My newbie obsessive questions about VW repair

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Aviacs

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(perhaps?) another clarification:
Checking & adjusting valves on a routine basis is not an issue.
I grew up with British sports cars and rode Triumph motorcycles until a few years ago.

I' talking about making a set of exhaust valves and guides-last- more than 300 hrs, if that is possible.
Again, 2276 & it does not appear to get overly hot. But the wear on guides and stems was considerable.

smt
 

Vigilant1

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If somebody wanted to get more continuous HP from the VW, it would be good to acknowledge the failure of some pretty smart people who had been there before, and accept that...
Just to be clear, that is where my questions start.
(I assume?) that i don't need more HP.
However, VW's are brand new to me.
So, in an engine that was in an airplane widely reported over quite a few years, that constantly ("constantly" = every few hundred hours, more or less) needed valve attention, how did the smart minds extend that reliability period?
I hope I didn't come across as trying to shut down your questions. Not at all. Your questions are (IMO) quite reasonable.

Re: Nikasil: the OP had Nikasil cylinders on, from GP, (had a complete GP Nikasil engine built and installed to replace an Aerovee that failed through destruction of the 8 pin flywheel to crank connection along with ignition & accessory components) and seemed excited to buy and install them. I don't think they lasted 300 hours and were replaced by the current cast steel jugs.
There are different qualities of Nikasil cylinders. Some are not good. Sonex sold some of those as an option, and lots of people were very unhappy. They basically got weak where the cylinders met the case and "slumped". It's possible your engine had some of those.
I do wish the VW could swing a longer, more efficient prop more slowly; for shorter TO. better climb, and for overall efficiency. That won't happen with direct drive; & a PSRU probably suggests a different power plant.
There are folks doing this (especially some of the Rinebeck airdrome guys). The Type 1 can be fitted with a PSRU and can then turn a longer prop. Theoretically, a low airspeeds that could allow more thrust (at the same engine HP). There are four factors to consider, though:
1) It will weigh more than a direct drive VW (PSRU plus that beefier prop)
2) Despite the PSRU, the engine cannot be cajoled into reliably producing more than about 75 continuous HP (say, by turning it at 4200 RPM because the PSRU now makes that possible with propeller speeds).
3) Whether direct drive or with a PSRU, if you are flying the plane slowly you may not be able to make a lot of continuous HP. It seems to me that 75 continuous HP is reasonable with good attention to ducting if the plane will doing about 90 kts or so.
4) PSRUs come with their own set of potential problems (especially resonance/vibration).
 
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Aviacs

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. It seems to me that 75 continuous HP is reasonable with good attention to ducting if the plane will doing about 90 kts or so.

I had no inkling when buying the airplane a few years ago.
After importing it & joining Sonerai.net, it became apparent that it had been owned by, and most of the mods/upgrades done by a (late) person formerly prominent on the forum. He was a Canadian A & P & flight instructor. So his posts about gradual improvements to make the airplane a reliable 160+ mph cruiser are probably credible. However, for weight and cruise, Sonerai 2's take a fair amount of runway to get airborne though they climb adequately. Tiny/short 52" props on the speedier versions. I'd trade a little bit ( :) ) of top speed, for significantly better TO performance, but those calculations are all in the future for me. Gotta get the AW first or it's all moot.

To the point of your note - yes, cruise above 90kts.

smt
 

TFF

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I grew up with British Sports cars; well I don’t know if grew up is accurate. Still have a few with a few Alfas. I consider airplane engines as a low stressed race engine. Club racer out to just make laps. It’s the manifold pressure not the RPM. Like if you daily drive to work is up Pikes Peak. Not racing, just driving. Lots of load to get the simple job done.

300 hours is pretty good because it’s under designed all around. Better guides, seats and valves will only do so much if the head can’t take the heat.

Lycoming has four one cylinder cylinders. Thermal differences between cylinders don’t affect the others. Case deformation doesn’t affect the others. All of course within reason. VW you are transferring heat from one cylinder to adjacent, good or bad. If the case is twisting from heat under one cylinder, it’s pulling on another.

