Post by White87GT on Jun 28, 2004 22:33:49 GMT -5
This was posted by a guy on the MR2 board who works with Aquamist Water Injection. Good info
In brief: Water injection cools the intake charge through the latent heat absorption of water in the evaporation process. Same principal as patio misters. The water vapor absorbs the heat in the intake charge and cools it down. I have seen 30-40 degree Celsius drops on my Power FC monitoring intake temps after the huge air/air intercooler has already done its job.
Since we know the engine is a giant air pump, and the amount of power it is capable of producing is direction proportional to he volume of cool dense air it is able to ingest, the technology behind water injection makes perfect sense. Think of it this way -- everyone is concerned about air volume:
"How big of a turbo should I run for my power goals?”
"How about my intake, can that be bigger? ”
"Can I run a bigger throttle body”
"Is the AFM restrictive? ”
"Is the TVIS restrictive? ”
"Will a brand X free flowing exhaust or downpipe help me move more air? ”
"What about a custom exhaust manifold? ”<br>"What about higher lift/duration cam profiles? ”<br>
These concerns each address the volume of air an engine can take in and how efficiently it can push it out again. They all, of course, come to play in determining an engine's power potential.
Equally important, and often overlooked, however is how cool and dense that intake charge is.
Its simple physics, really -- engines like a lot of air [volume], but they like a lot of cool, dense, air even better [volume + temperature].
Water injection systems like Aquamist displace a small amount of air volume from the combustion process by replacing it with water vapor. So wait, it is actually reducing air volume, right?
Yes. But that tiny reduction in air volume is made up for in the second half of the equation dealing with the temperature. A cool dense intake charge provides for better combustion than a hot one.
Want to address detonation? Look no further than the source of the heat that is brining it on.
OK, we all know our cars can make a whole lot of power with little more than a manual boost controller [“MBC”], fuel cut defenser [“FCD”], and a bigger turbo [“Big Ass Turbo”]. Small investment = big power. For a while.
What happens, however, is that as you crank up the boost, the turbo is now compressing and heating the air at a much greater rate as it reaches its efficiency limits. This doesn't necessarily happen at 20+ psi. It happens at as little as 16-17 psi.
Suddenly, the timing maps that Toyota designed into our cars anticipating stock boost levels (plus a certain margin of safety for people living at higher altitudes, those who fail to keep their ignition components in good shape, and/or those running lower than the required fuel octane) are out the window. Likewise, the intercooler, which was designed to cool the intake charge within certain parameters, can no longer effectively cool the much hotter charge coming out of the turbo.
That's right. A little turn on the boost controller knob, or switching to a bigger turbo, and Toyota's ECU tuning for ignition (and to a lesser extent, fuel) becomes far too aggressive. The little stock IC struggles to keep up and, before you know it, bye-bye engine.
And this is not just happening to the crazy monster horsepower guys -- this is happening to guys making less than 300 hp at the flywheel.
OK, so the obvious solution is bigger turbo (compresses air less = more efficient, even of the trade off is more lag), bigger injectors to fuel the bigger turbo, and ITC/AFC [ignition timing controller and air/fuel controller] piggybacks or a standalone ECU to remap the ignition and fuel curves, and finally a bigger IC to cool it all down. Lots of $$$$ spent, and then, on hot day, after sitting in bumper to bumper traffic or a after couple of hard boost runs against that Mustang in the next lane and...
the IC heatsoaks...
and Houston, we have a problem...
So does this mean that those guys running 116 octane race gas need to start jumping up and down exclaiming that this is all a bunch of BS and that water injection is not needed if you're running the "good stuff"?
Of course not.
But for those of us unable to afford $5 a gallon for race gas, water is free.
Plus, even on the "good stuff" take the same car on a road course, and run it on sustained boost for a few hours (yes, hours) on end and report back with whether the good stuff was good enough.
Water injection is not just used to run more boost. In fact, most of the extra power I found on my car (40 rwhp) was
attributable to being able to get away with running more aggressive timing and fueling curves than I ever could have otherwise. I never touched the boost controller. Oh, and this power difference was made going one octane point down from 92 octane to 91 -- thanks California oil refineries!
At a recent track day at Thunderhill Raceway (local road course), my IC pipe to the throttle body was cool enough to hold with my bare hand, (nice parlor trick to make jaws drop) even after driving the car at 18.8 psi for 10 consecutive laps at 3 miles each. In fact, my poor overworked turbo seems to have suffered some heat related stress on the shaft from working so hard, yet my stock engine was doing just fine.
