VW Heads Designed for Aircraft- Poll

[Hot Wings]

I did not read through the entire thread, but I though that there were all ready some water cooled VW heads out there, at least for a while.

Beetle Flyer 2004 by Great Plains Aircraft

There were some and there are at least a couple that have been developed, but never put into production. VW went down this path with the Vanagon. The productiion numbers were never high enough to make them attractive to the HBA crowd.

I'd skip the air-cooled and go straight to liquid cooled, but then we run into the chicken/egg thing. There just aren't any airframes available that were designed for liquid cooled engines in this Hp range. Trying to stuff the radiators in the cowl or under the belly in a plane designed for an air-cooled engine has been proven to be far more problematic than adapting one air-cooled engine to an airframe designed for another air-cooled engine.

 

[Tornado Flyer]

I see no mention of the SCAT heads. I would think they are designed for a lot more power than stock.

 

[STDJantar2]

"I'd skip the air-cooled and go straight to liquid cooled"

So did Subaru....

 

[Bill-Higdon]

I see no mention of the SCAT heads. I would think they are designed for a lot more power than stock.

The Scat heads were designed for racing, compare the cooling fins between the scat head & a regular VW head, also search Bob Hoover's VW blog for what he says about the Scat heads..

 

[Bill-Higdon]

Limbach Airplane Engines: Aircraft Engine Maintenance, Small Engine Manufacturer shows some liquid cooled heads on their type 4 derivative engines

 

[dougwanderson]

?? Why would water/glycol be needed? Oil alone will do the job in this case, just pump a lot of it through the heads using a high volume/ low pressure stage added to the existing pump. A second system, separate radiator, etc is a lot of weight.

The heat rejection ability of the present heads is the thing that limits the HP of theType 1 VW. But push it above 80 hp and other things start to break/wear out fast (case cracks, bearing saddles, etc). IMO, the goal should be even better reliability/longevity at 75 to 80 hp max (through lower head temps, among other things), not moving the goalposts (again) to more HP. It has been tried a lot.

Heat transfer coefficient may be why water is used instead of oil

 

[Vigilant1]

Heat transfer coefficient may be why water is used instead of oil

Yes, the heat capacity of water or water/glycol is greater than oil. But a lot of oil would be sufficient to get reduced CHTs at 80 hp. To get more than 80 hp (and thereby potentially benefit from the weight and complexity of water based coolant) we'd also need some combination of significantly higher RPMs and/or higher compression ratios. The Type 1 engine isn't mechanically suited to operating like that for a long time. So, no good reason to do it. It has been tried.

 

[dougwanderson]

I think people ask way to much of the humble aircooled vw in a 1600 to 1760 ish and to ramp it up and be a viable low maintenance engine is not realistic.
There are better engines that are more modern in design and ability IE Jabiru Rotax 912 4 stroke snowmobile engines.
for a single seat low cost the vw is fine or a briggs kohler 1000CC.

 

[paraplane]

There is a pretty simple way to repeatedly produce identical wax investment without direct wax printing. Though one stage of the process being mentioned could utilize a 3-D printed component(s) for ease and accuracy. I like the idea especially if it's a project that you're wanting to do more for recreational value than commercial and there is value in if you are successful on updating an older design.

 

[Daleandee]

I realize this thread is a few months old but wanted to post these "New - High Velocity" 044 heads (perhaps someone has seen/tried them?):

044 Cylinder Heads

044 Cylinder Heads

www.cbperformance.com

I personally think these are not even near what is needed for a flight engine but they claim extra cooling fins, more metal between the valves, and some other changes that might make them a better offering than the older CB-044 heads. Had the original (CB-044) heads on a VW conversion and was not impressed ...

 

[Vigilant1]

I realize this thread is a few months old but wanted to post these "New - High Velocity" 044 heads (perhaps someone has seen/tried them?):

044 Cylinder Heads

044 Cylinder Heads

www.cbperformance.com

...

Dale,
I don't know anything about these, but would like to hear any opinions or experience with them. The pictures are groovy, and the extra cooling and meat between the valves would be nice. I wonder if any other baggage comes with the slightly moved valve seats (and slightly different angle where the valve stem touches the rocker arm?).

So much depends on the attention to detail when the head is made. Extra fins aren't very useful if ll the passages are filled with flash.

We did mention these before in another thread, but I don't think anyone had used them.
Mark

 

[Bill-Higdon]

I realize this thread is a few months old but wanted to post these "New - High Velocity" 044 heads (perhaps someone has seen/tried them?):

044 Cylinder Heads

044 Cylinder Heads

www.cbperformance.com

I personally think these are not even near what is needed for a flight engine but they claim extra cooling fins, more metal between the valves, and some other changes that might make them a better offering than the older CB-044 heads. Had the original (CB-044) heads on a VW conversion and was not impressed ...

I think the Late R/S/ Hover would call the "added cooling fins" on the bottom of the head "Snake Oil meant for the Kiddy trade". I don't see a way for air to flow through them.

 

[stanislavz]

Out of the box thinking - but it may be wise to search for high temp heat-pipe. It is lightes possible solution, to take away heat from spot, and distribute on bigger plate.

 

[Hot Wings]

It is lightes possible solution, to take away heat from spot,

The heat pipe idea has been brought up before. It sounds good in theory but so far no one has spent any time implementing the concept.
There are other already proven methods to remove heat from the troublesome exhaust valve. Both Porsche and the motorcycle world have spent a lot of time on this air-cooled head problem. All we have to do is copy what they have done.
There are only 2 really good solutions to using the VW engine at higher power levels for aviation use:

A new purpose designed air-cooled casting that isn't constrained by the need to bolt onto a typical ground bound application.

