compound turbo question

[Miasma]

I've been dying to get some advice on this before I start, but I am currently restricted to the newbie section so I apologize for the duplicate thread.

I have done lots of research in books and online trying to educate myself on this as much as possible. My project is intended for daily street use, with the odd time at the drag strip. I am looking for a fast spool at early rpm resulting in high torque. Starting around 600whp 500wtq.

My turbo planned setup will included a T350 trim ar.48 and GT40R ar.1.06. With this setup I intend a total around 39psi ish... 22 psi on the 50trim and 17 on 40R.
I am still trying to wrap my head around the maps correctly to varify if my setup will spool fast enough with out to much back pressure to meet my objective. Once I have determined my official direction I am going to begin designing my manifold and hopefully start fabricating this summer.

 

[Black-Out]

I've been dying to get some advice on this before I start, but I am currently restricted to the newbie section so I apologize for the duplicate thread.

I have done lots of research in books and online trying to educate myself on this as much as possible. My project is intended for daily street use, with the odd time at the drag strip. I am looking for a fast spool at early rpm resulting in high torque. Starting around 600whp 500wtq.

My turbo planned setup will included a T350 trim ar.48 and GT40R ar.1.06. With this setup I intend a total around 39psi ish... 22 psi on the 50trim and 17 on 40R.
I am still trying to wrap my head around the maps correctly to varify if my setup will spool fast enough with out to much back pressure to meet my objective. Once I have determined my official direction I am going to begin designing my manifold and hopefully start fabricating this summer.

Turbo sizing will definitely be the key in getting it right otherwise the response will be less than ideal- That said a GT40R with a 1.06 hot housing would be fit for an inline 6 with a displacement for around 2.6-3.8liters and really ideal for around 3.2-3.8........ I think your hot housing A/R's are gonna make or break you in the long run.......and then there is the small turbo being big enough to flow and small enough to spool.....a 40R (which will support more than 800whp) isn't needed to make the power numbers your after- that can be accomplished using a 3076R with a normal set up....and would spool well at that. I would suggest using a GT28R compounded into a 3576R and I would bet you could get where you wanted to be with super flat response and good top end without the lag of a 40R with a 1.06 housing, and still be able to make over 600whp if you decided you wanted more-

You want the most efficient flow of the small turbo to be ending as the most efficient flow of the large turbo is kicking in. Too much A/R on the hot housing of the big turbo and that wont happen soon enough, the "island of efficiency" on both turbos will separate and it will feel like boost a plateau and a boost again at a higher rpm when the heat and flow reach the point where the big turbo will get into boost thresh hold and start producing the torque you're after-
Get it right and it will feel like a boost,followed by another big boost without a break in the delivery and it will happen from the spool up of the first turbo-

I'd re-think the turbo selection so that they are sized right for the response you're after.......unless your after 800+ whp and then the 40R will work but you'll still need a smaller hot housing and a larger "small" turbo. That said, compressor flow maps will indeed be you're best friend in building a proper compound twin turbo set up for your eclipse-

Will-

 

[viperlp01]

Spool is easy. How fast will the small one spool by itself. Thats about how fast you will build AT LEAST the pressure you have set on the small one. The boost from the big might raise the boost pressure a couple psi.

 

[Miasma]

Turbo sizing will definitely be the key in getting it right otherwise the response will be less than ideal- That said a GT40R with a 1.06 hot housing would be fit for an inline 6 with a displacement for around 2.6-3.8liters and really ideal for around 3.2-3.8........ I think your hot housing A/R's are gonna make or break you in the long run.......and then there is the small turbo being big enough to flow and small enough to spool.....a 40R (which will support more than 800whp) isn't needed to make the power numbers your after- that can be accomplished using a 3076R with a normal set up....and would spool well at that. I would suggest using a GT28R compounded into a 3576R and I would bet you could get where you wanted to be with super flat response and good top end without the lag of a 40R with a 1.06 housing, and still be able to make over 600whp if you decided you wanted more-



Will-

Thanks for the input. I want to be able to run 600 comfortably, so I will certainly look into some more options. I'm gonna take my time reading and getting info on this before proceeding with the build.

 

[Black-Out]

Keep us posted on the progress sounds like once you get it started it will be a pretty sick set up-

 

[Miasma]

O you bet I will,

Want to try and start drafting it soon, once I make my mind up on the turbos. Then I will put the plans to plot and start making it.

