Sequential turbos... do-able?

[North Maine]

I know that compounding turbos is usually used to just make huge boost pressures, which obviously is not anywhere a 6.5 wants to go, but would it also allow you to operate a turbo inside its efficient parameters and get more PSI/flow? Here is my idea...

6.5 with 18:1 compression ratio running a centermounted hummer GM-8 with mechanical wastegaste control that is quite light, as in if it were just that one turbo it would yield about 4-5 PSI under full load... have that GM-8 feed another turbo like the ATT on the pass. side, intercool, and into the engine.

Is this just a really stupid and expensive idea?

 

[6.5quest]

The centermounted H1 turbo is not actually a GM-8, it is called a GM-5 or something like that. But it is a much smaller lower boost turbo that could feed an ATT in theory. I get what you are saying but from my knowledge the ATT has a dual spline compressor wheel that acts kinda like having compound turbos. You still don't get that lightening fast spool up like a GM-4 would give you but all in all the ATT by itself would do what you are thinking about doing with half as much spent on both time and money.

However if you do decide to go the way your are thinking then please send me some pictures because I would love to see it and know how it works out for you.

 

[North Maine]

Yea I can see what you are saying, but could the smaller GM-5 keep the lightening fast spool-up still there and then the high-RPM powerhouse of the ATT would kick in? I'm trying to research this but there really isn't a whole lot of info on sequential or compound turbos.

 

[6.5quest]

You could try calling the guys up at BD performance. They do so much work with compound turbos. My knowledge is limited so I think they might be able to help you better than I could. You have a good theory and out of these theories great products can be born. If you have the ability to make your idea happen then by all means do it because you might discover something that no one else has been able to do. So you have my full support on this idea and I hope you can make it a reality and share your results with the rest of us.

 

[randomid25]

Not to be a buzzkill but can a ds pump even supply enough fuel to make use of more airflow from compound chargers?

 

[6.5quest]

Not to be a buzzkill but can a ds pump even supply enough fuel to make use of more airflow from compound chargers?

That was my thought as well, so I brought up the use of one ATT instead. Unless he wants to go with a larger 4-plunger pump with some fuel and timing upgrades.

 

[ak diesel driver]

I would think you could do it but you might need smaller turbos

 

[540s10]

I think the major problem would be that you are heating the air twice and with the IAT's being super high your egts would skyrocket and make you back out before you can take advantage of the larger turbo.

 

[randomid25]

Lack of fuel is the major issue with these engines. Find a way to fuel them and they can make more power with the proper mods. With all the enthusiasm that the 6.2/6.5 engines are gaining, I'm sure that we're gonna see more creative ideas being tried on these engines.

 

[North Maine]

I think the major problem would be that you are heating the air twice and with the IAT's being super high your egts would skyrocket and make you back out before you can take advantage of the larger turbo.

I think with this system it would be necessary to aftercool, but I also think that by keeping the boost low on the first turbo it would really help keep the IAT down when it got to the ATT, then aftercool it with an ATA like many have done. Also having the wastegate set on a loose control the first turbo would not provide nearly as much back pressure as it would set stock boosting 10+ psi, and the ATT is already known for its low exhaust backpressure... in my head I would think these two would combine to make the same exhaust backpressure of a GM-8 pushing 15-17 PSI yet yielding 23-27 PSI

 

[Big T]

On the Volvo Marine Diesels (i.e. KAD series) they used a supercharger for low end boost and passed off to a turbo for high end boost. So instead of sequential it was a hand off.

 

[635]

Ever see a 350 hp Detroit? A 318 comes with a blower but they call it a 350 when the add the turbo! I can hear that 2 stroke screaming. YIKES!!

 

[Matt Bachand]

I think the handoff w/supercharger would be a much easier possibility.

