TKPIXMR

Hi guys!

I wonder why the same boost level on stock make less power than upgrade turbo.

for example: same set up

Stock 24 psi = 330whp
50 trim 24 psi = 400whp

Thanks

stEVOx

im pretty newb too, but i think its the size of the turbo?

Redline06

iTrader: (45)

OMG I feel my IQ just dropped.. TKPIXMR you need help dude.. and your driving a Evo shame on you... I cnt beleive you dnt know the diff but okay.. ama let some one else tell you cuz I have to go but.. I'll be back..

AndyBandy

iTrader: (37)

i dont want to get into fluid and thermo dynamics, but it has to do with how much the turbo can flow (cubic feet per minute) at that pressure. (larger housing, wheel, etc.)

i guess what i would suggest is to read up on how a turbo works, maybe www.howstuffworks.com i think it is, and just learn the basic function.

tephra

iTrader: (6)

just think about the connection to your boost gauge, just because you are getting 24psi to your gauge doesn't mean its very powerful.

imagine 24psi coming out of a storm drain...

lol

Ralph

iTrader: (19)

Basically.. more airflow = more power

AutoXer

iTrader: (1)

pV=nRT

A smaller turbo will heat the air up more and result in less flow at the same pressure.

Why is this in the ecuFlash forum? Mods, Please move it.

KevinD

iTrader: (56)

^ that would be the correct answer. the bigger turbos are more efficient at higher pressure ratios. more efficient means the bigger turbo doesn't increase the temperatures as much as the smaller turbo during compression. lower temperatures means a higher density at the same pressure (24psi). higher density means more air. more air means more power. it should also be noted that with the bigger turbo, there is less back pressure due to the larger turbine. this means more lag, but also a high volumetric efficiency.

Titanium

Also, a larger turbo has less blockage on the exhaust side of the equation (this doesn't account for 70 hp, but it is a factor involved)

Another way to think about it is getting hit by a motorcycle going 60 mph and getting hit by a semi going 60mph.

l2r99gst

iTrader: (2)

The correct answers started with AutoXer's post.

It's funny that there were people making fun of the question, but didn't even know the answer.



Eric

merkzu

iTrader: (4)

Wow. What a completely worthless response, way to be an idiot and an ******* at the same time

Like KevinD said, a smaller compressor isnt as efficient and heats up the air a lot, and air is less dense when its hot. A bigger turbo can reach the same pressures more efficiently, and the air is much cooler. So 24psi of hot air is less air than 24psi of cooler air . Added to that is less restriction in the exhaust.

bvdawg13

iTrader: (3)

why is this thread under ecu flash topic if it has to do with a newb turbo question?

TKPIXMR

Thanks for your educate guys, I used EcuFlash too. Sorry I posted it wrong location.

iTune

iTrader: (3)

A turbo is made up of three main parts each having it's own sub-parts. 1)Turbine Section 2)Compressor and 3)Center Cartridge.

How Turbines Are Designed
The exhaust turbine's job is to convert the energy in the moving and expanding exhaust gasses into rotating kinetic energy of the shaft and turbines. The compressor turbine's job is to convert that rotating energy into the movement of the air that enters the engine. This air is compressed and (unfortunately) heated. The turbines in a turbo charger are measured by the sizes of each stage of the turbine. A turbine has two stages: the inducer stage and the exducer stage. The size and shape of each stage determines the shape of the turbine's fins and ultimately the characteristics of that turbine.
For the compressor turbine (or "compressor wheel"), the inducer part of of turbine is at the end of the shaft and can be seen by looking into the intake of the turbo compressor housing (looks like a fan). The blades that you see there extend into a larger diameter at the other end of the turbine. This is the exducer stage. The inducer on the compressor turbine is responsible for generating the vacuum at the compressor housing inlet that pulls air into the compressor. The air then "rides" the fins towards the exducer stage, which is a larger diameter, and gets sling-shot towards the outside of the compressor housing. The housing collects this moving air an expels it through the housing's outlet. The way that the air leaves the fins causes it to swirl as it leaves the housing. Since the intake manifolds on the early Turbo I engines were so close to the turbo, an anti-swirl fin had to be installed in the turbo outlet duct to stop this air motion from effecting the flow characteristics of the intake manifold.

