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Twin Turbo Setup

Dynamic
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Dynamic

Dynamic

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OK... So I have some down time for the Christmas season (intentionally scheduled). My plans are to go ahead with a twin turbo setup. The setup that I'm currently running is 100hp BD injectors (I'm not 100% sold on keeping these...I may go with 125's or 150's), Smarty S-03, FASS DDRP (no fuel pressure problems currently, but I plan on upgrading to a larger FASS), and I plan on, most likely, stacking an Edge with the new CTS2 with what I already have. So my question for those who have gone before me is this:

Which bottom turbo should I go with? I plan on using the HX35 that I currently have as the top turbo. I want a fairly quick spooling setup, and I use my truck most often for just driving around, but I do tow with it once in a while...usually fairly heavy. It's not necessarily my daily driver, either, as I do have other cars. It has been recommended to me to go with an S472 with 83mm turbine and 1.10 housing. This seems a little on the small side if I go with larger injectors but, then again, so does the HX35 up top. I see a lot of guys going with an S475 with 96mm turbine and 1.32 housing. These seem to be fairly cheap, too.

How should I mod the wastegate to work best with the compound setup. The turbo I have right now is currently unmodified... 

I really don't want to change the top turbo. In my opinion, that would price this project right out of the realm of feasibility. I can afford it, but at the end of the day, it's just a 2nd Gen 24V, and spending that much on a turbo setup just doesn't make sense.

Opinions...?

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TFaoro

TFaoro

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Posted (edited)
19 minutes ago, Dynamic said:

OK... So I have some down time for the Christmas season (intentionally scheduled). My plans are to go ahead with a twin turbo setup. The setup that I'm currently running is 100hp BD injectors (I'm not 100% sold on keeping these...I may go with 125's or 150's), Smarty S-03, FASS DDRP (no fuel pressure problems currently, but I plan on upgrading to a larger FASS), and I plan on, most likely, stacking an Edge with the new CTS2 with what I already have. So my question for those who have gone before me is this:

Which bottom turbo should I go with? I plan on using the HX35 that I currently have as the top turbo. I want a fairly quick spooling setup, and I use my truck most often for just driving around, but I do tow with it once in a while...usually fairly heavy. It's not necessarily my daily driver, either, as I do have other cars. It has been recommended to me to go with an S472 with 83mm turbine and 1.10 housing. This seems a little on the small side if I go with larger injectors but, then again, so does the HX35 up top. I see a lot of guys going with an S475 with 96mm turbine and 1.32 housing. These seem to be fairly cheap, too.

How should I mod the wastegate to work best with the compound setup. The turbo I have right now is currently unmodified... 

I really don't want to change the top turbo. In my opinion, that would price this project right out of the realm of feasibility. I can afford it, but at the end of the day, it's just a 2nd Gen 24V, and spending that much on a turbo setup just doesn't make sense.

Opinions...?

Hey to some of us spending that much makes sense! :lol: 

I think you'll hate the lag of the s475/96/1.32 with the hx35. They just do not match each other well. I had a buddy try it and all he succeeded in doing was making high egts with a laggy primary. He ended up selling the kit and buying a source automotive kit.

That said what kind of power are you looking for? I see you said you tow, but are you planning on racing at all?

The s472 should support high 5's to low 6's easily, so if your power goals are in that range that's where I'd go.

If you're skeptical of the amount of air the 72 will move you can step up to a 75, but I would keep the tight housing and small wheel to match the hx35 nicely.

I can't speak to modding the wastegate. Honestly I forgot what they look like.....

Edited by TFaoro
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Dynamic

Dynamic

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No... No racing for the truck. I just tow with it and drive it around town. The only racing involvement it has is to tow the race car to the track... LOL

I really don't have a specific goal for HP. If the S472 will support upper 500's, that's more than plenty for me. The main thing I want it a setup that's nice to drive, spools reasonably quick and makes around 50 psi of boost. I guess the S472 might be just the ticket...!

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TFaoro

TFaoro

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I'm making 62psi on a set of 125's. I know it's a bit apples to oranges, but I would "guess" you'd be around your goal of 50psi with the setup correctly tuned and a programmer set to kill.

I'd also check pricing on the two. If the 75 is just a bit more expensive why not have the extra air? Spool characteristics are more determined by the turbine than the compressor wheel anyway. 