This winter I've done a lot of custom interior work, now it's time to focus some more on motor again.

 

[Miasma]

Hoping you guys might be able to help me verify some of my numbers on this. I live in calgary, AB @ 3500ft.

Atmospheric psi is 14.5 here. I have been considering the advice given on my turbo selection. As I said I am looking for a comforatble 600whp with room to grow should I choose. So I am thinking the GT2876R (GT25R), turbine ar. 43 and GT3582R (GT35R), turbine ar. 82. However the compressor housings on these are both ar. 70 so I am hoping that since they are so close in range of each other I will be able to get the quick spool out of the 25R and limited back pressure.

If I am reading the maps correctly the 35R is at max efficiency 79% at 2.2 Bar and 40lbs/min. And the 25R is max at 2.4 Bar and 38lbs/min. 2.2 Bar = 17.4 psi boost, 2.4 Bar = 20.3 psi boost. = 37.7 psi boost, which is just below my goal. So with the increased boost I will be just shy of the turbos max efficiency.

ATP TURBO - The Premiere Provider of Turbocharging Components

ATP TURBO - The Premiere Provider of Turbocharging Components

Here is where I need a little help varifying lbs/min displaced my the engine.

4g63 displacement is 1997 cubic centimeters * 0.0610237441 = 122 cid

(122cic*3000rpm*0.5*0.85)/1728 = 90cfm

90cfm*2.2Bar = 198 cfm * 0.986 (Air Density Adjustment) = 195 lbs/min

That being said, am I reading the turbo maps correctly???

I know there is a couple guys on here with lots of experience using compounds so I appreciate as much advise as possible, to let me know if I am moving in the correct direction.

 

[Miasma]

Anyone?

 

[Black-Out]

Hoping you guys might be able to help me verify some of my numbers on this. I live in calgary, AB @ 3500ft.

Atmospheric psi is 14.5 here. I have been considering the advice given on my turbo selection. As I said I am looking for a comforatble 600whp with room to grow should I choose. So I am thinking the GT2876R (GT25R), turbine ar. 43 and GT3582R (GT35R), turbine ar. 82. However the compressor housings on these are both ar. 70 so I am hoping that since they are so close in range of each other I will be able to get the quick spool out of the 25R and limited back pressure.

If I am reading the maps correctly the 35R is at max efficiency 79% at 2.2 Bar and 40lbs/min. And the 25R is max at 2.4 Bar and 38lbs/min. 2.2 Bar = 17.4 psi boost, 2.4 Bar = 20.3 psi boost. = 37.7 psi boost, which is just below my goal. So with the increased boost I will be just shy of the turbos max efficiency.

ATP TURBO - The Premiere Provider of Turbocharging Components

ATP TURBO - The Premiere Provider of Turbocharging Components

Here is where I need a little help varifying lbs/min displaced my the engine.

4g63 displacement is 1997 cubic centimeters * 0.0610237441 = 122 cid

(122cic*3000rpm*0.5*0.85)/1728 = 90cfm

90cfm*2.2Bar = 198 cfm * 0.986 (Air Density Adjustment) = 195 lbs/min

That being said, am I reading the turbo maps correctly???

I know there is a couple guys on here with lots of experience using compounds so I appreciate as much advise as possible, to let me know if I am moving in the correct direction.

As far as I can tell you're reading the maps correctly....and by allowing the 35R to build more boost you should easily surpass your power goal.......If you lived in at a lower altitude you wouldn't need much boost at all but then again thats what is so lovely about turbos....keep the wastegate shut a little longer problem solved... Just don't forget to dump the wastegate from the GT28R into the hot side inlet of the 35R or you'll loose some of the flow that will help meld the two turbos boost thresholds into one big fat torque increase

 

[Miasma]

As far as I can tell you're reading the maps correctly....and by allowing the 35R to build more boost you should easily surpass your power goal.......If you lived in at a lower altitude you wouldn't need much boost at all but then again thats what is so lovely about turbos....keep the wastegate shut a little longer problem solved... Just don't forget to dump the wastegate from the GT28R into the hot side inlet of the 35R or you'll loose some of the flow that will help meld the two turbos boost thresholds into one big fat torque increase

Thanks, ya that is my plan, i'm looking for a good manifold to start with right now, gonna route the first wastegate into the 35R like you said and then the second wastegate will dump into the exhaust. I'm hoping to run a full exhaust and an o2 dump pipe out the side controlled by a switch.

