Well, fellas--

Let's talk about twins options using the stock turbo. I know Mark Kendrick and others (EEP) are using oem turbos in twins setups.

Which Primaries would match well to an HX35? HT3b? H2e? B2?

What are the relative costs of each of these turbos?

Do they need any special prep before you fab up your mounting (balancing the turbos, etc)?

Do you have to have an ATS manifold or can you use the stock piece? Btw-- You mount the manifold upside down for twins, right?

What pieces need to be fabbed? I am thinking the crosstube to connect the compressors (primary to sec) and then an exhaust flange to inlet adapter to mate the turbine outlet of the sec to the turbine inlet of the primary. Also, a new downpipe will obviously have to be made.

Will an HX60 fit in there as a Primary? Shoot, there a guys using an HT4B, and that can't be any smaller, can it?

How do you "match" turbos in a compounds setup? How do you know if they are to close to each other in size, or too far apart?

Is it a compromise? I mean, too close together and you lose a lot of the compounding effect. Too far apart in size and they end up working against each other (big turbo make the slow one spool slower, etc)

Are there any other "primaries" besides the B2 and BB that have opposite rotation to make the plumbing easier?

Has anyone tried a big Garrett as a Primary? Anything else in the Schwitzer catalog that's a possibility? Why does everyone seem to stock with the Holsets?

Anyway, that's just the first batch of questions that come to mind.

Justin

 

Cost. A HT3B can be had for $400. The larger Garretts and Schwitzers are better (i.e. more efficient & tougher), but they're much pricier. The 3B matches well to the HX-35 in cfm and works pretty well in most applications. A good turbo build (balancing, etc.) is always a good thing, and the manifold pretty much has to be turned over to create room. You could use your stock manifold, but the added weight is only going to crack it faster. All the piping has to be fabbed as well as a mounting bracket for the bottom turbo.

John

 

You can use your stock manifold upside down. A ht3b/22 works good with a hx35 till about 525-530hp. One big cost will be the external wastegate you will need. Cold pipe you can use 3" or 3.5" piping from Donaldson [you need 3 90s] Down pipe will have to be made also, ht3s have 5" outlets. You will need a second Cummins oil return pipe and o ring and a 30" oil supply line. Hot pipe you will need a 1/2" flange and and 3" elbow. There are other expenses to, hoses, silone couplers, clamps, air inlet pipe or hose and a big air filter. This is all I can think of now. Most of your piping you can get from big truck dealer and it helps if you can weld or know someone who can. Balancing will help spool up and routing the wastegate outlet to the 3b inlet makes it more efficent. Tim

 

How about a full B1 paired with the stocker 35/12? wouldnt that combo make for a quick spoolin set of compounds that would be "mild" enough to still tow and drive pretty normal with as well as allow for a little more fuel? Or would it be more benificial to go with say a 9 on the 35?
Also is it necessary to have a boost reading between turbos? Im not too knowledgeable with twins but I would like to have a combo for the "medium hp range" that has real quick spool up and a little cooler egts. The full B1 I have right now would be even MORE awesome if it spooled a little faster .I still have the stock 35 handy nd the welding and fabbing would be no problem as long as I can figure out the spacing and tubing size.
Thanks guys,
Scott

 

HOHN, a Stock 35 and a Stock HT3B are the first choice, then look at a Modified HT3B, then at a B-2, from there to a Modified 35 then to a 40. A Big Brother and a HT4B will barely fit but I don't know if a 60 will. All the about turbo's can be had at Piers Diesel and the last option is to have them modify your 35.

Jim

 

Jim, what was your big turbo when you made 700hp on the small twins (wasn't the hx35 your secondary?)

Justin

 

A B-1 and the 35 is not a good match.

 

Personally, I dont think there is any need for a $1,200+ turbo in a twin setup.


Zino

 

Can anyone answer my questions about turbo sizing in compounds? WHY exactly won't a B1 work with a '35? Too small? Why? How much?

Sorry, I am instanely curious. I have read almost EVERY article on howstuffworks.com I love learning!

Justin

 

The B-1 is too small to work with a 35 because a compound system is closed to the atmo between stages. The 35 still needs enough air to its compressor to deliver its rated CFM. Remember, the CFM is not additive in a compound system.
The total CFM of air you can get from a compound system is from the primary charger. This is before loss. Basically a B-1 in a compound system could give somewhat higher pressure but the volume of air you get into the engine will be less than a straight up B-1.

