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Kmccune

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If anyone is interested,over at the airvw and vw_conversions yahoo sites, these has been a pretty cool ;) new mod. It involves brazing or welding fin extensions onto the head. I'm not getting into a brazing vs tig discussion, so don't try. But they are having very good results. It is being tested on a redrive vw pulling a CH701, so very high rpms and drag with no cooling issues, even for extended taxi, fast cruise and long climbs. The idea was borrowed from Mr. Robert Hoover. I know a little bit about the guy doing it and I believe him to be a stand up guy that you can trust.

So the idea of a VW only being good for 36 or so hp is out the window, if this proves out in the long run.

Kevin
 

rtfm

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Hi,
Well, to a non-engine type, I have long considered this an obvious thing to do, but was puzzled by why no-one was doing it. I surmised that the actual welding would be difficult, and that the heat transfer between the head and the attached extensions would be poor.

But if this is working for these guys, then this is great news indeed.

Dan? Your thoughts?

Duncan
 

Kmccune

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Bob, said that the duraflux brazing was what made him announce it. Tig welding Al is outside the capability's of most home builders. If cooling proves out the Jab 2200 has a real competitor in build it your self form. Also read his blog google and yahoo know the way there.

Kevin
 

Kmccune

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Wayne Clagg, Has posted pics on the AirVW and Vwconversions Yahoo groups with temp info as well as a video. He has more on the Zenith bulders site but that info will cost you at least a set of plans to see;)

Kevin
 

Topaz

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...So the idea of a VW only being good for 36 or so hp is out the window, if this proves out in the long run.
It was never in the window, and whoever says so doesn't know what he or she is talking about. Great Plains, AeroVee, and Revmaster have been reliably getting 65hp out of airplane VW conversions for forty years or better. You need very good oil cooling to pull any more than 65hp out of even a Type 4 engine in aircraft use, but other than that... No problem.

I don't know where this "VW can only reliably produce 36hp" rumor got started, but it popped up about three years ago and just won't seem to die. It's just not true. Granted that the following is for automotive use and not quite as demanding as for an airplane, but my stock 914 2.0L produces 95hp out of essentially a standard Type 4 block with fuel injection and a different cam from Porsche. The European-spec 914 2.0L engine has higher compression and gets about 107hp, IIRC. All day long, every day. Even here in hot SoCal. The heads are externally little different than any other Type 4 engine, and use stock-type VW valve covers, the sole difference being that they have "Porsche" stamped into them instead.

Can we please put this "36hp" misinformation to rest? :ermm:
 

Hot Wings

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Can we please put this "36hp" misinformation to rest?
NO! (respectfully) Because it's not misinformation. Slightly exaggerated maybe.

65 hp throttled back to 60% is only 39 Hp and is about where those that have had good service life from a VW tend to fly. There is a reason most of the EZ's Q's and KR-2's have converted to Corvair, 0-200, or Jabiru. 65 Hp and 65 continuous Hp are 2 different things. The mentioned planes generally need the full 65 to perform as their ad specifications indicate they should.

Based on my limited experience of having built, installed, and maintained several hundred ground bound VW engines my opinion is that ~50 Hp of real, to the flywheel power on a continuous basis, is about the limit with a well sealed VW cooling system. Stick an identical motor under the average poorly sealed cowl with marginal pressure differential and it's going to cook.

I think I could build a Tp1 based VW that would produce 65 Hp and pass LSA certification with basically stock heads. I don't think I, or anyone else, can build one that will produce 65 continuous Hp, regardless of advertising claims.

One way to put this whole debate to rest once and for all is for one of the Big 4 VW conversion companies to publish results of a test run at a verified 65 Hp, preferably by a third party.

Once I see such, I may change my opinion. Till them I have to operate on what I've personally observed.
 

Topaz

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NO! (respectfully) Because it's not misinformation.
Yes, respectfully, it is. Absolutely is, 100%.

