Artsi_L

what a beauty

Joker12valve

Wounder how that would work? could use two smaller turbos from the car wourld. also what is the reason that some of the big car turbos are not used on our trucks? They use the 35 on imports. Don't mean to side track this thread but was just thinkingit

Artsi_L

Justin

I value your insight into this thread. I myself lack mathematical know-how as it comes to determining inertia of masses of certain diameter. Now I do comprehend more fully the advantages of this parallel turbocharger setup. I knew it there had to be some concrete reasoning behind all this, otherwise the companies mentioned in the 1st post would have definitely not gone the twin parallel layout avenue.

Thanks Justin

---

Everything in today’s world is marketing/profit driven. Even when some twin-turbo system is superior to single charger setup, it will not materialise on dealership floor unless usual profit margin can be maintained. It’s more expensive for vehicle manufacturer to come up with a twin charger setup, rather than sticking with a single unit (more complex/time consuming assembly work on shop floor, a few more items to pass final quality check, more plumming, a handful of more spareparts, initial cost of one additional charger, stocking all additional parts and cataloging them…)

None of the reasons above restrict end user from bombing his engine.

I am not challenging here two-stage charging (i.e. compound turbos) with parallel twin turbo idea. What I am challenging, is two small chargers versus one big single charger.

A really interesting setup would consist of parallel twin setup plummed into large bottom turbo in a compound setup, as I suggest in my original post. That would be totally so interesting to see.

HOHN

Thank you for the kind words.

I think there was a compounded parallel "triples" setup that was stillborn at ATS once upon a time. It's worth searching through the archives for.


Personally, I think that system would be ideal if someone could pull it off. The small parallel chargers would essentially have ZERO lag of any kind relative to a larger single with flow comparable to the pair (say the 44lbm-min range). The paired "secondaries" might also present less restriction overall to the exhaust to do the same amount of work.

Then you compound these paired turbos with a larger charger, and much greatness ensues--on paper.


The problem with such a setup (aside from crazy cost), is heat loss. You'd have to have EVERYTHING coated and/or wrapped and have the plumbing kept to a minimum to keep heat loss down.

Such a "triples" system is probably one of those things that's great on paper, but falls apart in execution. But if someone did a better job on the execution, perhaps the theory could be validated....

jh

signature600

There is a guy around here that does triple setups...2-HX35/16's, and 1-S300

Definately one of those "it looked good on paper ideas"...but it was done by a hilljack diesel man. It works, but he has no idea of the potential of a CORRECT setup!

I wonder if 2 HX30's from a 4BT, and a 71mm S400 would work Talk about hard to fit under the hood

Chris

Joker12valve

You can make any thing fit, just how tight do you want it. don't the big time farm tractor pullers (smokers) use triple turbo setups. thought i read that some were. triples would be cool, but might not be wourth the cost/time. still would be neet to see

signature600

Some are!! I've seen THREE HX82 class chargers on an alcohol tractor Some of the V8 tractors, and real wild ones are 4 charger!!!

Chris

Artsi_L

I seem to forget more stuff than I learn stuff. Here we go:
https://www.dieseltruckresource.com/...ad.php?t=88446

I quote the link on that thread:
"(from DaimlerChrysler Press Release) The SLK 320 CDI tri-turbo is based on the new V6 diesel engine, which achieves new levels of performance thanks to a two-stage supercharging system. It consists of three turbochargers, of which two are located on the outside next to the cylinder banks while the larger third turbocharger is situated between the V of the cylinders. At low engine speeds and loads, air flows through all three turbochargers (i.e., large and small), with the small turbochargers doing most of the work. When engine speed increases and the flow is continuous, the large turbocharger takes over supplying the greatest share of the charge pressure and the smaller turbochargers are turned off by means of a bypass system. At high engine speeds and loads, only the large turbocharger is running. Performance is further heightened as a result of an enlarged intercooler and larger pipe diameters for the charge air and the exhaust."

Mike Holmen

Sorry ab out hijacking here but how did that truck running the roots style charger and turbo combo work out. I'm throwing around the idea running a centrifugal charger in front of my twins and running an liquid intercooler in between the twin turbos. Engine space is tight, but thankfully we have space behind the cab to put in the stuff that doesn't fit under the hood.

HOHN

An HX30 is too big for just 3 cyl. You want a turbo essentially designed for a 3.0L engine like an older 300ZX (though those had two chargers, iirc).


