Compound Twin Turbocharging from Boost Logic

[HowlerMonkey]

I'm confused by your statement. As far as I know and can see from the picture, it's more accurate to say the exhaust from the small turbo could pass through to the big turbo.

 

 

I am wrong but the statement above is not completely right.

 

If you passed all the exhaust gas first through the small turbo, you would be limited to how much hp the smaller exhaust housing can handle.

 

That would make the big turbo not necessary.

 

Since a few of the pics seem to have disappeared, It looks like the big turbo is fed a branching off of the exhaust that bypassed the small turbo.

 

Personally........I would have designed the kit having the big turbo being fed all the exhaust and then branching the exhaust AFTER it passes through the big snail for routing to the small turbo.

 

With clever wastegate positioning, the setup would be a lot simpler.

[RB26powered74zcar]

As I've said, Very Nice, but ask me how I know the heats going to be excessive under that hood....

[ShaggyZ]

I am wrong but the statement above is not completely right.

 

If you passed all the exhaust gas first through the small turbo, you would be limited to how much hp the smaller exhaust housing can handle.

 

That would make the big turbo not necessary.

 

Since a few of the pics seem to have disappeared, It looks like the big turbo is fed a branching off of the exhaust that bypassed the small turbo.

 

Personally........I would have designed the kit having the big turbo being fed all the exhaust and then branching the exhaust AFTER it passes through the big snail for routing to the small turbo.

 

With clever wastegate positioning, the setup would be a lot simpler.

That's the deal, though. They tried other ways and this the way that worked. To my knowledge, this is how compound turbocharging works. So far, it seems that "small" turbo is "limiting" streetfighter's car to 706whp. I respectfully say that if you had designed it your way, it wouldn't work.

[HowlerMonkey]

NO......what I meant is that the pictures don't show the exhaust being branched off before it goes to the small turbo.

 

All exhaust gases destined for the big turbo are not going through the small turbo first because the small turbo's restriction would not allow enough gases to pass through it to even tickle the large turbo into producing boost.

 

That small turbo's exhaust housing will certainly not pass 700hp through it so it's obvious they bypass a good amount around the small turbo and send it directly to the big turbo.

 

My way routes ALL exhaust gases first through the big turbo and directly into the small turbo with the bypassing a certain of percentage of exhaust gases happening between the large turbo exit and the small turbo's inlet rather than before them.

 

There is also a nomemclature problem with using "compound" since aviation engines like the wright 3350 are called turbo compound but they use power recovery turbines which is far different than what is above.

[Daeron]

Okay, I just dug some stuff up and I think what we are experiencing here is, failure to communicate. I JUST read this stuff so my understanding is not that of an expert, but I'm gonna try to spell it out anyhow so bear that in mind.

 

Compound turbocharging and sequential turbocharging are (apparently) not the same thing.

 

In a sequential system, the goal is to use a small turbo and a big turbo to get the benefits of both, and you use wastegate controls to determine where the exhaust gases run to as well as what turbo is actually breathing into the manifold. For instance, we say that the small turbo tries to spool at 1300 RPM and builds boost to a max of like 8 psi. By 32-3500 RPM the smaller turbo gets bypassed and the big one starts coming on; once the big one is over 8 PSI the little one goes away entirely and your final boost is around 20 psi (or whatever, just for example) The goal is simply to have the lack of lag of the small turbo, with the flow and boost PSI potential of the large turbo. howlermonkey is talking about something like that; running ALL the exhaust gases through the small snail in this system obviously defeats the point.

 

In a COMPOUND turbocharging system, you snort up filtered air with one turbo, pressurize it threefold, and blast it into the inlet of the other turbo which then pressurizes that threefold, and then gets blown into the intake of the engine. The exhaust side goes, headpipe, inlet flange of turbo 1, out of turbo 1 into turbo 2, thence out into the atmosphere. Both turbos are usually the same size, and you result with 9x pressure increase (9 BAR!!!!) This is a diesel only type of setup because (obviously) these kinds of pressures will simply prevent spark from ever occurring, not to mention the pressure iginition (oy!) We are discussing a concept that sees up to 250 PSI in tractor pull engines!!!!!

 

Cummins compound system (clicky for a thread to read)

 

NizPro Marine quad turbo Sequential system (also clicky for website)

 

and as always, faithful wiki: http://en.wikipedia.org/wiki/Twin-turbo#Sequential_twin-turbo

[ShaggyZ]

For the record, I never pretended to know how it works. Given the plumbing pictures, my statement was accurate that exhaust often goes through the small turbo then to the big turbo. Boost Logic's compound setup could be considered a hybrid compound/sequential setup, I suppose, because it is not exactly like the designs used on diesel applications - the two wastegates is what allows the system to keep the boost regulated to low pressures. In fact, I believe they're even using two boost controllers but I don't know exactly how that is handled.

[JustinOlson]

[ShaggyZ]

Ha! Nice, Justin! I was wondering when someone would post up with their own copies. Thanks.

[NavyCuda]

Are there any good resources you would recommend for sizing turbos for a compound setup?

[Guest Pannoowau]

on seeing those photos i cant believe the model of engine.....

 

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[fairlady2jz]

my opinion just better use juice with a big turbo plus with the new billet 67 no need for that