water or methanol, pre turbo or post intercooler?
03-16-11, 11:24 PM
#1
Full Member
Thread Starter
water or methanol, pre turbo or post intercooler?
ok so im curious what wold be good for runin hi boost ive been reading that pre turbo is very nice but can be risky and post inter cooler is more comin. also whats better for what as far as water or methinal?
what do u guys think?
what do u guys think?
03-16-11, 11:29 PM
#2
I believe you would be best served by going into the section of this forum for AI and reading from the many posts in there that answer all of your questions. At the moment you are speaking in generalities that provide minimal opportunity to assist you. =)
Good luck
Good luck
03-17-11, 02:16 AM
#4
preturbo doesnt make any sense to me. the air will be heated by the turbo and thus make the ai properties negligible.
Note that with if an IC being the last in the chain, the coldest AIT's that you can hope for is ambient temps. Therefore AI post IC would be my choice.
For two reasons:
1) the ic does the grunt of the work in cooling the intake charge, and the ai comes in and cools it even more.
2) The closest that you are to the throttle body the more that you can take advantage of ai's steam cleaning properties.
Note that with if an IC being the last in the chain, the coldest AIT's that you can hope for is ambient temps. Therefore AI post IC would be my choice.
For two reasons:
1) the ic does the grunt of the work in cooling the intake charge, and the ai comes in and cools it even more.
2) The closest that you are to the throttle body the more that you can take advantage of ai's steam cleaning properties.
03-19-11, 01:10 AM
#6
Full Member
preturbo will cool the compression of the air. The farther you are from the throttle body, the more time the mix has to take heat out of the air. The water will not phase change until the combustion chamber, so don't worry about keeping the nozzle close to the TB unless you have to (TMIC)
Check out this thread for some info.
Pre-turbo injection
Check out this thread for some info.
Pre-turbo injection
03-19-11, 04:28 PM
#7
Full Member
Join Date: Jul 2003
Location: Florida
Posts: 54
Likes: 0
Received 0 Likes
on
0 Posts
I have never seen any real world proof of injecting pre compressor gives any benefit. There is plenty of speculation on the subject but very little proof, theory can only go so far... If you have proof post it up please.
Also using an IAT to measure after the compressor to show "gains" is flawed from the get go as im sure most of you know already.
Water should be directed to the combustion chambers so it can do what it needs to do, cool combustion. The best way to inject an A/I is port injection. Injecting before the throttle body does no distribute the water equally depending on manifold design. Water DOES NOT flow like air.
A great text to read if you want to learn more about engines and A/I...
The High-Speed Internal Combustion Engine by Sir Harry Ricardo Its out of print but it is still a wonderful text.
Also using an IAT to measure after the compressor to show "gains" is flawed from the get go as im sure most of you know already.
Water should be directed to the combustion chambers so it can do what it needs to do, cool combustion. The best way to inject an A/I is port injection. Injecting before the throttle body does no distribute the water equally depending on manifold design. Water DOES NOT flow like air.
A great text to read if you want to learn more about engines and A/I...
The High-Speed Internal Combustion Engine by Sir Harry Ricardo Its out of print but it is still a wonderful text.
Trending Topics
03-19-11, 08:24 PM
#8
I have never seen any real world proof of injecting pre compressor gives any benefit. There is plenty of speculation on the subject but very little proof, theory can only go so far... If you have proof post it up please.
Also using an IAT to measure after the compressor to show "gains" is flawed from the get go as im sure most of you know already.
Water should be directed to the combustion chambers so it can do what it needs to do, cool combustion. The best way to inject an A/I is port injection. Injecting before the throttle body does no distribute the water equally depending on manifold design. Water DOES NOT flow like air.
A great text to read if you want to learn more about engines and A/I...
The High-Speed Internal Combustion Engine by Sir Harry Ricardo Its out of print but it is still a wonderful text.
Also using an IAT to measure after the compressor to show "gains" is flawed from the get go as im sure most of you know already.
Water should be directed to the combustion chambers so it can do what it needs to do, cool combustion. The best way to inject an A/I is port injection. Injecting before the throttle body does no distribute the water equally depending on manifold design. Water DOES NOT flow like air.
A great text to read if you want to learn more about engines and A/I...
The High-Speed Internal Combustion Engine by Sir Harry Ricardo Its out of print but it is still a wonderful text.
03-19-11, 09:09 PM
#9
tard of teh century
Water should be directed to the combustion chambers so it can do what it needs to do, cool combustion. The best way to inject an A/I is port injection. Injecting before the throttle body does no distribute the water equally depending on manifold design. Water DOES NOT flow like air.