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TFaoro

TFaoro

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21 minutes ago, Dynamic said:

Good point...! A smaller turbine on a 475 might make sense as well.

Thanks for the info and experience!

My signature is now up to date. I've got a 62/65/12 over a 75/83/1.1

My brother has a 62/65/14 over a 75/96/1.32. The large housing works on his because of how much harder CR's can drive turbos. His setup made 724hp with my tuning. 

So I'm definitely NOT the most experienced with twins, but I have done some playing with them!

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Cowboy

Cowboy

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As far as the HX35.  Drill the divider, and enlarge the wastegate, bigger the better.  

http://articles.mopar1973man.com/2nd-generation-12v-dodge-cummins/69-air-intake-exhaust/492-oversized-wastegate-and-regrinding

Using this method you can easily get it out to 28mm, from the stock ~22mm.

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Dynamic

Dynamic

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Thanks! That's what I was figuring. I was also wondering about machining the divider down inside the housing and then enlarging the waste gate opening. I know that once waste gate pressure is reached, good flow out the gate is important to provide flow for the primary turbo.

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Cowboy

Cowboy

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Drilling the divider across from the wastegate hole works well, drilling in that location helps retain some of the advantages of the twin scroll, while still gating both volutes.

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Vais01

Vais01

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On Wednesday, December 09, 2015 at 10:04 PM, Dynamic said:

OK... So I have some down time for the Christmas season (intentionally scheduled). My plans are to go ahead with a twin turbo setup. The setup that I'm currently running is 100hp BD injectors (I'm not 100% sold on keeping these...I may go with 125's or 150's), Smarty S-03, FASS DDRP (no fuel pressure problems currently, but I plan on upgrading to a larger FASS), and I plan on, most likely, stacking an Edge with the new CTS2 with what I already have. So my question for those who have gone before me is this:

Which bottom turbo should I go with? I plan on using the HX35 that I currently have as the top turbo. I want a fairly quick spooling setup, and I use my truck most often for just driving around, but I do tow with it once in a while...usually fairly heavy. It's not necessarily my daily driver, either, as I do have other cars. It has been recommended to me to go with an S472 with 83mm turbine and 1.10 housing. This seems a little on the small side if I go with larger injectors but, then again, so does the HX35 up top. I see a lot of guys going with an S475 with 96mm turbine and 1.32 housing. These seem to be fairly cheap, too.

How should I mod the wastegate to work best with the compound setup. The turbo I have right now is currently unmodified... 

I really don't want to change the top turbo. In my opinion, that would price this project right out of the realm of feasibility. I can afford it, but at the end of the day, it's just a 2nd Gen 24V, and spending that much on a turbo setup just doesn't make sense.

Opinions...?

Several companies use a Borg Warner S300G (57/65/.70 A/R) over a Borg Warner S400 75mm compressor inducer with a 1.25 A/R turbine housing or the 1.10 A/R turbine housing if you don't plan on jumping over 60 PSI. The S300 with the 62mm compressor may work well also. Personally I would recommend the same S300G (57/65/.70) If I were you I would opt for the attenuator housing (race housing) it helps with smoothing out the airflow on the S475 and keeping that S475 from ringing your ears.

I hope you have already set in some good head studs too.

Edited by Vais01
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Dynamic

Dynamic

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I appreciate the advice! I agree that there are many top turbos that would be better suited to a set of twins than the HX35...no question about that! But, buying a 2nd turbo would double the cost of a project like this and, quite honestly, I'm just not willing to invest the money. It would be fun and all, but at the end of the day, I just can't justify spending the money on this project...!

And, yes, head studs are a given for a compound setup...

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JOHNFAK

JOHNFAK

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If cost is main concern just go s472 or even a ht3b.... 

Best setup on 3 sets if twins I ran was a 

He351cw/s472

S475 with a 96/1.32 are used as they are box turbos and cheaper. My 475 has 1.25 turbine housing turning a $750 turbo to an $1100 turbo. Due to 96 turbine.

 

In all honesty .... as long as you go small .... and have fuel matched appropriately .... you'll be like a schoolgirl after install 

 

I still enjoy them today ..... i hit 60 psi or higher every day just because I can ..... i used to pull/tow my 5th wheel on that smaller set at any speed up any hill 

 

Fun ;) 

 

 

 

 

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