CPR

Not sure if I follow you here?

What is the difference of charging air pre-TB, than charging air post TB? If you are simply reducing intake temps by ~20F I would think you want to minimize the duration of travel by injecting as close as possible to the cylinder, thereby cancelling induced heating.

It is also hard to block an injector, as the solution (methanol+water) practically cleans as it goes just by chemical construct. What would have to happen would be a single solenoid that fires all four (or none) injectors unison. The set-up I have here uses a microswitch based solenoid actuator that circuit closes based on pre-set/determined boost parameters (5 psi,7psi,10, 12...whatever you want to set it for).


JJust my two measily pennies though...

Chris White

Think about that one for a second….if you are ‘heating’ the meth/water that means that you are cooling the air….isn’t that the point? You want heat transfer into the water/meth.

CPR

That is what I am getting at. But cooling to soon allows heat soak later in the line negating the original effects no?

Chris White

Geez, I trying to keep up with you on both boards…

In realty the most beneficial phase of any intake charge cooling done with a liquid is when it changes phase – liquid to vapor. (check out enthalpy of evaporation) That is going to happen in the combustion chamber – where you want it to happen. The heat energy to change the phase of the cooling medium reduces the overall charge temperature. If you remember your physics the temperature of the gasses in the combustion chamber raise as they are compressed…a lot. This is why we have detonation – the pressure goes up due to mechanical compression – and therefore the temperatures go up too – eventually reaching a point where the mixture auto ignites (preignition) and that causes the nasty pressure spikes that makes the obnoxious “pinging’ sound.

So – in realty it does not make a big difference where the liquid is injected. The heat transferred by the time it gets to the combustion chamber is minimal compared to what it will absorb inside the cylinder.

It comes down to two factors – getting a homogeneous mixture and keeping the mixture suspended.

On one point it might make sense to inject it earlier to get a better distribution – but then you might have a problem getting it to remain suspended around the tighter corners. The stock manifold is a ‘dry’ design – not meant to flow a ‘wet’ gas.

If I were to set a system up it would be a second set of fuel injectors just upstream of the fuel injectors – running a system very similar to a fuel injection set up – a pulse width signal to meter the liquid. It can be programed via a general purpose output from a good standalone system fairly easily. You would have to run a 50/50 mix of meth/water or you will have corrosion problems with the injectors.

theedge

Theres two schools of thought really. Some say close to the intake valves, others say the further the water/meth is injected away from the engine, the better cooling there is due to time to evaporate.

Remember that no water injection systems that I know of uses an "injector", they use a fogger/mister. Any control is done via a solenoid (different internally than fuel injectors). No one uses actual fuel injectors because the water will rust them closed very fast. The foggers can be blocked easily with any dirt or grit, especially the low flow ones that would be used for port injection. Hence most or all the kits out there for water injection have a 30 micron filter. The systems that are truly variable use a very fast acting solenoid.

The system ill be installing in my car will be injecting right after the intercooler, but well before the intake temp sensor.

DanaT

Yes. And you can make a very neat installation. Just have to copy what has been done for motorcycles 15 years ago....remember, motorcycles have had indivual runners for many years.

-Dana

CPR

I was using the word "injector" in a very generic sense, NOT implying an actual fuel injector.

Chris White

The last thing you want to to really evaporate the water/meth mix – steam expands to take up 1600 times the volume of water. You don’t want that happening in your intake manifold – you want that to take place in the combustion chamber with the valves closed.

A 50/50 mix with meth would be fine to use with a fuel injector.

A properly designed injection system should be varying the quantity of liquid injected by load and rpm – most don’t. Most are pretty crude in nature and are not much more than an on/off switch.

reno808

Dam Chris you are the kind of multi-tasking. You can reply to bunch of posts and threads, still run a full shop and CNC shop. Props to you brotha

Chris White

It helps to like working in the middle of the night…