turbo Flow vs. PSI
- Thread starter 87targa
- Start date
imagine breathing through a soda straw and then trying to breath through a rain gutter. at the exact same power the larger turbo will make more power as more air can flow through it more easily.
theres another difference though too. a correctly sized turbo will make more power (area under the curve) than the largest thing you can find. there are several other aspects to consider (center sections, a/r of the rear housing etc etc) what alot of people dont realize is that the ct26 is a fairly large turbo, its just older technology. a turbo thats the same size as the ct but using more modern methods (variable vane technology for instance) would yeild more power all over the place.
theres another difference though too. a correctly sized turbo will make more power (area under the curve) than the largest thing you can find. there are several other aspects to consider (center sections, a/r of the rear housing etc etc) what alot of people dont realize is that the ct26 is a fairly large turbo, its just older technology. a turbo thats the same size as the ct but using more modern methods (variable vane technology for instance) would yeild more power all over the place.
42R, by a significant margin. Go to the Garrett site, pull up the turbos you are interested in, and look at the compressor maps for each.
First, notice that the 35R can push ~40lb / min, max. Notice that the 42R can push upwards of 80lb / min. More air means more fuel means more power. In this case, lots more power.
Secondly, pick an efficiency range and note the difference between the two maps.
First, notice that the 35R can push ~40lb / min, max. Notice that the 42R can push upwards of 80lb / min. More air means more fuel means more power. In this case, lots more power.
Secondly, pick an efficiency range and note the difference between the two maps.
Masssupra89:
just think of the motor as a perfect motor. everything is 100% efficient nothing is wrong. practically an ideal world. no other variables change other than the turbo (which means turbo flow changes).
others:
most of the explanations here is what I told a friend of mine. what his defense was that both turbos will make the exact same power. at 25 psi. what he says is that how can you make more power if your valves (restriction) never changes. ie. nothing has changed on the motor, which is the restriction. he says that the power will shift up or down the power band but at a fixed rpm (something of that comment), the power will be the same for both turbos. I say hell no.
about the straw and rain gutter, i tried that. he says that is changing the engine resistance (valves, etc).
what else can i to say/defend my side.
just think of the motor as a perfect motor. everything is 100% efficient nothing is wrong. practically an ideal world. no other variables change other than the turbo (which means turbo flow changes).
others:
most of the explanations here is what I told a friend of mine. what his defense was that both turbos will make the exact same power. at 25 psi. what he says is that how can you make more power if your valves (restriction) never changes. ie. nothing has changed on the motor, which is the restriction. he says that the power will shift up or down the power band but at a fixed rpm (something of that comment), the power will be the same for both turbos. I say hell no.
about the straw and rain gutter, i tried that. he says that is changing the engine resistance (valves, etc).
what else can i to say/defend my side.
check this thread.... might help. It did help me with the exact same argument with my friend.
http://www.supramania.com/forums/showthread.php?t=69249
http://www.supramania.com/forums/showthread.php?t=69249
His theory required 2 rather large assumptions.
1. That all turbos compress air at the same efficiency. This is not true at all - if it were, there would only be a single compressor map for any turbo.
2. That the engine itself (or the valves, if you prefer) is the biggest restriction in the system.
Furthermore, there is real world data to back you up, and nothing to back up his theory. Why do buses and tractor trailer rigs come with huge turbos, when they could just put on small ones and get the same power levels? Why do dyno queens always want a bigger turbo?
1. That all turbos compress air at the same efficiency. This is not true at all - if it were, there would only be a single compressor map for any turbo.
2. That the engine itself (or the valves, if you prefer) is the biggest restriction in the system.
Furthermore, there is real world data to back you up, and nothing to back up his theory. Why do buses and tractor trailer rigs come with huge turbos, when they could just put on small ones and get the same power levels? Why do dyno queens always want a bigger turbo?
87targa;1008554 said:
first off your friend is an idiot
second, listen to grimjack. Flowrates and efficiencies are the two biggest factors between the turbo and output power in this case
higher flowrate+colder air = more power
Ask your friend if your CT26 at 25PSI (if it doesnt blow up by then) will output the same power as a T88 at 25PSI. If he says it will have the same power....GIVE UP immediately :biglaugh:
People get caught up in the whole "Boost = resistance to flow" and loose sight of what happens when the Valves are open.
VOLUME is king, the 42 moves more volume when the valves are open then the 3540.
VOLUME is king, the 42 moves more volume when the valves are open then the 3540.
Well, you guessed right.
GJ said:
GJ said:
The person who posts the right answer shouldn't have to repeat himself like that. If you just don't know about theory, why post? No shame in just reading.
42R isnt as responsive as the 35R. No personal experience here, but simple physics etc.
35R isnt meant for as high power either. 42R's peak efficiency is 78%, just behind the 35R's 79%, which is still damn good. T4s are like 72%. My goals are at but not really more than 500rwhp, which the 35R would be an excellent turbo for.
The 42R, obviously, outflows the crap out of it. It really just depends how deep your pockets are and what you're building your car for
35R isnt meant for as high power either. 42R's peak efficiency is 78%, just behind the 35R's 79%, which is still damn good. T4s are like 72%. My goals are at but not really more than 500rwhp, which the 35R would be an excellent turbo for.
