Lets talk turbos. T4 big singles

[TooMuch03]

by gating around a smaller secondary youre not really losing its efficiency, its staying in its efficiency range without over speeding. You want to drive that low pressure as hard as you can. Gate the secondary into the intermediate pipe and let that thing sing. Of course there will be a point where one is too small and one is too big.

Just out of curiosity, at what pressure ratio do you think the compressor and turbine are typically most efficient? what is your definition of overspeeding, and how fast do you think the high pressure is actually spinning at WOT? Also, why the desire to drive the low pressure as hard as possible? If the entire system still created 65 psi, for example, Do you think the low pressure would generate more usable mass airflow at 35 psi than it will at say 25 psi?

 

[KCTurbos]

Just out of curiosity, at what pressure ratio do you think the compressor and turbine are typically most efficient? what is your definition of overspeeding, and how fast do you think the high pressure is actually spinning at WOT? Also, why the desire to drive the low pressure as hard as possible? If the entire system still created 65 psi, for example, Do you think the low pressure would generate more usable mass airflow at 35 psi than it will at say 25 psi?

LOL... these are the same questions I sent in a pm to try not to derail the thread... but as long as someone else is posting it then I will post my questions up here also. He answered some of the questions but I would love to get more into details...

A couple questions for you guys "gating around the HP turbo to make it more efficient". Assuming properly setup/sized turbos:

How much are you gating and why?

At what point is the HP turbo over speeding and how are you calculating that?

How are you calculating the efficiency ranges of each turbo?

Wouldn't driving the LP turbo as hard as you can potentially get it out of its most efficient range? The most efficient area of the turbo is not at the peak of the compressor map. It is dead center. Driving the LP too hard will potentially get both turbos out of their efficiency range.

Why would you consider the small turbo a restriction if it is simply compressing the air more? (kinda like the lp turbo is changing the atmosphere that the HP turbo runs at, like adding more atmosphere to the setup. The difference between running the turbos in outer space and below sea level. You are adding more atmosphere)



What I am getting at is there is a difference between staged turbos and compounding turbos. If you simply gate around the HP turbo to get it out of the way of the LP turbo then that can essentially defeat the purpose of a compound setup.

 

[SmokedF747]

my brain hurts. in this to learn something lol i guess no longer for sale josh? hope to see this thing over 7 this year for sure!

 

[Josh@DirtyDiesels]

my brain hurts. in this to learn something lol i guess no longer for sale josh? hope to see this thing over 7 this year for sure!

It did over 700 months ago lol and yes everything is always for sale

 

[KCTurbos]

It did over 700 months ago lol and yes everything is always for sale

For the right price I will sell you anything I own imp:

 

[Josh@DirtyDiesels]

Yep. Everything is always for sale for the right price. But for real though I am actively trying to sell my 6.0 to get into a 6.7

 

[SmokedF747]

i meant fuel only, no giggly

 

[MorganY]

KCTurbos

LOL... these are the same questions I sent in a pm to try not to derail the thread... but as long as someone else is posting it then I will post my questions up here also. He answered some of the questions but I would love to get more into details...

A couple questions for you guys "gating around the HP turbo to make it more efficient". Assuming properly setup/sized turbos:

How much are you gating and why?

At what point is the HP turbo over speeding and how are you calculating that?

Whenever the pressure differential becomes too large. If you are fortunate to have gauges, its when back pressure on that stage starts to spike.

How are you calculating the efficiency ranges of each turbo?

From the compressor maps

Wouldn't driving the LP turbo as hard as you can potentially get it out of its most efficient range? The most efficient area of the turbo is not at the peak of the compressor map. It is dead center. Driving the LP too hard will potentially get both turbos out of their efficiency range.

It all depends on the setup. Most low pressures aren't driven enough.

Why would you consider the small turbo a restriction if it is simply compressing the air more? (kinda like the lp turbo is changing the atmosphere that the HP turbo runs at, like adding more atmosphere to the setup. The difference between running the turbos in outer space and below sea level. You are adding more atmosphere)

Because more pressure does not mean more flow. Once you hit the choke line, that's it. You begin to stall the atmo

What I am getting at is there is a difference between staged turbos and compounding turbos. If you simply gate around the HP turbo to get it out of the way of the LP turbo then that can essentially defeat the purpose of a compound setup.