I am a fan of VWs, it’s not a hater position. It’s a realist position that a VW is pushed hard to make it useable. Cheap parts are the counter measure to the over stressed use. Because the extra work dollars comes in under the Lycoming cost is why it works. It’s also a hobby engine. Tinkerer vs easy button.
 

Vigilant1

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... However, for weight and cruise, Sonerai 2's take a fair amount of runway to get airborne though they climb adequately.
The Sonerai 2 page at Aircraft Spruce gives a TO distance of 900 feet, is that what folks typically get? It's definitely not a STOL aircraft.

FWIW, the Sonex has a similarly stubby wing and similar engine/prop, generally are a little heavier than a Sonerai 2. The factory claims a takeoff roll of 500 feet, but I think most folks see a takeoff roll of about 800 feet on pavement.
 

TFF

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There was a local Sonex Aerovee powered, I watched, and I thought it got off very fast. Vx was underwhelming though. A Cessna 150 with two aboard ate more runway, but is higher at the threshold. Not much higher. I have never seen a Sonerai fly only stood next to them. Thin airfoil. It has to eat quite a bit. If you are still sticking the RV wings on it, that’s a pretty thick relative airfoil. Same weight it would get off quicker. There really isn’t a magic propeller. You can trade an inch of diameter to an inch of pitch given the same prop manufacturer platform. You can have a 60” prop instead of a 56” prop but the 60” will have to have 4” less pitch to make the same RPMs. They will be very different props in function.
 

Vigilant1

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If the previous builder of the engine was focused on efficient high speed cruise, is it possible he chose a camshaft that moved
There was a local Sonex Aerovee powered, I watched, and I thought it got off very fast. Vx was underwhelming though. A Cessna 150 with two aboard ate more runway, but is higher at the threshold. Not much higher.
Regarding the bold portion: Do you mean the airspeed for best climb angle (Vx) was underwhelming or that the climb angle was underwhelming? Typical Vx for a VW powered Sonex is about 70MPH IAS. I think it is safe to say that most Sonex pilots will avoid climbing at Vx for very long unless it is necessary (obstacle clearance, etc). The engine cools a lot better at higher airspeeds (Vy is about 90 MPH IAS). So, if circumstances permit, the climbout most folks will choose will be relatively shallow (and fast) compared to a C-152. Yes, it could climb steeper and there are folks who do, but shallower is more common. It's a matter of keeping the engine happy.
 

Pops

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I got to respect the VW engine when we had a 1966 VW bus camper pulling a nimrod foldout camper. Week trip to Okhkosh each year for many years. Also wife and I and 3 children would spend 2 weeks on the road seeing the U.S. each year. I built a 1700cc, single port head engine for it. Only problem in all the years and miles was a wheel bearing went out and made it home before fixing, and the tube steel box tongue on the camper cracked and had to stop and have it welded. Had extra fiberglass air scoops on the air intake on the rear side and kept the rpm's low with lower speeds. Always got 24 mph, flat interstate of pulling mountains.
 

TFF

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Climb angle was not good. Even if they were climbing at best cooling speed, it should get up once it gains speed. He was never at patten altitude until well into the second half of the downwind. It was a pretty little plane. Above average. The owner had other things to fly so this was his knock around airplane. He was happy with the frugal flying.
 

Aviacs

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never seen a Sonerai fly only stood next to them. Thin airfoil. It has to eat quite a bit. If you are still sticking the RV wings on it, that’s a pretty thick relative airfoil. Same weight it would get off quicker.

Someone pointed out something that i really had not realized: "It does not have to fit or suit you, work on getting an AW, and then make the mods" . Though i don't know how i can fly off the test time, if i can't fit in the airplane.

Here's where i am: Wanted to go over (inspect, tune) and start engine, to give myself some encouragement, and because it is essential anyway. That lead to the heads off for rust inspection, and discovery of the worn out valves and guides in my recent posts. I have been waiting for parts from aircooled.net for 2 weeks at this point, though there was a note this past Friday that they were being shipped. But now i ran out of time. Have to do other things for 2 weeks before i can get back to it. If the parts come in tomorrow, it might be possible to get them and the heads to my engine guru. If not, there will be another lapse.

