I am going to build another set of twins and hopefully have finished by the time the Buda TX dyno day comes around and was wondering a few things regarding external wastegates around the TOP turbo. I've been told before that a bigger top wastegate will help spool the primary harder/faster, is this true? I want to run the stock HX35 on top with the 12CM housing and just disable the internal wastegate and run a larger external around it. I will have a brand new BHT3B on bottom with a 26CM non-divided turbine housing and it will have a 74mm inducer on the cold side.

In a setup like this would it be any better to run a 44mm external wastegate than a 38mm? If so why? I also want to run a external wastegate around the primary in the hot-pipe, I was going to use a 50mm for this as it seems that is pretty much the standard size for that application.

My truck is used mostly as a daily driver but I am pretty aggressive, I also tow a trailer occasionally. My biggest thing is with the setup I have now fuel wise I want to add Laser Cut DV's and Holders and get as close to 500rwhp as possible with the least amount of smoke I can. Sorry it's long but I would like as much feedback as possible, thanks!

 

I was kind of thinking I might do this as well. Remove the DZ and put the HX35 on top running an external. So I am interested in answers as well.

Jim

 

I can tell you both from experience that a stock 35 will get HOT at 500 RWHP. The 12cm housing will make things worse.
NoSeeUm, IMO you'd be better off using the DZ than the stock 35.
A 38MM external WG will flow more than you than you'll be able to give it, so you should be just fine with the 38.

 

No! 38mm is better choice, IMO. Too big an Ext WG will tend to flap or flutter....open & close rapidly. I ran a 38mm Tial up to 525 hp and it handled all I threw at it well.
Bigger is... and is not better in this case. It is .... if your talking a 38mm vs stock HX-35 WG. It is not ..... if your talking 44mm Ext EG vs a 38mm!

External WG is a great way to improve the wastegating on the 35, and help it push cooler air ...just need to plumb the bypassed exhaust gas into the bottom turbo....but a 14 cm turbine housing on the 35 is the only way to make it work well for twins.

RJ

 

x2

Chris

 

HMMMM..... Thats interesting that everyone feels the 12CM isn't even enough for 500rwhp. I would have figured with a bigger external wastegate that that setup would be good for 450-500ish ponies. Ok then, it's also the majority vote for a 38mm wastegate. So now which non-wastegated housing for the 35, 14cm? Again I appreciate the help...

 

I would think with a 38mm gate, you'd be fine with the 12cm...but I've never tried it. At 500hp with a 35/12 and 38mm gate, I would think you'd be good to go...should take you to 600, IMHO

Chris

 

I drove a 35/14 with a S400 on the bottom. It dynoed 510 hp and seemed to me to run on the hot side, with the bottom turbo being a little laggy.
I'm no expert but I believe this is caused by an imbalanced set up. Too much 'work' done by the top turbo. I suspect a 12cm turbine would agrivate this condition..... if I'm right??
Might aggravate it also

RJ

 

I want to use the 12cm mostly for spool up reasons, I don't like leaving a smoky haze behind me because the turbo isn't lit. Plus I might get the urge to haul some stuff lol. I know GotDiesel used a stock 12cm with the divider drilled out and 40mm gate he had 50PSI of boost with low 40's drive pressure. Until I get the head ringed and studded I want to keep the boost to 50PSI.
I am only looking for 500rwhp at Buda, eventually I want over 600rwhp on diesel only, but 500 will be ok for now, lol.
How much would everyone else think a 12cm HX35/38mm WG and BHT3B setup support?
Again I appreciate everyone's input and help...

 

or go with an internal 38 mm wastegate..... just milled out a 12cm housing today to 38mm internal.

 

Why?? An external gate is easier to control, and won't creep open as bad as an internal gate. They are a bit more work, but IMHO, they are worth it

Chris

 

why would an external gate be any easier to control??


no one uses internal gates because no one wants to bother having there hotside modified.

internal gate has smoother flow of gasses and less piping etc (less cost probably too)

 

Any pics of s 38mm internal? The biggest I've heard was a 19mm.

 

Thanks guys.

In my case I have a 2002 so re-clocking the compressor displaces the waste gate actuator mount. So a external works better and also lowers drive pressure. But my reason is similiar to Muddin's.

At any rate, I just thinking about it somewhat. The DZ over the S400 does work pretty good and I am not unhappy with the set-up.

Why am I always wanting to be dinking with things? No clue....

Jim

 

Even with a 14cm housing you'll have great spool. On my set up I had boost at about ~1200rpm and full boost by ~2000rpm.