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Discussion Starter #1
ok, so as far as my understanding, any psi from any turbo will produce the same power if all other circumstances are the same

so stick twins at 15psi will make the same power as a t78 at 15psi right?

only difference being spool up speed?

we only change/upgrade turbos to achieve higher boost levels (20+) and to be able to spool to max boost faster? correct?

dont flame me for asking, i just want to be confident in my turbo knowledge
and have the peace of mine knowing that my ebc set at 12psi for daily driving will have the same effect regardless of the turbo set up i have (stick twins, big single)
 

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For a given exhaust back pressure, tune, etc. yes. However, the stock twins are going to have a much higher back pressure than a single turbo. Engine delta p is very important (intake minus exhaust).

Daniel
 

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And what about efeciency?

Stock twins at 20PSI and T78 at 20PSI ?

Same presure but different power because at this presure is T78 more efective. ;)
Stock twins are optimal for about 15PSI may be up to 19PSI but if you make more boost on it you only heat-up the air but no power comes from it.
 

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Shawn Davis
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These two hit the nail on the head. Efficiency and reduction in pressure between the turbo and the head will give you more power with the t78.
 

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98bpu said:
ok, so as far as my understanding, any psi from any turbo will produce the same power if all other circumstances are the same

so stick twins at 15psi will make the same power as a t78 at 15psi right?

only difference being spool up speed?

as I know:

No it is not the same

here you talk about the volume the air volume in the T78 will be more that the stock turbos.

the engine need more air volume to product more power as you see when you strocker the engine you increase the cly. volume.

to by easy see the tire in :

passinger cars, truck, motorcycle and bicycle all this tire pressured to 35psi in normal condiction but the volume of the air inside the tire is diff. the truck tire need more air than the bicycle tire in the same 35psi.

and when you increse the pressure the volume will increase(the extra volume make the power not the extra pressure)

so it is about the volume

thanks
 

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PSI means nothing. Volume is everything. :D A small turbo at 15 psi will flow less volume at a higher temperature than a large turbo at 15 psi. Larger turbos flow cooler air at a higher volume with the same pressure level.
 

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Ok, sure pressure by itself isn't important. It's density. As Larry pointed out pressure is created by a restriction (the engine). But, I still hold that if two turbochargers with the same engine back pressure and compressor outlet air density will produce the same power.

As was pointed out the stock twins compressors are not going to be as efficient as the T78 at 20PSI. So, for that pressure you will get a LOT more heat out of the stock twins...lower density.

There is no need to talk about volume. If a turbo can make a certain pressure it is flowing enough volume.

Density is density.

Daniel
 

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Discussion Starter #10
ok, so basically we are down to density/volume,

a larger turbo flows higher volume of air, at a higher density
because of less heat being produced

correct?

so a t78 for example at 15psi would produce more power than the stock twins at 15psi

but now my question is, where does the higher volume go?
is it just sitting in the fmic, piping etc...?

is that why a large single can produve higher density air charge?
 

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Still Sportin' the Twins
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SupraWood said:
Ok, sure pressure by itself isn't important. It's density. As Larry pointed out pressure is created by a restriction (the engine). But, I still hold that if two turbochargers with the same engine back pressure and compressor outlet air density will produce the same power.
No, it's not density. Density only helps FLOW. The enginge isn't your only restriction. The turbine on the turbo plays a huge roll in the overall back pressure measured between the turbo and the engine exhaust. The more boost you try to squeeze into the engine, the more pressure you will get at the turbine inhibiting that flow of air out of the engine. Think of a small length of garden hose. Blow through it. Flows pretty well. Now put a small drinking straw on the far end. Harder to blow through now, huh? Blow as hard as you want to increase the pressure/density of the air in the garden hose and you will FLOW more, but you will never be able to move as much air through the hose as you would without the drinking straw restriction. Moving air is what makes power. AKA Volume or Flow.

David
 

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Discussion Starter #12
98bpu said:
ok, so basically we are down to density/volume,

a larger turbo flows higher volume of air, at a higher density
because of less heat being produced

correct?

so a t78 for example at 15psi would produce more power than the stock twins at 15psi

but now my question is, where does the higher volume go?
is it just sitting in the fmic, piping etc...?

is that why a large single can produve higher density air charge?

so to correct myself now that i read it a couple times...

the larger turbo provides less of a restriction to the flow of air through the engine.... u are essentially removing the "soda straw" when u remove the stock twins?
 

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David,

That is why I said for the same engine back pressure. I agree completely that a properly matched larger turbo will have lower back pressure.

If the exhaust back pressure is the same (not going to happen I know), but if it did, then manifold air density is the key.

Daniel
 
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