twin charging / compound turbos

[Akauf587]

been reading up on this and looking at the results several here and else where have had with twin charging and compound turboing a small gas engine.

Something I've been wondering that I cannot find much about, other than some rough flow calculations, is if the twin charge set up can be as efficient as the compound setup. I'm seeing some results but not nearly enough to satisfy my curiosity.

The compound set up is great for getting two turbos working well with great pressure ratios. This got me thinking about whether or not a supercharger could improve response more without sacrificing too much top end. I'll make up to set ups to compare that I've been thinking about.

twin charged set up:
intake > turbo > IC > supercharger > IC > motor

Is it feasible for say an eaton m62 @ 1.6:1 to get a hta82 up to 1.9:1 by 3.5k rpm?

45 psi @ 3.5k with the kind of flow these two paired would generate would feel amazing. selecting a turbo with a nice fat map at this ratio should prove to make good top end power.

Compound set up
intake > hta82 > IC > fp white (hta68) > IC > motor

hta68 can hit 3:1 by 4k rpm so it should bring the hta 82 with it and with any luck (and help if needed) the 68 would move to 2:1 as the 82 reaches about 1.5:1. Possibly 45 psi in combo by 4.5k?

I could link some maps in if anyone desires though at the pressure ratios assumed the compound set up is flowing more and more efficient at high rpm as the supercharger would likely be near 50% efficiency at 8k rpm in this set up.
Its important to consider that pressure is not the same as volume and one of these set ups will make more power with less boost. Back pressure differences are important to consider as well.

anyone care to speculate or share their experience as to which set up sounds most desirable?

things to consider:

Can the twin charged combo out spool the compound by as much as 1k rpm in reality? If not, is it still worth doing as opposed to a compound set up?

How much will the lower efficiency and pressure ration of the super hurt the top end performance of the hta82? Will the hta82 take up the slack of the super as it would a smaller turbo in a compound set up.

How much will the hta82 slow the spool of the hta68 with its added back pressure and inlet restriction?


Its all hard to wrap my head around when air volume, back pressure, and thermal efficiency must be considered to determine the expected performance of these set ups.

 

[1983gsp]

Do a search on ray peters. Lots of info for you on twin charging.

 

[Akauf587]

yeah read through his threads. I couldn't find his dyno graph though, just numbers.

 

[simple jake]

If you're a member on dsmtuners, I'd suggest PM'ing a member there with the name of 99gst_racer. He has a compounded setup. I think he's using a 16g and a 60trim. He's putting down some decent numbers at a really good spool time. He can help you out a lot.

 

[ed1380]

A twin scroll hx35 can be spooled by 3500 if done right, but it runs out of steam at 60lbs/min

 

[Black-Out]

I have plans to do a compund twin charged set up on my VW Corrado G60-
I just want to select the proper turbo for the responce and flow that I have in mind. The main thing That I would say you'll want to look after is wether you're compounding the set up into the turbo or simply doing a parallel twin charger set up where the blower will get by-passed to avoid restriction in the charge air path once the turbo begins out flowing the M62- something I could see happening fairly easily if the turbo you choose will flow beyond 400cfm...

The compound twincharger set up is pretty old diesel tech and should work good if you decide to use it but the limiting factor will become the flow rate of the supercharger. If you do it like a traditional diesel style set up, where the turbo blows down the throat of the supercharger, before anything gets consumed by the engine the supercharger will actually get in the way of an extreamely high flow turbocharger. I actually plan to run mine with the supercharger feeding the turbo but for good reason, design limitation.

My supercharger is located in a very unconventional spot (high up and in front of the engine) and that leaves me with little or no choice, unless I re-engineer the entire induction system. And then there's just the fact that the supercharger itself is also very unconventional. G-lader supercharger, with its spring loaded side seals and oscilating displacer, may not take to kindly to having the air inlet pressurized by another device so this forces me to compound the compressed air into the turbo rather than the supercharger, an issue you won't run into with an Eaton M62.