65 hp throttled back to 60% is only 39 Hp and is about where those that have had good service life from a VW tend to fly. There is a reason most of the EZ's Q's and KR-2's have converted to Corvair, 0-200, or Jabiru. 65 Hp and 65 continuous Hp are 2 different things. The mentioned planes generally need the full 65 to perform as their ad specifications indicate they should. ...
A few points:

No aircraft engine is run at 100% power all day long. Nobody is claiming 65hp continuous. Airplane engines aren't run that way. Saying they have to be able to run at 100% power "forever" is absurd. I'll even concede that that's what the FAA means by rated power. It's not what we actually use in airplanes, and it's not relevant to any reasonable discussion of power and reliability. Are you condemning the engine simply on the semantics of "rated power"?

None of the EZ's were spec'd for VW's. The first VariEZ proto had one for a little while, IIRC, but the aircraft was underpowered with it. 65hp didn't give it enough margin for hot-and-high operations in the very likely event of being used by heavy pilots. Rutan recommended, IIRC, the O-200 for the VariEZ and the O-360 for the LongEZ. Changing to an O-200 represents an increase from 65hp to 100hp. Apples to oranges. If he'd switched to, say, a 65hp Lyc O-145 or similar, I'd say you had a point. Same goes for the Q2, even though it was initially offered with the Revmaster. The aircraft was very short on span, and had a relatively high wing loading. Both mean more power required for climb. Within the spec'd MTOW, the airplane climbed reasonably. With common-weight pilots (which is to say, above the FAA-standard 175#, 5'10") and full fuel and baggage, the airplane had an insufficient climb rate. And pilots wanted even more speed. The O-200 powered Q200 was the answer to that. Again, a significant power increase, not an installation of a "certified" engine of the same rated power. This is in no way the fault of the VW engine, nor does it bear on their power output or reliability, which is what we're talking about here.

The KR-2s that were switched to other, higher-power engines were/are all well over the design empty weight, and were/are operating over design MTOW as well. This is an issue of the airplane being much heavier than it should be for the specified engine, not the engine failing to put out rated power. The pilots built overweight aircraft, operated them overweight, and needed more power to get back up to original specs. A KR-2, built and operated to the original specs (including empty weight and MTOW) flies just fine on a VW. I've seen a couple of them flying in to airshows. For years. Ken Rand was a little guy. He designed the airplane for himself, and the airplane performs just fine at those weights with the original VW installation. Cram a couple of 200# guys into an already overweight airplane and you can't fault the engine for what results.

VW's have been used successfully in thousands of aircraft here and in Europe since the 1960's. Tony Bingelis lists in the 1983 edition of Firewall Forward that VW's (of all displacements and power outputs, from 36-75hp) were, at the time, the #3 most-common installation in a list of 9780 homebuilts he surveyed, represented in 1075 of the aircraft. Are you saying that all those builders were duped? Or that their airplanes were falling out of the sky with burned-up engines? And everybody "kept the secret" for over forty years? All those Sonex and Xenos flying right now with AeroVee's? They're falling out of the sky with burned-up motors? I haven't heard such. Have you?

My Porsche is - I state again - rated 95hp. Stock from Porsche, off the showroom floor. The Euro-spec version with higher-compression pistons are rated 107hp stock from Porsche. This is a 1973 914 2.0L, so the only differences between my Porsche's engine and the regular VW Type 4 are the cam, induction, and the heads, because my car's engine uses fuel injectors. Those heads do not have any additional cooling arrangement over the regular V'dub heads. I've had my car running time trials at the old Riverside Raceway in 95°+ heat (prolly 110° on the black top), flat-out on 40% or more of the course length, pure stock, and the temp needle certainly wasn't moving much. (Riverside had a LONG back straight, a nice long sweeper at the end transitioning into another long front-straight. You could ride a 914 full-throttle through all but the very bottom and top end of the course - and had to, to keep up with the big-engined 911's and 944S and set up to pass them in the corners.) Are you actually trying to tell me that, in a properly-designed airplane cowl, that engine is worth only one-third of that power rating before it burns up? I completely understand that auto engines aren't "rated" at continuous power either, but again, nobody runs their airplane motor at 100% power continuously. Nobody.

...my opinion is that ~50 Hp of real, to the flywheel power on a continuous basis is about the limit... Stick an identical motor under the average poorly sealed cowl with marginal pressure differential and it's going to cook.
And a 65hp-rated engine, running at a completely-standard 75% power for cruise, is putting out 48hp. So where's the problem? Stick any engine in a poorly-designed cowl and it's going to cook. That's not an argument against the motor at all, it's an argument against sloppy cowl design. Please be reasonable.

