12valve

how much boost are you twin guys getting only from the primary turbo? i would like to hear from the HT3B? and where is theyre efficient range?

has altitude to do with producing more or less? im over 2000 feet above sea level.

HOHN

12V, I think you'll find a LOT of variance as to how some guys set up the big turbo.

I know that some of the midwestern puller types are pushing the big turbos HARD-- like 50+psi feeding the small turbo.

Personally, I think this is backwards. For best performance (i.e., best "compounding" effect) you want a little bigger top turbo and a little smaller big one (in housings).

HT3Bs are designed for N14s and such, and they're in their peak efficiency range around 17psi, but they can go over 20 without getting super bad. I'd keep it under 25psi, if it were me.


You're going to find out that twins combo are becoming more refined and purpose-built. Quick-spooling towing twins that cool really well generally don't make big dyno hp numbers.

Conversely, the big HP twin setups give up a lot of "area under the curve" on the low end in favor of a higher peak numbers.

When sizing turbos, I've been told that "when in doubt, pick the two that are closer to each other in size"-- in other words, bigger on top and smaller on bottom.

An example might be an HX40 on top instead of a 35 over a '3b with a 21hsg (or whatever the smallest is) instead of a 36 housing.

Remember that you generally want big small and large turbos to spool as close to each other in time as you can. If you're small turbo is maxed out before the big one makes any real boost, then you have problems.

hope this helps.

12valve

yes it does...thx ... at least to get more and more confused about twins

just i am wondering if the stock hx35 and a 40mm wg and a HT3B arent for me....

i would like to see around 500 hp.

wow i get more confused each time i read more. i was about to make a compound setup. now im in doubt...

95ram

IMO you'll need a bigger ex housing on the 35 if you want to go that route. The stock 12cm doesn't flow enough IMO. If your going to use an external WG try a 16cm non WG ex. housing. If your going to use a wg ex housing try a 14cm wg housing. Just some thoughts. I like the 26 or 27 cm ex housings on the 3bs. The 3bs with the divided ex. housing will flow more on top and the undivided will spool quicker and flow more on the bottom to mid.

Artsi_L

I read a study on two-stage turbocharging. I have material on another computer, so I can not quote exact numbers here. However, they were set on two turbo's which were sized up like (as far as I can remember):

- smaller top turbo (i.e. secondary turboo) was 90% of ideal size when comparing to an engine with a single turbo.
- larger bottom turbo (i.e. primary turbo) was 117% of ideal size when comparing to an engine with a single turbo.

I believe the people doing the study were not trying to extend engine powerband, nor were they trying to achieve ungodly boost pressures. They must have been on a mission to get up to stock boost asap, and keep it there until top rpm.

This suggests it's not a bad choice to retain stock HX35, and slap on about 15-20% bigger turbo as a primary, and off you go. Especially for towing this setup should be good.

RonA

Around 30 psi for modest hp level(500 or so).