Here's how I would calculate the flow rate I want from two small turbos.

Start with BSFC. Let's assume relative inefficiency and call it .400 lb/hp/hr.

Now, we want two small turbos that will basically replace an HX35 as a single. Let's say that the maximum HP an HX35 will support is 350.

So, if BSFC is .400 lb of fuel per hp per hour, and we want 175hp, we have 70 lb of fuel per hour. Let's call that 1.17lb/minute. Now this is FUEL!

What about air? Well, what air:fuel ratio do we need to maintain a reasonable EGT that will make good power? Just for giggles, let's say we want 20:1 for our air fuel ratio.

So we need each SMALL TURBO in a parallel setup to supply about (20*1.17)23.4 lb of air per minute (lb/min).

A Garrett GT2252 is almost perfect for this application. (see: http://www.turbobygarrett.com/turbob...2_452187_6.htm)
This turbo is in the fat part of it's map right around 20lb/min, and 23lb/min is doable for it, even accounting for the loss of efficiency. Look at the map at a PR of 2 and the low 20s for mass flow-- PERFECT!

So let's take a pair of GT2252 Garretts in parallel as our "small" chargers-- this gives us the airflow of an HX35, but pretty much ZERO LAG-- like blink and it's spooled.


Now we to select a single large turbo to feed BOTH these small Garretts. How much HP must we be able to support? Let's say we want 600hp, and recalculate using BSFC. 600hp*.400/60*20= 80lb/min to support 600hp.

Perusing the Garrett site, can we find a turbo that will do 80lb/min at a pretty high PR? A GT4202R can do this with over 4:1PR and still be over 74% efficient!!
http://www.turbobygarrett.com/turbob...2_731376_2.htm

A GT6041 MIGHT be doable in some HUGE twins, but in our case, it's way too big. Laggy and miserable.


Since the small turbos are operating at a much lower PR than the big one is, heating is less. The little guys are at 2 for a PR, while the big GT42 is pushing 4! Since both all our turbos can do what we ask of them with 70% efficiency or better, this system would be capable of (.7*8=) an overall PR of 5.6, or 67.6PSI of relatively cool, useable boost.


With this configuration, it would be useful to install water injection between the outlet of the GT42 and the inlets of the GT22s, because of the High PR the GT42 is operating under. This would be an effective intercooler, and greatly enhance overall system performance.


By my estimates, the above setup would spool instantly and cool 600hp comfortably. Someone build it and prove me wrong

GO 4LO

I can't see the pics at the top, but everyone keeps saying twin 35's off the manifold with an S300 on the bottom. Are you sure it's not the other way around? Twin 35's would be a nice primary stage to feed an S300 on the manifold, but it just doesn't make sense the other way - that'd be like running a 3B on the manifold and a 35 on the bottom... ??

Chris

GO 4LO

But doesn't the flow capability vary by the square of the diameter too? To supply the same air as a 3" single to an I-6, you'd need two 2.12" chargers, each effectively feeding an I-3. Which should have the same inertia, assuming all physical components of the chargers scale linearly, right? Or do we know that some components of a charger wouldn't scale linearly?
With the parallel secondary stage, you would have the advantage of being able to shorten piping so that less heat is lost between the head and the charger(s). And you might save money on big-setups (like a twin HT3B primary stage instead of a single HT80 primary stage). That's the main advantages I see...
Chris

HOHN

This is backwards to me. I'd say you want the parallel chargers as secondaries, not primaries. Plumbing would be easier, imo.

Can twin 35s provide enough air as primaries? I suppose that if one can support 350hp, maybe two could do 700 as primaries.

I guess that you could parallel the primaries instead of secondaries (or even both, doing quads).

Quads are interesting-- like parallel sets of twins.

GO 4LO

I agree - if I were going to do a set, I'd look at doing parallels for the secondaries. Cutting down runner length to decrease spool time for that stage would be a big plus in my book.
The twin35 / S300 setup seems like it couldn't be, though, from looking at the sizes - it'd be the equivalent of running a 700 hp turbo as a secondary and a 4-500 hp turbo as a primary. An HX40 or S300 up top would be sized right to feed a pair of 35's on bottom. With twin 35's up top, you'd need something at least the size of an HT4C / Big Brother on bottom and would probably be better matched with something HX80-sized, imo.

Chris

HOHN

With twin 35s as "small" turbos, they would NEVER spool!