Venturi to increase exhaust?

[Camar068]

See below. Would such a device increase exhaust flow? Basically it's a funnel forcing air through the end of the exhaust, causing an increase in flow. Might be too much, dunno. If it is too much you could put a gate valve on it thats controlled by speed, throttle positon, MAF signals, etc. Would/Could it be beneficial?

[edit] green is typical exhaust flow, blue is the "funneled" air flow due to speed.

Outside the box again, but I thought of it a few weeks ago and raised a few eyebrows with ford guys at work.

 

[74 Shortbed]

One way to find out, try it.

 

[Green79Scottsdale]

Theoretically, I think it would work. With that said, there are also variables that would need to be considered. The intake part of the venturi would need to be in the airflow path under the truck. The merge would need to be in an appropriate location, and possibly multiple locations to keep the speed of the exhaust up. The next question is how much time are you going to put into it and what will the true end result be? Basically what you are doing is introducing additional scavenging to help move exhaust gas out as effecient as possible. Interesting concept, but in the end probably not worth the time and effort for maybe single digit power gains, depending on your current exhaust situation.

 

[vkh]

I'd be most interested in how it would sound at speed. Far as flow I think you'd want to rest of the exhaust to be as free flowing as possible, if you had to much of a resistance after the Venturi you'd just have a slightly compressed column of air for your engine to push through. Perhaps after the muffler to regenerate some of the lost speed?

 

[Camar068]

if I had the money and time to do it, I would put that system close to the end of the pipes. Let the venturi draw the exhaust and not push it. Seems like it would be less resistance drawing instead of pushing it down a length of pipe.

 

[GTME94]

New GM diesel trucks have a venture device on the end of the tailpipe but that is mainly to cool down the exhaust when the DPF (Diesel Particulate Filter) is in regen, the exhaust gets super hot. Ford doesn't have a venture but they have some tabs in the exhaust to mix in fresh air.

 

[smoothandlow84]

I doubt that it would increase exhaust flow enough to make a difference. Like the duramax and superduty, all it would do is cool the exhaust gasses exiting the tailpipe. Instslling a chambered muffler or similar would probably have the same effect as the venturi.....less back pressure. If anyhting....the exhaust might whistle at highway speed.

 

[theblindchicken]

For anything with o2 sensors you'd have to place it way after that. Otherwise you'll skew the readings into appearing that its running extremely lean, then ecm will dump fuel into it to counter the "lean" mixture, thus running extremely rich.

You'd also probably have to determine what the maximum CFM's your muffler(s) could realistically handle. Would also have to determine the cfms of the exhaust piping as well and calculate the average velocity through the pipe too.

So, run true duals, throw in an x-pipe, and throw in your venturi idea in there somewhere and see how it goes. Could easily make it all bolt together while testing. Use a Y-pipe with a wide scoop to grab the air flowing under the truck.

 

[Honky Kong jr]

For anything with o2 sensors you'd have to place it way after that. Otherwise you'll skew the readings into appearing that its running extremely lean, then ecm will dump fuel into it to counter the "lean" mixture, thus running extremely rich.

You'd also probably have to determine what the maximum CFM's your muffler(s) could realistically handle. Would also have to determine the cfms of the exhaust piping as well and calculate the average velocity through the pipe too.

So, run true duals, throw in an x-pipe, and throw in your venturi idea in there somewhere and see how it goes. Could easily make it all bolt together while testing. Use a Y-pipe with a wide scoop to grab the air flowing under the truck.

And you would be plagued with an eternal rich code. I it would definitely need to be regulated. You could run cut outs threw a VSS before a restriction (muffler) so at town speeds the exhaust would be full system and at highway would be free flowing.

 

[Camar068]

And you would be plagued with an eternal rich code. I it would definitely need to be regulated. You could run cut outs threw a VSS before a restriction (muffler) so at town speeds the exhaust would be full system and at highway would be free flowing.

I've thought of that also. All this was an idea that popped in my head after reading a few articles. When I was done, I thought.....so who's right and who's wrong? Why is it such a science? Is it really a science? lol for that matter make your super charger a "dual" super charger.......push intake and exhaust.

lol here's one for ya...

