Finally got the truck out today for some testing.


First thing I did was to hook up my 'Single Breather' to my EVAC with the nipple/checkvalve in the downpipe. Upon start-up, gauge showed 1psi. Found Crankcase was the culprit. Then I took it for a ride.


All testing was done unloaded. I pushed it to 15psi Boost and couldn't get any vacuum reading from my EVAC set-up. To make matters worse, Crankcase was capable of building 2psi.


Suspecting my checkvalve was not helping my hunt for vacuum, I removed it from the hose. With a vacuum gauge hooked up only to the nipple welded into the downpipe, I was able to see 1 in. of vacuum. At least I didn't waste my time with the downpipe. Any vacuum is good I figured.


Now I reconnected hose to breather, with gauge in-line. Gauge didn't move, No Pressure, No Vacuum. I guess with the little bit of pressure that the crankcase develops, along with the slight vacuum the EVAC pulls, it's theoretically doing what I originally intended it to do.


So much for pulling 3-4 in. through crankcase. It's no wonder I ditched this set-up on the racecar for a Purpose Built Vacuum Pump.

Is there anyway you could compare your readings to the stock setup with the crankcase routed to the turbo intake? Just to see if you've made any improvements, if your setup is atleast comparable, or if you figure out a way to make it work better, I would consider it on mine as well.

Yes. Very easy.


I would just have to put a gauge in-line between the CDR and the turbo inlet.


If I had to guess, It would have similar readings as far as Vacuum/Pressure. The CDR won't restrict either way.


If the exhaust pulled a greater vacuum, it would be minimal.


My hopes of pulling vacuum on the crankcase are fading fast.


The only improvement so far is the re-routed fumes.

Good work, Billy - proveable, repeatable.


Could you define the exhaust system on your truck, so the numbers will be more significanct as relates to exhaust pressure?

Sure thing JD.


Downpipe is the standard 3". Crossover is Mandrel Bent 2.25. After that, I have about 1' of 3" pipe that immediately steps up to 4". Where the Factory Muffler used to sit is a Walker Straight Thru 4". Tailpipe is also 4".


When I decided to do the exhaust, I was really contemplating 3.5 and 4 inch. Now, I'm glad I went with 4. It was tight through the crossmembers and stuff but I think well worth it.


I'm wondering if the placement of the nipple in the downpipe is holding me back from pulling more vacuum. Maybe further down the exhaust system(Post Muffler), would be more beneficial. Then again I also thought that the DP was a good location before it stepped up to 4".


I never thought that I would get involved in transforming this truck to what it is becoming. Re-flashed ECM, Intercooler, WMI, Hi-flow Air Filter, Big Boost numbers...


Next are going to be Hi-Pops and a gear Drive.

Should get a reduction in pressure in or right after the step, as the gas expands and reduces velocity.......


Purpose of this folks, is you will have exhaust back pressure with the stock exhaust system - soot trap, muffler, tail pipe.


3" down thru the soot trap, 2.75" into the muffler, 2.50" out of the muffler.


Even more so in the long wheelbase vehicles.