 

[LandSpeed-DSM]

Hoping you guys might be able to help me verify some of my numbers on this. I live in calgary, AB @ 3500ft.

Atmospheric psi is 14.5 here. I have been considering the advice given on my turbo selection. As I said I am looking for a comforatble 600whp with room to grow should I choose. So I am thinking the GT2876R (GT25R), turbine ar. 43 and GT3582R (GT35R), turbine ar. 82. However the compressor housings on these are both ar. 70 so I am hoping that since they are so close in range of each other I will be able to get the quick spool out of the 25R and limited back pressure.

If I am reading the maps correctly the 35R is at max efficiency 79% at 2.2 Bar and 40lbs/min. And the 25R is max at 2.4 Bar and 38lbs/min. 2.2 Bar = 17.4 psi boost, 2.4 Bar = 20.3 psi boost. = 37.7 psi boost, which is just below my goal. So with the increased boost I will be just shy of the turbos max efficiency.

ATP TURBO - The Premiere Provider of Turbocharging Components

ATP TURBO - The Premiere Provider of Turbocharging Components

Here is where I need a little help varifying lbs/min displaced my the engine.

4g63 displacement is 1997 cubic centimeters * 0.0610237441 = 122 cid

(122cic*3000rpm*0.5*0.85)/1728 = 90cfm

90cfm*2.2Bar = 198 cfm * 0.986 (Air Density Adjustment) = 195 lbs/min

That being said, am I reading the turbo maps correctly???

I know there is a couple guys on here with lots of experience using compounds so I appreciate as much advise as possible, to let me know if I am moving in the correct direction.

You are on the right path, more or less.. its just some of the math is not working out, nor are the conversions you are using between CFM and LB/Min. One is a Fixed Volume rate, the other is Mass Flow rate, heavily dependent on temperature/pressure at the inlet.

Your maximum airflow is going to be limited by your Primary/Atmospheric compressor.

For room temperature air 65-75* which would be really favorable IATs.. off the top of my head converting 1 CFM to Lbs/min you would use a conversion along the lines of ~0.07 Pounds/CFM/Min

So using the figures you provided for your example engine's boosted "demand flow" - parameters of 85% VE, 122CID and 3000rpm crank speed... not accounting for actual charge density from the heat imparted by two compressor stages and their efficiencies at that engine demand.. would be roughly 13.65lbs/min not 195lbs/min.

Which is much more realistic. 195lbs/min is approaching 2000hp worth of airflow

But in any event, that 13.65lb/min figure is assuming a few things, and you are not necessarily going to be in the most efficient part of a given map at that point for a 2.0 @ 3000rpm and 85% VE.

Plot your engines NA demand flow out starting first with estimated VE based off its current NA torque curve. Using peak torque as peak VE of somewhere in the 90% range for a 4 valve head. Scale accordingly as torque climbs/falls on either side of that and plot from 2000rpm to your expected redline based on what your valvetrain/cam will support.

Then put that plot across your Secondary (Small) Compressor map, like this..

You must be logged in to view this image or video.

Afterwards you now have your effective engine size/mass flow to start picking your Primary (Big) compressor.

The Big turbo is going to treat the small turbo system more as the NA engine equivalent of Original displacement multiplied by PR multiplied by VE.

The comes turbine sizing, basically the same principal.. but it doesn't hurt to go a bit big on the secondary with a very large wastegate, with a large intermediate pipe between stages and an even bigger turbine wheel/housing combo on the primary with a very large/short downpipe after the primary and dumping the wastegate flow from the intermediate pipe to atmosphere.

Any backpressure after the primary turbine is going to be multiplied by the expansion ratio.. this then gives you the intermediate stage pipe. Then the pressure in the interstage pipe is multiplied by the secondary turbos expansion ratio to combine with the drive pressure requirement of the small turbines effort to turn its compressor.

I would work on the concepts, and the formulas, then work on exacting the numbers that apply to your setup.