The 42R, obviously, outflows the crap out of it. It really just depends how deep your pockets are and what you're building your car for
I did give up, sort of. he is a stubborn **** when it comes to this. he does a lot of supercharging and from the link given before, i can sort of see where his thought comes from. I try to explain how turbos are a little more complicated then supercharges but he just won't believe.
anyways, I will look through my thermo and fluid dynamics book to see if i can come up with something.
thanks guys
anyways, I will look through my thermo and fluid dynamics book to see if i can come up with something.
thanks guys
dont forget to look at the exhaust side of the turbo, everyone gets caught up in the compressor side. The air in has to flow through the back side too.. Bigger turbine = less backpressure and more flow. But less response comes with that.
a 3.2L supercharge will flow more air then a 2.8L supercharger, same concept for the most part
87targa;1008952 said:
a 3.2L supercharge will flow more air then a 2.8L supercharger, same concept for the most part
87targa;1008952 said:
show him this thread, tell him to post up if he'd like. He will get shot down...and QUICK. Or refer him to the Turbocharged section of the forum, someone just recently asked a question about this.
EDIT: here, http://www.supramania.com/forums/showthread.php?t=69249
GrimJack;1009094 said:
if 87targa is stubborn like me he willl go to great lenghts to prove him wrong, then laugh and tell him hes an idiot. it has more meaning this way bc you know they feel stupid :biglaugh:
I am going to take a stab at this.
When studying the difference between Roots and Whipple, it helped me understand how turbochargers work a little better.
Roots superchargers are just big fans. The blow in air into the intake manifold. So all you are really doing is taking air from a outside air pressure, and BLOWING into an intake manifold. This does of course increase the air pressure inside the intake manifold, but the blowing has to maintain the entire manifold at that pressure. They can generate quite a bit of heat and just isn't very efficient.
Now take Whipple or Screw type Superchargers. As they draw air into the screws, the screws actually compress the air before resleasing it into the manifold. I don't know the actual thermal dynamics of this, but whatever it is, it is much better so the air can reach a higher pressure without generating near as much heat. Then the air leaves the supercharger pre-compressed into the manifold where it MIGHT expands slightly(which would have a COOLING effect). I could assume that air pressure between the screws is higher than the actual manifold pressure, but I could be wrong. If I am wrong, then after the air leaves the screws, it gets compressed further like it would in the roots style SC, just dealing with higher pressures without the extra heat.
Compressor wheels act very similar, compressing the air as it flows through the fins. They don't call it a "COMPRESSOR" for nothing. If it didn't compress air the would probably just call it a FAN/BLOWER wheel instead.
Compressor maps represent how the wheel actually works. The pressure ratio is how much the actual compressor will compress the air before it leaves the fins, not how much pressure can be obtained by the BLOWING effect.
Anyway, that is how I see it, and why 25psi on a GT35R is different than 25psi on a GT40R.
Someone please correct me if I am wrong, I am still just learning.
When studying the difference between Roots and Whipple, it helped me understand how turbochargers work a little better.
Roots superchargers are just big fans. The blow in air into the intake manifold. So all you are really doing is taking air from a outside air pressure, and BLOWING into an intake manifold. This does of course increase the air pressure inside the intake manifold, but the blowing has to maintain the entire manifold at that pressure. They can generate quite a bit of heat and just isn't very efficient.
Now take Whipple or Screw type Superchargers. As they draw air into the screws, the screws actually compress the air before resleasing it into the manifold. I don't know the actual thermal dynamics of this, but whatever it is, it is much better so the air can reach a higher pressure without generating near as much heat. Then the air leaves the supercharger pre-compressed into the manifold where it MIGHT expands slightly(which would have a COOLING effect). I could assume that air pressure between the screws is higher than the actual manifold pressure, but I could be wrong. If I am wrong, then after the air leaves the screws, it gets compressed further like it would in the roots style SC, just dealing with higher pressures without the extra heat.
Compressor wheels act very similar, compressing the air as it flows through the fins. They don't call it a "COMPRESSOR" for nothing. If it didn't compress air the would probably just call it a FAN/BLOWER wheel instead.
Compressor maps represent how the wheel actually works. The pressure ratio is how much the actual compressor will compress the air before it leaves the fins, not how much pressure can be obtained by the BLOWING effect.
Anyway, that is how I see it, and why 25psi on a GT35R is different than 25psi on a GT40R.
Someone please correct me if I am wrong, I am still just learning.
But you're not changing the pressure by changing the wheel, you change the amount it blows (rpm).
When trying to get the most hp out of it, you're trying to get it to flow the most it can, so you increase rpm by closing the wastegate and flowing as much exhaust as you can through the turbine wheel. This creates backpressure. A larger exhaust wheel and more efficient exhaust wheel will have less backpressure (as itll use the flow more efficiently).
Now this is not to say that you only make HP on the exhaust wheel, the compressor helps. A bigger wheel can flow more air per revolution, so easier to achieve your desired boost pressure with less turbine speed (more exhaust gases bypassed the turbine, creating less backpressure).
When trying to get the most hp out of it, you're trying to get it to flow the most it can, so you increase rpm by closing the wastegate and flowing as much exhaust as you can through the turbine wheel. This creates backpressure. A larger exhaust wheel and more efficient exhaust wheel will have less backpressure (as itll use the flow more efficiently).
Now this is not to say that you only make HP on the exhaust wheel, the compressor helps. A bigger wheel can flow more air per revolution, so easier to achieve your desired boost pressure with less turbine speed (more exhaust gases bypassed the turbine, creating less backpressure).