To work as an eductor, the vented air would have to be flowing perpendicular to the pipe containing the exhaust gasses. That would produce a lower pressure at the point where the two systems connect. Generally, gas eductors are powered by liquids. Not sure how much pressure reduction you would actually develop with an air powered eductor. It works for crankcase evacuation systems, and it works for the "olde" draft tube type crankcase vent systems. It would also seem to depend on the relative volume of vented air, compared to the volume of exhaust. Cold vent gasses, of limited volume, would have to be passed through a relatively small diameter venturi to develop any real negative pressure, and that isn't going to move a lot of exhaust, when the combined volume tries to squeeze through the rest of the venturi.

The problem would then become, how large a tail pipe do you need to have to flow the combined volume of the air and the exhaust without having it become a restriction. You would have to figure the impact of temperature as well. What happens when the cold air draws the hot exhaust gasses in, and the combined flow stream produces some intermediate temperature?

 

http://www.flowfactor.com/penberthy_...mp_cutaway.htm

 

Barnett -

YES! That's exactly what I have been thinking of. Thank you for the link.



Injun -

I agree...
The tailpipe sizing question is the key issue for this notion. That's actually what I'm trying to find out and I was hoping that someone here might have some 'rules-of-thumb' that they could pass on.

In terms of the right angle, I believe that if I decide to test this idea, I would do so with right angle bends in the exhaust; just before the rear tires.

Bottom line is; everything except the plumbing to the exhaust and the "tailpipe" setup is going to be on the car anyway. As a result, it wouldn't be a big deal to try this idea.

Having said that, it'll still involve some time and effort, so it'd be nice if I could design this in a way that's most likely to produce a positive result.


So, any thoughts on the ratio between the size of the nozzle and the size of the exhaust pipe?

 

Maybe you could have some kind of flapper valve in it. That way when it is pulling a vacuum it will pull the exhaust out that way. But when there is no suction it would bypass it all together. I work on the cement side in oilfield services. A couple of the cement mixers use the jet mixers. The jet pulls a vacuum to help pull the dry cement to mix it. I just wonder how much of a vacuum you could get out of it.