Water Injection for SC or Turbo Engine?

[sjs]

I posted this at the end of a prior thread but got no response, so...

Has anyone tried one of the newer high pressure water injection systems such as Aquamist on an NSX with SC or Turbo? (Rather than backing off the timing at higher revs/boost)

[This message has been edited by sjs (edited 16 April 2001).]

 

[David]

I have not heard of anyone using either water or alcohol injection. There is no reason it wouldn't work, but the forced induction kits readily available don't need it as they run relatively low boost.

Water injection systems were really popular in Australia for a while, but faded as people got tired of maintaining them and dealing with the added complexity. Also, as programmable engine management systems have become more accessible, there has been less and less need for water injection.

 

[sjs]

Years ago I used a 50/50 mix of water and ethanol on my 72 240Z. I had a 260 engine and low-pop forged pistons, but it was a draw-through design and therefore no intercooler. Without the injection I was limited to about 11 psi, but with it I could run 16-17 without any detonation. Of course the water occupies part of the increased charge volume, but the added cooling effect also makes it more dense. The effect on my Z was clearly a net gain in power, but it was an admittedly crude setup by modern standards.

So, I'm wondering if it would make an otherwise as-delivered Bell system safe at 7-8 psi (or without retarding the timing) while yielding more power. Would the added cooling effect make it useful even on a system with programmable fuel delivery?

 

[JChoice]

We use water injection to safely boost 17lbs on a stock SR20DE Sentra SE-R 2.0 liter motor. The result is approx. 250 - 270 whp. The stock motor is fairly strong. It runs approx. 9.8:1 compression.

Without the Aquamist water injection, I believe that 10psi would be the limit. The ECU is programmed to handle the water injection.

If anyone is serious about it, I can refer you to someone who is a master at engine tuning and can do a setup for you.

 

[David]

Well, if you are planning to use H2O injection to run the boost up on the Bell kit, I think you are going to run into some other problems. I personally think you should not exceed 450hp or so at the crank on a stock NSX block, as it is an open deck design.

Instead of injection, you should consider decking the block and using forged pistons at 9 or 9.5 to 1. I am running 16 psi on my motor with a built short block with no problems so far. I also know a guy here in town who decked his block and dropped in pistons and he is running 8 psi with the Bell kit with no problems. He is making 370 hp at the wheels. He could probably safely run significantly more boost, but the turbos are pretty small. I get 504 hp at the wheels with my setup.

If you are serious about making hp, you should also consider a programmable engine management system.

[This message has been edited by David (edited 17 April 2001).]

 

[sjs]

Originally posted by JChoice:
If anyone is serious about it, I can refer you to someone who is a master at engine tuning and can do a setup for you.

I'm very serious and would like to speak with someone. (See my response to David as well)

Originally posted by David:
If you are serious about making hp, you should also consider a programmable engine management system.
B]

My impression is that the Bell system will need more than the recommended max 5-6 psi to make the upper limit of "safe" HP (~425) without internal mods. I'm shooting for that range for now. If Bell + H20 can get me there, great. I hope to build a new engine later but want to work with this first. However, I am willing to get a programmable engine management system as well if there is a clear best choice out there now. I have spoken with at least one company working on a new one that may be an option as well.

What did you end up with?

BTW, thanks to the H20 my Z motor always had very clean combustion chambers, which also reduces the risk of pre-ignition/detonation

Thanks for all the input!


[This message has been edited by sjs (edited 17 April 2001).]

 

[David]

Originally posted by sjs:
My impression is that the Bell system will need more than the recommended max 5-6 psi to make the upper limit of "safe" HP (~425) without internal mods. I'm shooting for that range for now. If Bell + H20 can get me there, great. I hope to build a new engine later but want to work with this first. However, I am willing to get a programmable engine management system as well if there is a clear best choice out there now. I have spoken with at least one company working on a new one that may be an option as well.

If you are going to run 6 psi or less on the Bell system, you do not need water injection. Especially if you are going with a fully programmable engine management system.

You might talk to Jim at MechTech (760-432-0555) about this. They have done several Bell TT installations with Haltec engine management systems.

If you have questions about water injection, you could try Bob Norwood at (972) 831-8111. I know he has done some high performance motors with water or alcohol injection.

 

[sjs]

Originally posted by David:
You might talk to Jim at MechTech (760-432-0555) about this. They have done several Bell TT installations with Haltec engine management systems.

Thanks David. I spoke with someone at MechTech some months ago and they didn’t think there was any need to change the Bell system as currently delivered, but I’m not sure if it was Jim. So I called him yesterday and talked for quite awhile. He pretty much repeated that if I could get 93 octane fuel, the extra injectors and controller were adequate for the practical boost limits of the turbos in the Bell system. Placing that at around 7-8 psi should also approach the safe limits of the stock block, although I haven't done the math on that yet. He also thought that the Aquamist option was a very good way to add a margin of safety if I wanted to approach those limits with less concern about the last point or two of octane in a given tank of gas. Of course, relying on such a system creates one more point of potential failure, but if I can hear it ping I can lift. (By the way, does your system incorporate knock sensors?)

Anyway, I asked him about complete engine management systems and gave him every opportunity to convince me that I needed one, but he insisted that the system was pretty well sorted now and that I shouldn’t bother until I'm ready to move to the next level and all that comes with it. Needless to say, I appreciate his time and honesty. I think I'll try the basic system first, then add the H20 (which I've already ordered) and see how it goes.

Thanks again for your insights and suggestions. I hope to tap your knowledge of the upper limits in the year to come.

 

[David]

Sounds great! Let us know how it works out. I know for sure you can run, 5.5 - 6 psi on the Bell kit as it ships. If Larry can tune it or help you tune it to run 7+ psi that is great!

IMHO if you stay below 380-400 hp at the crank, you should be within the tolerances of the stock block, as long as you don't beat on it. 450 crank hp seems to be about the limit, although this will vary a bit from motor to motor.

I don't use a knock sensor on my motor because I have a fully programmable engine management system (Motec) so it is pretty safe, even at 16 psi. You can hear it run at http://www.ojaspatel.com/media/davidsnsx/davidsnsx.mp3 though it's a bit out of tune right now.

I would also think about tuning your motor on slightly lower octane than you know you can get (91 or 92 oct) so that there is a slight margin of error. You can lift when it knocks, but that is not always easy to pick up at high boost (loud) and it does not take long to hole a piston.

Good luck with your project.

[This message has been edited by David (edited 20 April 2001).]