03-20-11, 02:03 PM
#10
Full Member
Join Date: Jul 2003
Location: Florida
Posts: 54
Likes: 0
Received 0 Likes
on
0 Posts
The purpose of water injection is as an internal coolant. Not a charge air coolant. The reasoning is the time it takes. There isnt enough of it for any appreciable cooling to occur pre-combustion chamber. Even if you cool the temp coming right out of the compressor the temperature difference at the combustion chamber is lower and you yield less cooling for your trouble.
The formula for the heat transfer coefficient... http://upload.wikimedia.org/math/a/c...c43b29499c.png
Where q = heat flow in input or lost heat flow , J/s = W
h = heat transfer coefficient, W/(m2K)
A = heat transfer surface area, m2
ΔT = difference in temperature between the solid surface and surrounding fluid area, K
The amount of time it takes heat to transfer to water, is several times more then it takes heat to travel from air. In a system that is closed where there are just milliseconds from when the particles of air leave the compressor or the ic for that matter to when they reach the combustion chamber. Its pretty silly to think that the water in such a low quantity would remove heat from the air traveling so quickly.
The heat drawn from the intake charge is a VERY small part of the overall process. Water does a bit of cooling to the air charge but mostly by the turbulance when it enters the combustion chamber, and its not measurable.
I say this all the time, water injection is really for cooling combustion. During AND after. It helps increase the knock limit and lower egt's while pulling heat away from the exhaust valves (piston) and thats always good for an engine.
I wouldnt take as gospel what any of the A/I dealers have to say. They are selling a product and as such want to make a profit. Im just putting this out there because people post go PRE compressor and have zero facts or real world values to prove that it works. If it does post it up I would like to see it. Log pressure and airflow. If the turbo really is pushing its map around with pre-turbo injection, if you eliminate the variables then you should see an increase in airflow.
I suggest you read up on the topic with valid sources. The internet has a lot of false/bad/backward information that makes it hard to get to the "real stuff".
The formula for the heat transfer coefficient... http://upload.wikimedia.org/math/a/c...c43b29499c.png
Where q = heat flow in input or lost heat flow , J/s = W
h = heat transfer coefficient, W/(m2K)
A = heat transfer surface area, m2
ΔT = difference in temperature between the solid surface and surrounding fluid area, K
The amount of time it takes heat to transfer to water, is several times more then it takes heat to travel from air. In a system that is closed where there are just milliseconds from when the particles of air leave the compressor or the ic for that matter to when they reach the combustion chamber. Its pretty silly to think that the water in such a low quantity would remove heat from the air traveling so quickly.
The heat drawn from the intake charge is a VERY small part of the overall process. Water does a bit of cooling to the air charge but mostly by the turbulance when it enters the combustion chamber, and its not measurable.
I say this all the time, water injection is really for cooling combustion. During AND after. It helps increase the knock limit and lower egt's while pulling heat away from the exhaust valves (piston) and thats always good for an engine.
I wouldnt take as gospel what any of the A/I dealers have to say. They are selling a product and as such want to make a profit. Im just putting this out there because people post go PRE compressor and have zero facts or real world values to prove that it works. If it does post it up I would like to see it. Log pressure and airflow. If the turbo really is pushing its map around with pre-turbo injection, if you eliminate the variables then you should see an increase in airflow.
I suggest you read up on the topic with valid sources. The internet has a lot of false/bad/backward information that makes it hard to get to the "real stuff".
03-20-11, 09:55 PM
#11
tard of teh century
I wasn't referring to the charge cooling at all. I was talking about cooling inside the turbocharger as the air is compressed, it would be the same effect it has on the air when it is being compressed inside the combustion chamber. Unless what you're saying is that the water isn't doing anything until the charge is actually burning and that is when the water is absorbing the bulk of its heat.
03-20-11, 11:49 PM
#12
Full Member
Join Date: Jul 2003
Location: Florida
Posts: 54
Likes: 0
Received 0 Likes
on
0 Posts
Again, its main function and gain is from being injected into the combustion chamber. These water droplets then form on the surface of the combustion chamber and directly cools it. This effectively raises the knock limit of the engine for its given fuel that you are running.
Cooling pre compressor does not really give you that much of a gain. That water has to go through all of the charge pipes and intercooler, which induces a pressure drop/turbulence mind you and causes a lot of the water to fall out of suspension. Fuel in carbed engines with long charge pipes have enough trouble getting to the proper cylinders and being equally distributed. Imagine heavy water droplets smashing around.