You will actually be able to experiment with which method of compound twin charging works best with a roots style supercharger as well as the more resent use of parallel twin charging to achieve the power you'r after, which is another issue all together. My reasons for compound twincharging the G60 are more than likely completely different than yours. I want torque. Mountains of it from my small displacement 1.8 liter single cam engine. The power delivery on a stock G60 is broad when the supercharger is in good health and the induction system is modified to allow for full boost without recirculation of pressure at part throttle (originally done by the manufacturer for economy) I simply want to extend that power delivery with the additional flow needed to make not only a bit more hp, but wider longer throws of increased torque. You may be wanting more power all the way around and that may force you to using a modified Eaton M62 just to get to the flow you want before the turbo even gets spooled. all in all the concept is awesome and I plan to experiment on a modest level with my own setup. would love to share info when you get down to the nitty gritty with it all.

Let me know

William-

 

[TSITurbo95]

If you're a member on dsmtuners, I'd suggest PM'ing a member there with the name of 99gst_racer. He has a compounded setup. I think he's using a 16g and a 60trim. He's putting down some decent numbers at a really good spool time. He can help you out a lot.

Umm were on DSMTuners?!?!?! HAHA.

 

[Akauf587]

I have plans to do a compund twin charged set up on my VW Corrado G60-
I just want to select the proper turbo for the responce and flow that I have in mind. The main thing That I would say you'll want to look after is wether you're compounding the set up into the turbo or simply doing a parallel twin charger set up where the blower will get by-passed to avoid restriction in the charge air path once the turbo begins out flowing the M62- something I could see happening fairly easily if the turbo you choose will flow beyond 400cfm...

The compound twincharger set up is pretty old diesel tech and should work good if you decide to use it but the limiting factor will become the flow rate of the supercharger. If you do it like a traditional diesel style set up, where the turbo blows down the throat of the supercharger, before anything gets consumed by the engine the supercharger will actually get in the way of an extreamely high flow turbocharger. I actually plan to run mine with the supercharger feeding the turbo but for good reason, design limitation.

My supercharger is located in a very unconventional spot (high up and in front of the engine) and that leaves me with little or no choice, unless I re-engineer the entire induction system. And then there's just the fact that the supercharger itself is also very unconventional. G-lader supercharger, with its spring loaded side seals and oscilating displacer, may not take to kindly to having the air inlet pressurized by another device so this forces me to compound the compressed air into the turbo rather than the supercharger, an issue you won't run into with an Eaton M62.

You will actually be able to experiment with which method of compound twin charging works best with a roots style supercharger as well as the more resent use of parallel twin charging to achieve the power you'r after, which is another issue all together. My reasons for compound twincharging the G60 are more than likely completely different than yours. I want torque. Mountains of it from my small displacement 1.8 liter single cam engine. The power delivery on a stock G60 is broad when the supercharger is in good health and the induction system is modified to allow for full boost without recirculation of pressure at part throttle (originally done by the manufacturer for economy) I simply want to extend that power delivery with the additional flow needed to make not only a bit more hp, but wider longer throws of increased torque. You may be wanting more power all the way around and that may force you to using a modified Eaton M62 just to get to the flow you want before the turbo even gets spooled. all in all the concept is awesome and I plan to experiment on a modest level with my own setup. would love to share info when you get down to the nitty gritty with it all.

Let me know

William-

even if it isn't a m62, perhaps a lisholm 1200ax, or eaton tvs 1320r (found on the 3.0tsi), I'm wondering how the poor high rpm efficiency will effect the system as apposed to a compound turbo.

The idea is as much torque as soon a possible and the capability to hold it out to 8k.

the small turbo in compound turbos simply multiplies the pressure and contributes its accompanying cfm given its pressure ratio so wouldn't a screw type charger do just the same? From what I'm reading I haven't seen much to suggest the super will restrict much aside from the lower efficiency that comes with a screw type charger at high rpm. Compounding would greatly reduce this inefficiency as the turbo would be feeding the charger with plenty of volume at high efficiency given the pressure ratios in the example.

I was looking through the turbo'd g60s as well. There's a scirroco with a decent build thread and some driving videos. Like every other thread it is missing the only things I really care to see:

boost plots and IATs at the outlets of both chargers!! Back pressure and egts would be a huge bonus as well.

I can calculate all day close theoretic examples and on paper it looks good but without hard data there's no way to really prove its better than a high end turbo on a 2.3 with a nice cam grind and could a compound set up benefit even the most effective of setups, think compound super charger for early torque onset or compound turbo for response with big flow on high revs.

