Sonex-A purchase - What to look for

[Kai]

At our low rpm 3000 +/-, why do we need dual ports and bigger valves. This is for high rpm power, no?

For (at least) two reasons:
1) nobody makes new single port heads any more (maybe remanufactured?)
2) the engines are by design basically so low on power that anything that could possibly restrict flow to the cylinders is done away with.

[Hambone]

Thanks for the wealth of advice and experience. I’m taking it all on board as I contemplate the way forward.

Edit: I’m certainly intrigued by the variety of heads on offer. I have a buddy who is an air-cooled VW specialist, albeit non-aviation. I’ll seek his advice, too.

[DCASonex]

Hambone, Kia is right, you have been flying alone. Find your local EAA chapter, Closest here is about 65 mile drive, but elected to join one about 85 miles from here. For the right group pf people, it is worth the longer drive. so if you have options, check out more than one local.

One way or the other life is one long learning experience. Enjoy the ride.

David A.

[Hambone]

Hambone, Kia is right, you have been flying alone. Find your local EAA chapter, Closest here is about 65 mile drive, but elected to join one about 85 miles from here. For the right group pf people, it is worth the longer drive. so if you have options, check out more than one local.

One way or the other life is one long learning experience. Enjoy the ride.

David A.

Thanks, David.

I'm a member of the EAA chapter here, but there really isn't any building going on. Perhaps I should find another one, even if it requires travel.

[Area 51%]

As I see it, the elephant in the room is Chinese parts made of Chinese materials.

Amen!

Hey Hey Hey...be nice...those are my old brake drums you're talking about.

[Kai]

Hambone, Kia is right, you have been flying alone. Find your local EAA chapter, Closest here is about 65 mile drive, but elected to join one about 85 miles from here. For the right group pf people, it is worth the longer drive. so if you have options, check out more than one local.

One way or the other life is one long learning experience. Enjoy the ride.

David A.

David, buddy

After all these years with Jabs and Camits and I don´t know what, is´nt it about time you reprogram your spell checker? Kia is a korean auto make- and my name is Kai. It is, by the way, ancient northern german (frisian, actually) dialect, short for Karl (or Charles).

Blueskies!

[Kai]

Thanks for the wealth of advice and experience. I’m taking it all on board as I contemplate the way forward.

Edit: I’m certainly intrigued by the variety of heads on offer. I have a buddy who is an air-cooled VW specialist, albeit non-aviation. I’ll seek his advice, too.

If you do, you need to thread with the utmost care! Bear in mind that the only kind of cooling he knows about is a huge fan that blows enormous quantities of cooling air over the heads. Compared to what he is used to, pressure differensial cooled VW-1 aeroderivatives have almost no cooling at all!

[Bryan Cotton]

...pressure differensial cooled VW-1 aeroderivatives have almost no cooling at all!

That's been said a couple of times. We do have some data courtesy of Peter:

Fyi something to consider. I measured the cooling air PD across the engine from above the engine to near the right side exit.
The values were...at IAS
2" at 65 mph
2.5" at 75 mph
3" at 85 mph
3.5" at 95 mph
4" at 100 mph
4.5" at 110 mph
5" at 120 mph

I used an old school manometer and my IAS is what it is. The values are rounded. Another airplane will likely have different results. But its a baseline. Attempts at flow improvements will yield greater (hopefully), the same or lower DPs at these speeds. I'll likely confirm the numbers before I make any changes. I'm also going to check the DP across the oil cooler.

It would be interesting to see actual data for a VW type 1 fan, rather than a subjective statement. It does have the advantage of maximum cooling at maximum RPM, which can be maximum power if your foot is on the floor. It also likely has less power - even if they build a 120HP race motor, how long can you hold that amount of power? Not for 20 minutes as you climb to 8000'. I really don't think a fan, assuming we could magically place one, would be the answer for our application. The place where the cooling is lacking is during max throttle climb at lower airspeeds.

[Kai]

Further to Bryan´s posting, I came across this on the net: http://www.offroadvw.net/tech/wes/fan.html

Further it appears that at 5000 crankshaft rpm the standard VW-1 fan supplies some 1700-1800 cfm- that is with the gearing supplied by VW. Interesting for us is what it would supply at say 3000 rpm, where the aeroderivatives are often operated. And how much heat would then have to be grotten rid of- that is the residual heat from the development of say som 65-70 HP on the crank.

The pressure differensial data between air inlet and air outlet in the Sonex cowling listed above do not correspond very well with the requirements listed in the Jab installation manual for their 4 cyl engines: 60mm (2.5 in) wg PD at 1.3 Vs. Of course it requires a super tight cooling plenum and nicely finished head fins, like the Jabs have coming out of production.

Of course some kind of fan cooling is not the answer to VW-1 cooling requirements. Still something has to be done with those engines that are cooking their heads and/or are overheating their valves. So I wonder what the Corvair community has done to get on top of this?

[WesRagle]

Hi Guys,

Concerning the pressure differential across the cooling baffles, this graph shows what we have to work with.



Most of us cruise around 100 Kts. 0.5 InHg = 6.80435 Inches of Water.

I measured the differential on my Onex but didn't record air speed.



The high pressure tube was routed through a blast tube and taped flat to the rear bulkhead of the baffling. The reference tube was taped to an oil cooler hose and basically just dangling in space behind the engine.

I climbed to 2000' AGL (~5000 ft DA), leveled off and throttled for 3000 RPM cruise. I let everything stabilize for about 4 minutes and then noted temperatures. Oil Temp 197, hottest CHT 327, EGTs in the mid 1200's, and pressure drop across the baffling was 6.5 in. H2O. 6.5 is what Capt. Google says is needed to cool an O-360.

So there is one more data point.

And here is a link to a study specifically targeting aero VW cooling.

https://www.mdpi.com/2504-3900/39/1/4/pdf

Wes