Once I see such, I may change my opinion. Till them I have to operate on what I've personally observed.
When have you seen a fully-independent test of any engine? You certainly don't see them for Lycoming or Continental. Even for certification they run the tests themselves for the FAA. You're setting entirely unrealistic expectations for "proof" here.

Hot Wings, I appreciate the experience you may have, but what you're saying conflicts with reality. With proven history. VWs have been pulling and pushing airplanes through the air successfully for decades, both here and in Europe. When you can prove to me that they haven't been doing that, I'll change my opinion.
 
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Topaz

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That requires fan cooling, right?
What do you think is spinning on the front of most VW airplane installations? ;) Yes, my 914 has forced-air cooling. It also doesn't have ram-air cooling intakes facing into a 90-150mph airstream, either, which airplanes do.

What we're talking about for airplane installations is 2/3rds the power output of my 914. And about 1/2 of the power output in real-world continuous operation.

Seriously, VW used to be the auto conversion. They've got simply decades of experience behind them. But those were the days when homebuilts were a lot lighter and slower than they are now. 65hp is not enough for most two-seat sport kitplanes today, no matter what's spinning the prop. That's simple fact. Only very light, fairly low wing-loading (or large span) designs will find that to be enough power. Some of the sub-scale Cub replicas, the Sonex or Xenos, the old Sonerai, etc. In nearly every case of a kitplane being "upgraded" to a larger engine, you'll find the airplane was either over its design weight, too heavy a design to begin with for that amount of power, or the pilot just wanted more speed. It's not the fault of the VW engine that we're not designing airplanes suitable for it anymore. People just don't seem to understand that.
 
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Hot Wings

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. VWs have been pulling and pushing airplanes through the air successfully for decades, both here and in Europe. When you can prove to me that they haven't been doing that, I'll change my opinion.
I agree that the VW has been successfully used as an aircraft engine for decades. The Tipsy Nipper is first example that pops to mind. It also is dependent on what your definition of "successful" is

"What we've got here is...failure to communicate." - Cool Hand Luke

I'm not just talking about you and I but the whole of the experimental aviation community that debates this issue.

No aircraft engine is run at 100% power all day long. Airplane engines aren't run that way.

Yes, they are. I've run across many Cessna drivers, including instructors, that think the only reason to reduce the power setting is to save fuel. After all, "It's an aircraft engine. They were designed to run at full throttle all the time."

This attitude gets reinforced on these forums every time the subject of auto conversions comes up. How many times have you read someone say "But it's an auto engine. They weren't designed to run at full throttle like an aircraft engine"?

I, and apparently you, know that there is a big difference between the rated Hp and continuous Hp. In the industrial engine world the distinction is common and both figures are generally included in spec sheets and advertising. This situation does not seem to exist when talking about auto conversions and VW conversions in particular. The end result is that there are plenty of people buying, installing and flying "65 Hp" VW conversions and then complain when they need a valve job every 200 hours. I find it interesting that an O-200 at 65% (65 Hp) and is the most common replacement for a burned up "65 Hp" VW. ;)

This is a 1973 914 2.0L, so the only differences between my Porsche's engine and the regular VW Type 4 are the cam, induction, and the heads, because my car's engine uses fuel injectors. Those heads do not have any additional cooling arrangement over the regular V'dub heads


I too owned a 914. A '74 with a 2.0 (105 Hp IIRC). Perfectly average little vehicle, but with the hand brake on the wrong side of the seat. :speechles Other than being air-cooled, bolting up to the trans with the same bolt pattern, and sharing a few mundane internal bits they have nothing in common with a standard "Bug" engine. Comparing a Tp IV to TP 1 is about as useful as comparing it to a Corvair.

But to use your example, my 914 would hit about 135 top end and got ~35 mpg at 75 mph. That works out to around 26 Hp. Using the standard cube root rule of thumb that means that top speed at a full 105 Hp should be ~120 mph. That's close enough for ball park calculations to validate the results.

