Originally Posted by JohnA

Remember that intake temps consistently below 20C at the throttle will rob you of power. If that is true under boost as well, then you're compromising the engine's efficiency.

Originally Posted by SteveR32GTR

interesting. is that 100% fact even with forced induction?

on various cars ive had i always fit the charge temp sensor at the throttle and the car seemed to go better the colder the temps were, even way below 20degC on some stupidly cold nights (and very good IC/WI setup, lol).

id almost be inclined to say thats true in n/a form where you havent got boost pressure messing with the fuel/air mix, but on turbo cars?

Originally Posted by rotrex (Post 22044)

Having done some experiments with pre compressor injection last summer and fall, I can add a little to this.
Rotrex C30-94, jets tried: Aquamist 0.3 and 0.5mm. Mix 50:50 water methanol by weight.
IAT is measured after a water cooled charge cooler half way before entering the intake plenum. Throttle body is before the SC. Boost is 0.83 bar at 7000 rpm.
There is almost no influence on boost. At least nothing I can distinguish from effects of ambient temperatures. So all constant within a few percent.
The air temperatures drop as you increase jet size. Going from 0.3 to 0.5 mm introduced IAT fluctuation that got worse as ambient temps were lower. The sudden nature of those drops, you can see this effect also in the original data plots of this threat, can in my opinion be attributed to condensation in the charge cooler. The big droplets hits the IAT sensor, it has a little frame around it, evaporate and cool it down. Once the droplet is gone, it heat up to the air temp again. The fluctuations go worse as ambient temperatures dropped and as jet size increased. You feel the car modulate its acceleration as the ignition timing was advanced and pulled accelerating though a high gear due to the ignition air temperature corrections. The data logs show only some of the fluctuations, but not all of them compared to the felt fluctuations. The data rate recorded on the PC is too low.
To confirm, I removed the correction and the feelable effect was gone, but the log stills shows the fluctuations. On a 40C ambient day last summer, there were virtually no fluctuations a served with IATs as has 70C.

The observation of the original poster was that the throttle plate temp vs CC output temperatures dropped as flow increases. This is clearly a indication of evaporation.
At 50C turbo exit temperatures, much of the water and part of the methanol are likely still in the liquid phase, the charge cooler condenses the stuff further.
This big droplets collide with the wall at any bend or any obstacle, and cool is via evaporation. Unfortunalty, due to this effect, little of the spray arrives in the cylinder and mist.
During a rebuild with direct port jets on top of u-turn plenum runners. I could see the traces of the water stream on the front part of the combustion chamber and piston tops. These areas were light brown vs black.
Since moving the direct port jets on top of the plenum, but right behind the fuel injectors in the flat section, I needed to add more ignition advance. A clear sign that more mix effectively arrived in the combustion chamber as mist and not a fluid stream.

Once someone goes to significantly higher boost levels, the corresponding turbo exit temps of well above 100C or even 150C will evaporate much more fluid thrown at it. Riceracers setup is a good example. Condensation in the chagre cooler will still be present, but to a lesser degree.

Overall my little 0.3mm jet used now drops the IATs a tad, but the main work is done by now 4x 0.4mm c-type (150 ml/min) direct port jets.

Originally Posted by rotrex (Post 22044)

Having done some experiments with pre compressor injection last summer and fall, I can add a little to this.
Rotrex C30-94, jets tried: Aquamist 0.3 and 0.5mm. Mix 50:50 water methanol by weight.
IAT is measured after a water cooled charge cooler half way before entering the intake plenum. Throttle body is before the SC. Boost is 0.83 bar at 7000 rpm.
There is almost no influence on boost. At least nothing I can distinguish from effects of ambient temperatures. So all constant within a few percent.
The air temperatures drop as you increase jet size. Going from 0.3 to 0.5 mm introduced IAT fluctuation that got worse as ambient temps were lower. The sudden nature of those drops, you can see this effect also in the original data plots of this threat, can in my opinion be attributed to condensation in the charge cooler. The big droplets hits the IAT sensor, it has a little frame around it, evaporate and cool it down. Once the droplet is gone, it heat up to the air temp again. The fluctuations go worse as ambient temperatures dropped and as jet size increased. You feel the car modulate its acceleration as the ignition timing was advanced and pulled accelerating though a high gear due to the ignition air temperature corrections. The data logs show only some of the fluctuations, but not all of them compared to the felt fluctuations. The data rate recorded on the PC is too low.
To confirm, I removed the correction and the feelable effect was gone, but the log stills shows the fluctuations. On a 40C ambient day last summer, there were virtually no fluctuations a served with IATs as has 70C.

The observation of the original poster was that the throttle plate temp vs CC output temperatures dropped as flow increases. This is clearly a indication of evaporation.
At 50C turbo exit temperatures, much of the water and part of the methanol are likely still in the liquid phase, the charge cooler condenses the stuff further.
This big droplets collide with the wall at any bend or any obstacle, and cool is via evaporation. Unfortunately, due to this effect, little of the spray arrives in the cylinder and mist.
During a rebuild with direct port jets on top of u-turn plenum runners. I could see the traces of the water stream on the front part of the combustion chamber and piston tops. These areas were light brown vs black.
Since moving the direct port jets on top of the plenum, but right behind the fuel injectors in the flat section, I needed to add more ignition advance. A clear sign that more mix effectively arrived in the combustion chamber as mist and not a fluid stream.

Once someone goes to significantly higher boost levels, the corresponding turbo exit temps of well above 100C or even 150C will evaporate much more fluid thrown at it. Riceracers setup is a good example. Condensation in the charge cooler will still be present, but to a lesser degree.

Overall my little 0.3mm jet used now drops the IATs a tad, but the main work is done by now 4x 0.4mm c-type (150 ml/min) direct port jets.