SloBaltS/C

25 lbs of boost inputted threw a supercharger the same 25 threw a turbo?????/ 25lbs is 25lbs no matter how it is inducted so whats the difference just askin

fredds-turbaltSS

Pressure wise yea, volume wise no....

Permafried-

One major difference is in how a turbo and supercharger are driven. A SC requires engine HP in order to turn as it's connected to the crank. A turbo is typically referred to as "free HP" because it is being driven by the exhaust gases that are on their way out of the exhaust mainfold anyways. So while the pressure is the same the resulting power output may not be.

As for how much HP a SC "robs" from the car is dependent on a number of things, pulley size, etc. This is a good question though I'm curious to see other opinions .

mofofernando

iTrader: (3)

^^ but im curious how the volume would be different. is it because of the different style inlets of the intake manis??

fredds-turbaltSS

the volume is different based on your charger. stock SC for these cars more like 1.1 liter of air where as like the TVS alittle bigger SC moves i think 1.3 ( i think those are the right numbers) but anyway if your building 10 PSI with each one the TVS is making more power bc its moving more air thru. same thing goes for the stock KO4 turbo compaired to a big turbo

BLAZIN07SS

iTrader: (7)

look at the turbo's rated flow. some can only flow 40lb/min and others can flow upwards of 60lb/min. the pressure can maintain the same at the example of 25psi, but airspeed has increased greatly

Permafried-

Both of you took the words out of my mouth . One thing to remember is PSI is simply a measurement of pressure whereas volume indicates how "much" air it is pushing at a time to fill a space to meet that pressure. The higher the flowrate the quicker the pressure builds and therefore the quicker the vehicle can make use of it. I think I got that right, if not someone correct me I'm a little zonked today and physics isn't coming easily to me .

fredds-turbaltSS

this is basic boost knowledge you noob gosh some ppl need to search befor asking such dumb quesstions,go kill yourself.


no im only joking

CudaJoe

iTrader: (1)

besides if your making 25psi with your S/C, that must be one helluva S/C. or your motor is gianormous.

BLAZIN07SS

iTrader: (7)

this makes no sense.

rnjmur

If you have two identical cars, set up exactly the same except one is SC and one is turbo, then 25 psi from the SC is exactly the same as 25 psi from the turbo. As permafried stated, there are differences in the amount of HP you gain from each though.

Parasitic loss is the main difference between the two. Basically, since the SC is driven by the motor it requires HP to turn the SC. The faster the SC turns, the more HP it requires to turn it, the less HP increase you get from the increase in airflow. With a turbo, the turbine is spun using the exhaust gas. Since the exhaust gas is being pushed out of the engine regardless of whether the turbo is there or not, the effect of its parasitic loss is very low compared to that of a SC.

The other big difference between a SC and turbo is "boost lag". A SC, since it is being turned by the motor, can increase the airflow almost instantaneously. A turbo requires that the engine cycle increased exhaust gas before the turbo can "spin up".

In higher horsepower applications, especially in higher revving engines, a turbo is usually the better choice due to the low parasitic loss. For lower end power, or in lower revving engines, a supercharger is usually a better choice.

There is of course much more to the differences and reasons between using each one, but these are some of the more basic explainations.

BYT*SS*TURBO

iTrader: (6)

PSI is just a measurement of the resistance of air entering the TB. The volume of air will change with the size of the s/c or the turbo. So 25psi is 25psi, but 25psi from your s/c isn't the same amount of airflow as 25psi from a ss/tc turbo.

rnjmur

Yes, 25 psi from a SS/SC is different than 25 psi from a SS/TC. I should have added that I was using the 25 PSI as a measure of the airflow, not as a measure of resistance as I was going from an "all things equal" point of view. People always want to associate the pressure they see on their boost gauge (which measures resistance) which the actual amount of airflow into the engine, which is not correct.

OriGinaL Condo

iTrader: (3)

Simplest explanation for a relatively simple concept. If you don't understand it in these words you probably won't get it.

mofofernando

iTrader: (3)

all this makes sense. still in the learning process on forced induction which is why i havent just thrown a ton of mods i know nothing about on my car. i wanna do it right the first time instead of just blowing money and my motor haha

fingerling

whats is the volume of air can a stock TC push or give

Stamina

Short answer: They are the same except for temp of the air after it's compressed.

Long Answer:

All things constant 25psi is 25psi and the airflow is the same... except for temp and humidity changing this. This is where one delivery method or size of the compressor is better than another, and why people talk about different flow.

If you have a small turbo that you're running out of its efficiency range then it will start creating more heat. Hot air is less dense and therefore contains less oxygen per unit volume. A larger turbo that is spinning at its peak efficiency range will produce say the same boost pressure, but will be doing it at a much lower temperature. Lower temperature means the air is more dense and thus more oxygen per unit volume.

Basically by bringing the compressed air temperature down you're improving effective airflow. That is why many people find that less boost pressure on a larger turbo creates equal or greater airflow/power.

There is only so much volume of air that can be ingested by the engine, so that's why you make the air more dense, to be able to get more air into the engine in the same volume (the whole reason for turbos/superchargers to begin with).

Now that being said, with engine mods you can bring up the volume of air that is ingested at a constant or lower pressure too. This is usually accomplished through tuning, cams/phasing, making the head flow more, making the manifold flow more, increasing the size of the valve openings, etc.

Saying that one psi is different somehow from the same identical psi can be slightly misleading.

eurochevy

if this hasn't been explained...as an example 25lbs on an m62 will not be the same as 25lbs on the TVS ..tvs is much larger..(don't know any actual figures but just throwing out numbers as an example)= m62 at 25lbs is like tvs at 15lbs->(making the same power levels)...if u were to put the tvs to 25 lbs then obviously you would be making a lot more power

BYT*SS*TURBO

iTrader: (6)

I believe its 36 Lbs/Min, but I have seen up to 38 in the logger with my Maf's dialed in perfectly.

SloBaltS/C

Thanks guys

fingerling

thankyou

selfinfliction

psi is the same

25psi with turbo A in a motor is the same as 25psi with turbo B in the same motor.

one can have more volume, it's irrelevant.

volume is what creates the positive pressure

the only time volume plays a factor is with replenishment speed

BoostedEcos

Hey just wanted to give you guys a real example of why psi is just a number and cfm is what is important. On my 04 cavalier I was running a t3/t4 60trim at 30 psi and made around 440 whp then upgraded to a garrett gt35r at 28 psi and make 540 whp. So if psi really mattered I should of made more on the t3/t4 but because the gt35r flows way more cfm it in turn makes more power on less pressure. Hope that helps and just remember its all about cfm not psi.

Cobalt_Daddy

why don't you just say this... 25lbs through a mcdonalds straw is easier to make than 25 pounds through a garden hose... if you blow through both .. the hose will require more effort because it's larger and less restrictive however... with a hose you would have to blow harder to make 25lbs... that's the difference... with that said... the larger the compressor type the more air you can get to flow at the same PSI. so in reality bigger is better because it's more efficient..