No because you aren't gating the high pressure out of the way; you are gating the high pressure at its peak efficiency where the pressure ratio across the turbine and compressor side is ideal. That's not defeating the purpose of a compound setup because you are receiving more torque off idle from having your secondary provide the boost down low where its needed.

The better your turbos are sized, the more you don't have to worry about this. An ideal, perfectly sized compound setup won't need a wastegate unless nitrous is involved.

 

[KCTurbos]

KCTurbos

LOL... these are the same questions I sent in a pm to try not to derail the thread... but as long as someone else is posting it then I will post my questions up here also. He answered some of the questions but I would love to get more into details...

A couple questions for you guys "gating around the HP turbo to make it more efficient". Assuming properly setup/sized turbos:

How much are you gating and why?

At what point is the HP turbo over speeding and how are you calculating that?

Whenever the pressure differential becomes too large. If you are fortunate to have gauges, its when back pressure on that stage starts to spike.

How are you calculating the efficiency ranges of each turbo?

From the compressor maps

Wouldn't driving the LP turbo as hard as you can potentially get it out of its most efficient range? The most efficient area of the turbo is not at the peak of the compressor map. It is dead center. Driving the LP too hard will potentially get both turbos out of their efficiency range.

It all depends on the setup. Most low pressures aren't driven enough.

Why would you consider the small turbo a restriction if it is simply compressing the air more? (kinda like the lp turbo is changing the atmosphere that the HP turbo runs at, like adding more atmosphere to the setup. The difference between running the turbos in outer space and below sea level. You are adding more atmosphere)

Because more pressure does not mean more flow. Once you hit the choke line, that's it. You begin to stall the atmo

What I am getting at is there is a difference between staged turbos and compounding turbos. If you simply gate around the HP turbo to get it out of the way of the LP turbo then that can essentially defeat the purpose of a compound setup.

No because you aren't gating the high pressure out of the way; you are gating the high pressure at its peak efficiency where the pressure ratio across the turbine and compressor side is ideal. That's not defeating the purpose of a compound setup because you are receiving more torque off idle from having your secondary provide the boost down low where its needed.

The better your turbos are sized, the more you don't have to worry about this. An ideal, perfectly sized compound setup won't need a wastegate unless nitrous is involved.

Thanks for your comments. I thought I disagreed with you until your last sentence...

this is key: "The better your turbos are sized, the more you don't have to worry about this. An ideal, perfectly sized compound setup won't need a wastegate unless nitrous is involved"


but theoretically with the right sized turbos there would be very little need to waste gate around the hp (unless you use nitrous)... to be truthful in the setup I have planned for later this year (hopefully) I might not even be wategating the hp... but waste gating the lp to keep it in is most efficient area of the comp map. This will require sizing the hp turbo correctly to also be able to run in the most efficient area of the compressor map. I might put a gate on the hp turbo and turn it up pretty high... but if I plan on making 75+ psi of boost then the gate is going to have to be set pretty high.


I just don't agree with the idea of people using the little turbo to spool up the big turbo and then gating around it. That (in my mind) defeats the purpose of compounding the air in a compound setup. It is more like staged turbos using a compound piping setup.


It makes me wonder how many people are accounting for the pressure ratio difference and the air temp change when looking at compressor maps and compounds?

 

[09stroker]

I just don't agree with the idea of people using the little turbo to spool up the big turbo and then gating around it. That (in my mind) defeats the purpose of compounding the air in a compound setup. It is more like staged turbos using a compound piping setup.

Why do you keep thinking that relieving excessive pressure is completely shutting off the HP??? It will still be hauling ass thus further compressing the air charge.

 

[Extended Power]

this is key: "The better your turbos are sized, the more you don't have to worry about this. An ideal, perfectly sized compound setup won't need a wastegate unless nitrous is involved"


I just don't agree with the idea of people using the little turbo to spool up the big turbo and then gating around it. That (in my mind) defeats the purpose of compounding the air in a compound setup. It is more like staged turbos using a compound piping setup.

Sorry...I gotta disagree with you on your idea of if they are sized right, you don't need a gate theory.
To make my setup "sized right", so it didn't require a gate, I would have to run a secondary with a turbine around 83mm...
So...it's just me...but I would rather have instant spool up off the line, instead of a smokey, laggy P.O.S waiting for it to spool up all the time.

And you don't agree with people using the small turbo to spool up the big one?
How, or where, the hell else would it get its drive pressure from?