Most people spray before the throttle body while they are spraying pre compressor. If your cooling the temperature between compressor and chamber you are dropping the temperature differential. Temperature differential speeds heat transfer so if you drop it you end up getting less cooling for the trouble of that extra nozzle.
Direct port water injection is the best way in my opinion.
Cooling pre compressor does not really give you that much of a gain. That water has to go through all of the charge pipes and intercooler, which induces a pressure drop/turbulence mind you and causes a lot of the water to fall out of suspension. Fuel in carbed engines with long charge pipes have enough trouble getting to the proper cylinders and being equally distributed. Imagine heavy water droplets smashing around.
Most people spray before the throttle body while they are spraying pre compressor. If your cooling the temperature between compressor and chamber you are dropping the temperature differential. Temperature differential speeds heat transfer so if you drop it you end up getting less cooling for the trouble of that extra nozzle.
Direct port water injection is the best way in my opinion.
03-21-11, 08:34 PM
#14
Full Member
Join Date: Jul 2003
Location: Florida
Posts: 54
Likes: 0
Received 0 Likes
on
0 Posts
Real proof? I just saw dyno runs, I couldnt really make out anything they were saying though. Also I never said water injection was not beneficial. I myself am a fan of A/I. I was mainly talking about placement. That car made good power on water. But did they change placement and have controls? I couldn't tell.
Rotaries with the way there intake manifolds are set up and just having two runners are a little more lenient compared to piston engines and their multiple runners. I do believe I went over that in one of my first posts though.
In my rx7 I would not bother with direct (unless I were to build an intake manifold for whatever reason) for the mere fact that shooting before the throttle is easier, cheaper and should do fine seeing that the manifold itself should not cause to much of an issue.
Now in my 4agte, its a different story. I am building another intake manifold for that car and its getting its nozzles in each runner. Same goes for my 4g63 ect ect.
Riceracing on the aquamist message board even said...
"All of the data I have found to date has showed pre turbo is more advantageous for a power increase comparing running with and without, where as post while reducing knock does not give the performance gains. Though I have never tested that myself personally I must mention." That was about over a year ago though.
Its whatever, think what you will, silly power can be made either way. I myself am not a fan of pre compressor for my stated reasons above. But water injection in itself is a wonderful thing for a car running pump and making fair amounts of power near its knock threshold.
Rotaries with the way there intake manifolds are set up and just having two runners are a little more lenient compared to piston engines and their multiple runners. I do believe I went over that in one of my first posts though.
In my rx7 I would not bother with direct (unless I were to build an intake manifold for whatever reason) for the mere fact that shooting before the throttle is easier, cheaper and should do fine seeing that the manifold itself should not cause to much of an issue.
Now in my 4agte, its a different story. I am building another intake manifold for that car and its getting its nozzles in each runner. Same goes for my 4g63 ect ect.
Riceracing on the aquamist message board even said...
"All of the data I have found to date has showed pre turbo is more advantageous for a power increase comparing running with and without, where as post while reducing knock does not give the performance gains. Though I have never tested that myself personally I must mention." That was about over a year ago though.
Its whatever, think what you will, silly power can be made either way. I myself am not a fan of pre compressor for my stated reasons above. But water injection in itself is a wonderful thing for a car running pump and making fair amounts of power near its knock threshold.
03-22-11, 12:11 AM
#15
Full Member
Again, its main function and gain is from being injected into the combustion chamber. These water droplets then form on the surface of the combustion chamber and directly cools it. This effectively raises the knock limit of the engine for its given fuel that you are running.
Cooling pre compressor does not really give you that much of a gain. That water has to go through all of the charge pipes and intercooler, which induces a pressure drop/turbulence mind you and causes a lot of the water to fall out of suspension.
Most people spray before the throttle body while they are spraying pre compressor. If your cooling the temperature between compressor and chamber you are dropping the temperature differential. Temperature differential speeds heat transfer so if you drop it you end up getting less cooling for the trouble of that extra nozzle.
Direct port water injection is the best way in my opinion.
03-22-11, 01:47 AM
#16
Full Member
Join Date: Jul 2003
Location: Florida
Posts: 54
Likes: 0
Received 0 Likes
on
0 Posts
You sir are reading to far into what im saying. By the water being on the combustion chamber walls it pulls heat from that surface, reducing hotspots ect ect. Simply being in the cylinder causes the heat energy to force the change of state with the water. Im not sure why you brought up stream lining water, the finer the mist the better. No fire hoses here...
