Nozzle location on a supercharged car

[Redfire427]

Hey folks,

I am researching to get all my facts straight before I do an install of a methanol injection system. I have a 2007 Roush 427R Mustang that has a roots style positive displacement blower. I read the installation instructions for the 1 gallon kit and It specifically states that the injection nozzle MUST be placed before the throttle body. As you know, a blower generates a lot of heat and I believe adding a methanol system will help me reduce the chance of detonation and possibly make a bit more power with a re-tune. My intercooler is directly below the blower, and my thoughts were to place the injector in the intake manifold directly below the blower so that I inject the methanol after the blower and allow it to go through the intercooler. I would think that this method would provide the best cooling.

Is there something wrong with my reasoning or is there some specific reason that it must go through the throttle body? I just see no reason to heat-up the methanol by running it through the blower. I believe this will reduce the overall cooling effect.

Please give me your opinions and help.

Thanks in advance,

Carmen

[NS]

Positive displacement blowers are an entirely different animal when it comes to efficiency and output.  Normally, we don't recommend placing a nozzle pre-compressor on a turbo but truthfully Roots-type blowers are actually better off having the injection point pre-compressor rather than post.  The cost and complexity to add nozzles into your intake manifold greatly out weighs any potential (if any at all) benefit over putting the nozzle ahead of the TB. 

You're reasoning is actually just reversed.  The water/methanol helps to absorb heat and the best place to do it is right at the source.  Remember, to anyone else reading this, this only applies to POSITIVE DISPLACEMENT SUPERCHARGERS! 

One caveat that I've found to running water/methanol injection on a Roots-type blower setup is that you almost always need twice as much fluid flow as normally recommended for a turbo setup.  This is especially true at higher boost pressures.  While Roots blowers are great for instant response and tons of low end torque they are pretty inefficient as an air compressor and they really heat up the air charge.  Water/methanol and positive displacement blower work GREAT together.  To run a second nozzle I suggest checking out our Injector Nozzle Kit AEM Part #30-3012.

[Redfire427]

You have me somewhat confused with your response. The sole purpose of injecting methanol/water mix is to absorb heat and increase octane rating. How could injecting it post blower be ineffective? My car has an intercooler which is post blower. How is this any different? As for the cost for installation, that is a non-issue as I am a machinist and can perform the necessary machining with my eyes closed. I have already dis-assembled the manifold and there is a perfect location at the front and rear of the manifold for the injection nozzles to be placed. The spray will be directly over the intercooler. Based on other information I have received, my intentions are to spray with two 225ml/min nozzles after the blower, and one 60ml/min nozzle in the intake elbow between the throttle body and the blower. Are you saying this set-up will be ineffective? Why would it be necessary to spray the meth before the throttle body?  I don't want to do this twice as the tuning cost is not cheap.

[NS]

A major player in the systems ability to reduce intake air temps is time.  We don't just blindly recommend placing the nozzle ahead of the throttle body; we specifically recommend placing it there because it generally gives the best compromise between air charge cooling and detonation control.  Introducing the fluid at a certain distance away from the intake port gives it enough time to vaporize and absorb heat.  The closer it is to the port the less time it has to reduce air temps. 

Intercoolers are a problem when it comes to water/methanol injection.  The internal air passageways present a huge surface area where the little droplets of water coming from the nozzle like to collect and puddle.  So instead of a nice finely misted spray you get big drippy droplets of water.  Big droplets of fluid can't absorb heat like billions of tiny droplets can.  Big droplet of fluid also aren't carried as easily in the air stream and you'll get uneven distribution of fluid across all the cylinders which is undesirable.

Injecting the fluid ahead of the blower allows it to fully vaporize and pull as much heat from the air charge as possible.  Another beneficial side effect is that running water/methanol through the blower helps to cool and lubricate it.  It also increases its sealing efficiency and you could actually see a small increase in boost at the same RPM.  In almost every Roots-type blower install I've ever done I've seen an increase in efficiency and longevity from the supercharger. 

