Leaky exhaust valves

[radfordc]

On another note, are there any of the VW type II / IV engines being used in aviation regularly? They have always seemed to be well suited for modification for aircraft
use. In stock form they provide more torque which would reduce the need to "go big or go home". The one drawback seems to be the drive hub on the crankshaft.
The weight might also play in with the lack of aftermarket parts. Just something to think about.
Frank
ONEX 090

One of the very first customer built Sonexs had a Type 4 VW. It crashed due to prop hub failure. https://app.ntsb.gov/pdfgenerator/Repor ... l&IType=LA

[NWade]

My GP VW did not use copper head gaskets, I never had any problems.

So I just want to point out that a single data-point does not prove a theory. I am not saying this to be critical of Phil; his experience is perfectly valid for him. But there are people who smoke cigarettes and never develop lung cancer. Their experience doesn't prove that smoking is safe for your health. :)

Frank - Good to know about your VW experience. It sounds like you've got far more hands-on time on the engine than I do! My comments were certainly not pointed in your direction in any sharp or negative way. I'm just trying to urge caution and critical thinking.

My main point in all of this is to be careful who you trust (i.e. figure out their credentials before you decide how seriously to take their claims or advice), and to try to thoroughly understand how something works and the whys behind any solution, before you make decisions or deviate from plans. Take a scientific approach when sussing out the "why" part: Is the information current? Are arguments for/against supported with solid evidence? Are they repeated by multiple reliable and experienced sources? How small is the sample size?
Most choices in aircraft design (and engines, too) are a compromise between several factors. If you don't understand those various competing requirements - or the impacts of a particular method/part - then you could unwittingly put yourself at risk for higher maintenance and/or in-flight failures. If you truly want to have confidence in your aircraft and its systems, you need to be able to point to any part and say "I chose that because of A, B, and C. Even though it means X, Y, and Z; because B is very important to me, and it doesn't outweigh X."

Stepping off my soapbox for now,

--Noel
"online" in some form or another since 1985...

[vigilant104]

On another note, are there any of the VW type II / IV engines being used in aviation regularly? They have always seemed to be well suited for modification for aircraft
use. In stock form they provide more torque which would reduce the need to "go big or go home". The one drawback seems to be the drive hub on the crankshaft.
The weight might also play in with the lack of aftermarket parts. Just something to think about.
Frank

That lack of aftermarket parts drives up their cost, and that's another major reason we don't see many Type IVs. It''s just a lot more trouble and work to go that route (rather than the Type I), and the Type I gives us all we need if its limits are respected. An important inherent limit is the ability of the head to shed heat. It's not a downfall or weakness of the VW, just a limit that needs to be understood. Folks have even tried using the "wasserboxers" to allow more heat to be shed, but the results have generally been expensive, leaky, unreliable airplane powerplants.
Good baffling is key to making the Type i work in our planes (just as it is in the automotive VW installation). Luckily for us in the Sonex world, the factory and many builders have been down this road, tried hundreds of things, and have provided a path (including parts and detailed instructions) that works. Sure, this is experimental aviation and people can try new things, but hopefully that won't result in disparagement of the engine if the results aren't what they'd hoped.

[rizzz]

On another note, are there any of the VW type II / IV engines being used in aviation regularly? They have always seemed to be well suited for modification for aircraft
use. In stock form they provide more torque which would reduce the need to "go big or go home". The one drawback seems to be the drive hub on the crankshaft.
The weight might also play in with the lack of aftermarket parts. Just something to think about.
Frank
ONEX 090

A good friend of mine owns a Grob 109B motor glider which is powered by a certified 2.5L Type 4 VW conversion which produces about 90hp.
I have flown his aircraft and I really liked the way his engine runs.
Here's a picture of one:

[rizzz]

OK, so I just got the heads back. They look like new!

My VW guy told me the machinist said the heads were in good condition, so where the valves & guides, however, the valve seats were "shitty" (that was the highly technical term he used), and they would have been the cause of the leak(s) I was experiencing. He could not tell me how they would have gotten "shitty" after running for only 70 hours or so.
Anyway, the seats have been cut etc. so they seal properly again.

Regarding the copper head gaskets, he is not a fan of them and generally does not use them. He says they are good if you have imperfections but given my heads have been flycut (they took 0.009 off) they should mate perfectly to the cylinders.

[rizzz]

Here's what they look like now:


I'm happy again, can't wait to put them back on the engine and go flying again, it's been weeks, I'm starting to show withdraw symptoms...
Unfortunately it won't be till Monday before I can get back to the airport.

[rizzz]

Yesterday I spent all day at the airport getting the engine back together and I’m happy to report she’s flying again.
I’m was getting good compression on all cylinders, even on a cold engine, so I decided to start her up for some ground testing. She ran like never before so after a few full power runs I put the cowling on and went for a flight.

The only issue I had was a massive AeroCarb burb on my take-off roll just after I opened the throttle. I have experienced burps before when taking off with a hot engine but they were more like little hesitations, this one was a huge burp, the aircraft really stopped pulling for a brief moment.

Anyway, everything was smooth after that hiccup and the aircraft climbed great, I noticed a significant improvement in power output so I guess the problem I was having must have slowly started creeping up on me over the last few months.

[mike.smith]

The only issue I had was a massive AeroCarb burb on my take-off roll just after I opened the throttle. I have experienced burps before when taking off with a hot engine but they were more like little hesitations, this one was a huge burp, the aircraft really stopped pulling for a brief moment.

Too rich, perhaps?

[rizzz]

The only issue I had was a massive AeroCarb burb on my take-off roll just after I opened the throttle. I have experienced burps before when taking off with a hot engine but they were more like little hesitations, this one was a huge burp, the aircraft really stopped pulling for a brief moment.

Too rich, perhaps?

Not sure.
I am still running way rich, yes, I do realize that now, even after another 1/4 turn towards the lean side. This is probably also the reason why my valve seats got contaminated so badly and eventually pitted.
I am going to go back to do some serious tuning on my AeroInjector, starting with putting the 2.0 needle back in. (I'm currently running the 2.5 needle).

[radfordc]

I would think the burp was not due to running rich. It is a sign of a bubble in the fuel line that interrupts fuel flow at the carb...same as you've experienced before. Keeping the fuel cool in the lines is the solution to that problem.