Once the heads are in good hands and it is clear whether i have to do anymore machine work, I need to get back to finishing the oven made last year before ski season set in, and finish wiring it. Then make a larger (taller) canopy. From that point continue inspecting and repairing (maintenance) to the point it makes sense to get a DAR involved. Or see how far our local FSDO guy might have moved toward considering E-A/B vs Exhibition.

Sometimes i have to stop and accept an outside job to fund things, too. Hoping to avoid that this fall, but might be necessary.

So: I really want to try the RV3 wings with flaps; & presumably still have an aerodynamicist to advise. But will likely put the original wings back on in the interest of expedience toward the AWC for now. They are complete, slide in, already fit, tested, and presumably rigged. The 3 wings need finished, and most likely some mods to fuselage structure.

It's a slow process.
Thank you for the interest and support.

smt
 

TFF

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With an experimental airplane once it has the paperwork, you can experiment and it’s still an airplane. It has to be finished to get the paperwork. Easy if you got all of it already. You can amend it forever if you follow the operating limitations guidelines.
 

Aviacs

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Re-hash to date:
I removed ex. valve guides. Bought all new valves and keepers. Went on vacation. :)

Now back....
"Dave" engine shop owner/pilot/aircraft owner agreed to fit the new guides, hone the guide bores, grind the seats and install the valves. He said it would be easier for me if he checks the spring pressure and sets the installed height. Since VW engines are new to both of us, more questions come up.

I have both Steve Bennett's manual for the engine, which is a Factory GP 2276.
Also an Aero-Vee manual, since the engine the GP replaced, was an Aero-Vee.

Neither mention a thing about spring setting height, nor spring pressure, for low rpm 2 liter plus engines, with 40mm intakes and 35.5 exhausts valves.

Stock VW values would not seem to apply?

The valves are bigger, the rpms slower, maybe it's a wash after all?

But part of making the cams live, is low spring pressure.

Bob Hoover lists the setting height as 2.016" with drawing.
He lists the spring pressure as "117 to 135" lbs at 31mm=1.220" & notes that while lower is better, even better yet is if all 8 springs are the same pressure within a 1lb or so. (IIUC he seems to be saying it would be better to have 8 springs at 130 lbs, rather than 8 springs that varied from 117 to 125 lbs even though that would be a lower overall pressure and within the gross tolerance?)

Does anyone have supporting data, better information, or corrections?

Thank you!
smt
 

TFF

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The same pressure means the cam should have the same surface work load, and if one valve floats, all valves float. Friction losses should be smoother, than loose then tight cycles. I’m sure your measuring the coil bind and guide to retainer clearances. Shimming the bottom of the spring should not be an issue with the right work. With anything, if there is more than one, safe bet that if it’s all the same there is less stress. Springs, pistons, rods, chambers… Everything if you can.
 

Aviacs

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That part i get.

Since the "manufacturer" (GP) does not appear to specify, does anyone know what the minimum recommended spring pressure for 40mm valves in a 2276 VW av engine should be? Does anyone know what GP setting height should be in that engine?

I talked to Art Box (GP owner) yesterday afternoon, but he was running errands and did not have the data at his fingertips. I sent an email that evening, and am waiting for a reply.....

smt
 

Aviacs

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After another follow-up call still waiting for an answer from the "factory"...

Striking out everywhere.
Does no one check these items; despite the opportunity for incremental improved engine smoothness & durability?

smt
 

Pops

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New stock valve springs are OK. You are not building a VW hotrod engine and need strong valve springs or double springs so you will not have valve float at 6K+ rpm.
Stock springs with a stock cam that has a lighter load on the cam means long life. For a straight drive VW driving a prop, forget all the high rpm auto mods. You are building for a low rpm, high torque tractor engine.
 