 

[6.5quest]

This entire thing is becoming overcomplicated. We are still talking about a limited amount of fuel. So unless someone comes up with a way to outfit a 6.5 with a P7100 style pump or anything else that can put out 120+mm fuel numbers, compound turbos or handoff concepts would do nothing but lighten your pocket book. We have so much tallent on this forum, maybe someday one of us will find a way to add the fuel and timing to these truck before they are all sent out to pasture.

 

[North Maine]

I've heard rumor of Bill having a P-pumped 6.2 that got stolen a long time ago? Is there any truth to this rumor? If so where did this P-Pump come from? When it comes to fuel, I'm wondering if Scania's V-8s that used inline P-pumps are an option.

 

[Matt Bachand]

This entire thing is becoming overcomplicated. We are still talking about a limited amount of fuel. So unless someone comes up with a way to outfit a 6.5 with a P7100 style pump or anything else that can put out 120+mm fuel numbers, compound turbos or handoff concepts would do nothing but lighten your pocket book. We have so much tallent on this forum, maybe someday one of us will find a way to add the fuel and timing to these truck before they are all sent out to pasture.

I'm not sure about that Ian. Indeed its more than needed, and over complicated, but thats the nature of this thread.

My thoughts about the nature of this thread was to achieve some low end boost/power, and then let the 2nd stage complete the system of mid-high boost/power.

All being done with the amount of fuel that is available, being plenty already.

Meaning a blower to provide instant boost with Idle - 1400 RPM for boost like pulling off the line, then handing off to ATT to achieve boost like pulling up into the 3000's.

Doesn't mean you will be doing this pedal to the floor, pushing the DB2 pumps to their limit every single time.

I know the fuel limit is a limitation to achieve high end HP/Torque numbers, and limits go-fast pulling heavy loads or dangerously high speeds, but to most 6.5 drivers I'm not sure we ever use 100% of fuel possible, whether it be from a stock chip or reflash.

 

[randomid25]

So unless someone comes up with a way to outfit a 6.5 with a P7100 style pump or anything else that can put out 120+mm fuel numbers, compound turbos or handoff concepts would do nothing but lighten your pocket book.

There is a guy that has a pulling tractor in Finland or somewhere with dual db2 pumps on it. Totally custom work and you might have already seen it.

When it comes to fuel, I'm wondering if Scania's V-8s that used inline P-pumps are an option.

Those engines are simply awsome. They have a WICKED sound to them, especially the 16L big boy they have. 625hp and over 2k lb-ft or torque would be cool to drive.

Doesn't mean you will be doing this pedal to the floor, pushing the DB2 pumps to their limit every single time.

I'm not sure we ever use 100% of fuel possible, whether it be from a stock chip or reflash.

I have a maxxed out db2829 with a GM1 turbo and it can't supply enough fuel to feed it. Once we figure out a VIABLE option to supply these engines with more fuel, the horsepower/torque will be there. There are already quite a few ways to increase the strength of the bottom ends.

 

[chevyinlinesix]

Would 650cc+ of fuel be enough? ):h :wink5:

I would really like to see someone put a sequential turbo setup on a 6.5, I have a very small AiResearch turbocharger that I could donate for very small dollars if someone is really going to pursue this. It needs a rebuild though.

 

[Matt Bachand]

RandomID, you cut out (or misseD) where I said 'MOST'....

I weigh on average 9500lbs, and I barely use any throttle to go about my business. I also have a stock program, so I know I've never used Max fuel output of my pump, yet I may benefit from a 2 stage system, where I'd get boost off the line, then hands that off to more efficient boost midrange up.

I would never do this, but I do believe it would benefit even with the amount of fuel I can supply.

Of course, with more fuel, it would only compound the benefits that much more.

 

[randomid25]

It's ok Matt, I'm not full throttle all the time either, but when I put as much money into my truck as i have, I want it to Haul Ass when I stomp on it. Its kinda disheartening to stomp on it and the turbo whistles and the boost gauge goes up but the egt doesn't really climb and you don't feel anymore power cause there isn't enough fuel. I just don't wanna see someone put big bucks into a compound setup and be disappointed after spending all that dough.