Don~

 

I just ordered what they call a ht3e, which I think is a smaller shaft ht3b. Going with a 23cm exhaust and teaming this with a 35-40 hybrid. I'm going to try to run a 12cm exhaust on the 35 and put a big external wastegate out of the spot where the original wastegate is. Got a 98 model housing and going to make a new plate cover for it , blocking off exit into exhaust and milling a larger hole where wastegate was. Don't know if this will work but it looks good on paper! This is suppose to be a good tow combo up to 500 horse. Should know in a month or so. Price was what was said above at 400 to the door. In my opinion any larger compound and towing ability starts going away, but all I know is what I've been reading in other threads. Doesn't the 9cm housing cause alot of heat or will a large wastegate help take care of this problem?

 

I would just build a spacer between the manifold and 35 to mount the wastegate to like Jim Fulmer did. The reason is because #1 it's fairly easy to do, #2 It wastegates both sides without have to modify the existing housing and WG, and #3 It will probably be easier to route your WG line with fewer angles.

A large WG will help the HY/9 but that isn't the only problem with using them. Besides a quick spool on a HX35/12 will spool nearly as fast.


Hohn (Justin),

A HX60 or HT60 will fit just about as easily as a HT3B. They are slightly larger but not nearly as big as a BB or HT4B.

I personally think the reverse rotation turbos (HT3B, HT60) are easier to mount then the standard rotation turbos (BB and B2).

Jason and I used 4" for the cold air pipe just because we both thought it looked better. The HT3B starts at 3.5" and then flares to 4" for the rest of the cold air pipe. That way you dont have your flare right in front of the top turbo.

As far as brands go my HT3B was a Garrett and Schwitzer also makes them. There are several turbos made by any of the "Big 3" that would make good primaries. I would actually bet most of the primaries used are Garrett or Schwitzer over Holsets. Holsets generally cost more.

 

Is there another turbo besides the B2 that will pair well with the B1?Keep in mind, Im just trying to add some spool up and a little cooler egts, NOT 700 ponies (right now ).
Scott

 

HT3B will work ok. I have a top secret charger that will work too. Its more cash than the B-2 though

 

Reader's digest version: Going with a B1 as a Primary defeats the whole purpose fo going to compounds, right?

So just so I have my theory straight here, the Primary is the main turbo in the setup (not just because it gets the air first). It is supposed to be doing most of the work.

Thus, the secondary is there mostly to provide some air while you wait for the monster primary to wind up. Going with a larger primary (and twins) allows more CFM with less heating a single setup.

So let's see how this plays out as the engine goes from idle to peak RPM@ WOT.

At idle, there is very little energy in the exhaust stream and the turbos aren't contributing much to the picture.

As fuel is added (and rpms come up a bit), the secondary begins to spool. It spools quicker than the primary because 1) it is physically much smaller, and 2) it is closer to the manifold so it receives more energy than the primary.

The increased airflow from the secondary supports the burning of more fuel. At some point, the primary will begin to spool since this higher level of enthalpy will now provide enough energy for it to spin up.

As the primary begins to enter its operating range, the total airflow to the engine increases dramatically.

Soon, the airflow from the primary compressor surpasses the secondary's. Since the secondary cannot increase the airflow beyond what it is fed, all it can do it increase the pressure of the air it gets from the primary.

As still more fuel is added, the secondary turbine housing nears its choke point. This is where a wastegate is a must to prevent overspeeding the secondary, as well as the spike in EGT that's associated with the choked exhaust.

The secondary will spool more slowly in a compound setup than it would by itself. This, because it must overcome the inertia of the primary and the resulting partial vacuum in the crosstube.

So in essence, we should size the primary turbo such that it is near the peak its operating map at peak RPM and maximum fueling-- accounting, of course, for the loss in efficiency created by the primary having to feed its airflow through the secondary's compressor.

We should size the SECONDARY such that it is large enough to allow sufficient airflow through both its compressor and turbine. If the compressor's too small, the the efficiency of the primary suffers. If the turbine's (housing, primarily) too small, the restriction to exhaust will be so great the it cannot be alleviated without an ENORMOUS wastegate. This is not optimal, since it's much less efficient to flow the air through a large wastegate/small housing (and then dump it into the primary's turbine) than if you had a larger turbine housing and wheel.

Of course, you go too big on the top charger and then your spoolup is crap.

Compromises, compromises....

Justin