Im very curious what all of you think. I have been getting alot of requests for n/a water injection and I'm considering to design one for the Rx-8. I'm curious if you think its worth it on a n/a motor and if the Rx-8 could benefit from it. I have had exceptional results with my rx-7 and am very close to designing and testing a kit on my Rx-8.

Any opinions appreciated, thanks!

 

I dont think it will have much of a benefit for the stock motor naturally aspirated. Forced induction is a different animal though.

 

I thought the same thing, but then someone told me his motor was pinging on 87 octain on a hot day. I also thought about ignition timing advance, etc. But again, I dont know.

 

Hello coolingmist, and welcome.

I wrote a thread about water injection a while back. Check it out.

https://www.rx8club.com/series-i-tech-garage-22/water-injection-13b-msp-32449/

 

If your motor is pinging with 87 octane on a hot day then the logical thing to do is to not use 87 octane. The water tank is only so large. It will run out. It is something best kept to the drag strip and used on forced induction vehicles. Water injection on a non forced induction car is really nothing more than a steam cleaner.

 

Thats why you are supposed to use premium. How do you know the motor was pinging? Using water injection to run the car on 87 octane will only add risk of detonation for very negligible power gains. Water injection is a great tool but is meant to provide an extra margin of safety to run more timing and optimize the fuel curve for power however doing these types of enhancements is beyond the average RX-8 owner and therefore most RX-8 owners aren't going to be able to see any gains for safe for everyday street driving. Doesn't mean there isn't a reason to build a water injection kit, but I don't see a very large market for it.

 

I have no pinging whatsoever running on 87 octane.

 

actually thats incorrect. If you used water injection you would have far less of a chance of detonation, not add to it.

 

Indeed. However, water injection is not infinite. It's not always going to be there, so you'll have to refill it. Also, I believe there are some sanctions in drag racing outlawing water injection, especially if there's water leaking onto the track. Water injection is a wonderful safeguard for forced induction motors, but is not ideal for every situation. In N/A applications, I don't think the engine would produce enough thermal energy to make water injection a viable solution. If you start knocking in N/A form, the first solution is to switch to a higher fuel grade. Water injection should never be a solution for N/A engine problems. In fact, it may mask the bad stuff that's going on in the motor.

 

I didn't mean the water injection would cause detonation I meant if you tuned the motor to have more time or higher air to fuel ratio to try and make more power and used water injection to compensate you run the risk of running out of water at an in opportune time. etc. and modifying the ECU like this properly is not easily accessible to the average guy. I use water injection myself on two cars and understand how it works.

 

That's what I'm talking about. Using water injection to compensate for other functions is a no-no.

 

That is the key! Don't use it as a bandaid. It has it's place. Just not in the stock RX-8.

 

Bandaid? I guess in a turbo car an intercooler is a bandaid too?



Im just curious how far you could push the button with water injection and the rx-8. Not necessarily for stock cars but more so for those with timing advance and fuel mods. For those that stretch the limits of the fuel system this would be a major help.

 

When I refer to it as a bandaid, I am stating that no one should rely soley on it, especially in forced induction. They should not use water injection instead of an intercooler. This may work fine for the quarter mile but isn't practical anywhere else. Unlike water injection, your intercooler won't stop working when you need it the most. The water tank is a finite supply. The intercooler is not.

It also isn't a worthwhile mod on a nonturbo car. From a marketing and sales standpoint I fully understand why you would disagree with this. I'm not selling product though and am the voice of reason. If someone has ping on a nonturbo then they are facing one of two problems. The first is that the tuning is terrible. There isn't much we can do about this if the car came this way. The second issue is that they are using too low of an octane gas. If they are getting ping on 87 octane then they shouldn't be using 87. They should be using 89 or higher.

It is only worthwhile on extremely high horsepower forced induction vehicles. You don't need it otherwise.