 

[Miasma]

You are on the right path, more or less.. its just some of the math is not working out, nor are the conversions you are using between CFM and LB/Min. One is a Fixed Volume rate, the other is Mass Flow rate, heavily dependent on temperature/pressure at the inlet.

Your maximum airflow is going to be limited by your Primary/Atmospheric compressor.

For room temperature air 65-75* which would be really favorable IATs.. off the top of my head converting 1 CFM to Lbs/min you would use a conversion along the lines of ~0.07 Pounds/CFM/Min

So using the figures you provided for your example engine's boosted "demand flow" - parameters of 85% VE, 122CID and 3000rpm crank speed... not accounting for actual charge density from the heat imparted by two compressor stages and their efficiencies at that engine demand.. would be roughly 13.65lbs/min not 195lbs/min.

Which is much more realistic. 195lbs/min is approaching 2000hp worth of airflow

But in any event, that 13.65lb/min figure is assuming a few things, and you are not necessarily going to be in the most efficient part of a given map at that point for a 2.0 @ 3000rpm and 85% VE.

Plot your engines NA demand flow out starting first with estimated VE based off its current NA torque curve. Using peak torque as peak VE of somewhere in the 90% range for a 4 valve head. Scale accordingly as torque climbs/falls on either side of that and plot from 2000rpm to your expected redline based on what your valvetrain/cam will support.

Then put that plot across your Secondary (Small) Compressor map, like this..

You must be logged in to view this image or video.

Afterwards you now have your effective engine size/mass flow to start picking your Primary (Big) compressor.

The Big turbo is going to treat the small turbo system more as the NA engine equivalent of Original displacement multiplied by PR multiplied by VE.

The comes turbine sizing, basically the same principal.. but it doesn't hurt to go a bit big on the secondary with a very large wastegate, with a large intermediate pipe between stages and an even bigger turbine wheel/housing combo on the primary with a very large/short downpipe after the primary and dumping the wastegate flow from the intermediate pipe to atmosphere.

Any backpressure after the primary turbine is going to be multiplied by the expansion ratio.. this then gives you the intermediate stage pipe. Then the pressure in the interstage pipe is multiplied by the secondary turbos expansion ratio to combine with the drive pressure requirement of the small turbines effort to turn its compressor.

I would work on the concepts, and the formulas, then work on exacting the numbers that apply to your setup.

Thanks, I thought my air flow seemed a little high . Appreciate the maps too. I'll post some more updates on this as I move along.

 

[ariman]

What do you think about this set up?, 18g top turbo and 6765 T3 ar .82, i wanna make 500 whps in a 2.2L engine.

 

[n0de]

I've been dying to get some advice on this before I start, but I am currently restricted to the newbie section so I apologize for the duplicate thread.

I have done lots of research in books and online trying to educate myself on this as much as possible. My project is intended for daily street use, with the odd time at the drag strip. I am looking for a fast spool at early rpm resulting in high torque. Starting around 600whp 500wtq.

My turbo planned setup will included a T350 trim ar.48 and GT40R ar.1.06. With this setup I intend a total around 39psi ish... 22 psi on the 50trim and 17 on 40R.
I am still trying to wrap my head around the maps correctly to varify if my setup will spool fast enough with out to much back pressure to meet my objective. Once I have determined my official direction I am going to begin designing my manifold and hopefully start fabricating this summer.

You should put a t25 on your exhaust manifold ad have the outlet of the compressor side of the t25 to into the inlet turbine side of a PTE6766.. Honestly I wonder if that would work to quickly spool a gigantic turbo.

 

[DROPthatCLUTCH]

That'll be one fast 420a.

 

[LandSpeed-DSM]

What do you think about this set up?, 18g top turbo and 6765 T3 ar .82, i wanna make 500 whps in a 2.2L engine.

That would be complete over kill for 500awhp.

14B in a larger 8cm2 Mitsu Housing or 10cm2 T3 with at least 44mm external wastegate would work well with a highwinding 2.2 in a compound setup paired to a 1.22A/R T4 S200sx-56 for a quick spooling efficient 500+ awhp.

You could run a smaller turbo to really take advantage of quicker spool and then use a smaller primary if you are confident that you could max it out, but your tune would have to be spot on and using something like E85 with water or water/meth between stages.

