3 stage vs 2 stage tripples

[bigrpowr]

Wayne , what we don't know is where the power is going to go when we drive the 106 at 55psi... I say the block splits. I will be happy with that.

 

[Corb@CorbinShipping]

I'm setting a personal longest post ever,:badidea: so here goes:

There are a lot of factors that come in to deciding how much cfm vs. boost at a reasonable temp. you need on these trucks. The greater amount of fuel you can efficiently burn, the more power you can make. To efficiently burn X amount of fuel across the RPM range, you need turbo efficiency the whole way through. Just adding turbos to show how much of a tough guy you can be is stupid IMO. I don't see anyone on this site doing this, but the technology behind the design is much more important than the quantity of turbos, and staging setup.

Turbo and super chargers have a compressor map, quantifying where the chargers efficiently move air, and thus make power at certain pressure ratios. The 6.4 (and all the other power strokes for that matter) have pretty crappy flowing heads, manifolds, etc in comparison to any turbo'd/non-turbo'd gas engine of comparable power, so we force the air in faster by cranking up the pressure. Of course, other things can be done to increase CFM, and without raising boost pressure by doing the proper cam, ported heads, manifolds, etc, but as of now, there's not enough technology to get the head flow to where we can do 1000 HP on low boost.

Parallel twins are more efficient than a single using identical technology, sized equal to the two parallel chargers combined because of efficiency, centrifugal force, and probably a handful of other factors. I'm sure there's a ton of info on the web comparing the two for those of you interested in doing parallels, but it's not my area of expertise. The downfall to parallel twins in the diesel setup is that when space is limited, and you can only have 2 turbos for example, you want the turbos in a compound configuration making more pressure than the parallels can to overcome the comparably crappy head flow.

Compounds allow multiple turbos to cover a greater rpm range efficiently in a higher pressure configuration by allowing smaller chargers to remain in their map range at higher pressures because they're being force fed by larger chargers. The max power compounds we offer can make 1000+ fuel only HP with comparably amazing results, and great streetability for a handful reasons that I can describe here. Godzilla's setup is a similar setup, but force-fed by a 106 mm charger, making things more efficient in the higher rpm/power range.

> The high pressure turbo has a reasonably sized compressor for off-the-line power in street driving situations, with the VGT allowing the charger to light faster than equally sized non-vgt turbos, while still allowing comparably more exhaust CFM past the (larger than stock) turbine wheel, and dumping excess back pressure to the next turbo once it's moving a lot of air because of the huge turbine housing.

> Properly sized atmospheric charger matching the high pressure VGT. Before the VGT is beyond it's map range, the atmospheric turbo is force-feeding it, allowing it to stay within the map range, and increase manifold pressure, thus increasing CFM past the crappy heads, which really matters.

Godzilla's triples work off the same principle, but have yet another turbo force-feeding both of the other chargers, thereby allowing pressure and CFM to further increase efficiently, and therefore make power beyond the high power X (62/82) base setup.

Here's a pressure example:

VGT/total pressure is

105 boost/105 BP

BP falls off as it goes into the 88 mm intermediate turbo, which runs at

70 boost/70 BP

All of this ends with the atmospheric turbo (106 mm) producing

35 boost/ 35 BP

Atmospheric turbo is generating 35 psi of boost at 1:1 ratio, intermediate turbo is making 35 psi boost at 1:1 ratio (70-35=35), and the high pressure turbo is making 35 psi of boost as well (105-70=35), equally splitting the work to efficiently allow 105 psi of boost, and still have low rpm, off idle power.

This is only an example, of course for explanation purposes, and there are a lot of other factors that come into play in making this configuration work properly. That's the idea behind the design we're using on Godzilla, and our other triple compound setups.

Thanks Wayne. This is also how I understood it, after talking with Mikey, and why I want to do it. I am not interested so much in adding more turbos, but more in keeping my streetability on the 250s non vgt setup, while adding a bunch of straight line power, once the skinny pedal is mashed downward far enough. Save alot of stress on each of the turbos, only having to work them at lower boost levels, but a combined higher boost, and make tons of air move through. Splitting the load, so to speak. I am looking at changing the housing size of the 75, from a 1.3:1 down to a 1.1:1, so it lights a bit quicker, and gating to the 91 hanging off the side, so we can drive it a bit harder, as well as control BP.

