Thinking outside the box

# Thread: Thinking outside the box

1. ## Thinking outside the box

So the other night I'm at my buddy's hot rod shop making up some bends for my new exhaust. We start talking over a few beers and he asks me if anyone has ever dumped the exhaust into the suction housing on a jet boat. I've never heard of, or even thought of that but it made sense at the time. You're essentially turbocharging the pump with the power of the exhaust. What do you guys think of this idea? Looking forward to some more education from the brain trust here.

2.

3. Lucky, my knowledge of turbochargers wouldn't fill a thimble, and what I know of jets is even less, but allow me to explain where I believe your idea is askew.
The entering exhaust gases impinge directly on the exhaust side turbine wheel, in you jet deal, I believe that would be difficult to do.

The velocity of the entering gases is only a small fraction of what makes the turbime spin. the real power comes from the gases expanding and giving up its energy to the turbine wheel. You deal will be giving up its energy primarily to the water.

Air/gases are not going to propel your boat. Why would you want to add gases to the mixture that only serve to take up space in the pump? You'll be trying to push the boat with foam.

Doesn't the suction housing go positive when the boat gets to speed? Now you trying to push hot gases into a pressurized vessel. And when you chop the throttle, and the RPM drop, and the exhaust gases go close to zero, isn't the suction housing under some serious pressure at this point. Isn't this why you guys use blow offs. If the pressure in the suction housing gets high enough, how do you keep water from going up the header?

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4. Introducing air into the suction housing would cause immediate cavitation.

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6. And that's why I brought it to you guys, knowledge! I thought about the cavitation factor, but half of me thought the water could/would overcome the gasses. I hadn't really even thought about the pressurization in the suction housing at speed. Again, this was thought up after a few beers by a couple of guys that like to think outside the box and grab any free (I know, nothing is free) HP. Good thing I haven't cut my suction housing yet!

7. Originally Posted by steelcomp
Introducing air into the suction housing would cause immediate cavitation.
And there is a possibility that if the boat was not moving with the engine running and the exhaust plumbed into the pump, the boat could sink.

8. Air in the suction=bad news. Dump it under the boat maybe, get some lift. Could be super restrictive maybe, dont know.

9. Originally Posted by cs19
Air in the suction=bad news. Dump it under the boat maybe, get some lift. Could be super restrictive maybe, dont know.
While owning two tunnel (v-drive) hulls and living in Minnesota where most all boats are quiet, I had considered dumping the headers down thru the the raised tunnels (as far back as possible), using those neat angled SS side exhaust tips. At speed the exhaust would be exiting into 'air' but be very quiet under the boat, however at idle it would just bubble up out & under the transom. Has anyone else ever considered doing this?? Jocko

10. Originally Posted by jockorace

While owning two tunnel (v-drive) hulls and living in Minnesota where most all boats are quiet, I had considered dumping the headers down thru the the raised tunnels (as far back as possible), using those neat angled SS side exhaust tips. At speed the exhaust would be exiting into 'air' but be very quiet under the boat, however at idle it would just bubble up out & under the transom. Has anyone else ever considered doing this?? Jocko
The big offshore cats do this a lot, and they have a smaller bypass that allows some ex to escape during idle or when the ex is under water.

11. I kinda figured SOMEBODY must have tried this before. I was going to use some water injected Basset thru-transom style headers then just turn them 45 degree down as close to the transom as possible. My thought was that this would be no different at idle than transom tips that are way underwater with the boat at rest. (Kinda like the tips you can barely see on my old Daytona in this pic). Hmmm.........guess I'll have to get another tunnel hull and try it! Jocko

12. Originally Posted by cs19
Air in the suction=bad news. Dump it under the boat maybe, get some lift. Could be super restrictive maybe, dont know.
Ok, what about introducing the exhaust after the impeller?

13. ?????why?????

14. Originally Posted by Luckie Stiff
Ok, what about introducing the exhaust after the impeller?
350-450 psi bowl psi U would hydraulic it.

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