The exhaust turbine also has an inducer and exducer, but because the exhaust turbine has the opposite function of the compressor turbine, the two are switched. The exhaust gasses are directed towards the outside of turbine through a nozzle. This is the inducer stage because it is the part of the turbine that collects the gasses. As the energy from the gasses is transferred into the turbine, the gasses slow down and exit the turbine through the exducer stage.

turbo charger Buzz Words
There are several factors that determine the performance of a turbo charger. The three most important ones are the type of exhaust turbine, the A/R ratio of the exhaust housing, and the size of the compressor turbine. Usually, it seems that the exhaust turbine is just referred to as the "turbine" and the compressor turbine is referred to as the "compressor wheel".
The Exhaust Turbine
The exhaust turbine design is a balance between absorbing as much energy from the exhaust gasses as possible and allowing the gasses to flow as easily as possible. This is closely related to the size of the exhaust housing. A larger turbine can absorb more energy from the gasses and spin the shaft with more torque and speed, but too large a turbine will restrict the flow of exhaust such that engine performance is greatly reduced. Typically, the inducer is only slightly larger than the exducer on the exhaust turbine. Generally, you would want to stick with the stock turbine because it's size is not nearly as important as the compressor turbine's size. If you want to reduce restriction through a smaller housing, you can have the turbine "clipped", which reduces the size of the fins and allows more air to flow around the turbine.
The Turbine Housings
The exhaust and compressor housings on turbo chargers use a "scroll" design. For example, the exhaust housing's scroll is where the exhaust gasses enter the housing and are directed at the turbine. It's basically a smooth, tubular chamber that surrounds the turbine with a slot all the way around that acts as a nozzle to direct the exhaust gasses at the turbine. It's called a scroll because it slowly gets smaller in diameter as a goes around the turbine. This pressurizes the gasses, forcing them out of the slot/nozzle at a fast rate. In turbo-terms, the scroll is measured by the cross-sectional area of the scroll's "tube" (A) and the distance from the center of the "tube" to the turbine shaft (R). The values by themselves are not meaningful to the user and for the most part, R does not change much for different housings, but by dividing R into A, you get the A/R ratio. So, the A/R ratio of the exhaust housing refers to the size and shape of the scroll that is cast into the housing. It basically determines how restrictive the housing will be, versus how quickly the turbine will spin up. A lower A/R ratio (smaller scroll area, A) results in a more restrictive housing. This restriction speeds up the exhaust gasses and increases the amount that the gasses will expand. It's the speed and expansion of the gasses that causes the turbine to spin. So with a low A/R ratio, the turbine will spin up quicker, but as engine output and rpms increase, the restriction of the housing begins to build up too much back pressure on the engine, which reduces performance. A good rule of thumb for when there is too much back pressure is when the pressure in the exhaust manifold is more the half of the pressure in the cylinder. So basically, a larger A/R ratio will improve your engine's top end, while losing some mid range power and increasing turbo lag. A smaller A/R ratio will help the bottom and mid-range, but may effect the top end.
On the compressor side, the housing also features a scroll design, but it has the opposite function. The air leaving the compressor turbine has a lot of speed, but not much pressure. The scroll on the compressor housing starts small and gets larger as it approaches the compressor outlet. This collects the air and builds up air pressure. So, the compressor housing is designed to convert the speed-energy of the air coming off of the compressor turbine into pressure-energy, which is much more useful to an engine.

The Compressor Turbine
The size of the compressor turbine determines the maximum amount of boost that the turbo charger can produce. It also effects the spool-up time of the turbo. The type of compressor wheel is usually designated as its "trim", which is a value that describes the inducer and exducer sizes. Typically, the exducer is significantly larger than the inducer on a compressor turbine.
So in conclusion, a turbo charger's design becomes a balancing act between these three factors.

