I see. Now that's something new to me actually. I was always under the impression that any amount of water in the cylinders would eventually cause hydrolock/damage to the motor. Could you please explain exactly what you mean by little water? Are we talking about water in liquid form or just the relative moisture in the air?
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Last edited by Harris : Jan 22nd, 2004 at 01:07 AM.
I see. Now that's something new to me actually. I was always under the impression that any amount of water in the cylinders would eventually cause hydrolock/damage to the motor. Could you please explain exactly what you mean by little water? Are we talking about water in liquid form or just the relative moisture in the air?
OK. I understand that water injection helps lower the air-fuel charge temperature to prevent detonation.
How about if I only cool down the fuel before mixing it with the air?
Would that also help prevent detonation & probably reduce the fuel octane requirement?
VERY VERY VERY small amount... the difference being the fuel temperature is immediately shot up to the point of combustion so why bother cooling it... the air is the part of the mixture you're concerned about because you know that the combustion of the fuel is going to release X amount of energy as heat anyways.
I was thinking that the chilled fuel would also help to cool down the air as they mix, and that would help create a denser & cooler air-fuel charge prior to combustion. Of course, the fuel will release heat energy during combustion, but if the air-fuel charge temperature was initially lower, wouldn't the peak combustion temperature would also be lower for the same amount of heat energy released?
How cold are you planning on chilling this air? YOu planning on freezing it? Like I said before it will help a little bit but never as much as nitrous, propane or any liquid-gas reaction.... you freeze the line and you freeze the gas... so how cold can you get it? And remember the ratio of air to gas 14:1!! The air has anywhere from 12-16 times the amount of fuel... think this through yourself...
The thought here is to cool the fuel to probably 10 degrees below the ambient temperature and reduce the chances of detonation.
Like James said, you've got anywhere from 11-13 lbs of air for every lb of fuel, so cooling the fuel is not going to be anywhere near as effective as cooling the air. Cooling the fuel only 10 degrees below ambient won't even have a noticeable effect, I would guess.
sometime "keeping it simple" is the best route to go. a well built air to air core will work very well on the street and is much less hassle than an air to water setup.
here's a buddy of mines car. civic, ls-vtec, 60-1 turbo, 20*8*3 extruded core FMIC, 2.5 in. IC piping. this graph was at about 17psi on a 105 deg day @ around 2:00pm in AZ. you can see the "heat soak" effect as the car idles, then how quickly the charge temp drops as flow across the FMIC increases
here's a little data from my car. b13, DET, FR T3/T67 turbo (T04R compresser wheel), 20*11*3 garrett extruded core anodized black, bumper covers almost 1/2 of the FMIC this graph was at about 17psi WOT on a mid 70's deg night/morning at 3:30AM here in AZ. i dont have my wheel speed sensor hooked up yet, but this graph represents the data while boosting 3rd and 4th gear WOT in the middle of the desert with no traffic around. you can see that the charge temp drops as soon as i start accelerating or boosting
Like James said, you've got anywhere from 11-13 lbs of air for every lb of fuel, so cooling the fuel is not going to be anywhere near as effective as cooling the air. Cooling the fuel only 10 degrees below ambient won't even have a noticeable effect, I would guess.
My primary concern is to prevent detonation without needing to use costlier high octane fuels. Just thinking that cooling the fuel would do it.
I believe water injection got its start during the era of piston engined airplanes in the 1940s (mostly during World War 2) where it was used to help avoid detonation at higher boost pressures for that short spurt of power. These aero piston engines (with forced induction of course) were already intercooled (they used to call it aftercooling) but wasn't enough to prevent detonation at higher boost levels. So, it does look like that water injection was originally meant to help complement intercooling.
yeah, now that ive done more research, I have to wonder, would watercooling almost be a "cheap way" to get the effects of higher octane gas, without having to pay the extra 20c a gallon
My primary concern is to prevent detonation without needing to use costlier high octane fuels. Just thinking that cooling the fuel would do it.
I believe water injection got its start during the era of piston engined airplanes in the 1940s (mostly during World War 2) where it was used to help avoid detonation at higher boost pressures for that short spurt of power. These aero piston engines (with forced induction of course) were already intercooled (they used to call it aftercooling) but wasn't enough to prevent detonation at higher boost levels. So, it does look like that water injection was originally meant to help complement intercooling.
If you're concern is that water injection would do much better than trying to chill the fuel. The latent heat of vaporization of water is very high and does much more for cooling the intake charge than fuel.
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