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Turbo-Cool Spinners or Vented Spinners on glow or gas?....why not?

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Turbo-Cool Spinners or Vented Spinners on glow or gas?....why not?

Old 08-12-2016, 06:29 AM
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Default Turbo-Cool Spinners or Vented Spinners on glow or gas?....why not?

I can't seem to find any information on exactly why it is that a vented or Tru-Turn Turbo Cool spinner can NOT be used on a glow or gas engine. Can anyone shed any light on this? I am just curious and wish to keep my Saito 180 as cool as possible, and noticed these when shopping for a new spinner. I don't want to use a Sullivan starter as it tears up the spinners so bad, so I hope to use a stick. Otherwise I cannot see a reason this cannot be used. Thanks.
Old 08-12-2016, 09:55 AM
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Who knows how wel they'd hold up, but I can say with certainty they won't help with cooling your Saito. 90% of the heat is in the engine's head, well away from the airflow that a turbo cool spinner creates. Electric motors have all of their heat directly behind the spinner which is why the vented designs help them. If you want to ensure good cooling, do some research on building effecting baffles to direct cooling air through the fins of your engine and consider making an NACA duct to create a good vacuum behind it.
Old 08-17-2016, 02:25 PM
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Originally Posted by jester_s1
Electric motors have all of their heat directly behind the spinner which is why the vented designs help them.

Ahh...good thought there. Makes sense. I figured extra air is extra air, or...extra frontal area not blocked by the spinner would just mean more air into the cowling area...but cooling the case isn't really necessary, at least in a system where the cool air charge moves through the crankcase (two strokes). Thanks. _MPH
Old 08-18-2016, 01:31 PM
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Also, more is not better when it comes to cooling air. A cowl can only flow as much air as it can exhaust. Intake flow is rarely a real problem, but getting the air out of the cowl is the real trick. What really keeps engines cool is for there to be a small vacuum behind the cooling area of the head inside the cowl that is pulling air through and then out. There are lots of ways to create that little vacuum and many threads on the subject, so I'll let you research that on your own. But when the intake area is allowing air into the cowling that is not actually being used to cool the engine, that air will flow around the engine and into the vacuum instead of the air you need going through the cooling fins. There are many, many threads on the various groups from guys who had overheating engines, many of whom had enlarged their air intake in front of the cowl to improve airflow. But the best cooling setups are the ones where the whole frontal intake area is closed except for just the area of the cooling fins. Then baffling is used to direct the air to the fins if the front of the cowl is significantly forward of the engine. Baffling prevents the air from taking the path of least resistance and going around the engine. Then an NACA duct or some kind of scoop setup will be behind the engine to create that vacuum. In such a setup, the actual air flow through the cowling is fairly low, but all of it is going through the cooling fins so it works better than a high volume setup that lets the air swirl around in the cowl and then exit without ever touching the hottest part of the engine.
Old 08-19-2016, 12:14 PM
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Thanks for information!

I do have a fair understanding of pressure differential, having a patent in pumping technology, and also having been a race mechanic in motorcycle road racing for many years. Having spent a few hours in front of a flow bench, porting cylinders, cutting valve seats and then retesting.........has not taught me a darn thing, which just goes to show you how tricky it can be, and not necessarily intuitive. LOL
The question arose as a result of my shopping for a spinner, and seeing these for the first time piqued my curiosity. Your point is well taken with regards to "effective" or more laminar air flow, vs. turbulence, and the damming effect when outflow is less than equal to inflow yada yada. Proper air "management" is, or course essential. After placing the cowling over my Saito 1.80 and looking at the stock results, I am pretty happy with what I am seeing, and don't think I will have to do much to optimize this. Great forum! Thanks!

_MPH



"Superman ain't got nothin' on me. I've destroyed 10 airplanes using just my thumbs!"
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Last edited by melttin; 08-19-2016 at 12:18 PM.
Old 08-19-2016, 06:44 PM
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It looks like your intake area is pretty much perfect there. You will probably benefit from blocking the side inlets though, as they essentially act as a vacuum leak in flight. It may not matter though in practical use.

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