The exhaust has to pass through the secondary turbo's turbine first, then the primary gets hit with whatever is left for heat and energy. Now if you have a quick spooling setup, it will have a smaller turbine on the secondary, and as soon as the heavy fuel starts to roll in, it will quickly be overwhelmed with drive pressure.....this, and anything more than what the little turbine can flow, is what you send to the primary.

 

[KCTurbos]

Sorry...I gotta disagree with you on your idea of if they are sized right, you don't need a gate theory.
To make my setup "sized right", so it didn't require a gate, I would have to run a secondary with a turbine around 83mm...
So...it's just me...but I would rather have instant spool up off the line, instead of a smokey, laggy P.O.S waiting for it to spool up all the time.

And you don't agree with people using the small turbo to spool up the big one?
How, or where, the hell else would it get its drive pressure from?

The exhaust has to pass through the secondary turbo's turbine first, then the primary gets hit with whatever is left for heat and energy. Now if you have a quick spooling setup, it will have a smaller turbine on the secondary, and as soon as the heavy fuel starts to roll in, it will quickly be overwhelmed with drive pressure.....this, and anything more than what the little turbine can flow, is what you send to the primary.

Let me ask you a few questions? Why would you need such a larger turbine for the HP? What calculations did you use?

Have you ever tried it with the smaller turbine? Did it in fact overspeed and blow up the turbo or is that something we just assume?

Have you ever plotted a turbine map accounting for exhaust flow going from one turbo to the next, the temp change, and the expansion rate?

Did you know that the exhaust gases are expanding as it comes out of the motor, and will continue to expand even after it leaves the turbine of the hp turbo?



Turbo sizing is everything IMO but not in the way most people think

 

[Extended Power]

Let me ask you a few questions? Why would you need such a larger turbine for the HP? What calculations did you use?

Have you ever tried it with the smaller turbine? Did it in fact overspeed and blow up the turbo or is that something we just assume?

Have you ever plotted a turbine map accounting for exhaust flow going from one turbo to the next, the temp change, and the expansion rate?

Did you know that the exhaust gases are expanding as it comes out of the motor, and will continue to expand even after it leaves the turbine of the hp turbo?



Turbo sizing is everything IMO but not in the way most people think

I just threw that 83mm size out there.

The smaller turbine I am using now has over 100psi going to it when at full steam.

When you fine the maps for the exhaust turbines for Borg Warner stuff, post it up.

Did you know that the velocity decreases, and pressure increases with every increase in pipe size or change?

Still wanna know where you thought the primary gets its drive from if not from the secondary...

 

[Extended Power]

I don't wanna start FA here, so you build your stuff, and I'll build mine.

To each his own.

 

[KCTurbos]

LOL... ok...

I never said it does not get the drive from the outlet of the hp... but like you said we understand things differently.


One reason I love garrett is it has more maps

 

[TooMuch03]

Ivan, here are your turbine maps. Not the best, but better than nothing:

Charlie, this discussion probably isn't worth continuing, not here anyway.

 

[KCTurbos]

I think you are right Adam...


I will stop. Sorry for the derail

 

[Six_Sloww]

I think you are right Adam...


I will stop. Sorry for the derail

I think the OP got what he was looking for.. And selfishly I don't want you to stop the derail.

I'm sure turbos and compound setups have been discussed ad nauseam around here, but the two sides of the discussion are very interesting to me.

I personally have no clue how to size a compound setup, and I'm sure I'm not alone, that's why we go to the vendors to size our compound setups for us.

Regardless of who is right and who is wrong, either setup has the potential for enormous amounts of power, as has always been the case it seems you may have to trade efficiency if you want the fastest spool up. And I would imagine KC would argue there is no trade off with a properly sized setup, and hopefully you build that setup and provide data!

It's a really informative discussion.. I'm going to attempt to re read it until I understand something about compound turbo arrangements :biggrin:

 

[09stroker]

Ivan, here are your turbine maps. Not the best, but better than nothing:

Charlie, this discussion probably isn't worth continuing, not here anyway.

Really?? You're gonna tell him to run away at the first signs of disagreement???

 

[TooMuch03]

Really?? You're gonna tell him to run away at the first signs of disagreement???

Charlie is a grown man, and he can and will do as he pleases. I simply suggested ending the discussion because of the confrontational, rather than open minded, tone of many of the posts. It's useless to continue talking about this unless someone is willing to post up hard data, which I have neither the time nor ambition to do right now.

If you have real information to contribute, be my guest.