more twin turbo questions

[6speedduramax]

I have a few questions about twin turbos Im hoping some of you turbo gurus can answer for me.

1. I know the exhaust goes from manifold, to smaller turbo, to larger turbo, to the exhaust. So why doesn't the air side go filter, smaller turbo, larger turbo, intercooler, engine??? Instead or filter, larger turbo into the smaller turbo??

2. Wouldn't this over speed the smaller turbo when the larger lites?? If it doesn't over speed it, what prevents the smaller turbo from over speeding and grenading???

3. Does the length of the hot pipe between turbos matter?

4. What size should the piping be for the hot pipe and for the boost tubes?

5. Where does the oil supply and return come from/go too for the larger turbo?

Sorry for all the questions guys. Just searching for knowledge...would like to build a kit in the future

 

[McRat]

1) Because of the volume of air involved. The big charger grabs XXXX air are reduces to XX worth. Now the small charger takes XX air and makes X out of it. The little charger cannot breath XXXX worth of air, only XX.

2) Not if you select the right sized charger.

3) The shorter the better.

4) 3" is fine.

5) Use two oiling sources if you can.

 

[TYREBOYZ_DEMAXIN]

let me see if i learned something here..if you were to run the air from the little charger to the bg charger it would be more prone to over speeding the little dude and still have little to no air since you only sucked in a small amount of air due to the smaller charger..or something like that

 

[ZR1160]

TT

I have a few questions about twin turbos Im hoping some of you turbo gurus can answer for me.

1. I know the exhaust goes from manifold, to smaller turbo, to larger turbo, to the exhaust. So why doesn't the air side go filter, smaller turbo, larger turbo, intercooler, engine??? Instead or filter, larger turbo into the smaller turbo??

It's kind of like the big turbo takes over, instead of the little turbo working to build pressure is just free spins....

2. Wouldn't this over speed the smaller turbo when the larger lites?? If it doesn't over speed it, what prevents the smaller turbo from over speeding and grenading??? Instead of sucking air, its fed air, just free wheels

3. Does the length of the hot pipe between turbos matter?
Shorter is better, coat it and wrap it.......

4. What size should the piping be for the hot pipe and for the boost tubes?
Mine are around 3" 's

5. Where does the oil supply and return come from/go too for the larger turbo? Mine comes off the small turbo and returns to the pan....

Sorry for all the questions guys. Just searching for knowledge...would like to build a kit in the future

 

[DuramaxPowered]

the big turbo takes a certain mass of air( say 80lbs ) and increases the pressure that it is at. this reduces the volume of air while still maintaining the mass. now at the smaller volume the small charger can handle an amount of air mass that it wouldn't normally be able to since it's volume has been reduced thanks to the big guy.....

 

[vortecfcar]

the big turbo takes a certain mass of air( say 80lbs ) and increases the pressure that it is at. this reduces the volume of air while still maintaining the mass. now at the smaller volume the small charger can handle an amount of air mass that it wouldn't normally be able to since it's volume has been reduced thanks to the big guy.....

This is where turbo maps get tricky...

 

[DuramaxPowered]

This is where turbo maps get tricky...

thats for sure... just giving a basic explanation

 

[Killerbee]

Wouldn't this over speed the smaller turbo when the larger lites?? If it doesn't over speed it, what prevents the smaller turbo from over speeding and grenading???

As Nick said, you have to become familiar with the compressor maps of each turbo. The answer to your question will become clear when you look at "Pressure Ratio" for each unit.

The rpm of a turbo that is moving X amount of air, is completely different when the compressor face is at different "pressures". This pressure is what changes with twin settups. It's conceivable for the rpm to be cut in half compared to its unboosted counterpart.

 

[6speedduramax]

If the hot pipe was going to be pretty long (possibly 8' ) should it be a smaller diameter then 3" like 2 1/2"? Or would that be to restrictive?

 

[dmaxfireman]

If the hot pipe was going to be pretty long (possibly 8' ) should it be a smaller diameter then 3" like 2 1/2"? Or would that be to restrictive?

this sounds like it could get interesting....

 

[malibu795]

first thing you need to understand is pump theroy.. turbos are non positive displacment pumps. this means is that a at a given rpm of the pump/turbo dishcarge volume is variable and most pump are rated for a nominal flow between a set operating range and discharge/suction pressure. now one can increase discharge volume by force feeding the pump onthe suction side.

