Dudemaaanownsanrx7

iTrader: (23)

Personally I find it pointless to try and ring every last drop of power at say 15 psi when you can keep things on the conservative side and just raise the boost. Increasing the boost to say 20 psi will net way more power gain then leaning it out from 11.3 to 12:1 on low boost levels while being safer. Rotaries still like more fuel then a piston engine, and they hate knock even more then they love fuel, the parameters for tuning piston engines will always be a bit different because of those 2 factors.

One thing I noticed when tuning my setup is that my knock on the ramp up was hitting 44 that is double what it is at high boost. When looking at the log It was right around 12-13 psi. My afr's were a bit higher then I would normally run, and my timing was a little more aggressive. While the knock wasn't too terrible, it sure stands out in comparison to low 20's for the remaining 20.5 psi run. My water comes on around 8 psi so this wasn't the issue. It Increases linearly as boost goes up.

From my experience the engine was happier at higher boost with more fuel and more conservative timing, then at the lower boost where it was tuned more aggressive, but I can tell you it makes a hell of a lot more power at the high boost prob 150 or more HP.

Viper GTSR

That's great information, thanks for your posts...

Question, how much was she putting down at the wheels at 20psi and what turbo are you running? Also, why stop at 20.5psi with knock readings as low as you were getting? Why not push it up to say 25psi? Do you feel straight water only inj will be able to safely allow that?? Also, what injectors & ingintion system are you using? Thanks!


~ Kayvon

Dudemaaanownsanrx7

iTrader: (23)

I plan to run up to 25 psi, but i like to do things slowly to make sure its safe. I ran up to 22 psi at one time but that was on accident, still no knock though.

I do all street tuning, so i can't be sure on exact power, but it should be around 500. Even with drag radials tires let loose in 3rd just throttling on.

I have a thread titled "my car is a handful" that has more details on my car, but basically it's a masterpower t70, large ported engine, 550/1680 with higher base pressure and dual stock fuel pumps rewired, duty cycle at 70. Ignition system is twin power, stock coils, greddy race plugs and 10mm race wires.

Yes i think water alone is enough to support over 25 psi. I expect 550+ at that level. When i get closer to being done with everything i'll put it on a dyno.

1ROTOR2NV

I know this thread is a little old but I would be interested to here from the guys that have tunes for both straight water, and then water/meth. How much boost can you increase when adding meth into the mix with the same safety margin. What are some corresponding horespower figures, anyone want to chime in?? Also what is everyone using for knock sensors?

Dudemaaanownsanrx7

iTrader: (23)

I have never used meth injection so I can only comment on the water side. Since my last post I have now been running 23 psi with almost 600cc/min of water. I think power figures will be more based on your total setup/tune. From the engine porting, to the turbo, and how much boost you ultimately run. I don't think you will see much of a hp difference between identical setups with the only differences being injecting meth, water, or meth/water mix.

Some people have reported the best results with 50/50 but there are so many other factors that it makes it difficult to compare. For instance one person might install water and have a shitty ignition system and lose power, so they have better results with 50/50 or meth. On the other hand another person with a good ignition system will gain power with water, and crank the boost up to make even more power, but not necessarily more then with adding meth. Just too many variables and combinations.

I'm using the stock knock sensor. Been injecting water for about 9 months at over 20 psi boost.

WaachBack

iTrader: (21)

What it really comes down to is how much fuel you tune out when running water injection. The more you tune out to 12.5 - 13 a/f, the more power you will make, but you will also be riding on your W/I system not failing and blowing your engine.

1ROTOR2NV

I guess i was referring more to how much the boost can be turned up with water injection vs water/meth, while still maintaining safety of the motor, not so much leaning out the A/F ratios.

Dudemaaanownsanrx7

iTrader: (23)

Sever people have run over 25 psi with just water. I'm at 23 psi. I would say you could go upwards of 30 with good tuning. I have no knock to speak of at 23 psi. Low 20's for a knock count.

WaachBack

iTrader: (21)

I personally have ran up to 22psi with knock readings in the 20's. If my turbo made power at 28+psi, I would have no problem running water injection at that boost pressure.

The Shaolin

iTrader: (5)

...which leads into my question...when is AI necessary?

I figured the limits of pump only were around 450-500, but then captain 280 up here wants to run it as well.

calculon

iTrader: (29)

There is no real good answer to your question.

It's never necessary.

It's almost always a good idea.

Dudemaaanownsanrx7

iTrader: (23)

There are still advantages to running water on a nearly stock, or even completely stock car. For one it cleans the carbon out of the engine. This eliminates the possibility of carbon breaking off and causing problems, seals sticking, and it saves time cleaning when you have to rebuild.

It raises the knock threshold allowing you to run lower quality fuel, leaner mixtures and more timing. (provided you have a way to pull fuel and advance timing)

Keeps the engine cooler

The Shaolin

iTrader: (5)

I was planning on running e85 for my goal of ~~400~~hp, just for the extra octane. I was thinking I was going this way because it's free, nothing extra to fill, and no way for it to fail and blow the engine. Here's my parts list if you want to see it: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/my-86-gxl-turbo-build-take-two-858835/

Is it worth running e85 at this low of a power goal? Should I be considering AI instead/in addition to?