How Boost Is Controlled
The amount of boost produced by the turbo is controlled with another device called a waste gate. The waste gate is a large valve that sits at the exhaust inlet to the turbo that, when opened, causes the exhaust gasses to bypass the exhaust turbine instead of through it. The further the waste gate is opened, the more exhaust is bypassed and less boost is produced. A spring in the actuator closes the waste gate (by pulling on the rod). The back-side of the actuator diaphragm is connected to the intake manifold. As pressure builds up in the manifold, the actuator rod pushes out and the waste gate opens. This pressure is bled off by a solenoid that is modulated (switched on and off quickly) by the logic module. The longer the duty cycle (amount of time it spends turned on) of the solenoid, the higher the boost pressure that is produced. There were two different configurations used to accomplish this, depending which turbo charger was installed on the vehicle. The function of both is the same and the only real difference is where the manifold pressure comes from.

Center Cartridge....

This is the section between the turbine section and the compressor. It houses the shaft that connects the turbine wheel to the compressor wheel. The shaft is supported by a bearing housing that is lubricated and cooled by an oil line from the engine. Since engine exhaust has such high temperatures, the exhaust side of the turbo can reach thousands of degrees F. This is why it is so critical that the engine oil be changed religiously (every 3,000 miles), because old oil can burn and leave deposits in oil lines and housings, called "coke". Coking can be virtually eliminated by using a synthetic oil and changing it frequently (every 6,000 miles). Some turbos feature an additional passage for a coolant line, to keep the bearing housing cool. This did little to keep temperatures down while running, but it had a huge effect after the engine was shut off. Without the coolant passage, the oil would drain when the engine was shut off and the turbo bearing housing would reach incredibly high temperatures from the heat transferring out of the exhaust manifold. This took its toll on the life of the bearings. The presence of the water keeps the housing cool.


Now, thats only half the story......

Running a larger turbine section(less restrictive) lowers backpressure. This lowering of backpressure has many great advantages. It lowers EGT's (exhaust gas temps) and allows you to run more ignition timing in boost. Being able to run more ignition timing in boost makes more power and also helps keep EGT's lower. If you ran a smaller turbine section(more backpressure) EGT's will be higher, and you will not be able to run as much ignition timing in boost, which also raises EGT's even more. So running a larger turbine section allows you to run more boost safer and with less danger. There is, however, a catch to this. Running a larger turbine section slows turbine spool and creates more "lag". This is why the proper turbine section needs to be choosen for the duty at hand. Especially if you are running a high static compression engine.

A larger compressor housing and wheel means that the air stays cooler(cooler air is denser air) once compressed and the larger turbo does not have to work as hard to create the same boost pressure as the smaller turbo, all else equal. THis is why you make more power with a larger turbo than you do with a smaller one at same boost pressures. You can clearly see this when you look at compressor charts and compare the effeciency of a smaller turbo to a larger one.

Obviously, the smaller turbo will spool up faster and make more torque than the larger turbo. The larger turbo will make less torque but will make more mid range and peak power. The reason why the smaller turbo makes more torque is because the faster you can build boost in the lower RPM's the more torque you will make. Basically, the lower you can make peak VE(Volumetric Effeciency) the more torque you will make at that peak. After peak VE, torque falls as RPM's increase. And because Horspower is calculated from torque(torque*rpm/5252), Horsepower increases as RPM's rise(even though torque is falling or steady) at same boost pressures until the engine reaches its peak power, then power falls. Larger turbo's make less torque because the spool is later in the RPM range, but these turbos make more peak power in the upper RPM range. So a balance must be made on which turbo is right for you.

CJ

iTune

iTrader: (3)

I see way too much of this rhetoric on these boards man. If you really knew the answer, you would of answered it. Seems to me you have a half working understanding of why it is what it is. And thats OK, but to bash somebody that knows even less than you, is....well......ignorant.

+1 for him for asking questions and trying to learn.

-1 for you for acting like you already knew the answer, even though your post shows you proably don't.

Read up......

CJ