Take essentially the same engine, stick it in a VW bus, pack it to 5000 lbs gross weight and "cruise" down the highway against a head wind balls to the wall at 50mph in third gear you get 10 to 12 mpg. (~50 Hp)

I've had customers do exactly that. They engine will survive, if the last guy that replaced the clutch put the engine seal back in place, but service life is reduced. It the engine seal was missing, or they tried to run in 4 gear at the same speed it came back on a hook.

but again, nobody runs their airplane motor at 100% power continuously. Nobody.

Yes, They do, and not just in overloaded VW buses. They are the same ones that think that when they buy a 65 Hp VW aircraft conversion that it should be able to put out 65 Hp all day long - "just like an aircraft engine."

So, it seems we aren't so much in disagreement on the actual limitations of a VW engine, we just aren't using the same reference points?

It's not the fault of the VW engine that we're not designing airplanes suitable for it anymore. People just don't seem to understand that.

On this point we are in total agreement :ban:
Yet, there are still some out there that are trying to build VW engines capable of 65 continuous Hp, or more. It may very well be possible with the appropriate modifications. I don't think it will ever happen with a stock head casting.

We have a responsibility and duty to not reinforce the urban legend of 100% power for an aircraft engine. Not everyone understands that aircraft engines are not designed to run at 100% all the time. Many are quite surprised to learn that an engine only needs to be run at full power for 5 minutes at a time for each hour of test time to be LSA certified. It's been a while since I read part 33 but I seem to remember a similar, but more rigorous, test schedule there as well.
 

Topaz

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Okay, this is a reasonable discussion. Thanks for that. :)

I agree that the VW has been successfully used as an aircraft engine for decades. The Tipsy Nipper is first example that pops to mind. It also is dependent on what your definition of "successful" is

"What we've got here is...failure to communicate." - Cool Hand Luke

I'm not just talking about you and I but the whole of the experimental aviation community that debates this issue.
Well, there are strong opinions on both side of the auto-conversion fence. Not all the opinions are rational, and we both know it. I've heard quite a few opinions that there is no auto-conversion that's appropriate for aircraft use, which is patently absurd.

'No aircraft engine is run at 100% power all day long. Airplane engines aren't run that way.'
Yes, they are. I've run across many Cessna drivers, including instructors, that think the only reason to reduce the power setting is to save fuel. After all, "It's an aircraft engine. They were designed to run at full throttle all the time."
Okay, you probably have a point. I shouldn't have been so absolute about it - there's always idiots to take into account.

Most of my time is spent around airplanes and pilots who keep the throttle in the "not installed" position, but many of our tow pilots (who often also fly gliders) are of the crusty old sort that's flown darn near anything and everything. One of them has his left-seat rating in B-17s and he's got a right-seat checkout in an Heinkel He-111, for heaven's sake. Guys like that would dump you out of the cockpit for running the engine at 100% in cruise.

That atmosphere may have skewed my perceptions a bit, as I'm surrounded by exceptionally professional pilots most of the time. If there are nimrods out there flying C-150's at full throttle the whole trip, then I hope they own the airplane, so that they get to pay the maintenance bill.

I, and apparently you, know that there is a big difference between the rated Hp and continuous Hp. In the industrial engine world the distinction is common and both figures are generally included in spec sheets and advertising. This situation does not seem to exist when talking about auto conversions and VW conversions in particular. The end result is that there are plenty of people buying, installing and flying "65 Hp" VW conversions and then complain when they need a valve job every 200 hours. I find it interesting that an O-200 at 65% (65 Hp) and is the most common replacement for a burned up "65 Hp" VW. ;)
Okay, and here's where things start to go awry, I think, and get incorrect rumors started. The problem isn't the motor, it's the airplane and the builder, and sometimes the designer. If the airplane requires a solid 65hp continuous to cruise at spec, then a motor rated at 65hp isn't the right choice. Never was, regardless of the manufacturer listed on the data-plate. A Lycoming O-145 would be an equally poor choice for such an airplane, and would suffer the same short lifespan, or nearly so.

So what they do is put a more powerful motor in the airplane, one that can put out 65hp when run at 65-75% power.

This is an entirely different situation.