Small turbo would need even more wastegate then. Something like a T25 and a T3 3076r. That would be a real mean street car. But under 500whp, as fast as turbos light up now.. it seems like there would be a real penalty in complexity for not a whole lot of gain.

You should put a t25 on your exhaust manifold ad have the outlet of the compressor side of the t25 to into the inlet turbine side of a PTE6766.. Honestly I wonder if that would work to quickly spool a gigantic turbo.

What?

 

[n0de]

That would be complete over kill for 500awhp.

14B in a larger 8cm2 Mitsu Housing or 10cm2 T3 with at least 44mm external wastegate would work well with a highwinding 2.2 in a compound setup paired to a 1.22A/R T4 S200sx-56 for a quick spooling efficient 500+ awhp.

You could run a smaller turbo to really take advantage of quicker spool and then use a smaller primary if you are confident that you could max it out, but your tune would have to be spot on and using something like E85 with water or water/meth between stages.

Small turbo would need even more wastegate then. Something like a T25 and a T3 3076r. That would be a real mean street car. But under 500whp, as fast as turbos light up now.. it seems like there would be a real penalty in complexity for not a whole lot of gain.



What?

Using a turbo to spool a turbo. If that makes any sense... Yes I know hot expanding gases spool the turbo on the turbine side but can a turbo spool > 180k RPM range if it was fed compressed air from a smaller turbo at X amount of boost. This is way outside my realm of expertise.

 

[LandSpeed-DSM]

Read the bits I underlined..

A series turbo setup has to be routed like this:

Atmosphere -> Big Turbo Compressor -> Small Turbo Compressor -> Engine -> Small Turbo Turbine -> Big Turbo Turbine -> Atmosphere

Small Turbo is the Last to get air and the first to get exhaust.

The exhaust coming out of the engine passes through the secondary turbo's turbine wheel and wastegate into the interstage pipe before entering the primary turbo's volute and the wastegate on the interstage pipe.

Your wording is proposing to route the small turbo's compressor outlet into the big turbo's turbine inlet.. by passing the engine basically

Besides that, a the difference in size between a T25 and a 67mm T4 turbo is too much. To be in an efficient part of the map on the T25 under boost, you'd be in a very poor spot and potentially well into the choke off the right side on the 6766 without running a ton of boost..not even accounting for the issue of having a T25 turbine wheel/housing plugging up your flow to the 6766.

You could use a large wastegate like a 60mm, but it could drop pressure and route too much exhaust energy around it that it snuffs out the T25 and you fall off boost. There's a balancing act in all of this.

 

[n0de]

Read the bits I underlined..

A series turbo setup has to be routed like this:

Atmosphere -> Big Turbo Compressor -> Small Turbo Compressor -> Engine -> Small Turbo Turbine -> Big Turbo Turbine -> Atmosphere

Small Turbo is the Last to get air and the first to get exhaust.

The exhaust coming out of the engine passes through the secondary turbo's turbine wheel and wastegate into the interstage pipe before entering the primary turbo's volute and the wastegate on the interstage pipe.

Your wording is proposing to route the small turbo's compressor outlet into the big turbo's turbine inlet.. by passing the engine basically

Besides that, a the difference in size between a T25 and a 67mm T4 turbo is too much. To be in an efficient part of the map on the T25 under boost, you'd be in a very poor spot and potentially well into the choke off the right side on the 6766 without running a ton of boost..not even accounting for the issue of having a T25 turbine wheel/housing plugging up your flow to the 6766.

You could use a large wastegate like a 60mm, but it could drop pressure and route too much exhaust energy around it that it snuffs out the T25 and you fall off boost. There's a balancing act in all of this.

You are absolutely correct, I was suggesting to bypass the exhaust all together with the larger turbo, honestly I didn't even think a series turbo setup existed at all, the idea i had was slight different by not by much, it was just a concept that I thought up a few hours ago.

 

[Rock2610d]

This is interesting but I would think a belt driven supercharger being fed by a big turbo would be a better route.....in diesel theory anyhow. E.G us army's Hemmits......turbo feeds the blower. Turbo actually sucks exhaust out at low RPMs.

 

[ariman]

That would be complete over kill for 500awhp.

14B in a larger 8cm2 Mitsu Housing or 10cm2 T3 with at least 44mm external wastegate would work well with a highwinding 2.2 in a compound setup paired to a 1.22A/R T4 S200sx-56 for a quick spooling efficient 500+ awhp.

