Tuning Twins

Graphic Man

Graphic Man

New member
Joined
Aug 24, 2006
Messages
963
I am running a B1 - B2 set-up with an Ext. wastegate.
neither turbo are gated

here is the drive pressures:

these numbers are close.......it's hard to drive and look at 2 gages at the same time while your WOT iso i could be off a few PSI on the Drive pressures

EGT's are around 1400 with everything on Kill

BOOST D/P

5 8
10 12
20 20
30 30
40 42
50 55
65-68 70-75

i guess if i gated it at 60 it will be close to 1:1

and thoughts on this?

Thanks
Scott
 
does ur truck smoke a ton. Cuz mine smokes liek crazy all the time. There is always a constant haze
 
What is the B2 making for boost? You want it to be really close to half of the total boost.
 
Goalie990 said:
does ur truck smoke a ton. Cuz mine smokes liek crazy all the time. There is always a constant haze
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at an idle it will haze a little but not to bad.....smokes a little taking off from a set of lights but will clean up at cruz'n speed
 
Idaho CTD said:
What is the B2 making for boost? You want it to be really close to half of the total boost.
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not sure ....i would need to plum in another gage to see
 
Idaho CTD said:
What is the B2 making for boost? You want it to be really close to half of the total boost.
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I have the same twins and see about 60-65psi total boost, what kind of boost should I be pushing throught the S400?
 
Idaho CTD said:
30-32psi
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Back in the day when I ran a HX40/B2 I was seeing about 34-35psi from the B2 at 76psi total.

I'd say Nathan is right on from experience!
Chris
 
i can hit almost 70psi at WOT with everything on kill

i ran it on the way home box on 2x1 and at 50psi my drive pressures are at 50 also

i am going to do some more playing when i get some more time, i'll hook up a gage to the B2 and see what i have

Thanks
Scott
 
dodge359 said:
Same for a 40/3b with a 26cm? I get 30 but really late. Sorry, didnt mean to hijack.
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no need to be sorry.....were all here to learn :Cheer:
 
Graphic Man said:
i can hit almost 70psi at WOT with everything on kill

i ran it on the way home box on 2x1 and at 50psi my drive pressures are at 50 also

i am going to do some more playing when i get some more time, i'll hook up a gage to the B2 and see what i have

Thanks
Scott
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I can hit 70psi with my box (foot/12ver) set on 15 pounds.:hehe: Thats total boost. The primary is kinda slow and isnt lit until 2800 rpm.
 
dodge359 said:
I can hit 70psi with my box (foot/12ver) set on 15 pounds.:hehe: Thats total boost. The primary is kinda slow and isnt lit until 2800 rpm.
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i am at 20psi of boost at 18-1900 rpm

you may be over fueled on the bottom end ???
 
Were you the one in the black cloud behind me today?

I am starting to build, on the bottom, at about 20. You are probably right about too much fuel. I am going to try the stock 181s and see what happens. If that doesnt work I am going to try a 23cm housing.
 
Good post Scott- I was going to ask this same thing the other week but forgot all about it. My pressures are close comparrison wise as yours from what I can see in the one good hook that I had at those PSI but once higher the drive gets higher. I had my larger turbo setup for a boost guage my first run and I had so much head in the pipe that it melted the plastic hose right off...landed up plumbing 5' of 1/8" copper and then the plastic just like my drive pressure setup. Not sure how much head a street setup like yours will see though. In one pass all my paint on my nice piping I had put together was blistered and lifting but the strange thing was it seemed to be worse on the downward side of each water nozzel.

So back to the tuning question...if your Drive Pressure were 5-10% higher than your boost pressure, how would you go about tuning the wastegate. Mine is around 5%-7%.

RyanB
 
I honestly wouldn't worry about a slight mismatch like that. Where it gets scary is 100-110psi of back pressure on 62psi boost. :evil
 
joefarmer said:
I honestly wouldn't worry about a slight mismatch like that. Where it gets scary is 100-110psi of back pressure on 62psi boost. :evil
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Been there done that!

If your not seeing boost on the primary until 20psi your top turbo wastegate is WAY to tight. Depending on the size of the twins you should see some boost out of the primary by 12psi at the latest. Even when I ran a Big Brother I would see boost out of it by around 12-14psi.
 
Idaho CTD said:
Been there done that!

If your not seeing boost on the primary until 20psi your top turbo wastegate is WAY to tight. Depending on the size of the twins you should see some boost out of the primary by 12psi at the latest. Even when I ran a Big Brother I would see boost out of it by around 12-14psi.
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Nathan: since your speaking about wastegates, in your opinion what effect does looser pressure settings have on a twin set up vs. tighter?
 
From my experience you'll see the lowest drive pressure and egt's but the highest boost when you hit the sweet spot on twins. Setting a wastegate too light means a lot of low end lag and huge initial egt's since it takes too long to create boost and then it's playing catch up to the fuel the rest of the time. Setting it too tight can do the same thing as well. If you use too much exhaust energy on the small turbo it takes the needed heat/flow away from the primary causing it to be laggy as well.
 
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