TFF

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Most of this stuff would be in a car manual. There is no secret sauce. Without a batch of springs and a spring tester, it’s not valid. Without measuring the valve space from the deck to retainer, same. The numbers are all over Google. The real issue is coil bind and bottoming out. You start there and do what you do to match them. Most engine builders will coil bind the spring right on the tester before they check the numbers. Take out the early settling as much as they can.
 

Aviacs

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New stock valve springs are OK. You are not building a VW hotrod engine and need strong valve springs or double springs so you will not have valve float at 6K+ rpm.
Stock springs with a stock cam that has a lighter load on the cam means long life. For a straight drive VW driving a prop, forget all the high rpm auto mods. You are building for a low rpm, high torque tractor engine.

I think everyone is on that same page. That is why i hope to find the data:
1.) Using the low end of possible pressure for the valve size and rpm means the cam, lifters, and valve stems will last longer.
2.) using all the same pressure means the engine will run smoother.
I did used to build motorcycle engines...
From what i've read, "new stock valves" are all over the map, some are out of tolerance, & some go out of tolerance upon heating up to high operating temperature. Somewhat depending on source. I'd almost rather use used springs, so long as they test well.

Most of this stuff would be in a car manual.

Yes - it is in the VW manual...if you are using stock size valves and occasionally run the engine up to 5K+ rpm.

There is no secret sauce. Without a batch of springs and a spring tester, it’s not valid.

Of course.. Not sure i get the point here?

Without measuring the valve space from the deck to retainer, same.

That is why i asked for that number (see original Q)

The numbers are all over Google

You can say that again!
Was hoping for something more definitive. :)

The real issue is coil bind and bottoming out. You start there and do what you do to match them. Most engine builders will coil bind the spring right on the tester before they check the numbers. Take out the early settling as much as they can.

Yes.
Of course.
And then what is an ideal value for the engine listed?

Relating to VW's, most of this is on Samba.
However, there are a lot of different opinions, and all relate to higher rpm and mostly higher perf engines.

I'm going to have to get back to the hangar and put an indicator on a pushrod, see what the lift is over several lobes, multiply by the rocker ratio, which will give some sense of the safe margin for installed spring height. Then will probably go with Bob Hoover's pressure numbers which are pretty much the stock values (117 to 135 lbs @ 31mm compressed height). See what comes up testing among the available springs, and then decide how many more to sort. Or maybe put all the lower ones on the exhausts (smaller, lighter) and the heavier on the intakes)

Thanks for thinking about it.

smt
 
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Aviacs

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I finally made it away from other necessary jobs, to the hangar today, and stuck a long travel indicator on a rig-up with a pushrod.
The cams lift aprox. .330" to .335". Both intake and exhaust. Multiple readings, the measure repeated though i would not assign better than +.005"/- .010 absolute value. Then i went home to set up and measure the rocker ratio. Upon arriving home, i remembered the rocker sets and shafts were stored back at the hangar, on a separate cabinet along one of the sidewalls. :rolleyes:

So i decided to clean up the exhausts, which were at home.
The flanges are corroded and were not ever smooth or flat to begin with, instead being installed over multiple gaskets. (previous builder), so i decided to finally get some use out of a flex-vise that came with another machine a couple decades ago. While setting an exhaust with the flange up in the vise on a surface grinder, faint flashes of light were noticed. 2 exhausts have holes through, in the tube, alongside welds. More corrosion and too thin already for me to feel welding is a good repair.

How long could a person expect new mild steel exhausts to last in this app? Airplane will be kept in heated hangar.
For background, these are not stubbies, they are all about 2' or maybe a little longer & exit the cowling together, more or less center fuselage, under the firewall. I will probably replicate the design, and possibly add a collector.

If stainless, is there something that bends a bit more easily than 321 and is still better than mild steel?
Are there kits of pre-bends like with mild steel?

Thank you.

smt
 

challenger_II

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The mild steel exhausts on my Longster lasted close to 30 years (but only 216 hours of run time).
Great Planes has pre-bent exhaust kits and parts. In my searches for exhaust parts for VW's, I have found stainless bends and tubes, but no flanges.
 
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