A water-cooled head. This, IMHO, is the best solution but unfortunately it also requires air-frames that can be easily adapted or air-frames designed with water cooling as part of the original concept. Very few of of either exist.

 

[stanislavz]

There are other already proven methods to remove heat from the troublesome exhaust valve. Both Porsche and the motorcycle world have spent a lot of time on this air-cooled head problem.

But they are not running wot all day long.

I have rotax 912 sitting in a garage - air cooled cylinders and water cooled heads. In nice and neat package.. Happy to run at 6000 ++ rpm. But it is not needed for 3600 max rpm solution. Kind of overkill..

Maybe some drilled channels could be an good idea.

 

[Daleandee]

I think the Late R/S/ Hover would call the "added cooling fins" on the bottom of the head "Snake Oil meant for the Kiddy trade". I don't see a way for air to flow through them.

I didn't see any improvement in these heads that I thought would be helpful to the needs of aviators. There is a bit more metal between the valves but I'm not convinced that it is enough to prevent the cracking that oversize valves in VW heads are famous for. But it's been said many times that for the RPMs that VW drivers need to turn a prop those large valves are not needed. But the aviation market is small so we get to experiment with what is available ...

 

[Hot Wings]

But they are not running wot all day long.

They don't need to be run WOT for extended periods to prove the technology. Once the head mass is heat soaked (at normal operating temp) it is just BTU transfer/time.
RPM is only indirectly related to waste heat generation. Put a turbo on the Rotax to make the same power at 3600 rpm as it does at 6000 rpm and the waste heat generated will be essentially the same - disregarding gains due to the turbo.

 

[stanislavz]

RPM is only indirectly related to waste heat generation. Put a turbo on the Rotax to make the same power at 3600 rpm as it does at 6000 rpm and the waste heat generated will be essentially the same - disregarding gains due to the turbo.

It is. But - it will have same area / volume. So we may speak up here on max power per cylinder area ?

 

[Hot Wings]

So we may speak up here on max power per cylinder area ?

That IS pretty much what we are trying to optimize, though not so much power/cylinder area but waste heat transfer from a limited area. On the VW the primary limit is the heat transfer from the exhaust valve. Solve that one and we may find another area to be the limit.

Right now the generally accepted limit is around 80 Hp - regardless of the displacement. It has also been pretty well established that a just adding mass, in the form of dead end fins, does little to help other than increase the time to heat soak. Good for takeoff but not much help for cruise.

Increasing the power available from 60hp continuous/80hp takeoff to something like 80hp continuous/100hp takeoff means increasing the continuous heat rejection capacity by 33%. That means 33% more functional fin area for an air-cooled only head. That turns out to be pretty hard to do on a head originally designed to produce 30ish Hp peak and still make it compatable with the original engine configuration. In the ground bound version the base head was designed for 30ish Hp, which was also expected to be continuous with some operational margin. Aircraft have used up that margin.

So far NONE of the aftermarket heads have managed to increase the functional fin area 30%. That task is going to be left up to those of us that really want the added capacity for aircraft.
IMHO a better way is to follow the lead of others that have had to face the limitations of physics while trying to increase the power density of air-cooled engines. Oil-cooling and water-cooling have been the choices of those that have succeed.

 

[Vigilant1]

The heat pipe idea has been brought up before. It sounds good in theory but so far no one has spent any time implementing the concept.

It has been mentioned a few times, I brought it up in one of my first posts on HBA. I'll just say there was no applause. In theory it would be a good way to move heat from the exhaust side of the head to "somewhere else" (?) where it can be disposed of, but the practical considerations of doing that are significant.

There are other already proven methods to remove heat from the troublesome exhaust valve. Both Porsche and the motorcycle world have spent a lot of time on this air-cooled head problem. All we have to do is copy what they have done.
There are only 2 really good solutions to using the VW engine at higher power levels for aviation use:
A new purpose designed air-cooled casting that isn't constrained by the need to bolt onto a typical ground bound application.

A water-cooled head. This, IMHO, is the best solution but unfortunately it also requires air-frames that can be easily adapted or air-frames designed with water cooling as part of the original concept. Very few of of either exist.

I like the idea of better fins. I also think there may be some potential for oil cooling (squirters for the underside of the pistons, channels in the heads, or at least fins in the rocker gallery and LOTS of oilflow to cool the head and valve stems).

On the VW the primary limit is the heat transfer from the exhaust valve. Solve that one and we may find another area to be the limit.
. . .
Increasing the power available from 60hp continuous/80hp takeoff to something like 80hp continuous/100hp takeoff means increasing the continuous heat rejection capacity by 33%.

My impression is that the max continuous HP of the present Type 1 VW aero engines is about 70 HP (assuming good baffling, reasonable OATs, etc). And, I suspect that's pretty close to the mechanical limit of the bearing saddles and the magnesium case itself, at least if we want the case to last more than a few hundred hours.
That doesn't negate the value of a better head for aircraft use. Better cooling (fins, oil, or water) will keep the CHT cooler at that 70HP continuous output, which will increase the time between top overhauls and improve the inflight reliability of engines run at high power outputs. Also, better cooling will increase the time an engine can run at 80 HP or more before very high CHTs are reached. Smaller ports and valves with more meat between them will improve VE and reduce head cracking/maintenance.

The best "street" heads are pretty good right now, if the limitations are recognized and respected. A purpose-built head would give us more cushion. But, IMO, asking for significant additional continuous HP because we have more head cooling will just invite other problems and ill-placed gripes about the reliability/suitability of the base VW design for aircraft use. That's happened in the past.