Boost vs backpressure

Joesixpack said:
You can't compare your primary vs the same charger in a single position. Your primary is seeing a great flowing huge displacement. As a single it's seeing the ****ty diesel head flow most of us are stuck with.

Those are pretty much the same numbers I had with a s480 in the primary position, boost near half drive, a good indication it's on its knees.
As a single boost was higher than drive at the exact same power level. As a single it was able to cram the same mass flow only at a much higher pressure ratio.
Click to expand...

Ok, I may have heard wrong then. (Others saying they have better ratios with the same primary.)

My poor S484/96/1.32 needs to be either a S588, or a nice GT5588...something with a bigger turbine wheel.

I would expect that with the bigger turbine wheel in the primary, it would reduce the back pressure in the whole system overall, making more power, less heat internally, and just be a BLaSt to drive.
 
Last edited:
Below is an overlay of two dyno pulls, one is an S400 88/96mm turbine with a 1.32AR housing, the other is an S500 99/110mm turbine in a 0.85AR housing. Both had very similar compressors and made within 0.02psi of boost pressure of one another.

03177a43-295e-4e06-9000-e4af9ca4334d_zpspdks1nxu.jpg
 
Smokem said:
Below is an overlay of two dyno pulls, one is an S400 88/96mm turbine with a 1.32AR housing, the other is an S500 99/110mm turbine in a 0.85AR housing. Both had very similar compressors and made within 0.02psi of boost pressure of one another.
Click to expand...


Note to self: don't buy an S500 with a .85 A/R housing...LOL
 
kjpcummins said:
Maybe the compressor didnt flow enough for the hot side of the s500. Not sure you will see much of a gain by going to a larger exhaust housing on a s500.
Click to expand...
Maybe it flowed too much. GT55 with 80 mm compressor would be much better for anything up to about 1100 hp.
 
Leiffi said:
Maybe it flowed too much. GT55 with 80 mm compressor would be much better for anything up to about 1100 hp.
Click to expand...

Clearly it did not, the backpressure shows it flows less than the S400, as well as the comment from BW on the previous page confirming this. There is absolutely no need for a GT55 turbine on something up to 1100hp and < 7.0L, especially with only an 80mm compressor wheel.
 
Smokem said:
Clearly it did not, the backpressure shows it flows less than the S400, as well as the comment from BW on the previous page confirming this. There is absolutely no need for a GT55 turbine on something up to 1100hp and < 7.0L, especially with only an 80mm compressor wheel.
Click to expand...

I think some Supras use that Garretts dragracing-special. They are only 3 litres and 1400 hp.
 
Leiffi said:
I think some Supras use that Garretts dragracing-special. They are only 3 litres and 1400 hp.
Click to expand...

This isn't www/competitionsupra/com, so I don't see how your comment is relevant to the conversation at hand.
 
Last edited:
Smokem said:
Clearly it did not, the backpressure shows it flows less than the S400, as well as the comment from BW on the previous page confirming this. There is absolutely no need for a GT55 turbine on something up to 1100hp and < 7.0L, especially with only an 80mm compressor wheel.
Click to expand...

Really?
So my setup, which only made ~790rwhp with a 63mm over a 80mm, with temps over 1600*F, and drive pressure on the secondary over 100 psi, and 50 psi on the primary, would not be any better if I was running a GT55?
 
Single vs twins. In a compound config the primary effectively sees a much larger displacement engine.
 
Extended Power said:
Really?
So my setup, which only made ~790rwhp with a 63mm over a 80mm, with temps over 1600*F, and drive pressure on the secondary over 100 psi, and 50 psi on the primary, would not be any better if I was running a GT55?
Click to expand...

Its hard to say. You may be able go a 1.58ar and achieve the same outcome.
 
Extended Power said:
So my setup, which only made ~790rwhp with a 63mm over a 80mm, with temps over 1600*F, and drive pressure on the secondary over 100 psi, and 50 psi on the primary, would not be any better if I was running a GT55?
Click to expand...

If you are simply wanting to lower drive on the primary yes a larger turbine would achieve this, but this alone will not increase power.
 
I think Weston is eluding to the fact that the 80mm compressor wheel is not going to take advantage of the gt55 flow potential. I would think at least an 88mm compressor would be mandatory when stepping up to that frame of charger.
 
CurtisEmery said:
I think Weston is eluding to the fact that the 80mm compressor wheel is not going to take advantage of the gt55 flow potential. I would think at least an 88mm compressor would be mandatory when stepping up to that frame of charger.
Click to expand...

Definitely....:evil

May have to sell the 84mm, and move up...
 
You must log in or register to reply here.
Top