Umm were on DSMTuners?!?!?! HAHA.

hahaha, when I read that I thought, done ...and done

 

[Black-Out]

even if it isn't a m62, perhaps a lisholm 1200ax, or eaton tvs 1320r (found on the 3.0tsi), I'm wondering how the poor high rpm efficiency will effect the system as apposed to a compound turbo.

Well me too........ but the difference between the 2 alone would be interesting to test, that said the real resistance to air flow will be determined when you decide which configuration your going after, and how big the theoretical superchargers in question would be.

like I stated before there are 2 different ways to compound the system and then there's running the system the way VW did in the Scirocco which is parallel twin charging where they bypass the supercharger all together once it becomes a restriction for the turbo chargers flow path,re-routing the charge air completely around the supercharger with a computer controlled actuator valve...... all these ways should have a huge bump in torque below 4k rpm but all that a side compounding the systems through the supercharger will work great- right up until the point the blower becomes the bottle neck to flow. The blower had better be a pretty good displacement otherwise it's just going to heat up the air charge or possibly cause cavitation or airflow turbulence within the blower inlet and more than likely disrupting the outlet flow. I believe the challenge will be tuning the turbo's efficiency to the blower so they are both operating in there best areas before the blower starts blowing hot air and peters out on flow...



The idea is as much torque as soon a possible and the capability to hold it out to 8k.




A decent sized supercharger and a good inter-cooler should make this possible along with good pulley selection which should tailor how bad the efficiency will end up at that rpm.




the small turbo in compound turbos simply multiplies the pressure and contributes its accompanying cfm given its pressure ratio so wouldn't a screw type charger do just the same?




Yea technically it should if your forcing air through the turbocharger and not the supercharger. Most traditional compound twin charging systems do it the other way around....this is the uncharted part of the territory that I'm not sure of, as most cases are with the turbo feeding an over sized supercharger to maintain good flow and efficiency through out the operating range. The issue here is compound twin charging has classically been done on typically low rpm high displacement engines (diesels) which won't over spin the supercharger to a point where it goes out of it's effective range and it becomes restrictive heat pump ... At high rpm the superchargers properties will be a road block and especially at an 8k rpm ceiling. This is but one reason why VW by-passes the blower and recirculates its outlet after the engine speed and turbo flow goes beyond what the superchargers ideal range is.



From what I'm reading I haven't seen much to suggest the super will restrict much aside from the lower efficiency that comes with a screw type charger at high rpm. Compounding would greatly reduce this inefficiency as the turbo would be feeding the charger with plenty of volume at high efficiency given the pressure ratios in the example.


It more than likely will be if the turbo you select is big enough to out flow it early on. What turbo are you planning on coupling up with this set up?.....unfortunately like you've stated before raw data is what you need to figure out what size turbo and supercharger will make music together, and until this is put to practice, this is all just educated speculation....




I was looking through the turbo'd g60s as well. There's a scirroco with a decent build thread and some driving videos. Like every other thread it is missing the only things I really care to see:

boost plots and IATs at the outlets of both chargers!! Back pressure and egts would be a huge bonus as well.





Agreed.. this makes it that much harder because unless you have sensor readings and rpm readings on the dyno we won't be able to see what happens when one takes over from the other....It'd be nice to see the torque figures and how it looks on a dyno graph this would help me with my little project.....



I can calculate all day close theoretic examples and on paper it looks good but without hard data there's no way to really prove its better than a high end turbo on a 2.3 with a nice cam grind and could a compound set up benefit even the most effective of setups, think compound super charger for early torque onset or compound turbo for response with big flow on high revs.



Well if this is what your comparing it to, then I think a compound turbo system is better for you.....I just don't see a supercharger system working well at 8k rpm and at a flow rate for what usually quantifies for a high end turbo kit for a DSM with a stroker 2.3 and a decent cam...just off of that description alone I get output numbers beyond 500whp stuck in my head and we both already know that a supercharger will displace at least 1.6 to 1.8 liters to flow enough to land close to that power level which will produce copious amounts of parasitic drag before boost thresh hold will benefit the engine response......If the engine in question was a V6 or a V8 it would be a little different but DSM's off boost are not all that powerful and I would think (though this isn't hard fact) that the theoretical supercharger in question would consume at least 60hp on the low end just to turn it which, would be directly related to the displacement it is. Overcoming the parasitic drag before boost thresh hold is just another criteria that hasn't been brought to light which will effect (to some degree) the initial response of the system.....


