s400?
 

installing a set of compound turbos. im sick and tired of the giggly juice shit so im taking it off and want to get around my juice dyno will all fuel, 600+. i am going to do a s400 under a hx40 and was wondering is the secondry a good choice. 75mm 1.32 Ar. i believe ts a s475. thanks

Whats the Size on the HX40 Theres a couple different ones. I would go with something along the lines of a 62MM or 64MM Secondary.

what size sticks are you going with? It's going to take a nice size set to get that number. the guys in my sig are really good at making custom twins up so if you need any help give them a call

im running 150 jammers right now and the hx40 is a 58mm. i can do all the plumbing and piping myself, that no biggie. just wondering about the 400.

That's a 2.96in S400.. it should be good.. most are using that turbo.. or a little faster spool if you drop to the 1.22 housing (or about that size.) but if your shooting for 600, you'll want the bigger housing.. I really do not know if you will get there.. but should be close.. might need a little more fuel... And you'll need a good wastegate.
As others said, you can upgrade the hx40 to a bigger compressor housing.. I can't believe that 40 took that much NOS, to get you too 600+... Nice numbers.. (Must have it wastegated, and able to allow it not to over spool??)
Bryan

actually i dont have it wastegated. i did a hy35 - hx40 swap. and i got 612 on that turbo. suprised me to, i was looking fr like high 500 with the nos. when he said 612, i think i shit my pants lol. is external better than internal wastegate? dont know alot about turbos just the cummins itself

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what recommend for a good wastegate? was looking at a hotpipe from Soucre Auto with a built in external wastegate tube.

The internal gate is just that. Inside the turbo. An external gate will be ported before the turbo flange. Either in the manifold or in a spacer. This can be routed back into the hotpipe pre-primary or dumped to atmosphere or into the exhaust.

An external gate will allow for more precise metering allowing for the use of drive pressure vs boost and give more flow potential depending on gate size. I think the hotpipe you are referring to is for a HX35 or HX40 and is NOT an external gate pipe. I had one if it's the type I am thinking of. There is no advantage to running that style of a valley plate style. I have run both.

Dave

I'd run an external gate if I were you. I personally run a 38mm external gate on mine which is fine for me. I'd say run a 40 or 44mm for your application. It will really help with tuning. The s475 is the 2.96", and there are a bunch of different housings you can get for it. the 1.32A/R will help you spool that 40 faster if you're running the 16cm ex. housing.
Sean