More boost = more power misconception..
More boost = more power misconception..
All:
I've seen this lingo thrown around like no tomorrow. Many people believe that increasing the boost beyond a certain threshold will yield more power. This one of the biggest myths in auto club communities. More boost does NOT necessarily mean more power.
Test case:
Our EVO8/9s come with a modified 16G turbo with 9.8 and 10.5 hotside turbine housings. The EVO 9 has a slightly larger compressor housing, but both run the same compressor/turbine wheel. Running on stock injectors with stock intercooler, you'd be hard pressed to find any extra power (i.e. 10whp per 1psi of boost increase) beyond 25psi. The turbo just doesn't flow efficiently at those speeds. So then, what about adding meth or race gas? Sure, you can get a little extra ponies from adding those knock-resistant components, but you are basically running a marathon race. The race is how much extra power can I extract given that I'm increasing intake temperatures dramatically while trying to supress knock with the additive. In the end, the hot temperatures from the boost continuing to increase will win over and your timing will retard due to detonation thus making you lose power and/or running the risk of a blown motor.
These turbos aren't designed to be run in the 25-30psi range for maximum efficiency. You will almost certainly get better reliability and more power from adding other mods and keeping the intake temps down.
Finally, I have heard a lot of guys saying, "Man your car is faster than mine and I have way more boost than you!!" throughout my automotive-hobby years. Well, aside from the major factor of tuning and the condition of the engine; straining the turbo beyond it's efficiency range could also be one of the reasons. So be leery the next time you think about turning that boost up when it's already too high.
Cheers,
-M
I've seen this lingo thrown around like no tomorrow. Many people believe that increasing the boost beyond a certain threshold will yield more power. This one of the biggest myths in auto club communities. More boost does NOT necessarily mean more power.
Test case:
Our EVO8/9s come with a modified 16G turbo with 9.8 and 10.5 hotside turbine housings. The EVO 9 has a slightly larger compressor housing, but both run the same compressor/turbine wheel. Running on stock injectors with stock intercooler, you'd be hard pressed to find any extra power (i.e. 10whp per 1psi of boost increase) beyond 25psi. The turbo just doesn't flow efficiently at those speeds. So then, what about adding meth or race gas? Sure, you can get a little extra ponies from adding those knock-resistant components, but you are basically running a marathon race. The race is how much extra power can I extract given that I'm increasing intake temperatures dramatically while trying to supress knock with the additive. In the end, the hot temperatures from the boost continuing to increase will win over and your timing will retard due to detonation thus making you lose power and/or running the risk of a blown motor.
These turbos aren't designed to be run in the 25-30psi range for maximum efficiency. You will almost certainly get better reliability and more power from adding other mods and keeping the intake temps down.
Finally, I have heard a lot of guys saying, "Man your car is faster than mine and I have way more boost than you!!" throughout my automotive-hobby years. Well, aside from the major factor of tuning and the condition of the engine; straining the turbo beyond it's efficiency range could also be one of the reasons. So be leery the next time you think about turning that boost up when it's already too high.
Cheers,
-M
Evolving Member
Joined: May 2008
Posts: 346
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From: Dallas, TX
Many varibles on this. But yes boost ( or rather heat produced by higher boost levels will start to have diminishing returns above the "sweet spot" for each turbo.) IX turbo I couldn't run above 24psi and make peak power. EvoRed turbo is just under 28psi and very happy about it. (93 octane for both)
uhh, that post is missing a lot of very important information
first of all, i promise you if your on stock turbo at 25psi, i can make more torque by a very significant margin by increasing the boost with meth. additionally, if the car is setup correctly, it can make a very significant amount of HP as well by increasing the boost.
certainly when out of the efficiency range of the turbo, it heats the air up more... but look at a compressor map and figure out how much that is by using the efficiency, and calculating it, not by just assuming it is "hot air". compressing the air more, even if it is more efficient at higher boost, will increase the temperature of the air coming out. the air is extremely hot regardless of how efficient the turbo is at 30psi.
