Ok, I had this thought. I have a bend coming from my downpipe that is smaller than the rest of the 3" exhaust so I have a low pressure venturi.
So, I'm wondering if I came off an external WG and ran it into this venturi, would it actually help suck exhaust through my WG faster?
I know venturies don't self power but in this case I think the main gas flow would have sufficiant flow to create a good draw. How does this sound or has anyone heard of this?
Positive waste gate ventilation???
The pressure creating the WG exit flow is going to be greater than that found in the venturi. So, it's likely that the WG stream will help evacuate the main flow gases, not the other way around.
It really doesn't matter, man. The best thing you can do is make it all one diameter pipe (main exhaust stream) and vent the WG to atmosphere.
It really doesn't matter, man. The best thing you can do is make it all one diameter pipe (main exhaust stream) and vent the WG to atmosphere.
Re: (KATwo40)
I'm hoping the venturi will create a vacuum and help suck the pressure out. You might be right though, who knows?KATwo40 wrote:The pressure creating the WG exit flow is going to be greater than that found in the venturi. So, it's likely that the WG stream will help evacuate the main flow gases, not the other way around.
It really doesn't matter, man. The best thing you can do is make it all one diameter pipe (main exhaust stream) and vent the WG to atmosphere.
Stop and think about this for a second.
A venturi creates a low pressure system on the backside. As a result, the front side (entry) of the venturi is going to have increased pressure, when compared to just a same-sized piece of pipe.
So, now, you're reducing the delta P across the turbine wheel by backing up the ehxuast pipe with this venturi section. Reducing the delta P across the turbine wheel gives slower boost response, higher exhaust manifold pressure, higher EGT's, etc.
Just something to consider.
A venturi creates a low pressure system on the backside. As a result, the front side (entry) of the venturi is going to have increased pressure, when compared to just a same-sized piece of pipe.
So, now, you're reducing the delta P across the turbine wheel by backing up the ehxuast pipe with this venturi section. Reducing the delta P across the turbine wheel gives slower boost response, higher exhaust manifold pressure, higher EGT's, etc.
Just something to consider.
Re: (KATwo40)
The venturi is already there and it's a small change. Like a 2.5" pipe in a 3". My exhaust will be ripping through there creating a lot of low pressure. Turbos create a lot of backpressure. The idea is that the low pessure will help vent the backpressure from the gas that can't pass through my small wheel. It's basically just exhaust scaveging. Guys do this with V8s by bringing the two pipes into an X section and back apart again. As one a pulse from one side passes it helps suck the other one through.
I'm going to look around and see if anybody is doing it.
I'm going to look around and see if anybody is doing it.
Yes, I understand the concept, but I'm tellin' you, the gases coming out of the wastegate dump are going to be under more pressure than the gases flowing through that little venturi you're runnin'.
You said it yourself...turbos create exhaust manifold backpressure. Therefore, the flow through the exhaust pipe post-turbine housing is going to be very low pressure, when compared to exhaust manifold pressure. The WG dump is under exhaust manifold pressure, so that's going to escape with a pretty high velocity itself.
You said it yourself...turbos create exhaust manifold backpressure. Therefore, the flow through the exhaust pipe post-turbine housing is going to be very low pressure, when compared to exhaust manifold pressure. The WG dump is under exhaust manifold pressure, so that's going to escape with a pretty high velocity itself.