( probably around 110 deg F)

 

I was also looking forward to the cleaning properties that water/meth injection offered. Will I still benefit from those running only water?

 

When the water vaporizes, you'll get the steam cleaning effect.

 

Cooling the intake would add power, but no better than a good intercooler. Maybe good for you since your'e staying stock. Yeah, I suppose you are adding some margin of reliability unless the boost spikes way up or maybe if the fuel goes way too lean. Though I think enough water could prevent the 2nd problem 100% of the time.

I suppose the real question is how much benefit it provides for the money compared to other options.

 

unless you run it at the track or beat on it for extended periods of time liberally i really don't see the necessity of it, for a stock turbo/stock TMIC setup that is. the only reasons it would blow is from a lean spike, auxiliary injection won't save the motor if that happens anyways. you can do the water treatment without the necessity of an auxiliary injection kit. if you were to say 14-15psi i would say yes, it is a good option.

without the ability to retune your timing maps you will need to spend some time jetting the injection system to minimize power loss. too much water= loss of power, not enough= no point.

 

It was my impression the stock TMIC reaches it limit's around 10 psi. Not to mention how much it heat soaks when I'm sitting still.

I know the auxiliary injection section here is pretty useful. But it gets very in depth on some things. And my application is more simple I suppose.

Having to set the injection amount would prove difficult.... :/

Everyday I lean more and more towards going standalone, and this just adds to it.. I need to start reading up on those systems.. And if I can still pass emissions, get decent mileage, etc.

But then I fall back on with me going through a divorce at the moment, this ended up bein my DD. So I'm trying to keep the mods down at the moment (for money and reliability). And an injection kit (on the surface) seemed like a good idea to add some reliability and safety to the car.

 

the normal causes of failure of these engines will still exist with a few exceptions which are usually caused under extreme situations where internal temps are sky high.

 

I've decided to re-visit this topic. A I've been considering some water only injection recently. And while some would argue it's not worth the cost, it will be some day when my HP demands go up. In the mean time, I'd enjoy it's other benefits.

Will running water only allow me to run 87 octane vs 91?

Any suggestions on nozzle size?

 

nozzle size depends on the injection kit and its rated pressure/volume

i wouldn't suggest running 87, even though i have tested it without water and found it to be sufficient up to 9psi, that is borderline. reason i say it's not a good idea is due to the fact that if the water injection system cuts off for any reason the motor is almost guaranteed to be toast.

 

I'm running a 70% meth 30% water mix on the stock ECU, top mount intercooler, motor, turbo, ect. with no tuning. What I found out after messing around with it is the amount you spray, and where you place the injectors has a HUGE effect on how well it will work.

Experiment with your set up and find what works for you.

 

Sen2two, can you elaborate more? Maybe explain your setup?

Karak, thanks for the info. I'll stick to 91 if you feel it would be safer.

 

Although I wouldn't say I've thoroughly searched on the topic, just read quite a bit as it popped up on this tech section, I wasn't aware anyone recommended increasing octane above 87 on a stock turbo / stock ECU (or rtek 1.*).

 

I run high flow exhaust, so boost levels run around 10-11 psi. I run 91 to help prevent detonation.

 

For stock-ish boost levels, there shouldn't be a need to run more than 87 octane. But once you start raising boost higher, it's a very good idea considering the stock timing maps. There's almost no change in timing when you increase load beyond what the ECU expects to see. Pocketlogger incorporates a little additional timing retard into the 1.x chips, but the 2.x use stock timing until you edit it yourself.

Stock S4 TII maps: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/stock-s4-turbo-timing-maps-warning-those-stock-ecu-943159/

 

The 1.7 chip I have does infact retard timing a bit (I believe its 1 degree per pound over 9lbs)

When you say stock-ish, would you consider 11lbs stock-ish? I'd love to save some money at the pump, but not at the expense of a rebuild.

 

Don't be so damn cheap. The price difference of a full gallon of 87vs. 93 is only like 3-4 dollars depending on what gas prices are that week.

We spends 1000's on crap for our cars then skimp on the gas? Makes no sense. Same thing goes for people who run window fluid instead of pure water or an actual water/meth mix. You only save like.50 cents, what is the point?

Stock boost levels, depending on s4 or s5 are from 4-6psi. So your either doubling or tripling the stock boost. NO, 11psi is not stock-ish...

 

Since going turbo, I have always used 91 octane in my car. Even if it's possible for me to get away using 87 or 89, I'm not going to take any chances. I don't drive an RX-7 to save money at the pump.

Stock boost would be 8 psi max by S5 standards. A 1.7 chip does pull a little timing, but IATs will climb when you take the stock turbo out of its efficiency range (raising boost).

 

And it's that rise in IAT's that I want to combat with the water/meth system.

Sen2two - What size nozzles do you use? 1 or 2 of them? What brand of system? Where do you inject?

 

Truer words were never spoken!

 

Why don't you inject pre-turbo? This will likely give you the best temp control. You are running the stock turbo, right? If you experience any compressor blade erosion, who cares, it will be slight and over an extended period of time. You can easily find another impeller on the FS board.

 

^^ I'm a little hesitant to inject pre-turbo. Why would that be best?

I appreciate the suggestions btw, so please, don't hesitate. While the section on the forums for this topic is very imformative, most of it's driven towards higher HP applications.

 

search my name. I show it and explain it in my RHD car build. And another thread i made in this AI section...

 

From what I've gathered, injecting pre-turbo just requires a high pressure pump & an injector capable of delivering a very fine mist. The advantage is shifting the turbo's compressor efficiency, which will help with IATs and increase power.

 

^^I'll have to look deeper into that... I've read mixed reviews on doing it this way..