Again, the main reason is to reduce knock. Im not going to get very deep into this. If you wish, show me some results that show a significant reduction in temperature after pre comp W/I. I would like to see what you come up with. Measuring with an IAT sensor is folly simply because of the wet thermometer effect, look into how a barometer works. Hense makes it null.
In addition saying that the pipes are "cool" to the touch does not fly either. The water/meth cling to the sides of the pipe and suck the heat out of the material. Also the heat that was pulled from the pipes and the manifold that would normally be radiated out into the engine bay is now being sucked into the combustion chambers. Not super bad, but less efficient in the grand scheme.
Furthermore its silly to say efficiency does not matter. Its the key goal in making power... The more efficient the more bang for your buck.
Finally I would not say direct is more dangerous. It is more costly but common sense would dictate more parts more cheese. If a nozzle fails pre comp, post comp, whatever youll have similar issues nonetheless. Just build in a proper fail safe however one might choose to and off you go.
Again, the main reason is to reduce knock. Im not going to get very deep into this. If you wish, show me some results that show a significant reduction in temperature after pre comp W/I. I would like to see what you come up with. Measuring with an IAT sensor is folly simply because of the wet thermometer effect, look into how a barometer works. Hense makes it null.
In addition saying that the pipes are "cool" to the touch does not fly either. The water/meth cling to the sides of the pipe and suck the heat out of the material. Also the heat that was pulled from the pipes and the manifold that would normally be radiated out into the engine bay is now being sucked into the combustion chambers. Not super bad, but less efficient in the grand scheme.
Furthermore its silly to say efficiency does not matter. Its the key goal in making power... The more efficient the more bang for your buck.
Finally I would not say direct is more dangerous. It is more costly but common sense would dictate more parts more cheese. If a nozzle fails pre comp, post comp, whatever youll have similar issues nonetheless. Just build in a proper fail safe however one might choose to and off you go.
05-04-12, 01:56 AM
#17
You sir are reading to far into what im saying. By the water being on the combustion chamber walls it pulls heat from that surface, reducing hotspots ect ect. Simply being in the cylinder causes the heat energy to force the change of state with the water. Im not sure why you brought up stream lining water, the finer the mist the better. No fire hoses here...
Again, the main reason is to reduce knock. Im not going to get very deep into this. If you wish, show me some results that show a significant reduction in temperature after pre comp W/I. I would like to see what you come up with. Measuring with an IAT sensor is folly simply because of the wet thermometer effect, look into how a barometer works. Hense makes it null.
In addition saying that the pipes are "cool" to the touch does not fly either. The water/meth cling to the sides of the pipe and suck the heat out of the material. Also the heat that was pulled from the pipes and the manifold that would normally be radiated out into the engine bay is now being sucked into the combustion chambers. Not super bad, but less efficient in the grand scheme.
Furthermore its silly to say efficiency does not matter. Its the key goal in making power... The more efficient the more bang for your buck.
Finally I would not say direct is more dangerous. It is more costly but common sense would dictate more parts more cheese. If a nozzle fails pre comp, post comp, whatever youll have similar issues nonetheless. Just build in a proper fail safe however one might choose to and off you go.
Again, the main reason is to reduce knock. Im not going to get very deep into this. If you wish, show me some results that show a significant reduction in temperature after pre comp W/I. I would like to see what you come up with. Measuring with an IAT sensor is folly simply because of the wet thermometer effect, look into how a barometer works. Hense makes it null.
In addition saying that the pipes are "cool" to the touch does not fly either. The water/meth cling to the sides of the pipe and suck the heat out of the material. Also the heat that was pulled from the pipes and the manifold that would normally be radiated out into the engine bay is now being sucked into the combustion chambers. Not super bad, but less efficient in the grand scheme.
Furthermore its silly to say efficiency does not matter. Its the key goal in making power... The more efficient the more bang for your buck.
Finally I would not say direct is more dangerous. It is more costly but common sense would dictate more parts more cheese. If a nozzle fails pre comp, post comp, whatever youll have similar issues nonetheless. Just build in a proper fail safe however one might choose to and off you go.
05-04-12, 06:54 AM
#18
What? I don't know about pre-turbo, I never really considered it for my car and will let others debate it's value. But you want proof that water undergoes a phase-change in the combustion chamber? That it removes heat? That it acts to reduce knock? Please.