this is where methanol really shines. it is not the higher octane that makes it so powerful, it is the cooling effect it has. methanol has a very high latent heat of vaporization, so when it goes from a liquid to a gas in the charged air, it absorbs tons of energy to undergo the phase change. this energy comes from the hot air, effectively cooling it more then an intercooler will. with a much cooler charge because of the methanol, the more dense the charge will be, thus the more power you are going to make.
so in review, when going from 25 to 30psi you increase the temperature of the air by quite a bit, even if the turbo has the same efficiency (pv=nrt). then if efficiency decreases in addition to the higher pressure, temperatures will increase even more following the adiabatic compression given the difference in efficiency.
density of the charged air is the important part (its the amount of air entering the cylinder), and density increases as temps decrease. with methanol cooling the charged air significantly in addition to the intercooler, you should see temperatures below atmospheric. this increases density beyond what it was at lower boost levels, thus more air in the cylinder.
you can reach a max flow of the turbo though, this would be called the choke point, where quite literally no more air can pass though (air is going to go supersonic)
so yes.... on stock turbo running 30psi with meth can and does yeild more power then at 25 psi with meth.
first of all, i promise you if your on stock turbo at 25psi, i can make more torque by a very significant margin by increasing the boost with meth. additionally, if the car is setup correctly, it can make a very significant amount of HP as well by increasing the boost.
certainly when out of the efficiency range of the turbo, it heats the air up more... but look at a compressor map and figure out how much that is by using the efficiency, and calculating it, not by just assuming it is "hot air". compressing the air more, even if it is more efficient at higher boost, will increase the temperature of the air coming out. the air is extremely hot regardless of how efficient the turbo is at 30psi.
this is where methanol really shines. it is not the higher octane that makes it so powerful, it is the cooling effect it has. methanol has a very high latent heat of vaporization, so when it goes from a liquid to a gas in the charged air, it absorbs tons of energy to undergo the phase change. this energy comes from the hot air, effectively cooling it more then an intercooler will. with a much cooler charge because of the methanol, the more dense the charge will be, thus the more power you are going to make.
so in review, when going from 25 to 30psi you increase the temperature of the air by quite a bit, even if the turbo has the same efficiency (pv=nrt). then if efficiency decreases in addition to the higher pressure, temperatures will increase even more following the adiabatic compression given the difference in efficiency.
density of the charged air is the important part (its the amount of air entering the cylinder), and density increases as temps decrease. with methanol cooling the charged air significantly in addition to the intercooler, you should see temperatures below atmospheric. this increases density beyond what it was at lower boost levels, thus more air in the cylinder.
you can reach a max flow of the turbo though, this would be called the choke point, where quite literally no more air can pass though (air is going to go supersonic)
so yes.... on stock turbo running 30psi with meth can and does yeild more power then at 25 psi with meth.
KevinD,
I never argued that you can't extract out more power by turning up the boost in cars WITH knock-supressing additives (i.e. Meth, C-16, etc..). You will get more power, but you won't get as much of a "delta" in whp/psi going from 25psi-30psi as you would going from 19psi to 24psi on the same turbo.
Since there are no public available compressor maps for the EVO turbo to compare, it's pretty moot. I'm willing to bet however, that the max efficiency island is nowhere near 30psi. It will also depend on how rapid the efficiency goes out the window as boost is increased. Even reading the compressor maps won't really show you how much the intake temps increased.
Very true, but I wasn't arguing that. And no matter how much the METH cools the intake temps, you can still make the compressed air even HOTTER. The METH will cool the charged air at a constant. That is, there is no such thing as proportionate METH cooling to intake temps (just before getting mixed with the METH).
Right. But you won't get 50whp going from 25-30psi, which reflects the entire system reaching a point of diminishing returns. I'd rather get that power elsewhere (which is my point) and save my turbo's reliability.
