Fabricating Twins

[JonKing]

I am thinking of fabricating a set of twins and was wondering how they are plumbed together. This there a special exhaust housing for the top turbo to connect to the bottom? Which turbo (big or little) is bolted to the exhaust manifold? If you use the stock turbo in a twin set-up are the exhaust pressures going be the same as when it is used by itself? Is it possible to install a larger exhaust housing on the stock turbo? How are twins wastegated? What is the best combo? I guess what I am asking is how twins are designed from beginning to end. Sorry for all the questions, but I'm just interested in doing it right the first time and the price of most kits seems high for the parts involved. If you use the B-1 ($1600. 00) and B-2 ($800. 00) turbos your only at $2400. 00 in turbo cost, that's along way from $4500. 00-5000. 00 that the major guys charge.

 

[cummins_crewcab]

I'm interested in this as well but I haven't done alot of research on it yet. I have a full fabrication shop and could do the work easily but just haven't had time to start planning/building.

 

[lmills]

you would be surprised out how quickly that 4500 gets used up doing a custom set. Not to mention if you do not have the skills to do the welding or fabricating, you will be paying someone to do that also.

 

[Jim Fulmer]

Out of all the people that build Twin kits I would say they are all in line with price, there not as easy as you think! I've built two sets on my truck and both were a pain.



Jim

 

[cummins_crewcab]

I completely agree there, extra cost is the labor and the trial and error it took to get the set just right before they could mass produce them. I just like doing things myself, especially when it involves metal working.

 

[JonKing]

I appreciate the reponses and I do understand the amount of work involved. However I have a friend that is a master fabricator and building a twin setup is well within our ability. I am more interested in building the set myself than buying one from someone else. The set I what to build will utilize stainless and aluminum in the construction, which nobody offers. What my real question is not how hard or how much, but how to. Just curious about the theory of compound twins and what parts are needed. I know the easy way is to buy from the big boys, but that's not me. In other words I'm just looking for advice on what turbos to use, what order, if I can use the stock turbo, can it be modified, do I need special housings, how to plumb the oil system, and how to control boost.

 

[DValentine]

Just a thought here Jon King... . an endeaver such as you are undertaking, could strain the bonds of your friendship. Building somthing like that yourself is one thing... .

My apologies if I am speaking out of turn. I just have been in a couple of different situations... . that got sticky trying to help someone build things with them.



Swankmetal in the first gen forum built himself a pair... . check his readers rigs or PM him... he will be glad to talk about the process. I know the trucks are different but the plumbing is similar... . oil lines and waste gates.



Dave

 

[JonKing]

Thanks for all of the info. I have already searched the 3rd generation forums with no luck and since I'm not building a set for a 1st generation it really doesn't help. I was just looking for a few technical answers and once again I already know it's alot of work. With this atitude it's a wonder we're still not riding horses!

 

[cummins_crewcab]

Some people just aren't into the whole fabbing thing and feel there time is better suited doing something else...



Anyway, I did take a look at the 1st gen thread and it was helpful. Most of the principles such as waste gate setup, oiling, which turbo goes first, etc was all addressed there. The tubing layout will be a bit different for us but not too much. I plan on buyin an ATS manifold and going from there. Probably run the same two turbos that the Piers towing twins use.

 

[JonKing]

Cummins,

Piers looks like one the best setups, but I believe his turbos are modified. I think using a wastegate to allow the exhaust to bypass the smaller turbo at some point is the only way to go (similar to the Piers set). The sets using the stock turbo without a wastegate would seem to me to produce the same drive pressure as if using it by itself. I have asked several times about the stock '05 turbo and it's limits. I have had mine to over 50 psi and some have said the drive pressure would exceed 70psi. The Piers Tow Twins uses a HX35 which would flow about the same as the '05 turbo, so at this level (50psi) it would seem using the stock turbo would be alright. But if you notice in the Piers setup the top turbo's exhaust is flanged allowing a stronger connection between the to turbos. I know my stock is not flanged.

 

[jhyatt]

i like the horse thing that was funny

 

[SRadke]

I built the twins on mine. Wound up about $2200 with an external wastegate and large charger. I reused the small charger I was running as a single. There are some pics in my readers rigs. Check it out for ideas. You can PM me your email address I've got some good pics of piers' setup as well.



-Scott

 

[JStieger]

Scott-



Looks good - I wish I had fabrication skills like you (and others) on this site!