05-04-12, 12:18 PM
#19
Racing Rotary Since 1983
iTrader: (6)
it is great to see some debate on the board 
i hope to be able to add some actual data shortly.
my new DUAL setup uses one special (6 orfice) EV14 1000 CC fuel injector suspended directly in the center of the intake tract 9 inches preturbo. the second EV14 1000 CC injector is in the greddy elbow.
both injectors are separately controllable using a 440 cell X Y map.
i will evaluate the elbow injector, then turn it off and enable the pre turbo injector.
i will be logging everything including charge air temps. i will have a K thermocouple just out of the turbo and another just out of the intercooler. unlike the usual IAT sensors, the Ks react in milliseconds and are accurate within one degree so we will see how the IC reacts. the injectors will be run at 125 psi to encourage atomisation.
WM50 will be the injectant.
given the debate, there may be alot to learn and it should prove interesting.
howard
i hope to be able to add some actual data shortly.
my new DUAL setup uses one special (6 orfice) EV14 1000 CC fuel injector suspended directly in the center of the intake tract 9 inches preturbo. the second EV14 1000 CC injector is in the greddy elbow.
both injectors are separately controllable using a 440 cell X Y map.
i will evaluate the elbow injector, then turn it off and enable the pre turbo injector.
i will be logging everything including charge air temps. i will have a K thermocouple just out of the turbo and another just out of the intercooler. unlike the usual IAT sensors, the Ks react in milliseconds and are accurate within one degree so we will see how the IC reacts. the injectors will be run at 125 psi to encourage atomisation.
WM50 will be the injectant.
given the debate, there may be alot to learn and it should prove interesting.
howard
05-04-12, 07:44 PM
#21
Arrogant Wankeler
Measuring with an IAT sensor is folly simply because of the wet thermometer effect, look into how a barometer works. Hense makes it null.
Wrong, and wrong, a baraometer measures atmospheric pressure
, and more importantly, a wet bulb thermometer for measuring relative humidity relies on the fact that there is an airflow over the wet bulb that is less humid than the air leaving it, thus there is a mass & thermal energy transfer between the wet bulb and air stream due to different relative humidity/vapour carry before and after to cool it below the air stream temp via evaporation. The IAT sensor is not introducing additional fluid to the charge air & thus does not get cooled below the intake stream temp, only subjected to it (or perhaps my mechanical & chemical doctorate lecturers where entirely flawed in their experimental techniques ). You are twisting, contorting & molesting scientific principles.
In addition saying that the pipes are "cool" to the touch does not fly either. The water/meth cling to the sides of the pipe and suck the heat out of the material. Also the heat that was pulled from the pipes and the manifold that would normally be radiated out into the engine bay is now being sucked into the combustion chambers. Not super bad, but less efficient in the grand scheme.
Again, with your wet bulb theory, albeit there may be some very modest wet walling (remember you are only delivering a tiny fraction of your total fluid flow relative to main fueling), you are missing the point. Under normal conditions that pipework would be hot, which means hot air. Even if the fluid is absorbing heat energy from the surrounds, the charge air is still colder and therefore denser at the same pressure going into the engine for the same required compressor shaft power at that mass flow, at the same pressure. System combined efficiency on a turbocharged engine is about getting mass flow in with minimum energy delivered to the turbo from the exhaust stream as that work is lost to the crank otherwise as exhuast stroke pumping loss. If you can deliver the same mass flow at a lower pressure, or more mass flow at the same shaft energy, you have improved system efficiency, you get more wheel power from the same mass flow of air.
Furthermore its silly to say efficiency does not matter. Its the key goal in making power... The more efficient the more bang for your buck.
One thing I can agree on, although you don't really seem to understand it, you seem to only want the knock suppression benefit rather than thermodynamic system benefit.
You still get all the knock suppression benefit with preturbo injection, it is folly to think that lifting density by a factor of one or two with a relatively efficient centrifugal compressor (relative to piston/rotor compressors, why do you think heavy industry no longer uses piston or gear pumps for anything other than very high pressure hydraulics where they need the physical robustness of those designs?), the thermal energy uptake (& dT) in that step pails into insignificance with theless efficient factor of 9 compression and addition of combustion energy within the engine
Wrong, and wrong, a baraometer measures atmospheric pressure
, and more importantly, a wet bulb thermometer for measuring relative humidity relies on the fact that there is an airflow over the wet bulb that is less humid than the air leaving it, thus there is a mass & thermal energy transfer between the wet bulb and air stream due to different relative humidity/vapour carry before and after to cool it below the air stream temp via evaporation. The IAT sensor is not introducing additional fluid to the charge air & thus does not get cooled below the intake stream temp, only subjected to it (or perhaps my mechanical & chemical doctorate lecturers where entirely flawed in their experimental techniques ). You are twisting, contorting & molesting scientific principles.In addition saying that the pipes are "cool" to the touch does not fly either. The water/meth cling to the sides of the pipe and suck the heat out of the material. Also the heat that was pulled from the pipes and the manifold that would normally be radiated out into the engine bay is now being sucked into the combustion chambers. Not super bad, but less efficient in the grand scheme.