-M
certainly when out of the efficiency range of the turbo, it heats the air up more... but look at a compressor map and figure out how much that is by using the efficiency, and calculating it, not by just assuming it is "hot air". compressing the air more, even if it is more efficient at higher boost, will increase the temperature of the air coming out. the air is extremely hot regardless of how efficient the turbo is at 30psi.
this is where methanol really shines. it is not the higher octane that makes it so powerful, it is the cooling effect it has. methanol has a very high latent heat of vaporization, so when it goes from a liquid to a gas in the charged air, it absorbs tons of energy to undergo the phase change. this energy comes from the hot air, effectively cooling it more then an intercooler will. with a much cooler charge because of the methanol, the more dense the charge will be, thus the more power you are going to make.
so yes.... on stock turbo running 30psi with meth can and does yeild more power then at 25 psi with meth.
-M
Last edited by BOOSTEZ; Sep 24, 2008 at 11:20 AM.
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uhh, that post is missing a lot of very important information
first of all, i promise you if your on stock turbo at 25psi, i can make more torque by a very significant margin by increasing the boost with meth. additionally, if the car is setup correctly, it can make a very significant amount of HP as well by increasing the boost.
certainly when out of the efficiency range of the turbo, it heats the air up more... but look at a compressor map and figure out how much that is by using the efficiency, and calculating it, not by just assuming it is "hot air". compressing the air more, even if it is more efficient at higher boost, will increase the temperature of the air coming out. the air is extremely hot regardless of how efficient the turbo is at 30psi.
boostez, to really prove your point i think you should show us some dynos compairing the same car, one with say 24 psi. and one with 30. both with meth etc.
this is where methanol really shines. it is not the higher octane that makes it so powerful, it is the cooling effect it has. methanol has a very high latent heat of vaporization, so when it goes from a liquid to a gas in the charged air, it absorbs tons of energy to undergo the phase change. this energy comes from the hot air, effectively cooling it more then an intercooler will. with a much cooler charge because of the methanol, the more dense the charge will be, thus the more power you are going to make.
so in review, when going from 25 to 30psi you increase the temperature of the air by quite a bit, even if the turbo has the same efficiency (pv=nrt). then if efficiency decreases in addition to the higher pressure, temperatures will increase even more following the adiabatic compression given the difference in efficiency.
density of the charged air is the important part (its the amount of air entering the cylinder), and density increases as temps decrease. with methanol cooling the charged air significantly in addition to the intercooler, you should see temperatures below atmospheric. this increases density beyond what it was at lower boost levels, thus more air in the cylinder.
you can reach a max flow of the turbo though, this would be called the choke point, where quite literally no more air can pass though (air is going to go supersonic)
so yes.... on stock turbo running 30psi with meth can and does yeild more power then at 25 psi with meth.
first of all, i promise you if your on stock turbo at 25psi, i can make more torque by a very significant margin by increasing the boost with meth. additionally, if the car is setup correctly, it can make a very significant amount of HP as well by increasing the boost.
certainly when out of the efficiency range of the turbo, it heats the air up more... but look at a compressor map and figure out how much that is by using the efficiency, and calculating it, not by just assuming it is "hot air". compressing the air more, even if it is more efficient at higher boost, will increase the temperature of the air coming out. the air is extremely hot regardless of how efficient the turbo is at 30psi.
boostez, to really prove your point i think you should show us some dynos compairing the same car, one with say 24 psi. and one with 30. both with meth etc.
this is where methanol really shines. it is not the higher octane that makes it so powerful, it is the cooling effect it has. methanol has a very high latent heat of vaporization, so when it goes from a liquid to a gas in the charged air, it absorbs tons of energy to undergo the phase change. this energy comes from the hot air, effectively cooling it more then an intercooler will. with a much cooler charge because of the methanol, the more dense the charge will be, thus the more power you are going to make.
so in review, when going from 25 to 30psi you increase the temperature of the air by quite a bit, even if the turbo has the same efficiency (pv=nrt). then if efficiency decreases in addition to the higher pressure, temperatures will increase even more following the adiabatic compression given the difference in efficiency.
density of the charged air is the important part (its the amount of air entering the cylinder), and density increases as temps decrease. with methanol cooling the charged air significantly in addition to the intercooler, you should see temperatures below atmospheric. this increases density beyond what it was at lower boost levels, thus more air in the cylinder.
you can reach a max flow of the turbo though, this would be called the choke point, where quite literally no more air can pass though (air is going to go supersonic)
so yes.... on stock turbo running 30psi with meth can and does yeild more power then at 25 psi with meth.
