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lumpdog

Twin Turbo Setup questions.

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As most of you know, I am pretty new to diesel performance. So I am really trying to gain information about twin turbos.

1. Which is the bottom and top turbo? Which one is bigger?

2. What factors determines picking a good compound setup?

3. Can one be built with turbos sourced from other engines, i.e. big trucks?

4. What are the benefits besides going fast? Better for towing? Cooler egts?

What about making a sticky thread or tech section topic about them?

Thanks!

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Ya what he said.........I have read more info on other sites but am more confused than ever. I want to build a good TOWING setup not go fast down the track or squash imports and crap like that.

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Well what you are describing and asking about is really a compound turbo setup.

There are three types of setups in reality.

  1. Twin Turbo in which you have two smaller sized identical turbos working together to create boost. (Parallel turbos) Typically seen on V style engines
  2. Sequential Twin Turbo: you have a smaller turbo working with a larger turbo. The smaller turbo handles the boost at lower RPMs and as the RPMs increase the boost duties are handed off to the larger turbo
  3. Compound turbos you will have a larger turbo feeding the inlet of the smaller turbo. (Series Turbos) At this point you are compressing air that has already been compressed.

The benefits are exactly as you described with the addition of spool up is quicker. it allows you to go to the effects of having a larger turbo without having the drawback of more lag of a single larger turbo.

Yes you can get turbos from large diesel engines, but you have to understand the charcteristics of how that turbo performs. Just going out and getting a big turbo and slapping it on may not provide the desired effect.

I've been meaning to post a few links on turbo chargers to help folks with the understnading of what a turbo is and how to know which is the right turbo set up for you. Let me pull those links and I will put up a thread.

As far as picking the brains of guys that have been there done that with compuonds. Pick away, there are lots of guys here with first hand experience. :thumbup:

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So what is the benefits and drawbacks of options 1,2,and 3?

If I read you statement right, then the following is true?

1. Side by side, same size turbos. (parallel)

2. Side by side, different size turbos. (parallel)

3. Inline turbos, different sizes. (series)

So how does one go about finding what the right size turbos would be as far as:

Inducer specs, exducer specs, housing sizing, etc.

Is it a good idea to run a mild compound setup for strictly a tow rig? That way you can get quick spooling with lower egts?

Could I stack my H1C with an HX35 to get decent results? Would it hinder or hurt me?

I have so many questions, the more I read, the more I am confused.

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Well the parallel turbo would be useless for you with an inline engine. Parallel turbos are more for V engines. It allows the turbos to be mounted closer to stream of exhaust from each bank of cylinders.

Sequential turbo required some wild plumbing on the charge air side and on the exhaust/turbine side. The benefit would be that you would have the advantage of a quick spooling turbo on the low end and big turbo to flow a large amount of air on the top end. Essentially giving you the benefits of both(Quick lighting small turbo, more air flow of large tubo) without the real drawbacks of either(Extreme exhaust back/drive pressure and choking out on the top end of the small turbo, bigger lag of the large turbo)

Compounds on the other hand are not excessively complicated to plumb. Will provide similar benefits of the sequential turbo set up, quick spooling smaller turbo with the big flow of a larger turbo. It doesn't reduce the back pressure quite as well as a sequential set up, but with proper wastgate set up you can work at keeping the top compressor working in it best efficency range while reducing the back pressure created by trying to spin the small turbo faster to get it to flow more air.

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1. True "twin" Turbos: 2 identical turbos, generally on a V type engine, operating independently, but functioning as one large turbo with quicker spooling.

2. Sequential Turbos: Two independent turbos, one smaller for quick spooling low rpm use, the other for high rpm use. Uses a plethora of complicated valving and plumbing. Turbos share the same exhaust and intake circuits, but use the valving to switch the larger turbo on and off. Like this:

Turbo_Sequential.jpg

3. Compound Turbo: Two turbos of different sizes, one for quick spool, one for higher rpm boost. Airflow of inlet goes into the big turbo, then to the inlet of the second turbo and on to the engine. Exhaust flows from the engine,to the small turbo, and finally out the large turbo. It seems like the small turbo is wastegated to allow more exhaust flow to the large turbo when under boost.

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Compounds are the way to go with out a doubt.

The top turbo is on top ( typically stock size or a little larger )

Bottom turbo is on the bottom. This is the large one.

Basically when you first take off youre just running on the boost created by the small top turbo. Once youre going the big turbo creates boost and then youre running on the boost made by that turbo. Its just blowing through your small turbo.

Twins let you keep a small turbo and gain all the benifits that a large turbo has with out all the drawbacks like lag.

My bottom turbo is basically a stock turbo from an over the road truck.

I run a HTT HTBG ( s 300 with a 57mm intake wheel) over the top of a Holset BHT3c. ( 78mm intake wheel. )

The 78mm turbo runs great on top but I would never spool it as a single.