Again, with your wet bulb theory, albeit there may be some very modest wet walling (remember you are only delivering a tiny fraction of your total fluid flow relative to main fueling), you are missing the point. Under normal conditions that pipework would be hot, which means hot air. Even if the fluid is absorbing heat energy from the surrounds, the charge air is still colder and therefore denser at the same pressure going into the engine for the same required compressor shaft power at that mass flow, at the same pressure. System combined efficiency on a turbocharged engine is about getting mass flow in with minimum energy delivered to the turbo from the exhaust stream as that work is lost to the crank otherwise as exhuast stroke pumping loss. If you can deliver the same mass flow at a lower pressure, or more mass flow at the same shaft energy, you have improved system efficiency, you get more wheel power from the same mass flow of air.
Furthermore its silly to say efficiency does not matter. Its the key goal in making power... The more efficient the more bang for your buck.
One thing I can agree on, although you don't really seem to understand it, you seem to only want the knock suppression benefit rather than thermodynamic system benefit.
You still get all the knock suppression benefit with preturbo injection, it is folly to think that lifting density by a factor of one or two with a relatively efficient centrifugal compressor (relative to piston/rotor compressors, why do you think heavy industry no longer uses piston or gear pumps for anything other than very high pressure hydraulics where they need the physical robustness of those designs?), the thermal energy uptake (& dT) in that step pails into insignificance with theless efficient factor of 9 compression and addition of combustion energy within the engine
05-04-12, 08:58 PM
#22
Could have sworn there was already a thread here addressing this exact issue with back to back dyno runs...
IIRC injecting pre-turbo increased the effective size of the compressor map resulting in better top end, at the expense of spool. Which would make sense seeing as how a mixture of water (albiet finely atomized) and air would be significantly more dense than air alone. Injecting post intercooler resulting in quicker spool, but lacked the additional benefit of increased compressor efficiency and thus suffered (compared to pre-turbo, NOT compared to no AI at all) on the top end. Regardless of location, water injection eliminated knock.
Howard: I am VERY interested to see your results, I considered running a system to inject water pre-turbo and meth post intercooler, but ultimately decided that the added complexity just wasn't worth it for my power goals.
Edit: I knew I wasn't crazy... https://www.rx7club.com/auxiliary-injection-173/pre-turbo-wi-vs-post-ic-wi-dyno-test-results-987107/
IIRC injecting pre-turbo increased the effective size of the compressor map resulting in better top end, at the expense of spool. Which would make sense seeing as how a mixture of water (albiet finely atomized) and air would be significantly more dense than air alone. Injecting post intercooler resulting in quicker spool, but lacked the additional benefit of increased compressor efficiency and thus suffered (compared to pre-turbo, NOT compared to no AI at all) on the top end. Regardless of location, water injection eliminated knock.
Howard: I am VERY interested to see your results, I considered running a system to inject water pre-turbo and meth post intercooler, but ultimately decided that the added complexity just wasn't worth it for my power goals.
Edit: I knew I wasn't crazy... https://www.rx7club.com/auxiliary-injection-173/pre-turbo-wi-vs-post-ic-wi-dyno-test-results-987107/
Last edited by sharingan 19; 05-04-12 at 09:01 PM. Reason: Found thread...
05-05-12, 03:06 AM
#23
Arrogant Wankeler
Could have sworn there was already a thread here addressing this exact issue with back to back dyno runs...
IIRC injecting pre-turbo increased the effective size of the compressor map resulting in better top end, at the expense of spool. Which would make sense seeing as how a mixture of water (albiet finely atomized) and air would be significantly more dense than air alone. Injecting post intercooler resulting in quicker spool, but lacked the additional benefit of increased compressor efficiency and thus suffered (compared to pre-turbo, NOT compared to no AI at all) on the top end. Regardless of location, water injection eliminated knock.
Howard: I am VERY interested to see your results, I considered running a system to inject water pre-turbo and meth post intercooler, but ultimately decided that the added complexity just wasn't worth it for my power goals.
Edit: I knew I wasn't crazy... https://www.rx7club.com/showthread.php?t=987107
IIRC injecting pre-turbo increased the effective size of the compressor map resulting in better top end, at the expense of spool. Which would make sense seeing as how a mixture of water (albiet finely atomized) and air would be significantly more dense than air alone. Injecting post intercooler resulting in quicker spool, but lacked the additional benefit of increased compressor efficiency and thus suffered (compared to pre-turbo, NOT compared to no AI at all) on the top end. Regardless of location, water injection eliminated knock.
