If the IAT sensor is located on the intake manifold people say it gets heat soaked. Lets talk about what that means. The IAT sensor is not metal so its not getting hot per say so how is it reading so high? Well when the throttle plate is closed the air in the intake manifold is getting hot therefore the IAT sensor is going to read high and the ECU is going to see this and react according to the tune.

If you move the IAT sensor in the Aftercooler and get the air temp right at the cooler then you get temps that are actually cooler than the air going into the intake manifold. Yes the small distance does make a difference as I have tested this on a number of applications.

If you put the IAT sensor right before the throttle body and not after it you will get a happy medium between temps right from the aftercooler and temps within the intake manifold post throttle body.

So the other comments made are what happens when you move the IAT sensor pre throttle body and that initial heat soaked air (which is not being measured by the IAT sensor) from idle gets sucked into the motor wont you knock and hurt your motor? The reality is at the end of the day your tune MUST be setup correctly no matter where the IAT sensor is. The easiest way to tune is for it to be right before the throttle body but you can tune for any of the other situations as well if boost levels are low enough. In this users situation moving the IAT sensor is probably a good idea (he is running a ton of boost for a SC) if he also intends to correct the tune and ensure his BOV is sized and setup correctly. Assuming the previous comments are correct the initial hot air being ingested is not under boost as you are just getting on the gas so knock is not a big factor when there is no real cylinder pressure as of yet. Obviously you dont want to see a ton of knock or any but if there is not cylinder pressure there isnt going to be damage.

 

Now for the money question... where would I install the meth injection nozzle it my iat sensor is closest to the throttle body? How far away should it be?

 

Doesnt have to be to far but not right next to it and it must be before and not after the IAT sensor.

 

Like how far apart?

 

6 inches +

 

For the best iat effective cooling with a dense intake charge, you want the nozzle back far enough from the TB to mix with the incoming air before it gets sent into the cylinders, generally 6" before the TB will suffice. The size cc nozzle you use and the pump pressure also play an important part in getting good atomization, so thats a consideration. I found with my set up that the larger 550cc nozzle was doable at the standard 150psi, but I would have rather had a 450cc available to me which I did not. The next size down I tried was a med/330cc and it had really great atomization, good enough to almost inject right into the cylinders, but it just wasnt enough volum to be as effective as I wanted. Part of compensating for possible deficit in atomization quality, wile still getting the cooling I wanted, was to lean a bit heavier on the meth ratio mix. I liked to run 60/40 or even 70/30. When I switched to my custom direct injection system i was using 180cc nozzle in each manifold runner and stuck to the higher meth %. You have to be mindful about how much water volume your injecting into the cylinders, making sure its well mixed or you can damage the engine. Meth cools as well, but unlike water it also burns.

 

Great info here and to add to the point about the pump being at 150 psi is spot on in that you really want a pump capable of 200+ psi to get good atomization. Standard 150 psi pumps have a quick limit.

 

All great info here guys. I just completed a Kraftwerks C38-91 install on a 07 AP2 and I'm considering water/meth injection before sending the car to the tuner. I have a couple of questions though if you guys wouldn't mind providing some feedback. I live in FL just for an ambient temperature reference.

1. Can this safely be used without a stand-alone ECM? The stock ECM wouldn't have a "boost safe" mode if the pump were to malfunction or if flow were restricted.
2. Expected gains?
3. Recommended kit/setup?

Thanks in advance!