Sorry, for taking up so much bandwidth... I enjoy the brainstorming and throwing back and forth of this idea as forced induction is one of my favorite subjects .....

So...are you dead set on a compound set up or would you consider moving to a parallel system that by-passes the supercharger? Or am I thinking way off base here?


William-

 

[simple jake]

Lol I thought I was on dsmtalk for a second.

 

[Akauf587]

I'm mostly here the brainstorming haha. I am certainly most interested in a compound turbo set up. It seems the turbo move to a sort of equilibrium as the big turbo takes over and efficient is maximized. This set up seems to be most conducive to a high revving small displacement motor. I have a evo 8 with a HTA68 evo9 turbo and gsc. S2 cams. I think moving to a tubular mani with twin 38 tials and a HTA82 or 86 or GTX equivalent with a huge turbine housing would be a torque monster on the street.

I'm thinking 47lb/min turbo reaching 30psi @4k rpm on a 2.0 bringing a 68-75lb/min turbo up behind it with little delay. Small turbo settles to 2:1 as big turbo provides around 2:1. Certainly has 600whp capabilities @ twin scroll 16g spool up potential perhaps on just 93 octane. Now add e85 and I'm getting a semi just considering the possibilities haha. Is it reality or just a pipe dream though.....

 

[LandSpeed-DSM]

I would consider using a bigger primary (LP) turbo and turbine. Like 62mm or 66mm compressor with a large open T4, something that can move closer to 85lbs/min. Are you going to be using meth between the compressor stages?

Two 38mm gates on a twin scroll TD05HR turbine should be enough, depending on how low you would like to be able to drop the boost at any point in the future. Obviously a large gate between stages would be a good idea as well. Again, dependent on how low you would like to be able to rein in the boost. I would consider a single 60mm gate here.

The setup I am having fabbed together over the spring for a 1.5L Honda project is using a 14B in a 7cm2 housing with a 60mm gate off the manifold, and then a 61mm Garrett with a big open T4 hotside and a 44mm gate between stages.

This is in the hopes that I can run each turbo as low as 1.2-1.1PR if I so choose.

Forget the supercharger, you'll get plenty of torque with the TD05HR hotside. And yes, you will want some nice big cams like a Kelford 280/276 with adjustable gears to take advantage of the big snail up top and wind out to 9.5k or more.

 

[Akauf587]

from what I've been reading meth doesn't do much to cool air. I want to spray between stages but I need to look onto it more.

HTA86 is a pretty serious 62mm compressor and looking at the comp maps of comparable turbo (fp doesn't publish theirs) the difference in flow would math well.

 

[LandSpeed-DSM]

You would be better off going with an S300sx3-66 (91-79) in a big open T4 housing. Not too mention you can snag one brand new for $725.

Water/Meth between stages is the way to go. How much water v. meth is debated, 50/50 is a happy miz for many. Chemical intercooling is very effective.

Just don't go too big on the nozzle because you want it all to change phase, and make sure you have a solenoid just before the nozzle.

 

[Black-Out]

I would consider using a bigger primary (LP) turbo and turbine. Like 62mm or 66mm compressor with a large open T4, something that can move closer to 85lbs/min. Are you going to be using meth between the compressor stages?

Two 38mm gates on a twin scroll TD05HR turbine should be enough, depending on how low you would like to be able to drop the boost at any point in the future. Obviously a large gate between stages would be a good idea as well. Again, dependent on how low you would like to be able to rein in the boost. I would consider a single 60mm gate here.

The setup I am having fabbed together over the spring for a 1.5L Honda project is using a 14B in a 7cm2 housing with a 60mm gate off the manifold, and then a 61mm Garrett with a big open T4 hotside and a 44mm gate between stages.

This is in the hopes that I can run each turbo as low as 1.2-1.1PR if I so choose.

Forget the supercharger, you'll get plenty of torque with the TD05HR hotside. And yes, you will want some nice big cams like a Kelford 280/276 with adjustable gears to take advantage of the big snail up top and wind out to 9.5k or more.
You would be better off going with an S300sx3-66 (91-79) in a big open T4 housing. Not too mention you can snag one brand new for $725.

Water/Meth between stages is the way to go. How much water v. meth is debated, 50/50 is a happy miz for many. Chemical intercooling is very effective.