Howard: I am VERY interested to see your results, I considered running a system to inject water pre-turbo and meth post intercooler, but ultimately decided that the added complexity just wasn't worth it for my power goals.
Edit: I knew I wasn't crazy... https://www.rx7club.com/showthread.php?t=987107
That thread, while good did not have anywhere near the control or rigour a manufacturer or any testing authority would go to, and without a dyno cell & closed loop PID controlled coolant (and oil) temp control amongst many other variables, it is very difficult to pin down individual parameter influences.
Influences effecting that back to back making it difficult to compare properly, especially in the 3500-5500 spool/bottom/mid torque range:
Pressure differential as WI ramps up pre vs post turbo, water flow rate will be slightly greater, giving less turbine energy to spool & engine power assuming it is somewhat "over rich" where the pressure differential across the injector is lower as the controller ramps it up.
Also, looking at the logs coolant temp was lower on the pre turbo run by 6 deg C, this will roll out in a slightly lower thermodynamic efficiency on that run as the block & oil was no doubt cooler (sounds like ambient was damn cold compared to most places in Australia), and whether as a result of oxygen displacement via greater evapouration of hte pre turbo WI or coolant temp compensation tipping in a little more fuel, or possibly the throttle not being quite as open as indicated by differences in TPS voltage in the log (more detail below), the pre turbo run shows slightly richer AFRs in the ~4500-5500rpm range which will influence the power (available to engine & turbine) produced via flame speed & heat absorption.
Also appears that throttle opens slightly more & earlier in rpm on the post IC run based on the logs he posted, this obviously depends on the range of motion and actual throttle angle achieved vs ecu calibration, but this will obviously impact spool, and turbine back pressure (at it requires more energy to lift intake to the required pressure pre-throttle to achieve the same post throttle pressure if it is presenting more resistance), which effects delivered power at the same intake manifold pressure.
As you can see, there are many, many engine operating parameters which need to be controlled to accurately assess what is happening.
I will also say that pre-turbo injection should not influence map width perse, unless it is actually dropping air inlet temp into the compressor and increasing mass flow at that point which would be minimal in cold US weather at 100% water, but perhaps provide some benefit at 50% meth or with acetone etc added, it will however increase the turbo/engine system efficiency in so far as achieving a mass flow at a lower post compressor pressure (thus requiring less exhaust pumping power) and can thus deliver more eccentric-shaft/wheel work for the same mass flow of air, dependant on dP & dT of intercooler with & without WI.
05-05-12, 08:11 AM
#24
Racing Rotary Since 1983
iTrader: (6)
"I will also say that pre-turbo injection should not influence map width per se, unless it is actually dropping air inlet temp into the compressor and increasing mass flow at that point which would be minimal in cold US weather at 100% water, but perhaps provide some benefit at 50% meth or with acetone etc added, it will however increase the turbo/engine system efficiency in so far as achieving a mass flow at a lower post compressor pressure (thus requiring less exhaust pumping power) and can thus deliver more eccentric-shaft/wheel work for the same mass flow of air, dependant on dP & dT of intercooler with & without WI."
based on what RiceRacing has done in the last year i would say that the evidence is solid that what he is doing WORKS.
do you know anyone that has beat on his car for a year and is currently running 34 psi boost w a motor that shows 117 compression? all fully and professionally instrumented.
his setup is 100% preturbo and is water 45% meth 55% based on volume... 50/50 based on mass. reading between the lines, his system came alive a year ago when he added the meth to water which he had been running exclusively for many years. (and generally running 20 psi w water alone). it was the addition of meth that allowed him to add another BAR of boost.
given that he is successfully doing what few have done on this board i say it is time to take a very close look... that is what i intend to do. Peter and i took different paths in 2004 w re to AI injectant... Peter water, Howard meth. it appears we both have found that an approx 50/50 mix is the answer.
maybe preturbo is the other answer... i intend to find out w real testing. one thing i know is that what Peter has been successfully doing may redefine how we think about the rotary's dual purpose limits. most today consider around 20 psi to be about the limit for a dual purpose pump/AI car. of course piston engines often run 35-40. we say, it is the engine's architecture... and the accepted wisdom lapses into apex seals, long combustion chambers, lots of internal surface area etc.
meanwhile Peter is running 34 psi on pump and has a happy motor. he is also going really fast as documented by his GPS based systems.
