explain turbo measurements!!

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pyrobee

Everything can go faster!
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Alright. I am getting to where I wanna learn as much as possible about diesel performance and the first thing I feel stupid for not knowing very well is how you guys measure turbo sizes inlets outlets all that can someone explain it to me a little better
 
Im not the greatest with some of it myself, but its really pretty simply.

If you see someone say they have a 62/71/14

The 62 would stand for a 62mm compressor wheel, the 71 would be for a 71mm exhaust/turbine wheel, and the 14 would be how big the exhaust housing was, in this case a 14cm.

Sometimes with turbo's like Garret's the exhaust housings are measured in A/R instead of in cm like holsets. Its just a different way of measuring the size of the housing. The numbers for an A/R ratio usually range from .60 being very small to 1.30 or maybe bigger, being pretty large. For example, I think a .80 A/R housing is about the same as a 14cm housing.

Compressor wheels are usually measured by their smallest diameter, right where the air is coming into them. The "major diameter" would be the biggest part of the compressor wheel where the air is exiting the wheel and being pressurized.

Well, there is a start on understanding them. I hope that is mostly right:hehe: They really are pretty simple though.
 
The smaller end of the wheels are measured. Its called the inducer on the compressor wheel and exducer on the turbine. Usually diameters are given in mm, but on the larger turbos its common to hear them in inches, here's a couple examples of compressor sizes: 66mm = 2.6 inches, 71mm = 3.0 inches.

The compressor inducers give a rough idea of how much air the turbo can move. Generally speaking bigger compressors move more air and are slower to spool. The turbine wheels will always be slightly larger than the compressor.

Then comes the turbine housings. Depending on the brand these are given by the a/r ratio or the volume in cubic cm. The most common ones are 12 cm^3 or 0.70 a/r and 14 cm^3 or 0.80 cm^3. A tight housing will spool quick and choke up top while a bigger housing would be slower to start spooling but will flow more on the big end.

This is where wastegates comes in. A wastegate allows for the quick spool of the smaller housing with the flow of a larger one by flowing air around the turbine when it comes to a certain boost level. That too is a generalization because while most turbos open the wastegate at a certain boost level, there also mods available which can make a wastegate open based on the pressure of the hot side. The flow of the wategates is determined by its size. Wastegates also serve to limit the speed of the wheels under the point where they heavily wear bearing and/or explode.

As far as inlets and outlets go the inlet on most the aftermarket stuff is the same as stock, 4". The stock turbo uses different downpipe hook up than most of the aftermarket. The one you'll hear about most of the time is a hx40 downpipe, its 4" out and hooks up with a v-band clamp. Turbine inlet for stock and what most of us are running is a T-3 sized, while the turbos used in twins can be as big as T-6. I forget the size of the compressor outlet, it something like 2.5-3" connected with a v-band.

You'll see a lot of different turbo configurations, but most of the aftermarket turbos are based on the hx-40, s300g, s400, k31, and a few garretts/ turbonetics also. There's a lot of stuff I'm skipping (blade counts, wheel shape, pitch, compressor covers,....) but that might be enough for you to get a basic level of understanding. Garrett's page has some turbo basics available also: http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech101.html
 
whats the correct formula to figure x=cm housng into the correct a.r. it is?
 
SMOKIN-U said:
whats the correct formula to figure x=cm housng into the correct a.r. it is?
Click to expand...

Well if 0.70 is a 12 cm and 0.80 is a 14 cm then we can solve.
12cm = .70x 14cm = .80x
x= 17 x=17.5

So an approximation would be 17 times the a/r = cm^3
or cm^3 = .06 * a/r

This is a rough approximation based on hear say, but its better than nothing =) :bang:hehe:
 
j-rod said:
There's a decent diagram here showing the A/R ratio.
Click to expand...

Thats showing the turbing housing inlet as the area, which I'm pretty sure is incorrect. If we deal with something like HTT turbos, which has 4 different housings for a 71mm turbine, and all are t-3 flange turbos, which means the ports just entering the housing is what gives you the measurement.

If you take a turbine housing off, there is the slot around the turbine where the gasses enter. I'm pretty sure its the area of this slot that is measured, vs. the radius of the turbine wheel. Hopefully someone who knows for sure will correct me. I'd also be interested to know what units are used for said measurements.
 
Looks like our Holset exhaust housings are described as area in square centimeters (cm2) and the rest of the world goes a little further and figures area and the radius to get an area/radius ratio (A/R).
 
Ph4tty said:
The compressor inducers give a rough idea of how much air the turbo can move. Generally speaking bigger compressors move more air and are slower to spool. The turbine wheels will always be slightly larger than the compressor.
Click to expand...

So if your saying the turbine wheel is most always larger. Then why is my sled puller smaller? 66-65-14
 
Some turbo's are built the way yours is built. That doesnt mean its a desirable combination for all applications.
 
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