I think Billman did this also but did it in the downpipe? Today i had a 3/8" nipple welded into my 3.5" x 4" x-over pipe hoping to draw some vacuum from there. When i first fired it up there was a fairly good blow coming out the nipple :mad: , i then put on a vac/pressure gauge and found no vacuum and maybe 1 PSI pressure throughout the rpm range so figured less than a pound wouldn't hurt the engine seals. Next i plumbed a hose from the CDR to the nipple in the x-over and went for a run with the scanner hooked up, my only purpose for this was to see what would happened with IAT's compared to my drive on the previous day. Well not the improvement i was hoping for but did manage to reduce IAT's by about 10F throughout the RPM range except for WOT runs which would still produce 300F by 95 MPH.

Minor improvement but not worth the effort IMO. I'll probably have to cut out the nipple and plug the hole now :mad: .

What is a "3.3' x 4" x-over pipe "? What's the boost at 95? Since your latest mods how is the truck performing?

Fingers move faster than the brain some days, i've corrected the post for 3.5"

Boost at 95 MPH? Have to look.........
Scanner said it was 16 PSI @ 96 MPH but thats as high as the scanner will read, could have been 17-18 PSI on the gauge... didn't look.

Performance is ok, want more though. Probably the 7200 lb weight is holding it back a bit.

To get a vacuum in the exhaust system is nearly impossible on street exhaust. The location would have to be at a venturi and then the exhaust would have to open up after that. Can't see it working on anything other than a wide open ,short exhaust pipe. Use the connection to check exhaust system back pressure on the muffler and tailpipe. Squirt fuel in it to really add some extra smoke. Transfluid makes good white smoke. Add propane there and shoot flames out the exhaust. Got to have flames, specially when you add the 6 inch stacks.

Back pressure is less than 1 lb from the gauge i had in it on about a 10 mile run. Flames, now that would look cool.

CR, I like your style. Keep experimenting.

To get a vacuum in the exhaust system is nearly impossible on street exhaust. The location would have to be at a venturi and then the exhaust would have to open up after that.

you can make it happen with street exhaust, but it needs to be more than a straight fitting... you need a section of pipe that extends into the exhaust pipe, with a angled cut on it facing away from the exhaust pressure source...

sorta like this...

exhaust flow =>
____________________

- - - - - - |\
_________||_________
- - - - - - || <- plumb hose here to crankcase breather

even 1 psi pressure in the crankcase can force leaks... the lower the pressure, the better [remember, pressure x area = force] at work, we we run crankcase eductors in our exhaust stacks on the loco's... at full engine load, there is like 3"-9" h2o negitive pressure... at those pressures, you can't open the rocker covers by hand..

[extra dots and dashes there to try and keep formating correct]

you can make it happen with street exhaust, but it needs to be more than a straight fitting... you need a section of pipe that extends into the exhaust pipe, with a angled cut on it facing away from the exhaust pressure source...Quote from Nickleinonen

exactly right. it works because the exhaust rushing by creates a low pressure area behind the fitting that is extended into the exhaust pipe. might work this way CR, keep up the good work :ro)

Try this: http://dieselplace.com/forum/showthread.php?t=13838&highlight=pressure+vacuum

Thanks for the info guys. I did find that thread Billman but didnt find the one on how you made/designed it. Are you still running it or not?

Here's a pic of what i did..... well drawing anyways.

you did it right CR. if that didn't work, it aint gonna work. i'd heard that evacuation stuff had to be done on a high RPM application, well here's our proof between you and billman :(

Um i think Billman managed to get vacuum in the linked thread above, i'll have to go back and check.
Nickleinonen might be correct on his design also and i'm contemplating cutting out the nipple i put in and doing it that way, i'm just not sure if we have enough rpm to put it on vacuum. Like i said above its just to see what i can do to IAT's, anything that lowers IAT's has to be a good thing, especially for a stock engine just running the exhaust upgrades. My IAT check was a quick thing, i haven't graphed the numbers yet to get a real good idea of the reductions but will.

Yes. Still running it.

Crankcase Pressure/Exhaust Vacuum documented by Small Oil Leak at Downpipe/Exhaust connection.

Some more info is in the Ever-Popular Dual Breather Thread.

That probe-type will offer a small reduction in pressure, measured in inches of water "H2O.

27" H2O = 1psi

The higher the exhaust velocity, the greater the drop

If exhaust pressure in the pipe is ~2psig, the 3"-4" reduction will still result in pressure greater than 1.5psig.

What is required is a 4-6" reduction below Baro - reduction below Exhaust Pressure is still greater than Baro.

So exactly how can i accomplish this gmctd?

On a street driven vehicle with muffler you'll have to plumb it to the rear most section of the exhaust. Remember all those bends and muffler creates back pressure. The suction tube must be in an area void of pressure. If you just want to blow the fumes in, do it anywhere, but there won't be a negative pressure in the crankcase.

Correct - check the angular relationship of your tailpipe end to vehicle axis.

Exhaust exiting at that angle into the sidestream takes advantage of the lower pressure there any time the vehicle is moving forward.

That pressure is some few inches of water less than Baro

The faster the vehicle speed, the lower the pressure there - really helps a naturally aspirated engine breathe at highway speeds

Even more so if the air intake is plumbed directly into the higher pressure area at the front of the vehicle.

OK that may have to wait until the stacks come then, maybe use it for propane in the mean time.... kaboom!