 

[SRadke]

Thanks J. Fabrication skills are not difficult to pick up if you're around it very much. Building twins is just a matter of mounting the two chargers then connecting point A to point B, point C to point D and so on. None of it is terribly difficult there is just a bunch of things that have to happen correctly so they aren't in the way of the others.



-Scott

 

[ChrisKringle]

what about ATS's Aurora variable geo. turbo . . . , I heard it was the stuff to go with, boost up to like 60psi or something. Just what I heard . . .

 

[ThomasLawrence]

I've got some good pics of piers' setup as well

Me too!



http://home.earthlink.net/~tlawrence52/pdr_twins.html



-Tom

 

[RDietze]

ThomasLawrence,



what is your spool up like? that's an hx-40 on the top... right?



ron

 

[ThomasLawrence]

what is your spool up like? that's an hx-40 on the top... right?

With a TST/Twins program on TE5, and an EZ on level2, as long as the RPMs are around 2,000 - it takes just about a second to hit about 35psi. Compared to stock, it lags a bit more, but not by much. However, tooling around now with the TST on timing-advance only (no extra fuel), the lag is pretty noticable. But given the $2. 889 I just paid to fill the tank, I'm not all that concerned about rocketship-like performance



Yes, it's an HX-40 on top... HT3B on the bottom. The 40 is wastegated at about 23psi, yielding a maximum boost of right around 60psi or so (where I currently have my blow-off valves set to). I have seen the boost needle bounce off the 60psi peg on a few occasions - one time it was enough to blow the boot on the discharge pipe off (sounded like someone knocked the valve off the top of a scuba tank).



-Tom

 

[sick_ram]

the ATS set up is killer the only way to go.

 

[justinp20012500]

I am thinking of fabricating a set of twins and was wondering how they are plumbed together. This there a special exhaust housing for the top turbo to connect to the bottom? Which turbo (big or little) is bolted to the exhaust manifold? If you use the stock turbo in a twin set-up are the exhaust pressures going be the same as when it is used by itself? Is it possible to install a larger exhaust housing on the stock turbo? How are twins wastegated? What is the best combo? I guess what I am asking is how twins are designed from beginning to end. Sorry for all the questions, but I'm just interested in doing it right the first time and the price of most kits seems high for the parts involved. If you use the B-1 ($1600. 00) and B-2 ($800. 00) turbos your only at $2400. 00 in turbo cost, that's along way from $4500. 00-5000. 00 that the major guys charge.

I built my set. Not that bad of a job.



It is quite frustrating, but you can do it.



Make sure you pay attention to inlet of the big turbo on the bottom. If it is too close to the oil filter you cannot connect an air filter to it.



If the biggun is too close to the fire wall good luck on getting a DP on it...



What are you planning on using for a bottom turbo? If I were to do it again I would use a S400. Reverse rotation compared to the HT3B's, much shorter in overall length also.



I had a friend take the backing plate off my HX and make a program on his flo jet.



I have made the inlet to the turbine housing for the HT3B's, the S400 and the backing plates to waste gated HX35's & 40's.



As for saving a bunch of money... You can build a set for cheap. Its the time that you spend.



Heres about what I spent.



$1000 HX35/40 w/ 14cm w/g housing

$525 Garret BHT3B 22cm non-divided housing

$90 All the cold pipe

$12 The hot pipe

$250 5" DP and the rest of the 5" to go over the axle and out the back

$40 BHT3B oil lines

$30 Lengthen the HX oil line

$15 Silicone hose for the oil drains on both turbos

$80 Clamps/silicone hose for intercooler connections

$17 Factory oil drain fitting for big turbo

$185 Chromed the cold pipe, t stat housing, heater core lines

$50 14" long AFE

$350 ATS manifold (not really needed, but if you don't use it you really need to support the bottom turbo)



Grand total = $2,694 +/- $300 for when something gets fouled up!



You also need to add something in there to re fabricate the oil drain line for the stock/top turbo, and also the heater core line that is under the factory exhaust manifold.





Remember, I did not mention any consumables in the above... (Grinding disks, chop saw blades, weld wire, tri mix inert gas)





O ya. . $1500 (At least) to do fire rings and studs after I lunched a HG at 60psi +$20 for the car wash after to clean up the coolant and oil that sprayed the engine compartment



By all mean, I am not saying don't build your own... But when I built mine I think they look much better then 90% of the other kits on the market. Maybe because I spent 2 months in the garage coddling them :-laf





Good luck! Stainless would be very cool!!







Justin