Compound tuning..... need a little help

Rollin Coal

Rollin Coal

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Oct 25, 2008
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Right now i have manifold boost, and primary turbo boost, as soon as i can afford it, ill get drive pressure.

I turned my drag comp down to keep boost at a reasonable level, im making just under of 60psi until i can get this worked out, with the box all the way up last night, i was breaking 80psi.

right now at 50-55psi, my primary gauge is showing 23-25psi
low end, boost at 10psi, the primary makes 3-4psi

should my primary be making more? is theres a good percentage of boost that the primary should be making? or does it not matter and i need to do my tuning by drive pressure?

for those that dont know, they turbos are hy35 with ported gate over s366

Thanks
 
Not quite sure on an s366 but I know the s400 you want to see around 25-30psi out of it.
 
well, the smaller turbo compounds the boost coming from the larger one at a certain ratio, like 2:1 (example....it varies from each set-up) so the large turbo has to first match the amount of air the small one is pulling in, then is can pressurize even more. So 20psi from the large turbo in a twin set-up would be like 50psi from the same turbo in a single set-up
(I think I said that correctly)
 
I would think that a vacuum/boost gauge after the larger turbo would be better for tuning as you can tell when it matches the boost, how long it takes, and then you see positive boost.....
 
I'm gonna guess that you have some insane drive pressure's at 80psi if you aren't running an external gate.
 
J.Keith said:
I'm gonna guess that you have some insane drive pressure's at 80psi if you aren't running an external gate.
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x2...for that setup, I would like to see total boost under 65psi, with no more than about 30-35 coming from the primary. Normally, 28-32ish is what you'd see from an S400, but in your setup, I'd rather drive the primary harder than that HY;)

Chris
 
I would guess that you shouldn't try to make more than 45-50psi out of that setup. HY's really don't like much more pressure than that. Also, you're gonna be blowing some HOT air into your motor.
 
J.Keith said:
I would guess that you shouldn't try to make more than 45-50psi out of that setup. HY's really don't like much more pressure than that. Also, you're gonna be blowing some HOT air into your motor.
Click to expand...

egts stay around 1200, got up to 1300 today with the lowered boost
 
i would definatly look into an external gate with that hy. with my setup dp and boost are equal till about 55 psi. mine will only make about 60lbs but the cam dropped my boost like 10lbs.
 
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