Last edited by booster9; Sep 24, 2008 at 11:17 AM.
so um yeah, I heard "someone" tuning the evored at 51psi and making 618whp. What about that?
KevinD,
I never argued that you can't extract out more power by turning up the boost in cars WITH knock-supressing additives (i.e. Meth, C-16, etc..). You will get more power, but you won't get as much of a "delta" in whp/psi going from 25psi-30psi as you would going from 19psi to 24psi on the same turbo.
Since there are no public available compressor maps for the EVO turbo to compare, it's pretty moot. I'm willing to bet however, that the max efficiency island is nowhere near 30psi. It will also depend on how rapid the efficiency goes out the window as boost is increased. Even reading the compressor maps won't really show you how much the intake temps increased.
Very true, but I wasn't arguing that. And no matter how much the METH cools the intake temps, you can still make the compressed air even HOTTER. The METH will cool the charged air at a constant. That is, there is no such thing as proportionate METH cooling to intake temps (just before getting mixed with the METH).
Right. But you won't get 50whp going from 25-30psi, which reflects the entire system reaching a point of diminishing returns. I'd rather get that power elsewhere (which is my point) and save my turbo's reliability.
-M
I never argued that you can't extract out more power by turning up the boost in cars WITH knock-supressing additives (i.e. Meth, C-16, etc..). You will get more power, but you won't get as much of a "delta" in whp/psi going from 25psi-30psi as you would going from 19psi to 24psi on the same turbo.
Since there are no public available compressor maps for the EVO turbo to compare, it's pretty moot. I'm willing to bet however, that the max efficiency island is nowhere near 30psi. It will also depend on how rapid the efficiency goes out the window as boost is increased. Even reading the compressor maps won't really show you how much the intake temps increased.
Very true, but I wasn't arguing that. And no matter how much the METH cools the intake temps, you can still make the compressed air even HOTTER. The METH will cool the charged air at a constant. That is, there is no such thing as proportionate METH cooling to intake temps (just before getting mixed with the METH).
Right. But you won't get 50whp going from 25-30psi, which reflects the entire system reaching a point of diminishing returns. I'd rather get that power elsewhere (which is my point) and save my turbo's reliability.
-M
read and enjoy
https://www.evolutionm.net/forums/ar.../t-256057.htmland here is a compressor map for you:
http://www.stealth316.com/images/td05hr-16g6-cfm.gif
oh and they make the efficiency maps by measuring how efficient the compressor is, so by using them to determine your outlet temps it will be very close.
Last edited by KevinD; Sep 24, 2008 at 12:53 PM.
read and enjoy https://www.evolutionm.net/forums/ar.../t-256057.html
and here is a compressor map for you:
http://www.stealth316.com/images/td05hr-16g6-cfm.gif
oh and they make the efficiency maps by measuring how efficient the compressor is, so by using them to determine your outlet temps it will be very close.
https://www.evolutionm.net/forums/ar.../t-256057.htmland here is a compressor map for you:
http://www.stealth316.com/images/td05hr-16g6-cfm.gif
oh and they make the efficiency maps by measuring how efficient the compressor is, so by using them to determine your outlet temps it will be very close.
http://i113.photobucket.com/albums/n...glarge-cfm.gif
and here is a compressor map for you:
http://www.stealth316.com/images/td05hr-16g6-cfm.gif
oh and they make the efficiency maps by measuring how efficient the compressor is, so by using them to determine your outlet temps it will be very close.
http://www.stealth316.com/images/td05hr-16g6-cfm.gif
oh and they make the efficiency maps by measuring how efficient the compressor is, so by using them to determine your outlet temps it will be very close.
-M
Last edited by BOOSTEZ; Sep 24, 2008 at 01:39 PM.
