Tuning Twins

inline6power said:
Makes much more sense to get them both in thief map rather than sharing work equally. That being said my secondary map is around 30. Three plus 28 from the primary would be crazy boost. How would you get both in their efficient range yet keep boost controllable

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I just said that....
 
RIGHTEYEBLIND said:
Why, if for instance you are making 60psi and 30 psi of that is out of the primary, would the secondary not be putting out the other 30 psi?
Not arguing with you just trying to understand.
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Not trying to be a dick, but do you not understand the concept of COMPOUNDING? Or the idea that PSI is actually a relative term?

In your example the secondary is outputting 60 psi...plain and simple. The seconday is actually compressing the incoming 30psi by a factor of 2...the pressure ratio! A turbo "sees" a certain amount of pressure (atmospheric or boost form a praimay) then compresses that air as best it can and spits it out at a higher pressure (boost or compounded boost). All rather rough estimate however.

It is laid out fairly nicely in the OP.
 
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Great Thread!!!

Reporting back on performance results after being educated from this "Thread"

HE351/Aurora 5K set up... WG opening to soon say, 23-25 lbs. performance was like crap! Primary charger PR was to high (80% of work load)

Tightened WG down a bit more (fully opened @ 40 psi) Primary work load was around 65%.. Engine ran much much better until WG fully opened then work load jumped up to 85% when @ WOT...

I believe Adjusting the gate tighter will yield still a better ratio for normal driving conditions between 30-80% throttle range..

After reading this thread and the help/input from others... THANKS :bow: :clap:

I have created a WORK SHEET to assist in tuning chargers and to quickly record and calculate Boost/Pressure Ratios and work loads between chargers...

IF YOU WOULD LIKE A COPY SEND ME YOUR E-MAIL ADDRESS... IT'S A MICROSOFT EXCEL SPREED SHEET..

GREAT THREAD!!!


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Yep, very informative for those of us with no compound turbo experience. Great read:Cheer:
 
Wow, loads of good information. I am subscribing so I can read and re-read it all again a few times untill I actually understand. I am planning a stock (hx35W) with something like a s475 5X.010 or 5X.012, stage 2-3 cam... Hope it will work well, seems to be what many people suggest.

There is a industrial truck place near me to get the turbo from so not sure what I will find.
 
Here is some old school stuff: HX-40/HT3B.....3B runs at 36 psi, total boost is 60 and drive pressure is 65, what I do with all twins is back the gate off on the top charger and creep up on it till it's 1 to 1 with drive pressure or close to it.......in this setup 60 sounded good to me so that is were I left it.....neither turbo is great but I had them, cost for the twins was very minimal......like $800!

Jim
 
Reporting back on some testing yesterday on a set s364 over s595. I remember seeing Big blue post that his interstage pressure was in the 50's or something along those lines. I encountered this yesterday tuning a set on a load dyno. First run the interstage pressure was 59 psi, made great power but was fairly slow to spool. The small charger was at a pretty low PR but I realized that the high interstage pressure may be due to not spinning the HP turbo fast enough. It makes sense to me the pressure goes up when there is resistance to flow, IE a slowly spinning charger. On the following runs we drove the HP turbo harder each time. The setting we left it on had a 450 degree drop in egts from the 1st run and we saw a significant hp increase with no fueling changes from run to run. I will see if the truck owner can send me the dyno graphs to give a definant hp increase number. Not saying all setups may be like this, as this may be a unique case with the primary being so large. But in the end the charger PR's were fairly close at WOT with drive to boost ratio being just a little over 1:1. Just trying to help this thread out some more.
 
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Stupid question but what makes a primary turbo a primary turbo and a secondary turbo a secondary turbo. I read through this thread and some cases the way that i understand the larger turbo is a primary and other times the samer turbo is the primary. are these terms used interchageable?
 
one question i have been thinking about here lately is where is the best place to take pressure from to control the secondary waste gate? exhaust manifold? i have heard of people using spring setups and getting the secondary to the desired boost without the primary to secondary boost pipe connected...i just haven't really heard this talked about.
 
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