Tell me about turbulence..

[Turbo6Smackdown]

Of course, anyone that spends over 5 minutes on this site, is eventually going to end up reading about turbulence. I've read over a few threads speaking on how it can actually hurt flow. Ok then, here's my question for the turbulence crowd. I think ungn may study this field, I forget.
The people who run cutouts on this board. The way they're run, with that cutout portion pointed back, towards the rear... When it's closed, doesn't air fill up in there, then have to back up, and re-join the rest of the air that's already rushing past it? Does this create a lot of turbulence, thus back pressure? Anyone flow it? Richard Clark?
I was wondering, would this be solved by running the cutout 'backwards' so to speak? So that the air rushes past it? And even if it does pressurise that little compartment, would it be easier for that trapped air to re-join the rest of the air that didn't get trapped? Am I slicing hair?

 

[notacarlo]

Hair slicer. :biggrin:

The cut-out portion of the pipe is a "high pressure" area. The exhaust fills it (almost as if it were a solid) then goes right by it. The rest of the system is free flowing enough that any "turbulence created by that area is negligible.

 

[Turbo6Smackdown]

I see..

 

[Turbo6Smackdown]

So what would happen if I mounted it backwards anyway. Anything?

 

[notacarlo]

Mount the dump backwards? Facing the engine?

Well, then it would be an area of incredibly low pressure and probably flow equally (but mostly favoring an early exit) through the system and dump.


On the other hand it may act like a siphon and pull air in at low pressure and pass it through the exhaust system. Till you put yer foot into it.

 

[notacarlo]

Whoops...
But if the dump is closed it will act the same way but with negative pressure. (like pipe facing back)

 

[Chuck Leeper]

Angled, 3" dump on a 3" TH down pipe= 3RWHP, and a lot of noise..Bout it.
Rest of exhaust was the BG designed, 21/2" with Ultra flows.
Flowed enuf to put a 3700# turd thru the traps at near 142....

 

[bison]

Angled, 3" dump on a 3" TH down pipe= 3RWHP, and a lot of noise..Bout it.
Rest of exhaust was the BG designed, 21/2" with Ultra flows.
Flowed enuf to put a 3700# turd thru the traps at near 142....

So its worth about .75hp on engines in question

 

[A2000RICH]

Of course, anyone that spends over 5 minutes on this site, is eventually going to end up reading about turbulence. I've read over a few threads speaking on how it can actually hurt flow. Ok then, here's my question for the turbulence crowd. I think ungn may study this field, I forget.
The people who run cutouts on this board. The way they're run, with that cutout portion pointed back, towards the rear... When it's closed, doesn't air fill up in there, then have to back up, and re-join the rest of the air that's already rushing past it? Does this create a lot of turbulence, thus back pressure? Anyone flow it? Richard Clark?
I was wondering, would this be solved by running the cutout 'backwards' so to speak? So that the air rushes past it? And even if it does pressurise that little compartment, would it be easier for that trapped air to re-join the rest of the air that didn't get trapped? Am I slicing hair?

i'll actually do a test tomorrow with a dump forward and backward-------my guess is that with it backwards (forwards) it will flow slightly better if closed and better rearward facing if open-------but i'll test it all four ways--------the cutout does create turbulance if closed no matter what way it is facing-------when a liquid or gas flows in a pipe the molecules closest to the pipe move very slowly and sometimes almost not at all-------the closer you go to the center of the pipe the faster they flow-------its the shearing of the molecules rubbing against each other from the different speeds that heat them up when forced through a pipe---------when those slow moving molecules passing down the pipe pass over the cutout they "free up" and are dragged faster by the nearby molecules until they reach the other side of the opening where they are abruptly halted again-------thats what creates the turbulance...........RC

 

[joe_schindler]

This should be interesting. I’m guessing that the 0.75 HP number is about right; for a lot of reasons.

One thing about gasses; they flow faster in turbulence than laminar flow.

 

[Pablo]

Depending on how free flowing your exhaust is after the cutout, It's quite likely that the cut out will suck air vs expel exhaust if you face it forward.
Bernoulli's principle at work here. Carburetors, slash cut evac systems, and about a million other things work based upon this concept. There's a relationship between the amount of flow vs angle and mounting of the pipe coming from the side vs the pressure differential between the two. The more flow the more pressure differential can exist while still creating a draw. Of course the angle and entry of the other pipe has a huge effect on the efficiency of all this.

 

[TR Custom Parts]

There's a lot more things to be concerned about on these cars than that.

 

[Turbo6Smackdown]

I agree mark, but it was just one of those turbulence questions, to ensure that I have the theory down pat. Though, I have never thought it the cutout actually creating vacuum if mounted backwards. It does make sense.
I asked this partially, because my mufflers will be doing just that. Muffling. I chose the quietest mufflers I could find period. So, I'm doubting my flow, with the dump closed. She's not going to be that free flowing. I'm using a 2.5 dual pypes stainless setup, with a 3" electric cutout, and 87 riviera mufflers.

 

[kjizzle]

actaully, welding a tube onto the exhaust of old volkswagen engines "backwards" (creating a vacuum) is a common poor man's crankcase evac...

 

[turbofabricator]

ACTUALLY I did run my dump facing forward 18 years ago. It caused so much turbulant flow under my right front tire that it caused me to hit a telephone pole! I'm SURE it was the dump pointing forward and NOT the 9beers and 25 psi of boost that caused the crash. :biggrin:

It won't make ANY difference as notacarlo stated. Worry more about the TERRIBLE turbulance in each intake port, plenum, exhaust port short side radius, intake pipe/MAF, or politicians opening thier mouths and telling you "they will take care of you"!!!

 

[Turbo6Smackdown]

Our politicians won't take care of us?

 

[boostingbuick]

Angled, 3" dump on a 3" TH down pipe= 3RWHP, and a lot of noise..Bout it.
Rest of exhaust was the BG designed, 21/2" with Ultra flows.
Flowed enuf to put a 3700# turd thru the traps at near 142....

I agree. My full weight car has been 130 through the muffs. I never installed a dump due to the fact I really don't think I will gain enough for the money. Plus I like the fact I can hear the radio.

 

[joe_schindler]

i'll actually do a test tomorrow with a dump forward and backward-------my guess is that with it backwards (forwards) it will flow slightly better if closed and better rearward facing if open-------but i'll test it all four ways--------the cutout does create turbulance if closed no matter what way it is facing-------when a liquid or gas flows in a pipe the molecules closest to the pipe move very slowly and sometimes almost not at all-------the closer you go to the center of the pipe the faster they flow-------its the shearing of the molecules rubbing against each other from the different speeds that heat them up when forced through a pipe---------when those slow moving molecules passing down the pipe pass over the cutout they "free up" and are dragged faster by the nearby molecules until they reach the other side of the opening where they are abruptly halted again-------thats what creates the turbulance...........RC

Richard:

I'd wager you didn't find much change; but I’d like to know what your results were.

Please let us know.

Thanks,

Joe

 

[A2000RICH]

Richard:

I'd wager you didn't find much change; but I’d like to know what your results were.

Please let us know.

Thanks,

Joe

actually i ran into difficulty since the only y pipes i had were sligtly different shape on the ends--------one end (convertor end) is oval and the other is round------trying to find one that is symmetrical so it doesn't skew the test

 

[MNwe4]

Reviving an old thread here since I was wondering the same thing and testing was never published.... If the dump pipe is capped does it disrupt the flow through the exhaust enough to be worse than just a straight 3" test pipe?