 

[Corb@CorbinShipping]

Wayne , what we don't know is where the power is going to go when we drive the 106 at 55psi... I say the block splits. I will be happy with that.

That would be cool! LOL Someone has to find the limits of that block... unless you believe that it has.... wait for it.......


No Limit.... LOL

 

[Lil' Pete]

Well a pressure differential is what drives the turbine (lower pressure on the turbine outlet). Therefore airflow goes through the high pressure first then the low pressure. There is less restriction from the low pressure then the high pressure turbine. Exhaust gas just wants to go to a lower pressure area. Up-pipes to intermediate pipe to down pipe.

If it were low pressure first then high pressure, the exhaust would be trying to exit the low pressure turbine into an area of higher pressure than it would be in a down pipe.
Hope that makes sense.

A Pressure differential is what happens when pressure flows over a restriction, in a traditional compound setup the primary turbo feeds the secondary turbo on the intake side, but on the exhaust side the secondary turbo feeds the primary turbo, so you have a large pressure differential driving a small turbo and a smaller pressure differential driving a larger turbo, thus high back pressure.

pardon my un-intelligent question.

why can you not parralell/compound?

one on each bank, being the atmos, both feeding the hp.

This was my question as well.

Setup correctly, smaller atmosphere chargers in a triple 2 stage configuration will spool almost instantaneously. Where as a non VGT 80/66 compound setup may not.

So basically a 2 stage system will spool faster compared to a compound set up that moves the same amount of air. But a 3 stage has the potential for more airflow and even higher boost levels.

So if i understand correctly, the only benefit of having two smaller primary's is faster spool up for the same max air flow, or the same spool up time with more max air flow potential?

I'm setting a personal longest post ever,:badidea: so here goes:

There are a lot of factors that come in to deciding how much cfm vs. boost at a reasonable temp. you need on these trucks. The greater amount of fuel you can efficiently burn, the more power you can make. To efficiently burn X amount of fuel across the RPM range, you need turbo efficiency the whole way through. Just adding turbos to show how much of a tough guy you can be is stupid IMO. I don't see anyone on this site doing this, but the technology behind the design is much more important than the quantity of turbos, and staging setup.

Turbo and super chargers have a compressor map, quantifying where the chargers efficiently move air, and thus make power at certain pressure ratios. The 6.4 (and all the other power strokes for that matter) have pretty crappy flowing heads, manifolds, etc in comparison to any turbo'd/non-turbo'd gas engine of comparable power, so we force the air in faster by cranking up the pressure. Of course, other things can be done to increase CFM, and without raising boost pressure by doing the proper cam, ported heads, manifolds, etc, but as of now, there's not enough technology to get the head flow to where we can do 1000 HP on low boost.

Parallel twins are more efficient than a single using identical technology, sized equal to the two parallel chargers combined because of efficiency, centrifugal force, and probably a handful of other factors. I'm sure there's a ton of info on the web comparing the two for those of you interested in doing parallels, but it's not my area of expertise. The downfall to parallel twins in the diesel setup is that when space is limited, and you can only have 2 turbos for example, you want the turbos in a compound configuration making more pressure than the parallels can to overcome the comparably crappy head flow.

Compounds allow multiple turbos to cover a greater rpm range efficiently in a higher pressure configuration by allowing smaller chargers to remain in their map range at higher pressures because they're being force fed by larger chargers. The max power compounds we offer can make 1000+ fuel only HP with comparably amazing results, and great streetability for a handful reasons that I can describe here. Godzilla's setup is a similar setup, but force-fed by a 106 mm charger, making things more efficient in the higher rpm/power range.

> The high pressure turbo has a reasonably sized compressor for off-the-line power in street driving situations, with the VGT allowing the charger to light faster than equally sized non-vgt turbos, while still allowing comparably more exhaust CFM past the (larger than stock) turbine wheel, and dumping excess back pressure to the next turbo once it's moving a lot of air because of the huge turbine housing.

> Properly sized atmospheric charger matching the high pressure VGT. Before the VGT is beyond it's map range, the atmospheric turbo is force-feeding it, allowing it to stay within the map range, and increase manifold pressure, thus increasing CFM past the crappy heads, which really matters.