I know there's no correct answer, just looking for opinions...hoping that posting in this section won't give me too biased of an answer...haha.

Based on what you just said, it sounds like it makes everything a lot more forgiving...seeing as how this is my first engine build and my first attempt at street tuning (with a standalone), I think all the forgiveness I can get against detonation is going to be a good thing....plus, the extra dynamic compression is going to help my lazy S4 TII rotors get up to speed...haha.

1ROTOR2NV

If people are running over 25psi with just water, how much could you turn it up with a 50/50 mix, (ballpark) ? Also what are the main reasons everyone doesn't run meth with the water, is it more hassle then its worth because its a fuel source, to hard to tune, too expensive, or what?

amunoz3

iTrader: (2)

well i run a 50/50 water meth and have also ran with just water. In my experience of using 50/50 i would say that meth lowers intake temps. I have ran water and then all of a sudden run water/meth without retuning and it looks like 50/50 helps with air intake temps. btw water injection (running just water) without an ignition upgrade feels like crap, 50/50 is good for non upgraded ignition systems.

Dudemaaanownsanrx7

iTrader: (23)

E85 will require a much bigger fuel system and uses 30% more fuel so mileage will decrease by 30%. You won't need any aux systems with e85 since its mostly alcohol anyways. It comes down to cost mainly. 400 hp is fairly easy to come by without any aux injection or e85, but obviously either one will be more reliable then pump fuel alone. Most likely you will want more power later so plan ahead.

I have no idea. I wouldn't say water, meth, or a mix necessarily allow you to run additional boost over each other. Provided you run enough of whatever you choose, and have the right tune, I think you would reach the mechanical limits of the engine before you reach the knock limits. Each system has it's advantages and disadvantages. Also it should be noted that 50/50 is technically supposed to be measured by weight not volume. A gallon of meth and a gallon of water would be more like 30/70. So it should be clarified when comparing certain systems with one another. I personally don't run meth because water does what I need it to, and its free. I might experiment with mixtures at some point just out of curiosity.

Yeah thats the main advantage of meth. (cooling IAT's) Making sure the water is atomized will go a long way in helping the ignition burn it, and not running overly rich either in water or in fuel will also help. I agree 50/50 or some other mix may be beneficial for stock ignitions. It would also help with systems that have trouble keeping IAT's reasonable.

I did some testing lastnight with the preturbo water only injection. Cruising temps were 33c (91*F) A good pull in 4th gear caused temps to increase to 42*c (107.6F) this was at 15 psi (low boost) I then let the temps settle back to 33C and did a pull on high boost (23 psi) temps went back to 42c. So it seems that even though the water isn't lowering the temps it's keeping them at a constant temperature regardless of how much boost I run. I would do a pull from 1st to 4th to further test, but my drag radials are too narrow and just spin all over the place. (even in 4th they spin @ 23 psi)

Oh yeah I use the fast reacting sensor with the pfc as mentioned in other threads so temperatures are accurate.

1ROTOR2NV

Thanks for all the insight , for the record I still cant decide weather to run with meth or just water. I wish these were clear cut answers. I suppose the only worry i have is having all these tunes for different injection setups, i was hoping to decide on an aux injection setup and tune for that on its own. Anyone else that wants to chime in on the advantages of meth and water over just water, i would appreciate it.

AlexG13B

iTrader: (7)

ok so im not the only one with temps that dont cool down as others and ur running heavy boost. u have a intercooler and cai?

Dudemaaanownsanrx7

iTrader: (23)

Well it depends on your goals and expectations out of the car. Is money an issue? Is the car street or track driven? how much space do you have for a tank? Are you going preturbo or post turbo injection? how much power do you want? is your ignition upgraded?
Yeah, no meth though. Intercooler is 24 x 12 x 3 ebay core. Cold air intake under the headlight. It was probably 75- 80*F last night, which would mean after going through all the piping the temp reaching the engine was about 15*F warmer, then under full boost it was 30F warmer over ambient. Not bad considering the turbo outlet temperature is like 300*F.

1ROTOR2NV

As far as the money goes, everyone has budgets, or i would be driving an Enzo, but yeah I am putting alot of money into the project. You could say I havent spared any expences thus far. It is going to be a street car, i do have an upgraded ignition, and if it helps my driving style is suited more to the freeway. Also I am not well versed with the pros/cons of pre or post turbo, feel free to educate.

WaachBack

iTrader: (21)

It would first depend on your water to fuel mixture. If you at the recommended.
10%, you actually have to turn it down. Water has more then twice the cooling capacity of meth.
To keep the same cooling capacity, you'd need a bigger jet. For example:
500cc Water = 750cc 50/50 Mix = 1000cc Meth.