It's no reflection on the VW that it was put in such a heavy airplane that it had to be run at 100% all the time to meet the performance specs. As I said, an O-145 or similar wouldn't last much longer under those conditions, or at least wouldn't get anywhere near its rated TBO. In "that" airplane, an engine rated at 65hp is just too small, regardless of manufacturer.

The above is THE extremely important point, and one that generally gets lost in these discussions.

BTW, you'll note that Great Plains, for one, shows continuous and takeoff power ratings for all their engines, right up on the web page. Anybody that then expects to run "takeoff" power all day long for cruise is going to get exactly what they deserve. The different power ratings are out in plain sight.

Other than being air-cooled, bolting up to the trans with the same bolt pattern, and sharing a few mundane internal bits they have nothing in common with a standard "Bug" engine. Comparing a Tp IV to TP 1 is about as useful as comparing it to a Corvair.
Except that a Type IV is just as much a "VW engine" as a Type 1. Great Plains sells Type IV conversions for aircraft. I believe the others do, too.

So, it seems we aren't so much in disagreement on the actual limitations of a VW engine, we just aren't using the same reference points?
Fair enough. Now, let's get that word out to the people saying that VW's aren't any good as aero-conversions, and that "you can only expect 36hp out of them or they'll burn up." That's completely misleading, for the very reasons you and I are talking about here: If you tell a pilot that, they think you're talking about takeoff power, and that you can only reliably get 36hp out of any kind of VW even at full throttle. Which, I believe you and I agree, is simply not true.

That rumor has been circulating and spreading for about three years now. It's popped up a couple of times on this forum. People are rejecting VW installations on aircraft perfectly suitable for them based upon this unfounded rumor. It's helping to gut the lower end of the kit/plans aircraft market, because there are very few affordable 4-cycle engine choices in the 50-65hp range.

We have a responsibility and duty to not reinforce the urban legend of 100% power for an aircraft engine. Not everyone understands that aircraft engines are not designed to run at 100% all the time. Many are quite surprised to learn that an engine only needs to be run at full power for 5 minutes at a time for each hour of test time to be LSA certified. It's been a while since I read part 33 but I seem to remember a similar, but more rigorous, test schedule there as well.
Amen. I agree with you there absolutely! You and I are coming at it from different directions, but the same conclusion is true for both of us.

(Moving the 914 discussion down here as a sidebar)

I too owned a 914. A '74 with a 2.0 (105 Hp IIRC).
Yours must've had the Euro-spec pistons to get that much power out of it. IIRC the '74 2.0L had the same D-Jetronic injection as my '73, and I think the L-Jetronic injection (which gave more power) didn't show up until the '75 model year. I could go over to the bookshelf and check, but I'm feeling lazy and this is a sidebar. ;)

But to use your example, my 914 would hit about 135 top end and got ~35 mpg at 75 mph. That works out to around 26 Hp. Using the standard cube root rule of thumb that means that top speed at a full 105 Hp should be ~120 mph. That's close enough for ball park calculations to validate the results.
35mpg out of a 914? Are you sure? Mine gets 17mpg city and maybe 21mpg highway. Maybe. With the top on. Quite a bit less out on the track, although I don't recall ever really calculating it.

135mph. LOL. Yeah. That is the real, serious, absolute top-speed on that car. And you lost about 3 mph with the headlights up. ;) On courses with long straights we were in trouble. On anything with a lot of corners, though, the "go-kart with license plates" gave some drivers of much more expensive Porsches some very nasty surprises!!! :gig: The thing handles like a slot-car.

How much transmission experience do you have with the 914? Mine's starting to develop a really bizarre fault and for the life of me I can't figure it out. If you've got some experience with the transmission, I'd like to PM you and run the symptoms by you for your opinion, if you don't mind.
 
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BBerson

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The Limbach L2000 (1994cc) aircraft engine used in numerous two seat motorgliders such as my Grob G109 is based on VW parts.

From the L2000 engine manual:
Takeoff power (5 min)---- 80hp at 3400rpm min
Max. continuous power-- 72hp at 3000rpm min
compression ratio-- 8.7 to 1


The L2000 engine has a somewhat higher compression ratio that most VW aviation engines and needs premium fuel.

