signature600

It's the cross sectional area of the exhaust housing and wheel I believe...14cm^2 or 14 sq. cm!

Someone else can explain it further...I've never set my mind to learning that particular are of chargers. I just know which one should work for what use

Chris

4x4dually

I figured it was the cross sectional area of the exhaust turbine. Approx 66mm or 6.6cm, divide by two, square, multiply by pie, that equals 34cmsq. Not correct. What am I missing? I'm all about learning the particulars. I like to know that things work...and how they work. It is the dang Eng in me.

signature600

Remember it's also a relationship between the housing AND wheel...AFAIK

PM HOHN, or wait and see if he responds. Maybe he can explain it better than me
Chris

gman07

I think the 14 sq.cm. refers to the area of the scrolls at some point.

A/R ratio is used by other turbo manufacturers and refers to the area of the scrolls divided by the radius at that point. A smaller A/R = higher velocity exhaust gasses = better spool-up.

HOHN would know for sure.

HOHN

The number like "14sq cm" refers to the cross sectional area of the turbine housing at a predetermined point. Where is that point?

Well, that's the problem. Depending on where you measure the cross-sectional area, the size will be different. This is why the much more descriptive approach of Area/Radius (A/R) was developed, because A/R has no units.

To illustrate the difference between these systems, consider what effect you'd see in different situations.

For example, if you have the same size housing (in cross-sectional area) in two differently sized turbine wheels, then they'd both still be considered "14 cm housings", but the A/R values would be much different! This, because the "R" part of A/R changes with the turbine wheel size.

The "14 sq cm" is only the "A" part of A/R, so without the radius, the meauurement is pretty meaningless.

Put another way, area alone (the "A" part like 14 sq cm) is only useful when comparing different housings on the SAME turbine section. So, it's valid for comparing a 12cm vs a 14cm housing for a stock turbo.

But it's COMPLETELY INVALID for comparing a "12cm" housing on a stock turbo to a "12 cm" housing for something like an HTT Killer B2. The larger turbine of the HT turbo will flow a lot more air, even given the "same " size housing. The A/R would tell you this. The "area" alone will NOT!


We truck guys need to get with it and start using A/R values, instead of the almost-worthless sq cm sizes.

justin

4x4dually

Thanks Hohn. Sorry to hyjack the thread fellas! Didn't mean it to take such a dymanic turn. Now back to your regularly scheduled programming.

HOHN

There's more involved because it's not quite a circular cross section. Then again, it's not quite square either.

What you really have is something closer to a circle that's split in the middle and has a rectangular shape inserted between the two semicircles.

Let me show you a guesstimation based on what I'm picturing from my HX35.

On either end of each scroll hole, you have a semicircle of radius 1.5cm. Hence, an area of 1.5^2*pi*= 7.07cm sq.

Now add in a rectangle measuring about 2cm x 3cm. Now we have an additional 6cm sq to add to our initial 7.07cm, giving us 13.07 sq cm for a size. But this is just ONE SCROLL. Since we have twin scroll housings, we have to double this to get 26cm.

But these are the measurements I'm picturing for the housing where it meets the exhaust manifold! The farther away from the manifold you go, the smaller the cross-sectional area goes.

IIRC, the "stated" size is measured a certain distance upstream from the housing exit (where it dumps into the pinwheel), but I dunno how far. Far enough to where it shrinks from 26cm at the manifold down to about 12 or 14cm.

Keep in mind that a 12sq cm opening is about the same size as a hole of 1.5" diameter.

Not very big.

jh

PanteraGSTK

I know what you mean. I'm in the process of getting my EE degree. Turbo's are a mystery to me thats why I wanted to get info in some sort of thread like this one. I'd like to get my ME degree after I graduate so I can be "well rounded"

You diddn't hijack it, this is what I was attempting to accomplish. I want in depth info so we can all learn from it. I was wanting people to be able to figure out what turbo would be better for a given application be it a twins setup or single charger, towing or drag racing or sled pulling. That and what manufacturers turbo compares to another.

Keep it coming

4x4dually

Now then....I have to go search on idea on how to drive this stick without barking the turbo every time I shift.... Anyone care to expand on that issue with some tips for a turbo flunky? My boost reaches a max of 42. Then I shift, BARK! I've tried to let off the pedal a little before I clutch it, and that helps, but who the heck wants to slow down while racing? Any one have some in depth info? Can I adjust my wastegate down a little or defuel a little at like 38 or something? I'm going to go search for info on this, but any responces would be great!

signature600

If you back the wastegate down to about 35-38psi, it won't bark as bad, but it'll still bark!

a Blow off valve is the only way to cure it!
Chris

4x4dually

I don't mind the bark, I just want to make sure it doens't hurt anything! I will scare the crap out of you the first time it does it and you aren't expecting it! WHAT WAS THAT???? O. That was that bark I have heard so much about on DTR!

signature600

Is this on the PS62??

If so, 42psi is fine, and I'm sure it likes to bark. Call Industrial and see if they see a problem with barking. I ran a B1, and it would BARK LOUD and OFTEN, but in 15K miles I never hurt it... these Schwitzers are tough!!

Chris

4x4dually

I was going to call them and just make sure everything is fine for my peice of mind when the time over there catches up with the time over hear this morning. I figured HOHN would chime in here and explain exactly what makes it happen, oh great TURBO MASTER! I kind of know why it does it, but I have trouble explaining it to others.

In depth detail on this "barking" anyone?

PanteraGSTK

Please explain the difference between a BOV and a waste gate.

dodgezilla04

hey 4x4, do a search dork sorry had to do that because of your other thread.



maybe I can try the last one.

a wastegate is a device in the turbine housing that opens and closes to regulate the max boost pressure by bypassing exhaust gases around the turbine and straight into the exhaust.

a bov, is a relief valve in the cold side piping that limits boost, generally when at high boost levels and quickly getting off of the pedal.