Question in fluid dynamics - any engineers on board??

[lakercr]

I have a water cooled turbo mounted on my RX in the space that was previously occuped by the exhaust can. Ideally, I'd like to 'T" into the heat exchanger (cross pipe) on one side of the sled, run a line from the "T" through the turbo, then return it at the other side of the cross pipe. My question is, will I actually get flow through this line, or will the pressure equalize between the take-off and return? At first I thought this would work, then I got the equalized pressure idea in my head and figured it wouldn't, my latest thought is that I seem to recall a law of fluid dynamics that says for a fluid moving through a venturi, the pressure upstream is always greater than the pressure at a given point downstream (assuming constant diameter), which would mean it would work...

Thoughts??

 

[monker]

If the flow is unrestricted the I think you will get some through the turbo. If you need pressure, then it's hard to say. I would think the coolant would take the easiest path which would be through the crossover tube. Why not just remove the crossover tube and go straight through the turbo? What is the layout on the turbo like? Could you go out of the heat exchanger-into the turbo-out of the turbo-into the crossover tube?

 

[lakercr]

Too restrictive. You'd be going from a 1"i.d. hose to a 1/4" i.d....

 

[vmaxjohn]

I'm not an engineer, but I play one on the computer...

It's ok to have equalized pressure I think, as long as there's good velocity of the coolant. If you add alot of coolant and piping, I'd have to guess that the water pump would have a hard time keeping up.

Coolant systems operate at a steady pressure all the time, it'll fluctuate when the thermostate opens with a spike just before that event.

Basically, if you look at it, and don't have many restrictions in your add ons, I think you should be ok.
The venturii thing is correct, it speeds up through the restriction and the pressure is greater on a push system. On a pull system, you'd have lower pressure. Interesting topic!

 

[monker]

With the different diameters you're dealing with the path of least resistance. There will be some flow through the 1/4" line to the turbo, but very minimal. If you could somehow decrease the diameter of the crossover tube between the 2 T's, you would increase the flow through the turbo.

 

[lakercr]

Yeah, but I wouldn't want to restrict the daimeter of the main tube, as all of the coolant for the engine has to pass throught there. The bearing in the turbo also has an oil supply/return that will help cool it, so I'm wondering how much the water is even going to be neccessary. I know that the OEM's put the water cooling in to keep warranty claims down for those people who were too lazy to do frequent oil changes on their torbocharged cars. The added cooling to the bearing pretty much eliminates coking of the oil. I plan to change the oil frequently, so I'm not sure how much of an issue this really is (don't mind the idea of having the extra insurance though).

 

[vmaxjohn]

The quality of the oil is almost more important. A turbo timer helps there too.

I see your diliema now, with the two lines. Here's an idea, might be crazy.

If you built a small holding tank that sits above the turbo, when you shut it off, the coolant would trickle down through the bearing passage even though the motor would be shut down. Not sure if this would work, but it might be a way to keep things circulating.

What about a second pump of the electric nature? Hell, what about a secondary system?

 

[lakercr]

Oil supply isn't a problem. The RX makes plenty (almost too much) oil pressure. The oil return is gravity fed, and I'm returning it to the bottom of the sump, so I've got a pretty good gradient to work with. The water is a seperate issue. Worst case scenario, I take the carb heat supply line and run it throught the turbo then return it to the system where Yamaha does now. I'd prefer not to run another line to the back of the sled if I don't need to (i.e. tap into the rear tube). I have a conduit running down the pto side of the sled under the tunnel for my oil lines and the wiring for the O2 sensor. I could run the water in there as well if I had to...

 

[kmer]

I have a water cooled turbo mounted on my RX in the space that was previously occuped by the exhaust can. Ideally, I'd like to 'T" into the heat exchanger (cross pipe) on one side of the sled, run a line from the "T" through the turbo, then return it at the other side of the cross pipe. My question is, will I actually get flow through this line, or will the pressure equalize between the take-off and return? At first I thought this would work, then I got the equalized pressure idea in my head and figured it wouldn't, my latest thought is that I seem to recall a law of fluid dynamics that says for a fluid moving through a venturi, the pressure upstream is always greater than the pressure at a given point downstream (assuming constant diameter), which would mean it would work...

Thoughts??

The venturi effect will be minimal, if any. The diameter would have to be reduced (venturi throat) to see an increase in pressure.

Build a new cross over tube, 'slightly smaller' but only enough to compensate for the cross-sectional area of the turbo cooling line. Measure the inside diamter (I.D.) of the turbo line, calculate the area and subtract that from the area of the cross over tube to get your new size. Then, neglecting friction losses, you should have fairly well balanced flow.

If the reduced diameter of the cross over tube doesn't suit your liking, you could try an inline valve that you could close partially and adjust. That might cause other concerns though.