[hotrod]

Could we do that with the DEi cryo intake system? If we used a 50/50 methanol/water mix (which doesn't freeze) and pump it past the cryo bulb, immediately before we inject it into the intake tract, wouldn't that work?

Yes that would work but is not terribly effecient. The cooling capacity of the small amount (mass) of liquid is not all that significant. If your flowing 10 - 15 Kg /min of air and injecting 300 -400 gms of water /methanol its specific heat capacity is only a small fraction of the heat capacity of the air. The evaporation process or a conductive heat exchanger has far more ability to cool the air charge. The basic process has been used for years in specialty racing environments like land speed record runs and drag racing, where they would use acetone chilled by dry ice as the coolant liquid in an air to liquid intercooler. (NHRA now outlaws these systems due to the hazards of the super cold acetone during an accident and fire risk if it gets sprayed around from a leak)

I'm sorry but I don't understand the part where you can have ice build up in the combustion chamber!! if you can explain this to me that would be nice!

I was not talking about in the combustion chamber but in the intake tract. As the very small mist dropplets passed through and mix with the CO2 or Nitrous plume they could flash freeze to ice crystals which would liberate a lot of heat from the latent heat of fusion of the water that would be better used to cool the air.

I too have a question, can their be a point where cooling would make loose power instead of making some??

Yes there is a point of dimishing returns, as the intake mixture gets colder and colder it becomes more effecient at drawing heat from the intake manifold etc. The result of this is it gets very difficult to get and maintain very cold intake temps.

In theory a drop in absolute temperature should be as effective at increasing power as an equal increase in pressure but that is not the case. Most mathmatical simulations vary the power at the square root of the temperature for a couple of reasons. Critical flow through an orfice is determined by the local speed of sound, hot gasses have higher sonic flow speeds and during the low lift portion of the intake valve where the pressure ratio across the valve exceeds 1.89 ( the pressure ratio required for critical flow) a hot intake charge will flow faster than a cold intake charge.

Also the issue of heat pickup from the intake and manifold and intake valve becomes more important as the intake charge gets colder. For an extreme example -- suppose you had an intake charge that was at 400 deg F, -- your 180 deg F intake manifold would now act as an intercooler and draw heat out of the air charge rather than warm it.

It seems based on those issues that density gained by lower intake charge temperatures is not as useful as the same density change achieved by increased pressure. (ignoring the change in detonation sensitivity)

Your VE will go up due to the cooler denser mixture but at some point you need to modify your ignition timing to compensat for the slower inital period of combustion.

There is a rule of thumb in chemistry that every time you increase the temperature by (IIRC) 10 deg F, the speed of reaction doubles. In the first moments of ignition the spark forms a kernal of flame about the same diameter as the spark plug gap. This small kernal has very little volume and lots of surface area, so it loses heat rapidly. It grows slowly (compared to normal combustion) for the first few milliseconds of the combustion stroke before it warms the surrounding fuel air charge up enough for very rapid combustion to take place. It then grows exponentially until a large fraction of the fuel air charge is burning.

If the fuel air charge is too cold, it is difficult to create and maintain a combustible mixture because the gasoline only burns when it is in vapor phase. The dropplets effectively only burn on their surface as they warm up enough to release combustable vapors. (one of the advantages of the propane is it side steps this issue due to its very low boiling point being essentially 100% vapor when it enters the combustion chamber).

If you cool the mixture too much you need to richen up the fuel air ratio to maintain combustion ( thats why cars run rich mixtures on cold start conditions). You also need to add ignition advance to compensate for the slow combustion process to maintain MBT timing.

Larry