I have seen it mentioned, and most say that this actually does happen. But what actually happens? Any proof or testing been done?

Im running a 50/50 mix right now post turbo and i will be adding a Pre-turbo injection as soon as UPS drops off a few boxes that are on the way. One major reason i am adding the pre-turbo is for the effect it supposedly has on the smaller turbos. As i am running a modified stock turbo (similar to the BNR stage 2).

From what i have read, it "shifts" the compressor map. Meaning, a smaller turbo will have its same great low end spool and give better torque numbers. But in the top end where it would normally start to die out, it breathes new life by having the compressor map itself shift higher. Having the effect of a larger turbo in higher RPMS...

What is actually happening here?

 

the talk about that has been the change in output heat from the turbo's pressurized charge. basically making it SLIGHTLY more efficient for the high end. so basically if your turbo is 78% efficient the addition of the pre turbo water absorbs the heat DURING compression to increase efficiency rating lets say to 82% at that point well now you can take the turbo up higher on the map because of the increase in efficiency or basically les heat put into the charge letting you get more VOLUME of air as its cooler upon exit. thus extending your compressor maps islands I.E. shifting map.

also there was a thread that used big words for it like...... making the turbo more ISOTHERMAL compression as opposed to the normal ADIABATIC compression it has.

z

 

heat is the reason why a compressor becomes less efficient at higher boost levels, and water injection takes the heat out of the compressor. turbos do have the ability to produce higher levels of boost than they are rated for, they are just out of their efficiency range, because of the heat.

i remember rc72r mentioned he had a car running a 35r at 30psi somewhere on this forum.

I'm extremely interested to know if this really just means that having a bigger turbo is as simple as using water injection.. which is a good idea anyways.

 

Hmmm, very interesting!

 

I did a back to back a while ago. I moved the injector from after the inter cooler to in front of the turbo. It actually made less power in front of the turbo, even though the intake temps were lower. Same jet...Going to try and repeat the test a few more times...

 

How much less power?

I guess it would make sense, that it would produce a bit less power pre turbo. The water might slow down the blades marginally.

I guess if it raises the efficiency with pre turbo, you could then increase the boost.

Finally can you explain how you did the back to back testing?

 

what mix was this? I'm sure that would play a large role in this...

But i did do a run with AI, then unplugged it and ran without the 50/50 mix. Change was almost nothing. i lost 2hp without it. But i did the run back to back instantly. And the engine was probley much hotter and that might of effected the hp loss. This was post turbo, pre-intercooler.

damn, so many variables...

 

It was 50/50. I did several pulls on the dyno with the jet after the inter cooler only. Then I pulled it out and ran the extension hose I brought with. I then plugged it into the bug before the turbo. Then I did another pull. I want to say it was 10rwhp, and about 3/400rpms in spool time..Pretty straight forward test.

 

man, that's a big loss... I don't see why. The only thing i can think of is the fluid slowing the compressor blades down. But i dont see how that would make it lose power.

When do you plan on doing some more testing? I have my Pre-turbo stuff and i'm ready to throw it on, but your making me second guess this whole pre-turbo thing.

 

If you did back to back runs a 10HP drop could be because of the car starting to get warmer. I might be wrong but I believe when I did back to back runs without changing anything the first run was always the best.

You mentioned you did several runs then switched.....

 

That wasn't an issue. I did over 30 passes that day and never had any real change in any temps( air/oil/water). Like I said the test needs to be done back to back several more times..

 

I think you will lose some power, BUT you will be able to run higher boost levels with the preturbo setup due to the heat loss.

 

Could the drop in h/p be because the water vapor hitting the blades of the turbine... I also worry about wear on the leading edge of the blades.... anyone care to chime in

 

its been said anything bigger than 15micron will damage the wheel just like a waterjet does in cutting metal. but in all the treads iv seen on it the only ones actually destroyed they couldnt prove it was water injection or it wasnt perfect when installed so inconclusive... for the most part i did see one which was said to be water related but the guy had like 40-50k miles on it last i remember. but i do believe in the larger droplet will damage your 100k+ rpm comp wheel yet i still have every intention of running it with my aquamist kit along with post intercooler then also direct runner in the secondarie a few inches up from the sec injectors.

z

 

If there was a compressor wheel speed drop due to the water, wouldn't the waste gate just close a bit and bring the speed back up?

And what size jet did 1revvin7 use? The pre-turbo injections usually run less CC/min.
Maybe add a third test option of splitting your current jet size into two jets and spraying half pre and half post.

Also, @proz07 who said 15 micron or larger does damage?
I don't think anyone's mechanical pre turbo injection has produced droplets that small?

What about pure water vs 50/50 in regards to compressor wheel damage and atomization properties?

 

Back from the dead.

 

If you read through tom94rx-7 s post on his tests you would have some answers.

Spraying pre-turbo will slow down spoolup which we expect to happen as the fluid being compressed is now more dense and thus takes more power to compress it.

Once that is passed and the turbo is fulling spinning, the WAI cools the air making it more dense than spraying post IC as it has more time and better dynamics to chill the air.

Preturbo: loss of power in the lower revs, more power in higher revs.
Post IC, the reverse of above.

My suggestion back then was to spray 50/50 "both locations" for best overall results for street use. That is what I do. Rice Racing only does pre turbo.

 

Preturbo 50/50 here. Using a T3 GT35r 1.06 a/r with longtube manifold I saw 23psi by 4000 rpm. AI triggered at 8psi. I ran 15psi on the identical setup before I started running AI. Comparitively, my spool was the same if not a little faster while running more boost.

I feel that pre-turbo works really well for mid-frame turbo's running 20+ psi. The spool is likely less noticeable because the do spool so quick anyway.

 

good info!