I am currently running an A/F of 10.8 at 16PSI with 550cc's of water on the stock twins.

I tuned the car like it was running straight gas NOT 90% gas 10% Ethanol.

Is this safe or should I go even richer on the A/F ratio because of the fact that it contains 10% Ethanol?

My knock in the high boost high RPM ranges are under 40 and my mods are in my sig.

Thanks

 

knock is key and you are fine at 40. the problem is that knock readings are generally after the run and if you get alot of knock all of a sudden it could damage your apex seals before you become aware.

what octane is the gasoline?

additionally, the stock turbos start to cavitate above 14 psi so running 16 you are superheating the air. you might make more hp at 15 or 14 psi as the compressors might not be heating the air as much. (it is all about how many oxygen molecules per volume... hotter air has less)

i would be cautious w AFRs because you are running alot of boost w the stock turbos. if you had a single i would tune for mid 11s.

good luck,

hc

 

You should be safe there especially with that much water. Water will raise the knock threshold of the fuel you're using. If you're concerned about the water system running out of water or failing then you might be on the risky side but would prob still be ok.

 

The gasoline is 92 octane.

I am aware that the stock turbos become inefficent above 15psi. This is just a drag tune. It's just so I am sure that I will run my time .

So you think that I should run even richer than 10.8? If I go to around 10.5 or less, I start getting breakup because it cant ignite all that water and fuel.

Also, my IGL at that boost is 13 degrees. Also, my air intake temps are around 40-45c. The water usually drops it 15 or so degrees.

 

I am not worried about running out of water or my system failing as I have an AEM system and it is pretty advanced. I also fill up water each time I use the car.

I've heard people say before that water raises the the knock threshold of gas. But, last night I read Brian Cains article that is stickied on this forum, in that article, he says water doesnt not raise the knock threshold of gas. Gas will still auto-ignite at 490F no matter what.

With that said, I understand that water cannot bring up a fuels auto-ignition temp, but in theory, wouldnt it cool the combustion chamber thus allowing more leeway?

 

I'm still getting in trouble for that.

Yes, that's exactly right and it's what I should've said in that article I wrote a few years back. By what degree it works, however, I don't know. I won't knock water injection like I have in the past when I first started goofing with this stuff. I still don't think it's anywhere near as good as alcohol when it comes to the whole Aux Injection thing, but I can see water having its benefits for high load. It certainly should be yielding substantial durability and reliability to the engine but I just don't know by what degree and with how much water would be necessary.

B

 

Good to know, so, with that said. What type of A/F can I tune up to? My current 10.8 with 550cc's of water is pretty rich don't you think?

Also, my first question still hasnt been answered. I tuned for gas, which is 14.7 stoich. E10 is 14.3 stoich, so, wouldnt it be a little leaner? I am sure it won't be by much, but I just want to make sure.

 

IMO, thats just fine AFR wise.

As for the ethanol content of pump gas....don't even factor it in. Ethanol content varies, and the itsy bitsy amount won't make or break things.

10.8:1 is plenty safe, and bordering on being too rich. As you stated, you likely won't be able to go much richer if you're not running an arc welding ignition system.

I've had good success with straight water, but the gains have been hard to nail down so far because I've had a myriad of other problems that break my engines

 

Lol yeah I think this is the second thread in 2 days where Brian's comments from awhile back were brought up and questioned.

I think with the amount of water you're pushing that running leaner should be fine. Especially if you keep air temperatures within check. This is one of the benefits of running AI. You can run more boost, raise timing, and use less fuel. Of course the further you tune up the more you take away from the safety net of AI. There's one guy on here that's has been running the stock twins to over 20 psi for a couple years, he doesn't use water even though he has a kit. I would call his results the exception rather then the rule, and personally wouldn't do this.

My suggestion is to keep timing on the conservative side, and pull some fuel out to 11 flat. Keep an eye on knock and air temps. This should still be safe while being conservative with the water on. You could probably even go leaner then that but one issue with the stock twins is they are so restrictive that they hold a lot of heat and the leaner you go and the more boost you run the hotter everything will get. Which puts more stress on the turbo's the manifold, and the internal parts of the engine. The main thing to keeping a rotary healthy is keeping the heat down. Oil, water, intake temps, combustion temps the cooler you can keep them the happier the engine will be. (within reason, don't just dog on a stone cold engine)

As far as my view point between alcohol and water, I'm really not biased towards one or the other. Water pulls more heat out of the combustion chamber per volume, alcohol pulls more out of the intake charge, alcohol burns easier so requires less out of the ignition system, water is free. Both get the job done, both make more power reliably.