You could run a smaller turbo to really take advantage of quicker spool and then use a smaller primary if you are confident that you could max it out, but your tune would have to be spot on and using something like E85 with water or water/meth between stages.

Small turbo would need even more wastegate then. Something like a T25 and a T3 3076r. That would be a real mean street car. But under 500whp, as fast as turbos light up now.. it seems like there would be a real penalty in complexity for not a whole lot of gain.



What?

ok, and that happens if put an intercooler between the two turbos, something like that
big turbo compressor --> intercooler--> small turbo compressor?
Will that be more efficient?
Thanks

 

[LandSpeed-DSM]

You are absolutely correct, I was suggesting to bypass the exhaust all together with the larger turbo, honestly I didn't even think a series turbo setup existed at all, the idea i had was slight different by not by much, it was just a concept that I thought up a few hours ago.

Well, when you see "compound turbo" on this forum and others, or magazines, youtube videos etc.. they are really referring to staged turbos, asymmetric turbos arranged in series or in some cases, two turbos feeding into one and then into the engine as seen on some pulling tractors.

This is interesting but I would think a belt driven supercharger being fed by a big turbo would be a better route.....in diesel theory anyhow. E.G us army's Hemmits......turbo feeds the blower. Turbo actually sucks exhaust out at low RPMs.

They do that on some 2-stroke diesels from the factory, but it is more efficient to use two or more turbos to accomplish that effect.

Also, because the the turbo is driven by the turbine.. the turbo cannot be sucking the exhaust out. A turbo uses exhaust energy to spin up and compress air. The supercharger is aiding the 2-stroke cycle diesel, and the waste product of that relationship is what powers the turbo. The turbo then force feeds the supercharger.. which then compresses the air by whatever PR its geared for and then presses that into the engine.

It's been proven that the roots/screw blowers etc are less efficient secondary stage compressors than a properly matched turbo.

ok, and that happens if put an intercooler between the two turbos, something like that
big turbo compressor --> intercooler--> small turbo compressor?
Will that be more efficient?
Thanks

Yes, and that would be true "inter-cooling" technically the way we use a charge cooler is "aftercooling"

And you can use fluid injection (water and/or meth), an air to air intercooler or a water to air intercooler.

My project will be using a water nozzle between stages and then a front mount "intercooler" between the small turbo and the engine with another nozzle at the throttle body.

Sort of like the 3 nozzle setup on my race car. 1st nozzle pre-turbo, 2nd nozzle immediately post-turbo, then an intercooler and finally the third nozzle at the throttle body.

 

[Miasma]

That'll be one fast 420a.

No way I'm doing this to the 420a, it would blow to pieces... Might be fun to try though.

This is going into a 96 talon tsi

Yes, and that would be true "inter-cooling" technically the way we use a charge cooler is "aftercooling"

And you can use fluid injection (water and/or meth), an air to air intercooler or a water to air intercooler.

My project will be using a water nozzle between stages and then a front mount "intercooler" between the small turbo and the engine with another nozzle at the throttle body.

Sort of like the 3 nozzle setup on my race car. 1st nozzle pre-turbo, 2nd nozzle immediately post-turbo, then an intercooler and finally the third nozzle at the throttle body.

I've been thinking about this as well, however I want this car to be mainly street machine. If I can find a small but efficient enough intercooler I will route it between turbo's. But in a 2g space is limited!!

Each nozzle you are spraying fluid injection? That would be a great idea, do you have them routed to spray in sequence or all together?

 

[Black-Out]

Sense there seems to be a little confusion Ill post up a few vids of my friend Marc's car (the Street Fighter as it's known on the streets of Austin) He explains it and you actually get to see the piping and turbos in it's mock up phase before he actually put it on the car.....He's a fabricator so he built the system himself- This should help shed some light on the subject...... Click the link for the vid to the set up out of the car- the other two are after he had the car set up........

Marc's 2JZ Turbo Compound Setup - YouTube



[ame=http://youtu.be/JbFr_BW_278]Marc's SC300ZX BL TT - YouTube[/ame]



[ame=http://youtu.be/jtmkNtyawu8]The Street Fighter on the Dyno, 6/2/2010 - YouTube[/ame]