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rv6ejguy

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The Beech Queen Air used supercharged IGSO-540s. After that, everything from Lycoming and Continental have been turbocharged to my knowledge. If you want to experiment with supercharging, that's fine, a number of people have done it and had decent results. I helped out on a Harmon Rocket which has raced at Reno for the last 2 seasons with a Vortec supercharger. It worked but we had belt slipping and boost control issues and it's really only set up to run properly at one altitude.

A couple of my customers have tried superchargers on Rotax 912 engines. They work all right within a narrow altitude window but again, controlling boost is a recurring problem.
 

nerobro

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The Beech Queen Air used supercharged IGSO-540s. *snip*
A couple of my customers have tried superchargers on Rotax 912 engines. They work all right within a narrow altitude window but again, controlling boost is a recurring problem.
I love your posts. Interesting, useful, and relevant.
 

bmcj

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My DGA-15 had the 450hp version of the R-985 with the internal supercharger. Never had any problems or complaints with it.

(I know the R-985 was called the Wasp Jr, but for some reason I always felt more comfortable calling it the 985)
 

rv6ejguy

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My DGA-15 had the 450hp version of the R-985 with the internal supercharger. Never had any problems or complaints with it.

(I know the R-985 was called the Wasp Jr, but for some reason I always felt more comfortable calling it the 985)
Single stage, single speed stuff in the radials and Allisons was usually very reliable because it's simple but the critical altitude is usually pretty low. Probably ok for most GA aircraft though.
 

rv6ejguy

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And then there's Rotrex.. :) Rotrex A/S
Interesting but it still draws 5000 watts- 357 amps @ 14 volts to move enough air for 80hp at an unspecified pressure ratio, obviously only for transient response which is unimportant in aircraft since it draws about double amperage ofwhat a starter motor does. Must be running some hefty cable to it.
 

mcrae0104

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Here is an example of a supercharger with an intercooler (actually I think it's an aftercooler since it's not between the two compressor stages) on a Merlin:

merlin-supercharger.jpg
 

cheapracer

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For those technically interested in all things mechanical, just for fun research Comprex Supercharging and get your head around how they work.

Same principle as a 2 strokes exhaust expansion chamber wave supercharging, incredibly simple while being complicated at the same time.
 

rv6ejguy

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For those technically interested in all things mechanical, just for fun research Comprex Supercharging and get your head around how they work.

Same principle as a 2 strokes exhaust expansion chamber wave supercharging, incredibly simple while being complicated at the same time.

I believe Ferrari fielded some Comprex supercharged F1 cars in the late '70s or early '80s but they were quickly supplanted by turbos.
 

BobbyZ

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Its common knowledge that once you get past mild displacement increases with VW's that you lose reliability and run into other issues.

Its just ironic that when someone mentions another way to increase hp the consensus is go bigger.But in a different thread increasing displacement tends to get frowned upon at times.

I personally would prefer a close to stock displacement bottom end built with bullet proof components and forced induction over a displacment increase to 2+ L in a VW to reach the same level of HP.People tend to think that HP levels alone are the sole limiting factor to the VW's head heat issue and while it is the largest factor one way around this is to make more power at a lower RPM to enable more cooling between strokes.This is where forced induction comes into play ;)

Now I doubt this is the right supercharger for the job but if the OP wants to learn the real facts about FI principles there are plenty of resources where he can find out if this charger will flow enough for a VW.Even if the project never materializes,just doing this will teach you a lot along the way;)

I'm partial to Lysholm chargers as I have one on my G60 Corrado but realistically for my project and planes I'd go with a turbo.Like rv6ejguy there are plenty of modern turbo's available that will spool quite nicely at rpm ranges that are ideal for aircraft and while I may not use a VW in my plane.I have a few K03 and K04 turbos from other projects over the years that I intend to play around with on my Karmen Ghia's motor.I firmly believe that i can get close 90hp+ from a VW without having to spin it to the moon to get there with the proper cam,fuel injection and turbo.If it works out as I hope then I'll build a VW for the air and if not I'll still have a torquey and quick little Ghia in the garage ;)

It's 2016 folks we have the technology to safely turn up the boost more than just "normalizng" these days.I sometimes just dont get how people can complain so extensively about the lack of technology in areas on one hand yet they'll shoot down anyone who asks about things on the other and I mean this for a whole range of things not just this thread.
 

Vigilant1

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People tend to think that HP levels alone are the sole limiting factor to the VW's head heat issue and while it is the largest factor one way around this is to make more power at a lower RPM to enable more cooling between strokes.This is where forced induction comes into play ;)
Can you explain how that works? High RPM or low RPM, the exact same share of time will be spent in "cooling" strokes and "heating" strokes.