 

Oh yeah and as far as tuning AFR because of alcohol content, it doesn't work that way. You use the exact same numbers you're used to with straight pump fuel. The wideband reads oxygen content not fuel content. It doesn't care what fuel you use. Even If you run straight alcohol, while it has a different stoich value, if you tune with the wideband just like it was normal gasoline, the mixture of alcohol will be correct.

So take an engine and feed it straight alcohol. You tune it to 14.7:1 AFR (stoich for gasoline), well the actual fuel being put into the engine will be more then that. It will be whatever stoich is for alcohol. (6:1????) So don't bother confusing yourself with whatever stoich values different fuels have, it will always be correct if you use the same values your used to with gasoline. Widebands read in lambda and convert it for us so we can see numbers we are familiar with. 1 lambda is stoich for whatever fuel you are using. 1 lamda = 14.7 on the wideband display unless the wideband has been screwed with to display a different stoich value for some peanut that's trying to complicate things.

 

I'll be tuning to 11 A/F's then. Thanks for the good info.

 

Some of the responses above are a joke and show some of the inexperience in this place.


WATER INJECTION is one of the BEST for killing out knock.

I am running 30PSI OF BOOST from a gt42r on a 13b on normal pump fuel. No Knock what so ever.
My engine is very reliable and makes healthy power.I will say here. I run 0 alcohol, 100% water.


The setup you detailed in your first post is excellent. You will have no problems. Continue tuning the way you are you will be fine. The AFRS you have chosen will net a healthy power output as long as your ignition is up to the task.

 

How much water are you running with your setup?

 

He runs a lot of water. I know one engine he refered to running something like 1100 cc pre turbo and an additional amount after the turbo. I think this may have been a different car though? I'm only running 500 cc preturbo at 20 psi on a t70. I've wondered if more water would be better. I've already increased it from 380cc.

 

wow isnt a m5 alot preturbo? im considering doing a m2 preturbo and m10 post. running 30% alky/70% water

 

As long as the water is well atomized you can run quite a bit of water through the turbo without damage. I use an air atomizing nozzle for my setup. It uses boost pressure to pressurize a tank and force the water out at low pressures.

I think mine flows similar to an m7.

 

im using a devils own nozzle

 

On my car its a 1150cc nozzle from coolingmist running at a 150psi and turbo is fine. No damage what so ever.

the above amount of water i am using is too much. Should be 7-900cc. (cant tell you exactly, still expirementing). I know for sure the current amount of water for 30psi is too much. More appropriate for 40psi.

 

What HP are you making at 30psi with the water?

Also, not sure if you are into drag racing but have you ever timed the car?

How does the car respond on full throttle between shifts?

Anthony

 

Too much water why? Does it misfire? Lose power?

 

I thought my 550cc were a bit overkill for my setup. :P

 

I'll be honest I was running 10psi~300hp at the track and just turned my water inj. on to see how much it would cool everything off with a 500cc nozzle and it was to much. It started misfiring and I could tell a noticable difference in power.

I installed it for higher boost levels, 16-18psi, I just don't run more than 10-12psi on the road course and wanted to see what it would do.

 

550c for 10psi of boost is too much. But if you had a good ignition it wouldnt break up.


With my car. I know its too much water because i have to run lean mixtures to get it to make hp. Were as other Water injected cars that have the right amount of water, can run mixtures in the high to mid 10s and make more power then mine.

Car has made 543rwhp which is low. And it was much lower trying to run the mixtures i wanted to. I will note that my car is NOT PORTED. IT HAS FACTORY PORTS.

I will have some more data soon when i get some more dyno time(been busy) with the smaller jet. And i am very confident 600+rwhp will be a walk in the park.

 

If that's directed at me then I'm happy to accept it. I'll admit I've got little experience with WI so I don't have much of a pool to draw on. I could be mistaken about some of the conclusions I've come to about it. And while I'm not meaning to turn this thread into an "alcohol is better than water" fight (again), I can say with the utmost confidence that alcohol has been very good to me. Perhaps my cynicism with water is unfounded; I'd love to be proven wrong about it as all it would do is show yet another great AI avenue to pursue.

B

 

I think alcohol is great. Its just not practical for everybody, certainly not for me.
Water is cheap

The comment was not mean to be an attack or anything like that, i just get frustrated alittle. Water is great if used correctly. Alcohol is the same. Used in the wrong amounts will give you different effects.