Our system is also not designed to have the injection point in an area of high vacuum like you would have post-throttle body.  It is quite possible that during deceleration there would be enough vacuum to crack open the check valve and suck fluid into the intake which again would be undesirable. 

Your suggested total flow rate of about 500 cc/min will simply not be enough for this application.  I whole heartedly suggest using two of our big nozzles and placing them ahead of the throttle body.  I've done extensive testing on applications like these and I highly recommend going this route for the best possible performance gain.   

[Redfire427]

I truly appreciate the time you have taken to respond to my questions with some technical info. I am trying to educate myself and completely understand the "technology" so that I can make the best decision I can based on my requirements. I have received conflicting information from "other" methanol injection system suppliers and I am trying to make some sense of it. Competitor "A" says the cost to install post blower would not be worth it, however, once I explained there is no cost as I am doing all the work myself, they state post blower would be great. Competitor "B" says use one large nozzle before the blower and another after the blower. Now, your comments state both of my nozzles should be placed before the blower. As you can see, I have 3 completely different trains of thought from the "pros" and I must make a decision as to what is the right way to go. I would have no hesitation to test different locations and volumes of nozzles, but the tuning cost would be horrendous.

As for your comment about creating enough vacuum on deceleration to open the check valve, I fully intend to install a solenoid right before the nozzles to prevent this. Would this address your concerns about this, or, is the check valve and a solenoid the same thing?

My main reason for wanting to install a methanol injection system is because I track my car at the road course and the car sees a ton of high rpm. As I am over-driving my blower to the design limits, I am producing a tremendous amount of heat in the intake. Although I would like the system to provide me with a little extra power by allowing the tuner to advance the timing a little, my main goal is to reduce the air intake charge temperature to create a somewhat "safer" condition for my engine. Detonation at my current tuning level would be catastrophic. Obviously, I am taking action to to prevent that situation from happening.

I am a very technical person and I like to base my decisions on physics rather than opinion, which is why I appreciate your advice about possible issues. I guess the way I could look at it is that my air intake temperature is lets say 200 degrees. I have 3 possible scenarios to inject. All of them will lower my intake temperature to some degree, but one of them may be more beneficial than the others. Is this a fair comment?

[NS]

I'm sure if you asked 6 more "pros" you'd get 6 different answers.  In the years that I've been doing this I've found that there is usually little to no measureable benefit in having multiple nozzles in different locations when you can have one or two nozzles in the same general area.  In the end the net amount of fluid being injected is the same.  You can throw physics at it and theorize about it as much as you want but in the end there is very little difference and knowing this comes from experience.  And to another point, the general thought is why spend more time and money when the outcome is the same?  Making something more complicated and involved doesn't always make it better.

On a side note, we don't provide a solenoid in our system so we won't ever recommend mounting the nozzle somewhere where a solenoid is required.  If we felt using a solenoid was a better approach we would include one in the kit but then it would cost more.  Using the kit in a way that requires extra components or major changes to the installation procedure is using the system outside of its intended and engineered use. 

On another side note, I helped a customer with a GT-500KR track car and he too was seeing major intake air temps.  He had done the standard install and wasn't seeing the normal results everyone else was reporting.  Knowing that his Kenne Bell blower was making something like 20 psi of boost with the barely upgraded intercooler and knew his IATs were unbelieveable high.  It was so bad that he couldn't even finish a full session on the track.  I think we wound up going to 3 nozzles right ahead of the throttle body before the temps finally came down.  We didn't pull the blower and we didn't put any nozzles in the intake manifold.  It made a night and day difference for him and he finally was able to push the car to its full potential.  This was something he couldn't have done without water/methanol.   

[Redfire427]

Thanks again for the reply and also your experience. I have chosen to follow your advice and inject into the intake tube rather than into the intake manifold.

Two questions:

What difference does it make if you spray in front of the throttle body or just after it, and why?

In the example you wrote about above, what size nozzles did you use?

Thanks again.

[NS]

No real difference in performance injecting from either before or after the throttle body.  The problem is that under high vacuum there is the chance that fluid could be siphoned from the nozzle if it's mounted after the throttle body. 

Nozzles used on the KR were two 550's and one 330.