The best measure of the amount of heat that needs to be shed by the heads (and cylinders, and everything else) is the amount of fuel burned. If you plan to boost a 1600cc engine to make 75HP, it will be burning the same amount of fuel and making the same amount of heat as a 2180CC NA engine producing 75HP, and have the same issues with that heat. Maybe more. It will also cost more, have more things to go wrong, and be heavier. Since you'll be running them at far higher than "stock" pressures, you'll also need to make sure you get high-quality small pistons, cylinders, crank, bearings, rods, etc--the same race-quality parts that are widely available in the larger sizes.

But, maybe you can make it work.

Forced induction makes a lot of sense in many applications, but in this case I don't see the advantage over just bolting on some easily available displacement (that weighs far less than a TC and the necessary plumbing). I'm not "shooting you down," just asking for details on the advantages you see.
 
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Swampyankee

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Screw, Roots, Lysholm, piston, scroll, and rotary vane machines are positive displacement compressors: their pressure ratio is set by their geometry. Centrifugal, mixed-flow, and axial-flow compressors are dynamic compressors, where the pressure ratio depends on rpm (and geometry and Mach number and Reynolds number and...) and the flow conditions.

As an aside, dynamic compressors tend to be much more efficient than positive displacement units.
 

BobbyZ

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Can you explain how that works? High RPM or low RPM, the exact same share of time will be spent in "cooling" strokes and "heating" strokes.

The best measure of the amount of heat that needs to be shed by the heads (and cylinders, and everything else) is the amount of fuel burned. If you plan to boost a 1600cc engine to make 75HP, it will be burning the same amount of fuel and making the same amount of heat as a 2180CC NA engine producing 75HP, and have the same issues with that heat. Maybe more. It will also cost more, have more things to go wrong, and be heavier. Since you'll be running them at far higher than "stock" pressures, you'll also need to make sure you get high-quality small pistons, cylinders, crank, bearings, rods, etc--the same race-quality parts that are widely available in the larger sizes.

But, maybe you can make it work.

Forced induction makes a lot of sense in many applications, but in this case I don't see the advantage over just bolting on some easily available displacement (that weighs far less than a TC and the necessary plumbing). I'm not "shooting you down," just asking for details on the advantages you see.

The simplest way to put it is,you can generate the same amount of power at much lower RPM's along with being able to create a long flat power curve and that means less friction and therefore less heat in the oil.Now I know that isnt directly related to the head heat issue as most will see it,but something else you need to think about is if you are able to generate HP at a lower RPM there is also more time between power strokes to allow for cooling then you'd have at a higher RPM.

Cooler oil,more material in the head and cylinders and more time between power strokes all equals a cooler running engine.Now some of this is offset by heat generated from the turbo but with the amount of airflow generated by a aircraft this is going to be a lot less than most assume.Most if not all of the examples of a similar setup are located in rear engine vw's ;)

As far as "running them at far higher than "stock" pressures",goes.This is something that gets thrown around all too often without a complete understanding of internal stresses on a engine.Chances are that the stresses on internal components like the rods,crank and bearings will be less then you'll see on a "Big Bore kit" that has to sling heavier parts around.This is because you are slinging less weight around at lower RPM's.As a bonus the cases will also see less stress and for the most part all the components are going to be seeing stresses closer to their original design,except for the pistons,rings and valves.While they will see increased stresses it wont be that far out of line of that of the big bore motor.

To simplify things a 80 HP bang is pretty close as far as stresses between the two go.Yes the turbo will increase the stress over a stock motor but ironically it will see less stress in most areas when compared to the big bore motor ;) Most of the VW case issues are created by slinging heavier parts around at increased RPM's,ironically the forces created by the increased bang is the least of these issues in the big picture.

To put things simply,with the right turbo you'll be able to generate the same HP levels(if not slightly more) at lower RPM's spinning lighter components around.

Yes they add some more parts and a little bit of complexity and cost but this is another argument that is almost a moot point these days.Modern turbos are extremely reliable and in the rare case of failure it is usually not without some warning nor is it usually completely disabling to the engine.As far as cost goes,the turbos that would be ideal for this purpose most likely can be sourced from a OEM application where people generally replace them with aftermarket units for increased HP.I've yet to compare flow numbers with the compressor map but I'm leaning towards a Borg Warner K03 series turbo from a OEM later model VW and these are extremely reliable and can be had for cheap.

In my opinion there is simply very few if any reasons to avoid using a turbo these days.With modern turbos we're able to spool them very early and create more power down low with a linear curve on up.I see no reason why adding one to a VW wont allow a nice boost of usable power down low while allowing it to be maintained at altitude and it honestly may put the mythical 100 hp VW conversion withing reach :lick:
 

rv6ejguy

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My company proved the reliability of stock block based turbo engines long ago in racing. Our turbo engines were able to slay atmo engines with over twice our displacement race after race going on to win 7 championships. The engines were way cheaper, way more reliable and way more powerful than our competitors high revving big displacement non-turbo engines. The bottom ends were completely stock except for forged pistons and SPS rod bolts. I actually used OTS Mahle VW pistons in our 1700 and 2400cc Toyota engines. The mechanical stresses are indeed lower at lower rpms, with a bit of boost, at the same hp level.