Posted on Celica.net by Luni
In brief: Water injection cools the intake charge through the latent heat absorption of water in the evaporation process. Same principal as patio misters. The water vapor absorbs the heat in the intake charge and cools it down. I have seen 30-40 degree Celsius drops on my Power FC monitoring intake temps after the huge air/air intercooler has already done its job.
Since we know the engine is a giant air pump, and the amount of power it is capable of producing is direction proportional to he volume of cool dense air it is able to ingest, the technology behind water injection makes perfect sense. Think of it this way -- everyone is concerned about air volume:
"How big of a turbo should I run for my power goals?”
"How about my intake, can that be bigger? ”
"Can I run a bigger throttle body”
"Is the AFM restrictive? ”
"Is the TVIS restrictive? ”
"Will a brand X free flowing exhaust or downpipe help me move more air? ”
"What about a custom exhaust manifold? ”<br>"What about higher lift/duration cam profiles? ”<br>
These concerns each address the volume of air an engine can take in and how efficiently it can push it out again. They all, of course, come to play in determining an engine's power potential.
Equally important, and often overlooked, however is how cool and dense that intake charge is.
Its simple physics, really -- engines like a lot of air [volume], but they like a lot of cool, dense, air even better [volume + temperature].
Water injection systems like Aquamist displace a small amount of air volume from the combustion process by replacing it with water vapor. So wait, it is actually reducing air volume, right?
Yes. But that tiny reduction in air volume is made up for in the second half of the equation dealing with the temperature. A cool dense intake charge provides for better combustion than a hot one.
Want to address detonation? Look no further than the source of the heat that is brining it on.
OK, we all know our cars can make a whole lot of power with little more than a manual boost controller [“MBC”], fuel cut defenser [“FCD”], and a bigger turbo [“Big Ass Turbo”]. Small investment = big power. For a while.
What happens, however, is that as you crank up the boost, the turbo is now compressing and heating the air at a much greater rate as it reaches its efficiency limits. This doesn't necessarily happen at 20+ psi. It happens at as little as 16-17 psi.
Suddenly, the timing maps that Toyota designed into our cars anticipating stock boost levels (plus a certain margin of safety for people living at higher altitudes, those who fail to keep their ignition components in good shape, and/or those running lower than the required fuel octane) are out the window. Likewise, the intercooler, which was designed to cool the intake charge within certain parameters, can no longer effectively cool the much hotter charge coming out of the turbo.
That's right. A little turn on the boost controller knob, or switching to a bigger turbo, and Toyota's ECU tuning for ignition (and to a lesser extent, fuel) becomes far too aggressive. The little stock IC struggles to keep up and, before you know it, bye-bye engine.
And this is not just happening to the crazy monster horsepower guys -- this is happening to guys making less than 300 hp at the flywheel.
OK, so the obvious solution is bigger turbo (compresses air less = more efficient, even of the trade off is more lag), bigger injectors to fuel the bigger turbo, and ITC/AFC [ignition timing controller and air/fuel controller] piggybacks or a standalone ECU to remap the ignition and fuel curves, and finally a bigger IC to cool it all down. Lots of $$$$ spent, and then, on hot day, after sitting in bumper to bumper traffic or a after couple of hard boost runs against that Mustang in the next lane and...
the IC heatsoaks...
and Houston, we have a problem...
So does this mean that those guys running 116 octane race gas need to start jumping up and down exclaiming that this is all a bunch of BS and that water injection is not needed if you're running the "good stuff"?
Of course not.
But for those of us unable to afford $5 a gallon for race gas, water is free.
Plus, even on the "good stuff" take the same car on a road course, and run it on sustained boost for a few hours (yes, hours) on end and report back with whether the good stuff was good enough.
Water injection is not just used to run more boost. In fact, most of the extra power I found on my car (40 rwhp) was
attributable to being able to get away with running more aggressive timing and fueling curves than I ever could have otherwise. I never touched the boost controller. Oh, and this power difference was made going one octane point down from 92 octane to 91 -- thanks California oil refineries!
At a recent track day at Thunderhill Raceway (local road course), my IC pipe to the throttle body was cool enough to hold with my bare hand, (nice parlor trick to make jaws drop) even after driving the car at 18.8 psi for 10 consecutive laps at 3 miles each. In fact, my poor overworked turbo seems to have suffered some heat related stress on the shaft from working so hard, yet my stock engine was doing just fine.
Posted on Celica.net by Luni
