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I've tried a while back to get Rowland to buy my BD twins...no luck Good thing I sold them to someone else!

I'm sticking with the idea of big twins, then tweaking to get spoolup. Some guy in Texas has a head for me, and I'll probably have him throw me a cam in the box so it doesn't get lonely on the long ride to Ohio I'm also getting rid of the HXScatterbomb for something Industrial Injection can whip me up. Trying to make up my mind there

You guys and your fancy boxes and variable timing. You make me sick
Good thing my buddy has on '02 he lets me play with

What's wrong with having 900hp worth of fuel, and only making 450hp??:whistle:
Chris

RowJ

Chris, Last I remember...you had a guy ahead of me to buy either your B-1... or you BD twins. Never heard back from you so I figured I lost out?
Sorry if I misunderstood! Still want BD small twins!

JH, nice compliment. My truck feels the love and she says "Thank you"

Devil Diesel Dan .... I like it!

RJ

RowJ

JH - On this subject, I have been bugging anyone that will talk to me, that has BD twins.
While I think the S300 top turbo is bigger than the HX-35, they match it with an S300 on the bottom... with 12cm2 and 26cms turbine housings respectively. With enough fuel, the spool up is amazing, reportedly better than an HX-35/12 on a stock truck!
I think the secret may be in a smaller bottom turbo allowing great spoolup on top. My mind kind of wraps around that idea and says "sure"...but I can't explain it? Anyway, I'm not convinced the size of the top turbo is the determining factor, by itself, for quick spoolup.

Sorry to hyjack this thread....
no, wait, it's your thread, and you already hyjacked it!

RJ

signature600

Oh Crap!!! I thought you told me you weren't ready. Darn miscommunication That's what I get for being thickheaded:whistle: Oh well!

To try and help out a bit...this B2 I have spools really well at my fueling level...not quite BD fast, but by 2000RPM the B2's @ 10psi and going fast. Especially in Full Power mode on the valet.

The HX40 does OK, starts to spool hard between 16-1700.

Total Boost---By ~2100 I'm at 40+ psi (even in valet IIRC). I wish I could pay more attention, but at 2000RPM things are starting to get wild in the drivers seat, so I tend to pay more attention to the road than guages
So bigger turbos will spool OK when pushed. It's a little smokey though

Now, the reason I said all that is because I'm not completly happy with my spoolup. I'm going to call Industrial Injection sometime and see what they think, SPS62 for airflow, or something a little "smaller" for spool. That will be after I get straightened back out after taxtime though

Hopefully some goodies I've got coming from a screwy little Texan can help me out too
Chris

Whoops, I've bored everyone to sleep again!

Dr. Evil

[QUOTE=infidel]I use one of these with a rotary switch that will allow me to use five different senders.
http://www.jcwhitney.com/autoparts/I...D:100000183357

Infidel, do you have a source or p/n for a rotary switch? Ive seen them but any of the ones Ive seen are too big.

HOHN

Alright, as hijacker in chief, I reserve the right to continue on this rabbit trail



I think the reason the BD twins spool so well is that they basically spool at the same time, or very close to it.

I think a lot of people have the misperception that the small turbo "hands off" to the big turbo. In reality, you want *compounding*, which means that they BOTH have to be doing some work. Ideally, your two turbos would be operating at the same relative PRs.

Even more ideally, your two turbos would be operating at the centermost points of the compressor maps under full load. This setup could make some really clean cool boost with low drive pressure.

I'll say something controversial right now (there's a surprise ):

If your twins setup doesn't have a boost/drive pressure ratio that's SIGNIFICANTLY better than 1:1 in favor of boost, then you have a bad setup that's mismatched or poorly executed.

An efficient turbo can have boost higher than DP because the incoming air is so much cooler than the exhaust, so thermodynamics tells us that we can have more boost then DP and still be comfortably within the laws of thermo.

Now when you configure a twins setup, you multiply this reality. That super-efficient single that's making 40psi boost with only 36psi drive should now be capable of 60psi boost with only 45psi drive or so when compounded.


The problem, as far as I can tell is that most twins builders are trying to keep costs down and use cheap dinosaurs of turbos that are horrendously inefficient. I've often read twins guys posting things like "Boost is 1:1 with drive until 60psi", and it's said with great pride. They are using ancient turbos (HT3Bs, etc) and they give up a LOT of efficiency.

***I'll tell you this, you should NEVER be settling for a mere 1:1 with a twins setup***.

Heck, you can do that with most of the singles out there now.


Remember, when you go twins, every turbo effect is multiplied, so that sweet efficiency or bad inefficiency becomes either much worse or much better compared to it's potential.

But how often do you see twins built with sophisticated turbos? Who builds twins where JUST the turbos cost $5K???


I'm excited about these new Garrett BB chargers, as they could be *the* choice for a top charger in future twins setups.

JMO

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Well said HOHN,

I guess the real problem is that cheap turbos+bandaids=good enough for most! Maybe I'm included in that, at least halfway.

That ancient HX40 is gone ASAP. I'd love to go ball bearing, but I don't want my daily driver/tow truck being somebodies test dummy for their new turbo. Especially how I treat my truck

I need a drive pressure guage, and a wastegate on the big charger. Right now I'm limiting boost with Pop-offs :yuk:

Chris