Just don't go too big on the nozzle because you want it all to change phase, and make sure you have a solenoid just before the nozzle.

All this is super solid info right here........And as stated by Landspeed DSM, I believe that compound turbocharging is just going to be much more effective as it would be better suited to high rpm use. My friend Marc used compound turbocharging on his 2JZswapped Z31 and that car is reving beyond 8k rpms. The power transition from turbo to turbo is smooth and the car makes boat loads of torque at 3,200rpm. It spools like a single turbo Z despite having two fairly large turbos. He was making about 780whp last time I was in the car. and going from about 70-180mph was nothing short of rediculous......I think for sure if your going with a high engine speed this is the better choice, in my car I'm not going for such high power numbers and my G60 runs into the electronic leash at about 6500rpm....I'm after a torquey 270whp and thats it. if I'm lucky I'd make 300 flywheel at the most. your going after more than double that...the last thing you need is limitations...

William-

 

[Akauf587]

Is it possible I've seen pics of this z online. Saw a 2jz z32 posted somewhere. I'll see of I can find the pics tomorrow

 

[Black-Out]

More than likely you did that thing is e-famous...

 

[99gst_racer]

Is it possible I've seen pics of this z online. Saw a 2jz z32 posted somewhere. I'll see of I can find the pics tomorrow

Search "Boost Logic".

 

[thomyd]

this isnt dsmsource? well in that case... we have a company out here called F.A.T.

forced air tech that does compound forced induction with an amg supercharger and a gt35r on subies. i know its a crazy set up but they are running 9s.

 

[Black-Out]

Search "Boost Logic".

^^^This...^^^^^

That car has come a very long way...I wish you could've seen it when he first started that project. It literally started with a conversation we had about his car at a small shop I started by myself yrs ago....it was just crazy watching that car make that transition from run of the mill to strait nutty......

He no longer fabricates for Boost Logic though he left them about a year ago.....

 

[LandSpeed-DSM]

3.0L and two extra exhaust pulses per cycle would be a lot of fun. That's double the displacement of what I have to work with on the Honda and a much more stout foundation to build off of.

My only goal is to crank out 300wtq over a few thousands rpm if possible. A stock 2JZ can do nearly three times that.

 

[turbotalon1g]

I heard he ended up getting rid of it and went back to big turbo and spray I believe.

Car was badass I got to see it in person, great work that guy does.

 

[LandSpeed-DSM]

I could see that. The setups are pretty complex. And with only 2 wheels with no engine over them in a light car to put the power down, having all that torque was probably a real handful.

A big single is going to make a bit more sense on a gas motor anyways. But the challenge of doing it and the ridiculous power curve that results is worth it for me. The noise especially, since you hear them spool seperately.

Like the noise the BEP triple turbo Cummins Ram makes as the two LP turbo's start to spool.

On diesels the compound turbos really shine as they don't have to worry so much about the knock limit of the fuel, among other things.

 

[RWD4G63]

You guys are forgetting that on a twin-charged setup, you should use an electronic clutch to turn the supercharger off at high-rpm.

Unless of course you're using a twin-screw blower, which is extremely efficient. Of course, if you're doing that, you might as well forget the turbo and run a big twin-screw.

They make kits for the Corrado btw.

I'd do a twin-charge if you're looking for a crazy powerband up to 500whp or so, and a serial (compound) turbo setup if you're looking for more than that but with better spool than a really big turbo will allow.

 

[99gst_racer]

You guys are forgetting that on a twin-charged setup, you should use an electronic clutch to turn the supercharger off at high-rpm.

Unless of course you're using a twin-screw blower, which is extremely efficient. Of course, if you're doing that, you might as well forget the turbo and run a big twin-screw.

They make kits for the Corrado btw.

I'd do a twin-charge if you're looking for a crazy powerband up to 500whp or so, and a serial (compound) turbo setup if you're looking for more than that but with better spool than a really big turbo will allow.

Centrifugal superchargers work great in a compound configuration. They do well at high RPM.

I can't find it right now, but I used to have a dyno sheet for a small displacement engine that used a turbo and supercharger. It was a pheonominal power curve. Basically instant power, very flat all the way across, and it made about 1000 WHP.

And I know compound prochargers have been done. That set-up set the new record for that class this year.