I have run it more than 5 min at full throttle in climb, the oil gets to redline after about 10 min and a higher climb speed is needed to improve ram air cooling. Or the power needs to reduce. If cruise starts after a climb to only 3000feet, then the high cruise speed keeps the oil temp normal.
 

Hot Wings

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BTW, you'll note that Great Plains, for one, shows continuous and takeoff power ratings for all their engines, right up on the web page.

I've missed that bit of info :emb: GP moves up a notch in my opinion for that. Commendable.
 

Jake Levi

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Great thread Gentlemen,

one factor I didnt see discussed is aircraft weights;

what gross weights, among other factors are the base for thos hp expectations? I am doing a Biplane, gross weight of ~ 1100 lbs,

I am looking at adding a radiator so add another 30lbs to be safe.

Your thoughts/comments appreciated.
 

Topaz

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...one factor I didnt see discussed is aircraft weights;

what gross weights, among other factors are the base for thos hp expectations? I am doing a Biplane, gross weight of ~ 1100 lbs,

I am looking at adding a radiator so add another 30lbs to be safe.

Your thoughts/comments appreciated.
Not quite sure I understand the question. What engine does the designer spec for the airplane? Or are you the designer?
 

Jake Levi

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Hi Topaz

Its a Graham Lee Nieuport 12,

gross weight of 1070 lbs, they have been built with Rotec 503s(too small) and bigger rotecs plus the 2180 AND 2280 VWs. There will be some tweaking with heavier gear, etc, gross will go to about 1150lbs. To help that my weight is 50lbs lighter then the anticipated pilot weight. The plan is to use the larger VW engine.
 

Topaz

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That's kinda strange. On the website they spec either the Rotec 2800 (110hp and 224lbs.) or the Rotax 582 (64hp and 130lbs.). That's quite a weight and power spread! Both are swinging a big, slow prop through a pretty big reduction.

I guess one of the larger VW conversions with a reduction would fit in that power-weight space, and Great Plains has just such stuff on sale. But I'd definitely run it past the designer before I went off on my own like that. There may be other considerations beyond just weight and power.

At any rate, in most airplanes, required engine power is usually set by hot-and-high climb rate requirements at the maximum takeoff weight. For our kinda birds, you pull back to 65-75% power for cruise and whatever speed you get is the speed you get. If you want to go a lot faster, you should'a picked a faster airplane.
 

Jake Levi

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Hi Topaz

The designer is gone from us, a number have been built with a number of tweaks, by the Dawn Patrol and several others, the 2180 and 2280 cc VWs have done well with it, and cruise 70-75 mph, which is great to me, thats all I do on the expressway. The listed 'spec cruise' is 75 mph.

So I am looking at cooling options to get longer engine life and better all round efficiency and performance .

My last correspondance with Mr Lee was he designed it for two 200lbs passengers, plus 75 lbs fuel. I am just swapping the weight of one passenger for fuel and cooling. We are doing a heavier gear, and slightly larger rudder which has become a standard for the DP guys and other recent builders.
 

Topaz

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Is there a builder's group? The piece of information I'd want to confirm is that the guys using the VW were getting the 70-75mph cruise at 75% power or less. As HotWings reminds us above, some people will push the throttle up trying to get an arbitrary cruise number, and running the engine higher than the continuous power rating for any significant length of time will drastically shorten the TBO.

...So I am looking at cooling options to get longer engine life and better all round efficiency and performance...
If you don't already have it, definitely get Tony Bingelis' book Firewall Forward. It contains, IMHO, one of the best "layman's" discussions of how to do cooling and cowlings right. (Along with just about everything else you'll ever want to know when doing your engine installation! Outstanding book.) When you do yours, pay special attention to keeping the heads cool - they're the weak point on the VW. Install CHT sensors and pay attention to them during your flight-test phase, and adjust your cowling accordingly. Check out oil coolers for the engine, too. They help a lot in higher-power models.

Finally, cruise at 75% power or less, regardless of what speed that gets you. If it's 75mph or more, great. If it's not, well, the Nieuport wasn't known for speed anyway. Sacrificing engine life for a couple more MPH just isn't worth it, IMHO, but it's up to you.

Neat plane, BTW. :)
 
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