After any sensors you have, put a variable size exhaust.....like a fighter jet has. Have that enclosed in a 4" pipe. Within that 4" pipe there is a 3.5, 3, 2.5, and a 2.25 pipe.....right at the edge of that variable exhaust. Run that the full length of your exhaust (pricey I'm sure as it would be super custom). Tune it to your throttle on the carb or computer.

Man I swear i think outside of the box too much lol.

 

[Honky Kong jr]

I've thought of that also. All this was an idea that popped in my head after reading a few articles. When I was done, I thought.....so who's right and who's wrong? Why is it such a science? Is it really a science? lol for that matter make your super charger a "dual" super charger.......push intake and exhaust.

lol here's one for ya...

After any sensors you have, put a variable size exhaust.....like a fighter jet has. Have that enclosed in a 4" pipe. Within that 4" pipe there is a 3.5, 3, 2.5, and a 2.25 pipe.....right at the edge of that variable exhaust. Run that the full length of your exhaust (pricey I'm sure as it would be super custom). Tune it to your throttle on the carb or computer.

Man I swear i think outside of the box too much lol.

There are cars that run variable discharge mufflers kinda work like variable displacement intake manifolds actuate via switched vacuum threw the ECM. And it's that little voice that don't stfu. I believe we discussed this little bastard before.lol

 

[Camar068]

lol yeh when I saw a reply, a little light came on before I clicked. Guess I need to come up with something and test it out....or shut up LOL. Was hoping other people had stuff laying around with free access to a dyno to possibly test.

 

[Camar068]

seriously....did I break 1,000 posts? Wow....do I yap that much LMAO.

 

[chengny]

See below. Would such a device increase exhaust flow? Basically it's a funnel forcing air through the end of the exhaust, causing an increase in flow. Might be too much, dunno. Would/Could it be beneficial?

IMHO you shouldn't make this modification. Rather gaining an increase in the flow of exhaust gases from the engine, it's actually more likely to reduce it.

Introducing an external supply of pressurized air - as indicated in the sketch - won't create a venturi effect. Most likely, all it will do is cause an elevated pressure to develop between the point of injection and the tail pipe. Consequently, the flow rate in the entire exhaust system will be slowed - due to increased back pressure.

I think I can see what you are attempting to do. The idea is to induce a greater flow rate in the system using a pressurized "motive media/liquid" to propel the exhaust gases through the tailpipe and out to atmosphere.

There are devices called "eductors" that are used to create low pressure zones (i.e. suction) in the piping systems they serve. The eductor pulls the "suction media" up from it's original system and into the flow of motive media. Then the mixed motive & suction fluids are expelled - together - from the eductor outlet.


But, looking at the sketch above, there appears to be several fundamental issues:

1. There is no nozzle at the end of the motive media (i.e. the outside air stream) pipe.

2. Even if a nozzle were installed at the exit of the outside air pipe, no increase in flow would result because a second nozzle is required downstream of the motive fluid nozzle. IIRC it's called a convergent/divergent nozzle.

3. The direction of the fluid flows are backwards. The flow of the motive media should be straight through - in line with both of the nozzles and into the outlet piping. This effectively requires that the suction fluid has to be introduced perpendicular to the motive flow.

4. The motive media must be at a significantly higher pressure than the area of discharge into the convergent nozzle (the exhaust gas). Unless you go like 800 mph, no motive force will be developed.

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BTW - this area of study is called Fluid Mechanics. I had to take that class a long, long time ago and have forgotten most of what they taught me. But, one thing I do know for sure is that I raised the flag on that class (got a big fat F)... so as always consider the source.

 

[Honky Kong jr]

lol yeh when I saw a reply, a little light came on before I clicked. Guess I need to come up with something and test it out....or shut up LOL. Was hoping other people had stuff laying around with free access to a dyno to possibly test.

It's a good read with real world documentation. http://www.headersbyed.com/hc_ventext.htm