AFAIK Subaru did that with V1/2 STI RA's for holomogation reasons. In the car that rolled off the showroom floor it did nothing but it allowed them to run it on their rally cars which is far from what most people on here are doing. The couple of cars I have seen with the the 5th injector confirmed to me that it really wasen't doing much.

I don't see how it related tho. They are two quite different things.

Back on topic?

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[DBR]

I was just trying to make the point that I don't see how using water/meth injection is any less safe than using a 5th injector. I don't see why it is any more likely to fail than any other part of a fuel injection system, and from what I can see this seems to be your main reason for not liking it.

Water injection has been used in piston aircraft for years and years with much success, and not only for supressing detonation (safety measure), but also for making more power, so I don't see why it couldn't be used in a road going car.

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John Stamos fan club lifetime member

water meth injection used on turbo prop engines is a lot more sophisticated then whats being attempted here.

even as per rally teams (pre 07) who used water injection, it wasnt a single point of injection, but a staged multilevel calculated (in closed loop) over multiple points of the inlet and intercooler systems.

water is the flame retardent, methanol is the heat soak.

relying on this alone (on a stand alone controller) is dangerous, as engine conditions change so rapidly that you cannot accurately tune against it for any tangible gains.

a 5th injector on the otherhand is controlled under closed loop.

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Long live the WRC

I agree to a certain extent in what your saying. It does have it's plus side and in extreme situations can be a very viable option. In an application where motors get a vast amount of pre-checking before use (Aircrafts and high end race vehicles) then it's a great thing for getting a little bit more power out.

But in the situation of a road car why keep stacking up things that can go against you for relative small gain.

I can see the merit of running it for added safety in the Australian summer, but don't agree with pushing the tune to the ragged edge when 99% of vehicles don't run engine managment that will facilitate an issue.

Obviously it has it's pro's and con's and its a discussion forum.

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[DBR]

Not that I wish to harp on but....

Water is used at the "heat soak" due to its high specific heat capacity, i.e. it can take a lot of energy without substantially increasing in temperature. It is then also useful once it turns into a gas in the combustion chamber, further increasing combustion pressures. Methanol is often added to slow the combustion process, allowing a more complete burn. I'm not sure what you mean by flame retardant.

How would you control water injection in a closed loop environment (what variable would you measure to adjust the amount of water injected), and what benefit is there to having multiple injection points? I could understand if you had one injector per intake runner as with fuel, but surely the closer you have the nozzles to the combustion chambers, the less effective water injection would be?

Also, relying on water injection is no more dangerous than relying on closed loop fueling under rapidly changing engine conditions. You have to remember that AFR's are measured after combustion has taken place, and by that stage it's already too late.

I'm not sure of any 5th injector systems that operate under closed loop (considering closed loop fueling is a fairly new and still rarely used technology, surely you would just go with larger injectors)

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John Stamos fan club lifetime member

closed looping has been available for years in a race/aircraft, its only the budget racers/home-brew that dont make use of it.

water is the anti-knock agent (flame retardant), methanol is the heat soak agent (alcohol), water offers nothing other then a reduction in volatility of the air/fuel mix (a reduction in power, but allows you to increase timing to match what you would have made without water).

water injection done properly is controlled by duty cycle of a pre-pressurised water line on a solenoid.

parameters would include inlet air temp, compressor air temp, atomosphere relative humidy (why bother injecting water when its muggy or raining), engine load (based on EMAP) and inlet manifold air temp,

this would be a 3D table with open loop trims (on each parameter) with closed loop PID on fine tuning for the rapid changes in engine conditions.

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Long live the WRC

Okay. Water is used to cool the incoming air, not the alcohol. The only reason that you would get a reduction in power due to injecting water is due to the decreased oxygen content in the air due to it being saturated, not due to a lower volatility of an air/fuel mixture. What would be the point of injecting water if you only had to increase the ignition advance to make the same amount of power anyway? Alcohol does evaporate and as a result will cool the surrounding air, but not to the same extent as the water. It is this cooling effect that reduces the chances of det, much the same way as adding extra fuel does, but to a greater extent.

When I talk about water injection systems I assume we are not talking about a dumb system that simply turns on a water nozzle and leaves it on constantly. Most systems available these days take into account air temp and engine load, which can be faily easily derived from the injector duty cycle.

Whilst the parameters you mention are important, they would be measured pre-injection, ideally you would measure something after you have injected the water and then trim it to suit, like fuel is done with a wide band, after the combustion process.

I do understand that water injection has it's downsides, I just find it strange that people jump all over an idea without fully understanding the process.

What happens to a closed loop fueling system when the sensor fails? This is my point, water injection is no less safe than any other part of a fuel injection system.

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John Stamos fan club lifetime member

put the water injection to practice and see what the results are, having seen what it can and cant do, i'll be impressed to see a significant improvement from anyone with a home-brew solution.

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Long live the WRC

home-brew... now we have something to talk about...

hmm pissed

the most sophisticated car WI kit on the market a home-brew solution?