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Old 09-11-2018, 01:02 PM   #1
PDXREALTOR
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Default Placement of nozzle

I'm on speed density using the gm IAT sensor. I'm adding a snow performance stage one kit for cooling.

I'm wondering how far before the IAT sensor I should put the spray nozzle?
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Old 09-12-2018, 09:25 PM   #2
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Old 09-12-2018, 09:35 PM   #3
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Edited to address your edit ^^ I saw that - but it doesn't take into account speed density.

Since I post that question I've done nothing but read, which just mind f**ked me more. Actually, there are arguments that make sense for before and after the IAT sensor on speed density.

I decided the tie breaker would be asking my tuner (actually more of a mentor in a way at this point as I have been tuning myself for a few months) and he said the best place for the nozzle was as close to the throttle body as possible. I'm guessing he remembers I'm on speed density.

However, since then SNOW performance replied back to the same question and said the main thing is to have the IAT read the actual charge temp. This would mean placing the nozzle before the IAT sensor as the charge temp is cooler, the air is denser.

I also stumbled across a post from Aquamist. I will post it here in a few.

In my mind, which seems to always steer towards logic, it makes more sense to have the IAT read actual temps. If the tune gets messed up, it will get fixed. Just like anything else that requires a re-tune.

In my case I'm not after any of the octane raising benefits (of which getting the methanol as close to the CC as possible would be ideal. I'm after cooling. So, injecting before the temp sensor and keeping a true 'air density' calculation and IAT makes the most sense to me.

I'm always open for more input. Don't be shy.
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Old 09-12-2018, 09:39 PM   #4
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I'll correct myself - this was found on the AEM meth injection forum and reposted elsewhere -

Quote:
Nutz, you bring up some very good points that highlight the general misunderstandings that many people have about water/methanol injection. First, when a liquid changes state and becomes a gas the change is endothermic meaning that energy is absorbed and in our case the energy is the heat in our air charge. So, as the atomized water/methanol vaporizes it absorbs heat from the air charge which in turn cools the air charge. In my years of testing and tuning water/methanol injection systems I've seen IAT reductions as large as 100 degrees F.

Now, following the Ideal Gas Law, which is further supported by Charles' Law and Boyles' Law, we know that when you cool a gas it condenses and its volume decreases for a constant mass so effectively, a gas will take up less space when it is cooled. Obviously our volume constraint is fixed (volume of intake manifold, intake ports, combustion chamber, etc, stays the same) so with a cooled and condensed air charge we are able to essentially increase the mass of air that will physically fit inside our engine. When you increase the mass of something while keeping its volume fixed you increase its density, not decrease.

The suggestion that water displaces oxygen to a point where the density of the air charge is decreased in this application is incorrect. It is generally understood that water vapor will in fact decrease the density of air IF and only IF there is no change in pressure or temperature. This is obviously not the case with water/methanol injection as the temperature is significantly decreased which thereby increases the density of the air charge which greatly offsets the potential displacement of air when introducing water vapor into the air charge.

This will be the one and only time I post this information. These points are unargueable and can be verified in any high school physics book. The merits of water/methanol injection have been well reviewed and documented by people like Sir Harry Ricardo and organizations like the Society of Automotive Engineers for decades. There are countless resources available if you should choose to further research this yourself.
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Old 09-13-2018, 11:14 AM   #5
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Also with the post intercooler, obvious point that I'll restate, the further it is placed from the actual cylinder, the more time it has for phase change.

Similarly, the closer to the cylinder for the temp sensor, the more accurate your intake temp will be.

Last edited by Homemade WRX; 09-16-2018 at 12:37 AM. Reason: Because temp sensor
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Old 09-13-2018, 02:50 PM   #6
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How will moving the nozzle closer to the cylinder give more accurate intake temp readings?

I am moving my iat up closer to the throttle body, or am even considering back of intake manifold.
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Old 09-13-2018, 06:00 PM   #7
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IAT in the manifold where with access to flow, I pointed it out for you in your other thread
nozzle on the outlet of the IC as far from the TB as possible for better atomization time
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Old 09-13-2018, 06:15 PM   #8
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Just got done tapping the manifold for the iat sensor. I used the old pcv port just next to the spec location.

Thx for the motivation. 👍
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Old 09-15-2018, 11:03 PM   #9
badaily16
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Default Placement of nozzle

I have my iat sensor about 6-7inches from the throttle body. My single meth nozzle is right after the intercooler and there is about a 3- 3 1/4ft separation between the iat and meth nozzle. With this setup we had no problem with tuning and the methanol seems to be atomizing well before it passes the iat.
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Old 09-16-2018, 12:38 AM   #10
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Edited my post above. Closer to cylinder the temp sensor is....
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