not to be overlooked is his tuning philosophy:
airflow is everything... add the proper injectant at the right place and turn up the boost. do not attempt to make more power by tuning at the edge.... run it rich w very modest advance but at high boost. it is working.
i do agree w much of the Slides/quote. assuming that pretubo works, especially w an alcohol component, you win anytime you inject. by cooling the compressed mix inside the compressor housing you add additional oxygen molecules which is THE central power component. this makes the turbo more efficient and also increases the product of the force needed from the turbine.
it is an ADD at any boost level, not just at max boost.
i believe, if this proves out, that it will be the most important new rotary concept since the introduction of AI in 04.
howard
based on what RiceRacing has done in the last year i would say that the evidence is solid that what he is doing WORKS.
do you know anyone that has beat on his car for a year and is currently running 34 psi boost w a motor that shows 117 compression? all fully and professionally instrumented.
his setup is 100% preturbo and is water 45% meth 55% based on volume... 50/50 based on mass. reading between the lines, his system came alive a year ago when he added the meth to water which he had been running exclusively for many years. (and generally running 20 psi w water alone). it was the addition of meth that allowed him to add another BAR of boost.
given that he is successfully doing what few have done on this board i say it is time to take a very close look... that is what i intend to do. Peter and i took different paths in 2004 w re to AI injectant... Peter water, Howard meth. it appears we both have found that an approx 50/50 mix is the answer.
maybe preturbo is the other answer... i intend to find out w real testing. one thing i know is that what Peter has been successfully doing may redefine how we think about the rotary's dual purpose limits. most today consider around 20 psi to be about the limit for a dual purpose pump/AI car. of course piston engines often run 35-40. we say, it is the engine's architecture... and the accepted wisdom lapses into apex seals, long combustion chambers, lots of internal surface area etc.
meanwhile Peter is running 34 psi on pump and has a happy motor. he is also going really fast as documented by his GPS based systems.
not to be overlooked is his tuning philosophy:
airflow is everything... add the proper injectant at the right place and turn up the boost. do not attempt to make more power by tuning at the edge.... run it rich w very modest advance but at high boost. it is working.
i do agree w much of the Slides/quote. assuming that pretubo works, especially w an alcohol component, you win anytime you inject. by cooling the compressed mix inside the compressor housing you add additional oxygen molecules which is THE central power component. this makes the turbo more efficient and also increases the product of the force needed from the turbine.
it is an ADD at any boost level, not just at max boost.
i believe, if this proves out, that it will be the most important new rotary concept since the introduction of AI in 04.
howard
Last edited by Howard Coleman; 05-05-12 at 08:13 AM.
05-05-12, 12:06 PM
#25
"Elusive, not deceptive!”
Howard, I remember when you and Peter were bickering about which injectant was best.
Some of us just went to studies done during desperate times of WWII for answers.....
where opinions and theories were great but research was crucial.
If you study Report No. 815 under NACA papers. The tests show the limits of the
different injected coolants on CFR test engine.
Both Indicated Mean Effective Pressure (IMEP) and Boost limits are listed.
Their tests were done by increasing pressure till knock was detected
and then backing off power 7% (so somewhat conservative).
Knock limit for rich fuel- IMEP 285 lb/sq in. (about 14 psi)
...................For water IMEP 325 lb/sq in. (about 18 psi)
..........For water/meth- IMEP 460 lb/sq in. (about 30 psi)
My tests so far show that the Rotary behaves similarly.
By the way the Germans who were also "injecting" didn't see as much
improvement as our pre-compressor method because they were using
"higher-tech" direct-injection into the cylinder.
Cliff Notes... Cooler/denser air into through the compressor, cooler/denser air into the engine. Water helping the burn process.
Barry
Some of us just went to studies done during desperate times of WWII for answers.....
where opinions and theories were great but research was crucial.
If you study Report No. 815 under NACA papers. The tests show the limits of the
different injected coolants on CFR test engine.
Both Indicated Mean Effective Pressure (IMEP) and Boost limits are listed.
Their tests were done by increasing pressure till knock was detected
and then backing off power 7% (so somewhat conservative).
Knock limit for rich fuel- IMEP 285 lb/sq in. (about 14 psi)
...................For water IMEP 325 lb/sq in. (about 18 psi)
..........For water/meth- IMEP 460 lb/sq in. (about 30 psi)
My tests so far show that the Rotary behaves similarly.
By the way the Germans who were also "injecting" didn't see as much
improvement as our pre-compressor method because they were using
"higher-tech" direct-injection into the cylinder.
Cliff Notes... Cooler/denser air into through the compressor, cooler/denser air into the engine. Water helping the burn process.
Barry