Yes :smile: , small clarification here: it's not that you will NOT see any EGT drop, such a sweeping statement for WI would be *really* wierd :lol:
What I'm saying is that you won't necessarily see EGT drop in each and every case (although conventional wisdom would indicate otherwise)
I remember reading in the old lab tests where they were pouring LOTS of water (compared to fuel) that EGTs were not affected that much. Detonation is eliminated ofcourse.

Anybody else have input or experiences with their pre-compressor systems?

It's getting towards winter time here in the frozen north and I need ideas for next years setup. :cool:

I`m going to give it a go, got some material ordered to knock up a pair of jet holders, similar to Richards install on the Skyline.

My car runs out of boost at 6000+ rpm (only holds 12psi to redline due to small 9b turbos), so first measure of any sucess for me will be higher boost. I`ve got some 1/4 mile info to compare results also, so the next test will be the trap speed with pre-turbo injection.

I`ll try and get some good pictures of the compressor wheels before fitting the injection, to give a starting point for the condition before and after.

How my car/ system is set up I`ll have to be using a 0.9-1.0 nozzle on each turbo to keep my tune close, can always re-jig if it overcomes the turbos, if it runs well on 1.0 jetting I can directly compair the results to mylast 1/4 mile info as I`ll be injecting the same amount of water/methanol.

Keith,

Excellent, please take as many pictures and measurements as possible :cool:

Definitely keep us posted on your results. The more info the better as pre-compressor injection works great "on paper" but seems to need some tweaking and R&D in practice.

You're planning on running a .9-1.0 nozzle on each 9B Mitsu turbo?! (6G72? Since you mentioned the 9B's) That nozzle seems awfully large for that small of a turbo and boost level. A few pages back hotrod runs through his experiences with injecting too much water pre-compressor. May want to take a browse back there.

compound compression
 

so I've kept up on this thread for a few years, and now have a variant for you all. masterp2 shares some interest with me from another site, as well as being an owner, like me, of a diesel. I run a compound compressed 5.9l cummins. Low pressure turbo is a BW BHTB3 currently peaking at 37 psi absolute. High pressure turbo is BW S3A with a self made variable turbine. post high pressure turbo boost peaks at 82 psi absolute. An OEM aftercooler is employed post secondary, and no current compression stage intercooling is present, chemical or otherwise.

I have experimented with precomp WI in the past, and have recently been motivated to continue the R&D, but have some questions requiring your input. Knowing the harsh operating conditions the high pressure turbo operates under such as blistering inlet temps, having to ingest and compress a second stage of charge hovering in the 90 lb/min range, there is definite room for improvement in the high pressure turbo efficiency. Because of of the heat present in the inlet in excess of 350*F, my goal is to drop this temperature as drastically as possible. For lack of room for a second charge air cooler (CAC), in addition to the reluctance of adding that much more intake tract in an already dizzying amount of intake tract volume, precomp WI is my choice. Now for the nuts and bolts. I had previously experimented with WI at the inlet of the secondary charger with varying results and crude fabricating. I now wonder, after reading all 25 pages over again, if my purposes wouldn't be better suited by injecting pre-primary turbo? Two things come to mind...firstly, injecting at ambient pressure, with the minimal depression at the primary's inlet, vs injecting inter-stage, where the environment pressure is 37 psi and 350*F. Which would be more beneficial I wonder...injecting in a hot, pressurized environment, or the adverse, pre-primary turbo?

Additionally, I am talking about large quantities of water/meth, and am going outside convention regarding injection pressures and nozzle types. In my first attempt, I utilized furnace nozzles. High flow rates, and a hollow, spiral, 45* cone, placed an inch in front of the secondary's compressor wheel. I raised the nozzle's spec operating pressure from 100 to 200, hoping for more flow, and a higher atomization rate. I plan on going the same route, but with a different pump. I plan on belt driving a 3 stage high pressure pump on a clutch in excess of 1000 psi, or as much as 3000 psi. These pressures, of course, will be dictated by what the nozzles can handle, and some pretty crucial testing will take place on the bench before any mounting will occur. My initial thought is if I can find the nozzle will hold 1000+ psi, atomization rates should be quite high. The other option , of course, is a lower pressure system with narrow angle hollow nozzles that will provide high spray quality. I wouldn't mind going narrower than 45*, as this would allow me a little more space between the wheel and nozzle. All my findings in the past showed me that a hollow cone that avoids the wheel nut, yet is narrow enough and close enough to enter the wheel in its first 1/4' inch of radius showed no signs of erosion of impingment in the 10,000 or so miles i had it operating....at maybe a 30% to 50% duty cycle (I have a lead foot and see high boost frequently hehe).

All I need to do now is affect an injection system that will yield an efficient nozzle arrangement, and maintain that efficiency at say 20 gal/hr!?!? Is it feasable?

Chris

Air Atomizing Nozzles
 

Okay, after looking at all of the fantastic responses on here I am convinced of the effectiveness of pre-compressor injection as a way to maintain the spool up of a small turbo while getting good top end performance. That being said, I am concerned about impingement.

I've just spent the last couple of hours on the Spraying Systems Co. website, and am very interested in their flomax air atomizing nozzles. Autospeed has an article about water injetion using one of this companies air atomizing nozzles using boost pressure as the air source. The Flomax nozzles work on pressures as low as 5psi, which I'm assuming is a pressure differential, so it means less than 5lbs of manifold pressure since the turbo is creating a vacuum on the intake side. They also are available in pretty small diameter spray patterns, and they make a 90 degree lance. I'm thinking that one could place the lance not far from the compressor, with the nozzle directed right at the center of the wheel. The fine spray (around 30 micron max from what I gather) combined with a targeded spray at the center of the wheel should make impingement negligable. They also produce nozzles that can be pulse width modulated like an injector.

how would you control such a system? I was thinking a small pre-compressor nozzle at high boost and rpm, and a larger nozzle (not air atomized) just after the intercooler that would be on more than the pre-comp nozzle.

I`ve had a good look at my setup and think if I go directly before the turbos the jet holders will cause too much of a restriction to the turbo, plus if I need to service the jets it`s a big job to get to the rear one.

My other option is to inject after the MAS meter (draw through type) with 2 jets on a T to feed both intake pipes to the turbos, the pipes are aprox 2 foot long each. It won`t be as good as direct spray at the compressor centre but 0.3mm jets will hopefully atomise well before they hit the compressor. This setup would be simiar to the wetted airfilters that`a been talked about already on here.

May have to increase the jet sizes to get a noticable effect but that would just mean pulling out the MAS which is a 2 minute job.

Will keep you all updated as I go.

accre:

I too looked at the air atomizing nozzles. If they utilize boost pressure air that has already been metered then they look like a good bet. I was reluctant to try them in a MAS metered car because any air injected post MAS is unmetered and could damage the tune significantly. If you are running SD you can of course ignore this.

keithmac:

My only concern ith what you are suggesting is that whilst injecting further from the turbo allows time for atomization, there is a very high risk that those tiny droplets will het the sides of the intake where surface tension will lead to many attaching themselves to each other forming larger droplets that will damage an impeller. Safety really does rely on a sufficiently well atomized spray injected staright into the impeller.

I also seriously like the idea of the hollow cone spray avoiding the nut on the impeller shaft altogether and going straight into the blades. That sir is genius!