Godzilla's triples work off the same principle, but have yet another turbo force-feeding both of the other chargers, thereby allowing pressure and CFM to further increase efficiently, and therefore make power beyond the high power X (62/82) base setup.

Here's a pressure example:

VGT/total pressure is

105 boost/105 BP

BP falls off as it goes into the 88 mm intermediate turbo, which runs at

70 boost/70 BP

All of this ends with the atmospheric turbo (106 mm) producing

35 boost/ 35 BP

Atmospheric turbo is generating 35 psi of boost at 1:1 ratio, intermediate turbo is making 35 psi boost at 1:1 ratio (70-35=35), and the high pressure turbo is making 35 psi of boost as well (105-70=35), equally splitting the work to efficiently allow 105 psi of boost, and still have low rpm, off idle power.

This is only an example, of course for explanation purposes, and there are a lot of other factors that come into play in making this configuration work properly. That's the idea behind the design we're using on Godzilla, and our other triple compound setups.

WOW i think i got all that, thanks for the detailed post.



In my thinking, on a parallel compound set up, there are two smaller primary (atmo) turbos, one off each head then the exhaust gasses merge together to feed the secondary (hp) turbo.

Because of the heat and pressure drop across the two primary's the BP in the hot pipe may only be 35psi, but because the intake pressure on the compressor side of the secondary Is already 35psi (fed from the primary's) a 35psi drop on the turbine side of the turbo, equals a 35psi increase on the compressor side 35+35=70psi.

Even tho you only have 35psi driving the HP turbo its still a pressure differential, and because the atmo's have already spooled, the HP is not having to pull air through the atmo its work is easily done.

That is if we lived in a perfict world, and all turbos ran at a 1:1 ratio.

Now make the two primary's VGT's and i think it would be a killer setup.

Any of that make sense?

 

[09stroker]

Umm what?

 

[madman1234509]

The two 62mm turbos feeding a 66mm should be the same amount of air flow as a 80-82mm feeding a 66mm but should in theory spool faster

 

[powerlifter405]

The two 62mm turbos feeding a 66mm should be the same amount of air flow as a 80-82mm feeding a 66mm but should in theory spool faster

How did you come up w/ that data?

I'd like to see what a double setup into the stock VGT would be like. Would it require something smaller than a 59? Dustin pointed it out in a different thread that the stock VGT w/ the vanes open is a 62mm, so that being the case would a pair of 62's into the VGT work?

 

[SSpeeDEMONSS]

the stock VGT w/ the vanes open is a 62mm,

What?

Garrett

probably getting paid at work to post this from my bionic

 

[Matt]

The exhaust wheel maybe, not the compressor.

 

[SSpeeDEMONSS]

Wheel size doesn't change with a vgt. It's the housing size that, in affect, gets changed.

Garrett

probably getting paid at work to post this from my bionic

 

[powerlifter405]

Yes that is correct however I read the original post that the VGT in that instance will respond as if it is a 66(corrected), not a smaller (corrected). As the conversation revolved around how to add triples and compressor sizing, amoung other things.

http://powerstrokearmy.com/forums/showthread.php?t=3545

:
Originally Posted by Dzchey21
At that point you are spooling basically a 66 on its own so you would get a feel for it as it would be as a single.

This has peaked my interest. Sorry for the slight derail..... So if I was to unplug the Vgt actuator I could have an idea of how the truck would run with a single 66? I say this because I am interested in putting my 66 that I have on it but am worried that towing will be greatly affected. So if this give me an idea of what it would run like I am all for trying it.

 

[BOSS450]

It responds that way because the other stock turbo is about a 66mm turbo. when you open the vanes on the vgt it essentially wont spool before the other one. Making it spool like a single.

 

[Dzchey21]

It responds that way because the other stock turbo is about a 66mm turbo. when you open the vanes on the vgt it essentially wont spool before the other one. Making it spool like a single.

Yes thank you

 

[powerlifter405]

Yes thank you

ok, trying to understand the VGT better.

 

[kdogg85]

I'd love to see the y-pipe setup with one hanging off each bank and coming together in the middle.

I have wondered this on top of what you guys are coming up with, is there a point where the hp charger becomes a restriction for the lp charger in either a push/pull or push/push setup?

 

[Dzchey21]

Cylinder head becomes the restriction in most cases

Plenty of 62/95 combos in the dodge world that spool great and make over 1000.HP