The typical kit VW components like cranks, rods and pistons are easily capable of taking the loads imposed at the 100hp level and and 3500 rpm pretty much forever. You'd need a bigger oil cooler almost for sure. The only big question is- could you reject the heat from the heads?
 
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Vigilant1

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if you are able to generate HP at a lower RPM there is also more time between power strokes to allow for cooling then you'd have at a higher RPM.
Thanks for your explanation.
What you've written above is problematic. High RPM or low RPM, a 4 stroke engine spends 1/4 of its time on the power stroke. The time between individual power strokes makes no difference (after all, at low RPMs the heads/cyls are also absorbing heat >during< each power stroke for longer than they would be at higher RPMs). If you're making the same amount of horsepower, you are making the same amount of waste heat that needs to tolerated by the exhaust valves/seats and eventually shed by the fins to the air.

Good luck with your project.
 

Aviator168

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I am not an engine expert but I dealt with heat exchangers before and slept in Holiday Express Inn last night ;). As temperature goes up, heat transfer becomes much quicker. You will be surprised the extra amount of heat transferred from the source if the temperature was raised by 1 degree. And beside, a lot of the heat is carried away by oil; that's probably why BobbyZ said you might need a bigger oil cooler.
 

Vigilant1

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I am not an engine expert but I dealt with heat exchangers before and slept in Holiday Express Inn last night ;). As temperature goes up, heat transfer becomes much quicker. You will be surprised the extra amount of heat transferred from the source if the temperature was raised by 1 degree.
Here's the equation for forced convective heat transfer:

heat transferred per unit time= Area x heat transfer coefficient of the fluid x difference in temperature between the fluid and the heat exchanger surface.

So, the heat transferred varies as a linear function of the temp difference between the fluid (e.g. air or oil) and the engine temp. Example:
If the air doing the cooling is 75 deg F and the cylinder head temp is 375 degrees, then we'd get 350 arbitrary cooling units. If the temp of the cylinder head goes to 450 deg F (expect very short valve life), then we'd get 375 arbitrary cooling units, or an increase of just 7%.
Not a big difference in cooling, and a big difference in expected valve/valve seat life. One degree would make a difference in some other applications (e.g air conditioning units, etc), but not this one (since the delta T is already so high).

And this is before we talk about detonation.
 
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Aviator168

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heat transferred per unit time= Area x heat transfer coefficient of the fluid x difference in temperature between the fluid and the heat exchanger surface.
I just want to know what you are using for "heat transfer coefficient of the fluid" because this is critical to a heat exchanger. I am sure BobbyZ wants to increase cylinder head oil flow to remove heat through higher convection.
 

BobbyZ

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I just want to know what you are using for "heat transfer coefficient of the fluid" because this is critical to a heat exchanger. I am sure BobbyZ wants to increase cylinder head oil flow to remove heat through higher convection.
With my project my goal is to make big bore power at a lower RPM so his point of the heat is pointless for the most part to be honest.I'm looking for around 80 hp but lower in the curve,anything else we get will be icing on the cake so to speak ;)

Second I hope to have a little extra "emergency power" on tap but for the point of this argument there's no point in muddying the water.

I've been dealing with air and watercooled VW's for close to 20 years now and I feel my goals are well within reach but we'll see when I pull my Ghia a part.I've got several different heads to play with along with access to a dyno cell and just about everything I need to undertake such a project.

Lastly while I doubt that I'll go through the trouble I've had some talks about adapting oil squirters from a 2l ABA VW or Porsche motor to cool the pistons if need be ;) It's nothing that hasnt been done before it just isnt the most popular mod around.:speechles
 

Vigilant1

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I just want to know what you are using for "heat transfer coefficient of the fluid" because this is critical to a heat exchanger. I am sure BobbyZ wants to increase cylinder head oil flow to remove heat through higher convection.
I thought the point you were trying to make was that BobbyZ's engine would shed heat better because he's be raising the temperature of the heads, thus more air cooling. For that purpose, the heat transfer coefficient of the air makes no difference if we're only addressing your point ("normal" head temps vs higher head temps yield only a small difference in heat lost, much shorter valve/valve seat life)

Use of lots of extra oil to cool the heads in a VW can be done. It requires an additional high-capacity oil pump (or an oil pump with another stage, which are available), a pickup line in the pan and spray bars under the valve covers. It can help somewhat, takes gallons of oil per minute (which costs some power), but still is not especially effective at keeping the valve seats cool. All the extra oil inside the rocker assembly gets frothed up a lot and also robs a bit of HP. It's been tried by those pushing a VW to the limits, and it hasn't gotten the job done. The BMW boxer engines do use oil to cool the heads, but they are designed for that. Oil has a considerably lower heat transfer coefficient than water or water/glycol, so more of it has to be pumped.
 

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