turbo exhaust housings & wastegates

[Beast2B]

Ok turbo gurus, I have been thinking again and my brain hurts. Here’s the question (with a few qualifications up front):

• All of the B1 turbos have the same compressor and housing,

• All of the B1 turbos are optimum at 46-48# boost with near 1:1 PR,

• I am externally waste gated (soon, and may go twins later) and it would be nice to change as few parts as possible!

• A kwik-spool exhaust housing will get to 46# boost sooner that a full B1 exhaust housing,

Now the question: Why would anyone use an exhaust housing larger than the KS housing when you can spool quicker to 46#, bypass any additional exhaust with the waste gate, and have less rotating mass because of the smaller turbine wheel? What is the downside to this equation?

I always read that the larger turbo exhaust housings have better top end versus the smaller housing’s spool-up, but if both turbos are most efficient at the same boost then top end should be the same **IF** they are wastegated to the same max boost.

OK, LET ME HAVE IT!!!

 

[Beast2B]

nobody gonna give this a shot? take a deep breath and start from the beginning...

 

[jwilliams3]

Are you talking external or internal wastegates?

 

[JHerrlich]

I'm curious too...

 

[Beast2B]

whatever wastegate is available, as long as it will pass the gas! My B1-2 is not wastegated, I'm fabbing up an external. I can also use it later if necessary. A KSB1 with a wastegated housing for top turbo, an external wastegate for limiting overall boost with twins...

 

[Cooker]

• All of the B1 turbos have the same compressor and housing,

• All of the B1 turbos are optimum at 46-48# boost with near 1:1 PR

I'm not sure that I agree with this. Remember boost isn't everyting. Jetpilot has spent some time on a dyno adjusting boost with a B1 and found that it produced the most HP below the 46-48 pounds you suggest.

Now the question: Why would anyone use an exhaust housing larger than the KS housing when you can spool quicker to 46#, bypass any additional exhaust with the waste gate, and have less rotating mass because of the smaller turbine wheel? What is the downside to this equation?

I always read that the larger turbo exhaust housings have better top end versus the smaller housing’s spool-up, but if both turbos are most efficient at the same boost then top end should be the same **IF** they are wastegated to the same max boost.

The smaller turbine wheel will move less air. For this reason top end will not be the same between two turbos that are efficient at the same boost pressure. Again, boost is not everything. The volume of air is also key.

 

[Beast2B]

mass of air and charged air temp seem to be the major players (obviously interrelated, hotter = less dense). Dyno tuning will be easier with an adjustable external wastegate, but the only adjustment for fueling would be changing injectors (or adjusting Comp, is TSTPM3 or Redline better with finer adjustments?).

If you tune a combo (say EDM3, DragComp, B1-2) to an optimum hp will that boost value be optimum for a larger injector as well? ... and if you add too much fuel at that boost, what will the symptoms be? ... EGT? ... smoke?