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sequential turbos


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In the quest for more power, Current plan is try to find a s480, not much luck, Thoughts of a supercharger always take top honors, even if just casue it looks cool. :lol: On the other forum with the superchargers, a previous setup he ran was triple turbos. Basically splitting primary turbo in half. More or less.What about using one of those 351 variable turbos parallel with my turbo. The vgt should spool quick get it going and then the bigger turbo will catch up, then the combined turbos would equal a big single that wouldnt normally be able to be streetable in a DD. Some high end cars have sequential turbos, but I am not sure if the other takes over completely or if they run in unison. I would be worried about the quicker spooling turbo pushing air back through the slower spooling turbo.Just an idea, havent put a lot of time into research but it got me interested.:shrug:

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If you do I wouldn't run a super charger. In a super charger application you have a blower for low speed operation and a larger turbo, S400 or the like, feeding the blower at higher boost/rpm.To run a parallel system you really need two equal sized turbos, and doesn't work overly well on a I-6, more of a V-8 thing. The tripples do run the primary in parallel but its easier to split the exhaust in the hot pipe off the secondary. The HE351VE makes a good secondary turbo, but not big enough to be a primary on a CTD, it actually flows less than your 62/65 and only has minimally better spool. You could sell your 62/65 get a HE351VE, a Fleece controller and a S400 as the primary.. would be a slick set of twins with an exhaust brake. There are lots of S400's out there, or are you looking used only?

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I am really wanting to turn up the power a bit more. :ahhh:I was afraid of the unequal sized turbos not playing nice with each other. unbalanced flows etc..My current turbo is almost new. Only been on there about a year. As for the s480, more lookign for cheap, or actually just a good deal. Guys alsways say you can find these turbos for 500. Umm not me. :broke: Only finding them hovering around the 1K mark +/-$200. In the supercharger thread else where it was dicussed that depending on which turbo you have the S/charger can be either primary or secondary. In my case I would have it force fed my turbo, making it run as a secondary which is my intial plan with the s480. I was hoping that splitting the turbos I could simulate a (just a guess) s480. Would be nice, but either way I end up with 2 turbos. This was from a cost angle, as it seems cheaper to get a 351 turbo. So how does a exhaust brake work on a set of twins? Is it only on the secondary turbo? I have no programmer other then a smarty, kinda wanna go backwards and build it before tapping it. :smart:

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Running tubro's in parallel will do nothing for spool unless you go much smaller than a 62/65 as you only have 1/2 the exhaust volume to help. Even a HE351VE would spool slow on a 3 cyl.

An S480 is a big turbo! With the fueling limitations of a VP truck I would think a S474 would be a much better turbo and light much easier.

You can find S400's in the 600-800 range, but they all have the larger 1.32 a/r, which is fine if you only want upper rpm performance from your twins. A waste-gated .80 a/r for towing or a non-gated 1.1 ish would do much better for a street performer.

The biggest cost to twins, unless talking BB turbo's, is the piping, or do you plan to do that yourself?

On a variable vane turbo the turbo itself is the exhaust brake, so its within the secondary. If you go with a non-variable turbo the brake is external and in twins is in the downpipe.

--- Update to the previous post...

Personally I want to put a .85 non-gated housing on my GT3782R, use an external gate and put a GT4202R under it! Crack the gate on the secondary at about 15 psi, and get 45ish total. Now that's some $$$$$

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Yea I was hoping the variable vane would spool quick then my 62 would catch up then combined flow of a typical big single. Most common s480 I found was the 1.32. From the typical vendors I haven't found a s400 series available as a single turbo. They are either in a twin kit or a 3/4 kit. I will be doing the piping myself just buy some of the specific parts. Have you found a s474? A link maybe?I like your choice for twins. Before my current turbo I was looking at a garret as well.

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  • 5 months later...

62/s475 is overkill for your 7x.010. 62/s475 will support 750HP If you need flanges and clamps or turbos I have them available on my website.

Yea been reevaluating my goals. Looking at a S472/475. Hoping for around 600 and still be able to be a useful tow rig. I checked your site and I swear before the 400's werent listed as single turbos, but I see differently now. Can you get different exh sides like the mentioned 1.1 housing?
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