I have a few questions about twin turbos Im hoping some of you turbo gurus can answer for me.

1. I know the exhaust goes from manifold, to smaller turbo, to larger turbo, to the exhaust. So why doesn't the air side go filter, smaller turbo, larger turbo, intercooler, engine??? Instead or filter, larger turbo into the smaller turbo??exhaust is waht drive turbos. the small turbo does majority of the work. say the small turbo as a 2.6 inlet and the big turbo has 3.0 inlet. the 2.6 turbo can suck more then enoguh air throught he 3.0 turbo. and not be restircted. now if the 3.0 was sucking throughthe 2.6 turbo you can effectively restricted the max out put of a 3.0 turbo. or basicly a 3.0 turbo bushed to 2.6

2. Wouldn't this over speed the smaller turbo when the larger lites?? If it doesn't over speed it, what prevents the smaller turbo from over speeding and grenading???
when running compound tiwns especialy on the street it is almost mandatory to run at least one waste gate located ont he exhaust side of the small turbo. keeping wiht the 2.6/3.0 setup sayt he 2.6 can hanld a max of 50lbmin before over spooling. when the 3.0 lites it willl def create more then 50lbmin of exhaust flow and would blow the 2.6 turbo. thus a waste gate is installed between the 2.6 turbo and the engine. this allow anything more then 50lbmin to by pass the turbine housing of hte 2.6 turbo thus keeping the 2.6 turob in a smae operating range
3. Does the length of the hot pipe between turbos matter?

4. What size should the piping be for the hot pipe and for the boost tubes?from what i have seen a 3.0-3.5" hot pipe form a the small turbo to the large trubo is more then enough fr most aplication.. personaly i would keep it hte same size and the exhuast houing on the small trubo. boost tube keep the small to engine the same the 3.0 to 2.6 (normaly 3.5-4" intake house on the 2.6 turbo most 3" turbo runs a 2.5-3" discharge hose..

5. Where does the oil supply and return come from/go too for the larger turbo?
i have seen 2 setups Teeing of the oil suply one the 2.6 turbo and the other is a dedicated line off the oil cooling/filter housing
Sorry for all the questions guys. Just searching for knowledge...would like to build a kit in the future

ker word here is waste gate save turbos

 

[malibu795]

As Nick said, you have to become familiar with the compressor maps of each turbo. The answer to your question will become clear when you look at "Pressure Ratio" for each unit.

The rpm of a turbo that is moving X amount of air, is completely different when the compressor face is at different "pressures". This pressure is what changes with twin settups. It's conceivable for the rpm to be cut in half compared to its unboosted counterpart.

Wouldn't this over speed the smaller turbo when the larger lites?? If it doesn't over speed it, what prevents the smaller turbo from over speeding and grenading???

you didnt even answer the man's question micheal.

 

[malibu795]

If the hot pipe was going to be pretty long (possibly 8' ) should it be a smaller diameter then 3" like 2 1/2"? Or would that be to restrictive?

big turbo going in the bed or under the bed penind tubo size of the big turbo. i might go with a 2.5 either way... heat drives turbos. smaller pipe would keeping air velocity up and increase repsonsive ness.

as i hinted to earlier pending on what your overall goal is

 

[6speedduramax]

big turbo going in the bed or under the bed penind tubo size of the big turbo. i might go with a 2.5 either way... heat drives turbos. smaller pipe would keeping air velocity up and increase repsonsive ness.

as i hinted to earlier pending on what your overall goal is

Under the bed..hopefully.

 

[03 D-max]

Under the bed..hopefully.

going with an STS move

 

[McRat]

going with an STS move

I've been trying to talk STS into this for over 2 years. They aren't interested in diesels.

 

[03 D-max]

I've been trying to talk STS into this for over 2 years. They aren't interested in diesels.

I wonder why that is... there would probably be a pretty good market for em too

 

[McRat]

I wonder why that is... there would probably be a pretty good market for em too

I talked with them at SEMA again this year. They are about 1% interested now. Up from -100% two years ago.

 

[ZR1160]

What if you put both turbos under the truck? Custom headers straight under the truck, two compound turbos side by side, air intake up in the bed, cold boost pipe routed up where the down pipe used to be........interesting thought, not for me though.....

 

[McRat]

It's a harder path, but I feel it would work.