I have been using the truck to haul some descent loads lately ( 6500 lb trailer with at least 5000 lbs on it ) and even at full throttle the egt's stay below 1250 at all times.

At the dragstrip I was full throttle through all 5 gears and the pyro never even went past 1200 the whole day. Before with just the single and smaller injectors (Old were Lucas POD's and now theres a set of New Era 435's in it ) I couldnt get through 3rd gear much less 4th and 5th befre the pyro was past 1600.

I have my waste gate on the top turbo start opening at 15psi and run the lower turbo non-gated. It will easily make 50-55 psi and spike past 60.

Even with all the work involved just the sound the truck makes was worth it. The truck has never been this quiet and my entire exhaust consists of 6' of 5" pipe that dumps on the ground right before the rear axle. NO drone and quiet as a stocker except for the cool whistle.

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Okay my question should have been more specific. I understand how compounds work, just not which size. For towing twins what size exhaust housing is best for the primary? You can't just say an s400 because they come in several diffrent sizes, so which on will work best for towing? I am planning on using my stock turbo on top.

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Nice write up.

I have a few turbos lying around to play with. I wonder if any of them would work.

8v92 silver turbo

Cummins big cam turbo

Detroit 82 turbo, schwitzer I believe, would definitely need a new exhaust housing.

HX35

H1C

Maybe a few others.

I don't know how to identify turbos and what size wheels and housings they have though.

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Okay my question should have been more specific. I understand how compounds work, just not which size. For towing twins what size exhaust housing is best for the primary? You can't just say an s400 because they come in several diffrent sizes, so which on will work best for towing? I am planning on using my stock turbo on top.

Ditto!

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Guest ShanesLB7
Okay my question should have been more specific. I understand how compounds work, just not which size. For towing twins what size exhaust housing is best for the primary? You can't just say an s400 because they come in several diffrent sizes, so which on will work best for towing? I am planning on using my stock turbo on top.

I had the stock turbo and s400 in my old set up!! awesome towing set up ...

THe s400 was a 71 mm i believe... PM pat (liskouski) or Nathan wright (idaho ctd) they are turbo gods...

Maybe they will even chime in..:train:

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Yes Pat and Nathan have had much experience and can tell you which turbos will work. The items I provided in the tech section are there to help you figure out which turbos and why that turbo best suits your needs.

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I guess I made it seem like I didn't understand compound turbos...But I do.

I didn't understand sequential twins until today. What I was trying to figure out today was the differences in performance between the types and how it applied to our situation.

From the reading I have done, it seems that sequential turbos would give the best of both worlds, quick spool, lots of boost, and less backpressure. They are fairly complicated system to build, and even harder to tune properly.

Compounds however, perform much like sequentials with a few downfalls, although very minor in a properly sized system. Relatively simple to build, and seem to be the most forgiving in the sizing and tuning (between the small turbo wastegate opening and the large turbo spooling up) parameters.

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You could always use a supercharger/turbo compound set up... :lol:

Whoa.....settle down!

I wonder how hard it would be to make the Cummins a two stroker.....:train::coal

What about.....a blower under a pair of matched twins. 3cyl per turbo...

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I think we start getting to turbos/induction/air end of this week. I'm not sure how indepth it goes but I'll have the basics. You should see some of the turbos at the shop.... HUGE.

And it would be probably really difficult to make it a two stroke :lol:

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Been in that shop way back when.....Graduated the auto program there in 97. Used to harass the diesel guys all the time, they were wimps then, couldn't hold their alcohol at all!

It will be interesting to see how in depth your training is. Be sure to ask lots of questions.

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I had the stock turbo and s400 in my old set up!! awesome towing set up ...

THe s400 was a 71 mm i believe... PM pat (liskouski) or Nathan wright (idaho ctd) they are turbo gods...

Maybe they will even chime in..:train:

It was a 74mm or S475 as some call it. The actual inducer is 74.6 or 7.

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Been in that shop way back when.....Graduated the auto program there in 97. Used to harass the diesel guys all the time, they were wimps then, couldn't hold their alcohol at all!

It will be interesting to see how in depth your training is. Be sure to ask lots of questions.

They have a few newer engines. They have a 00+ cummins N14 and I think an 06 or 07 Detriot 60 series that is a forking monster!

I would never never ever drink alocohol... gross.... specially underage :nono:

j/k( | )

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They have a few newer engines. They have a 00+ cummins N14 and I think an 06 or 07 Detriot 60 series that is a forking monster!

I would never never ever drink alocohol... gross.... specially underage :nono:

j/k( | )

The turbo on that detroit is AMAZING:shock: :shock:

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you guys oughta see the turbo that i got at the house... now that thing is freakin huge... it come off an 1100 hitachi track hoe. they put a cummins motor in it cuz the mitsubishi motor crapped out... anyway this thing is huge it weighs like 60 or 70 lbs....

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