Quicker turbo spool

[BLampinen]

I was thinking about an idea a friend of mine was telling me about. He said that he'd heard of some people who took their A/C compressor off, and replaced it with an ambient air compressor. Then they would save that compressed air in a bottle and inject it into their exhaust manifold to spool their turbo at lower RPM for drag racing. Well, this seems like a good idea to me, but it seems somewhat inefficient. So, I came up with a similar idea that I wanted to see if anyone that has more experience could tell me if it's feasible or not.

Rather than just injecting compressed air into the turbine housing of the turbo, what if you were to inject a water mist into the exhaust manifold just prior to the turbine inlet. If your exhaust temp is above 1000*, the water would vaporize almost instantly. Water, above 600* expands to ~1700 times its volume at 34*. With this massive volume of water vapor being forced through the exhaust manifold and turbo inlet, you would think that it would the dramatic increase in exhaust pressure would spool the turbo almost instantly.

Anyways, what do you guys think? Would the resultant back-pressure be too much for a car spinning at say 1000rpm be too much to overcome? Also, would the dramatic cooling effect of the water warp the manifold and turbo? Feel free to flame me if this idea is completely retarded, I just thought of it and decided to see if anyone had any ideas.

 

[dustyb]

how are you going to get the water into the exhaust manifold or turbine housing? that is a pretty hot area for a water injector.

plus, whats the point of spooling at a lower rpm anyways, you have your foot on the gas feeding your turbo anyways.....

 

[BLampinen]

I'm speaking in theoretical terms here. The primary use would be in drag racing. Imagine if you could use a huge turbo like from a 12L Detroit Diesel engine on a 4-cylindar 2.0L gasoline engine. Of course, this may not be possible for other reasons. But this application could also work for nearly any turbo setup. And, I have enough trouble keeping my 16G fully spooled as it is. I'm just trying to think of different ways to make turbo-charging more efficient.
I've posted this on a different forum, and someone brought up that water vapor would be corrosive to your exhaust. Would a stainless steel exhaust system over-come this? Or would steel be too susceptible to the temperature fluctuations?

 

[Defiant]

Interesting concept in theory. In reality, that steam will destroy an exhaust turbine. You won't get complete vaporization, and water impingement will blast the blades. Further, the latent heat of vaporization removed from the exhaust gas and used by the water for its phase change will reduce the energy normally imparted to the turbine.

 

[leet]

Um, yeah.

Cooling exhausts gasses reduces their velocity, which in turn will slow spool up. Not to mention all the possible destructive aspects, steam is quite corrosive to metals.

 

[BLampinen]

ok that's what i was wondering about... now (ignoring the corrosivity) wouldnt the added volume of the water replace the effect of the heated exhuast gasses? in other words, if water is going to make such a massive volume of vapors in the manifold, wouldnt the overall pressure actually increase, despite the dramatic cooling effect?

and defiant, what if the water were sprayed in such a fine stream that vaporization were garaunteed. now i under stand this is "perfect world" and perfect efficiency is useless in real life... but i'm speaking in "what-if's" at the moment

 

[psychlow]

I'd think that it could be feasible, assuming it was 100% gaseous by the time it hit the turbine blades.

I'd thought of a similar concept to save gas during idling on ICEs. Instead of using 100% gasoline to keep the engine idling, turn off the injectors to each cylinder every 4th revolution or so and inject a measured amount of water. The idea would be that the heat from the cylinders would hopefully be enough to vaporize the water and create steam pressure that the car would still keep up idle speed, use less gas, emit less pollution, and shouldn't vibrate too much (if you did it in the correct sequence)

I imagine if it worked, though, it'd already be in use.

 

[Defiant]

ok that's what i was wondering about... now (ignoring the corrosivity)

It's not the corrosion. It's the impingement. It's like blasting the wheel's fins with sand.

wouldnt the added volume of the water replace the effect of the heated exhuast gasses? in other words, if water is going to make such a massive volume of vapors in the manifold, wouldnt the overall pressure actually increase, despite the dramatic cooling effect?

Nope. Best you could hope to come out with would be even, but you'd never even attain that.

and defiant, what if the water were sprayed in such a fine stream that vaporization were garaunteed. now i under stand this is "perfect world" and perfect efficiency is useless in real life... but i'm speaking in "what-if's" at the moment

Not even if you admitted it as steam. It's only going to suck up energy.

 

[alex01tib]

remember that you can not create energy... the pressure that would be created by the water vapor would come from the heat of the exhaust gasses, and the energy you just took from the exhaust gasses was going to go to turn the turbine, you essentially just shot yourself in the foot and could only decrease performance by increasing lag. it was quite an interesting concept tho, always gotta be thinking of new things, who knows about that compressed air injection thing, probably the idea with better chances...

 

[BLampinen]

ok, so judging by your responses and the responses i got from another forum, this one is shot to hell... oh well i was just trying to be creative . need to find an inert, non-corrosive gas that has a very high vapor density now

 

[BlackTopPat]

i am a jet mech in the air force so this is just my cup of tea. more pressure in the exhaust isnt going to spool the turbo faster, its the high velocity air running into the turbine the turns it, and also adding water to the exhaust will cool it and make the air molcules come closer toghter and take up less space which is counter productive, u want lots of air going into the convergence right before the turbine blades.

 

[BLampinen]

i am a jet mech in the air force so this is just my cup of tea. more pressure in the exhaust isnt going to spool the turbo faster, its the high velocity air running into the turbine the turns it, and also adding water to the exhaust will cool it and make the air molcules come closer toghter and take up less space which is counter productive, u want lots of air going into the convergence right before the turbine blades.

cool cool, im a fire fighter in the air force at fairchild

 

[97EclipseGS-T]

umm...you were worried about the "stream" of water turning into vapor and vapoo-rizing (sorry, had to throw it in) the blades. Are you just trying to keep the pressure to allow it to spool, because if thats the case, what if you can heat the water and turn into vapor before it even hits the turbo. For instance, pumping the water through a heater or just running stainless hosing around the hotest parts of the engine and using the engines heat and then exit that pressure (now theoretically vapor pressure) out the turbo?

 

[BLampinen]

Yeah thats what i think im going to do, throw a 50-shot wet on the car.

 

[DSM90AWD]

Yeah thats what i think im going to do, throw a 50-shot wet on the car.

Not that it's a bad idea but isn't it a bit of overkill for a 16G WTF

Some easy ways to reduce lag:
- eliminate intake restrictions
- reduce intake system volume (i.e. smaller FMIC, less piping)
- eliminate post-turbine exhaust restrictions (restrictive O2/exhaust)
- ensure that all the compressor output reaches the engine (no boost leaks)
- ensure that all the exhaust energy is reaching the turbine (no pre-turbo exhaust leaks, wastegate adjusted properly)
- swap to an external gate
- shift quickly or use a NLTS (keeps boost up btw shifts)