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True or False: Boost pressure

  #1  
Old 08-27-2011, 06:40 PM
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Default True or False: Boost pressure

True or False:
On the same engine, all else being the same, the engine will make identical horsepower, torque, mass air flow, etc. at a given boost. No matter HOW the boost was generated (whether it comes different turbos, or a gigantic compressed air reservoir).

(all else being equal includes tune, IAT, MAF, pipes, fuel, etc.).

I say: TRUE.

The hydrodynamic conditions after the intake are the same; same lossses, etc. Therefore the same flow at a given pressure. With the same temperature (IAT do not change), the massflow also remains the same. Ergo: same power, torque.
 
  #2  
Old 08-27-2011, 10:21 PM
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That is incorrect. If you used an outside source ie: Air compressor, then the engine has no power/ torque loss from generating the compressed air because the engine is not having to turn a supercharger or use exhaust to spool a turbo ect... Therefore at the same boost pressure the engine using an air compressor would make more power.

In most cases a turbocharger requires less power from the engine than a supercharger does to make equal boost pressure on identical engines.
 
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Old 08-28-2011, 08:21 AM
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Originally Posted by tiresmoke69 View Post
That is incorrect. If you used an outside source ie: Air compressor, then the engine has no power/ torque loss from generating the compressed air because the engine is not having to turn a supercharger or use exhaust to spool a turbo ect... Therefore at the same boost pressure the engine using an air compressor would make more power.

In most cases a turbocharger requires less power from the engine than a supercharger does to make equal boost pressure on identical engines.
Drive losses make a difference. Correct.

If both compared sources are turbos, the "drive losses" (from exhaust restrictions) will be the same.

Under the stipulations above: Two totally different turbos will produce equal power/torque at identical boost levels.
 
  #4  
Old 09-09-2011, 11:56 PM
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that is really wrong. ^^ guys running GT turbos at my boost (26psi) will kill my car when they reach equal boost levels. the volume is another thing to take into consideration. if i have an injector plummed into a water hose, and am using a pulse width modulator to control flow. i get maybe enough water out of a 1 sec pulse width to notice it in a cup. then use the same modulator to open a valve that has the same circumference as the hose itself. open it as long as i had the injector open.. and i get enough water to fill the cup or knock it out of my hand. you have to consider volume as well..
 
  #5  
Old 12-12-2011, 02:38 PM
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Default False....

Originally Posted by vtraudt View Post
True or False:
On the same engine, all else being the same, the engine will make identical horsepower, torque, mass air flow, etc. at a given boost. No matter HOW the boost was generated (whether it comes different turbos, or a gigantic compressed air reservoir).

(all else being equal includes tune, IAT, MAF, pipes, fuel, etc.).

I say: TRUE.

The hydrodynamic conditions after the intake are the same; same lossses, etc. Therefore the same flow at a given pressure. With the same temperature (IAT do not change), the massflow also remains the same. Ergo: same power, torque.
"FALSE.

CFM is the ultimate answer there.

you can boost 6psi on a t25 and make 180 hp or you can boost 6psi on a t3/t4 and create well over 300hp."

thats is what i would have said until i read "therefore the same flow at a given pressure."

its a completely pointless question because in theory it is almost impossible to keep the same cfm at every boost pressure.

you change the size of the turbo you will have more lag and higher cfm.

if you went with a comparison of two turbos and one huge one you would run the same cfm during one crossover point, but at low rpms the two turbos would create more cfm.

"Horsepower is defined as work done over time. The exact definition of one horsepower is 33,000 lb.ft./minute. Put another way, if you were to lift 33,000 pounds one foot over a period of one minute, you would have been working at the rate of one horsepower. In this case, you'd have expended one horsepower-minute of energy." What is Horsepower?

even if you took a dyno test ran two vehicles with different set ups and found the crossover point where they had identical cfm, psi, and rpm or whatever..... the horsepower would be different.

lets say you used a twin turbo and a single turbo. twin having two smalls and the single having one big. at a crossover at about 2500rpms in theory should make more hp. but if the crossover occured around 5000 rpms the large turbo'd motor would in throery would be at a higher hp.

blah blah blah science and other confusing garbage...

the answer is FALSE no matter how you look at it
 
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Old 12-12-2011, 03:36 PM
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Originally Posted by ziggyTT View Post
"FALSE.

CFM is the ultimate answer there.

you can boost 6psi on a t25 and make 180 hp or you can boost 6psi on a t3/t4 and create well over 300hp."

thats is what i would have said until i read "therefore the same flow at a given pressure."
If the IAT are the identical, the same engine will always produce the same horsepower/torque at a given CFM, as far as I know.

Since the pressure is just the by-product of having to push the air (CFM) through a restriction (here: engine), and the restriction is the same (same engine), the engine will make the same power at.

Different turbo can generate different power because they may generate
different MASS air flow at the same boost (different IAT).

"CFM is the ultimate answer there."

If anything mass air flow is the ultimate answer.

"6psi on a t25 and make 180 hp or you can boost 6psi on a t3/t4 and create well over 300hp".

6 psi at 3000 rpm from t25 with the same IAT will create the same HP ast 6 psi with the same IAT from t3/t4 at 3000 rpm"
 
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Old 12-12-2011, 04:03 PM
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Originally Posted by vtraudt View Post
If the IAT are the identical, the same engine will always produce the same horsepower/torque at a given CFM, as far as I know.

Since the pressure is just the by-product of having to push the air (CFM) through a restriction (here: engine), and the restriction is the same (same engine), the engine will make the same power at.

Different turbo can generate different power because they may generate
different MASS air flow at the same boost (different IAT).

"CFM is the ultimate answer there."

If anything mass air flow is the ultimate answer.

"6psi on a t25 and make 180 hp or you can boost 6psi on a t3/t4 and create well over 300hp".

6 psi at 3000 rpm from t25 with the same IAT will create the same HP ast 6 psi with the same IAT from t3/t4 at 3000 rpm"
i think its time to use google man....

IAT - INTAKE AIR TEMPERATURE - calculated also in the audi by the MAF determines the temperature of the charged air to determine weather or not to add fuel or subtract.

MAF- MASS AIR FLOW - is measured by a MAF SENSOR, which is the mass of air and how fast its traveling. the sensor use's info from the MAF to determine the amount of air CFM so it can calculate the amount of fuel to add or subtract off of the default fuel mapping system.

anyone that knows anything about automotive theory or electrical systems just facepalmed themselves during the reading of your last post.

not to be a jerk or imply that your ignorant. but honestly read what i just said here then re-read what you wrote.
 
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Old 12-12-2011, 05:35 PM
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I typed:

"6 psi at 3000 rpm from t25 with the same IAT will create the same HP ast 6 psi with the same IAT from t3/t4 at 3000 rpm"

Tried to say:

"T25: 6psi with IAT x degree = same HP as 6 psi with IAT x degree from t3/t4"

Its just physics: 6 psi will force y cfm through the engine (it does NOT matter WHAT pushes the air through the engine. And since the temperature is the same, the MASS flow is the same.

Physics: mass air flow = HP (given same engine and same IAT).

The ONLY reason different turbos CAN generate different power at the same psi is different IAT (resulting form different compressor efficiency at the given operating point).
 
  #9  
Old 12-12-2011, 06:40 PM
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Originally Posted by vtraudt View Post
I typed:

"6 psi at 3000 rpm from t25 with the same IAT will create the same HP ast 6 psi with the same IAT from t3/t4 at 3000 rpm"

Tried to say:

"T25: 6psi with IAT x degree = same HP as 6 psi with IAT x degree from t3/t4"

Its just physics: 6 psi will force y cfm through the engine (it does NOT matter WHAT pushes the air through the engine. And since the temperature is the same, the MASS flow is the same.

Physics: mass air flow = HP (given same engine and same IAT).

The ONLY reason different turbos CAN generate different power at the same psi is different IAT (resulting form different compressor efficiency at the given operating point).
dude who taught you this? that was the biggest load i ever heard of....

IAT INTAKE AIR TEMPERATURE (DEGREES)
MAF MASS AIR FLOW

maf does not equal hp ?



now what your saying here "6 psi will force y cfm through the engine (it does NOT matter WHAT pushes the air through the engine. And since the temperature is the same, the MASS flow is the same" is correct but back to your original question it will only do it at a crossover not the entire band so the engines will produce different hp all together. and because they start out different the hp at the crossover will be different and that is a fact.
 
  #10  
Old 12-12-2011, 06:42 PM
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BUT yes at a certain rpm it is possible to happen, but it wll never happen because the ROA rate of acceleration is different between the two vehicles one with twin and one with single may cross at 3000 rpm and have all the same iat and maf.... but the twin will be at a higher hp because it required less work to make it to 3000 rpm. less work = more power.
 

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